CLOSED LOOP OXYGEN CONTROL

FIELD OF THE DISCLOSURE

[0001] The present disclosure relates to methods and systems for controlling oxygen delivery in a flow therapy apparatus.

BACKGROUND

[0002] Respiratory apparatuses are used in various environments such as hospital, medical facility, residential care, or home environments to deliver a flow of gas to users or patients. A respiratory apparatus, or a flow therapy apparatus, may include an oxygen inlet to allow delivery of supplemental oxygen with the flow of gas, and/or a humidification apparatus to deliver heated and humidified gases. A flow therapy apparatus may allow adjustment and control over characteristics of the gases flow, including flow rate, temperature, gas concentration, such as oxygen concentration, humidity, pressure, etc.

SUMMARY

[0003] In accordance with certain features, aspects and advantages of a first embodiment disclosed herein, a respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising: a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to: receive patient parameter data indicative of oxygen saturation (Sp02) of the patient from at least one sensor; execute a control phase, wherein operation of the respiratory apparatus during a therapy session is based at least in part on the patient parameter data; and a gases composition sensor configured to determine at least oxygen content (Fd02) of gases flow during operation of the respiratory apparatus, wherein the gases composition sensor is an ultrasonic sensor system.

[0004] In some configurations of the first embodiment, the respiratory apparatus comprises a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

[0005] In some configurations of the first embodiment, the nasal cannula is a non-sealed nasal cannula.

[0006] In some configurations of the first embodiment, the respiratory apparatus is configured to deliver a nasal high flow (NHF) flow of gases to the patient.

[0007] In some configurations of the first embodiment, the at least one sensor is a pulse oximeter.

[0008] In some configurations of the first embodiment, the controller is configured to receive device parameter data indicative of an oxygen concentration of the gases flow.

[0009] In some configurations of the first embodiment, the respiratory apparatus comprises a supplementary gas inlet valve.

[0010] In some configurations of the first embodiment, the controller is configured to control operation of the supplementary gas inlet valve.

[0011] In some configurations of the first embodiment, the supplementary gas inlet valve is a proportional valve.

[0012] In some configurations of the first embodiment, the supplementary gas inlet valve is an oxygen inlet valve.

[0013] In some configurations of the first embodiment, the supplementary gas inlet valve comprises a swivel connector.

[0014] In some configurations of the first embodiment, the respiratory apparatus comprises an ambient air inlet.

[0015] In some configurations of the first embodiment, the oxygen inlet valve is in fluid communication with a filter module and the respiratory apparatus is configured to entrain oxygen received from the oxygen inlet valve with ambient air from the ambient air inlet in the filter module.

[0016] In some configurations of the first embodiment, the gases composition sensor is positioned downstream of a blower module of the respiratory apparatus.

[0017] In some configurations of the first embodiment, the filter module is positioned upstream of the blower module of the respiratory apparatus.

[0018] In some configurations of the first embodiment, the blower module mixes ambient air and oxygen.

[0019] In some configurations of the first embodiment, the closed loop control includes using a first closed loop control model configured to determine a target fraction of delivered oxygen (Fd02).

[0020] In some configurations of the first embodiment, the target Fd02 is determined based at least in part on a target Sp02 and measured Sp02.

[0021] In some configurations of the first embodiment, the target Fd02 is further based at least in part on measured Fd02.

[0022] In some configurations of the first embodiment, the target Fd02 is further based at least in part on a previous target Fd02.

[0023] In some configurations of the first embodiment, the closed loop control includes using a second closed loop control model configured to determine a control signal for an oxygen inlet valve based at least in part on a difference between the target Fd02 and the measured Fd02.

[0024] In some configurations of the first embodiment, the control signal for the oxygen valve is determined based at least in part on the target Fd02 and the measured Fd02.

[0025] In some configurations of the first embodiment, the control signal for the oxygen valve is determined further based at least in part on a gases flow rate.

[0026] In some configurations of the first embodiment, the gases flow rate is the total gases flow rate.

[0027] In some configurations of the first embodiment, the controller is configured to transfer to a manual mode of operation when a signal quality of the at least one sensor is below a threshold.

[0028] In some configurations of the first embodiment, the controller is configured to generate a notification for a user indicating that signal quality of the at least one sensor is below a threshold.

[0029] In some configurations of the first embodiment, the notification requests input from the user indication whether to transfer to a manual mode of operation.

[0030] In some configurations of the first embodiment, the controller is configured to transfer to a manual mode of operation when the patient Sp02 is outside of defined limits.

[0031] In some configurations of the first embodiment, the controller is configured to trigger an alarm when the patient Sp02 is outside of the defined limits.

[0032] In some configurations of the first embodiment, control of the delivery of gases includes control of Fd02 of the gases flow, and the controller is configured to receive an indication of signal quality of the at least one sensor, and apply a weighting to the control of the Fd02 based at least in part on the signal quality.

[0033] In some configurations of the first embodiment, the indication of signal quality corresponds to specific Sp02 readings.

[0034] In some configurations of the first embodiment, the control phase is configured to be executed using a patient specific model

[0035] In some configurations of the first embodiment, the patient specific model is generated during a learning phase of the therapy session.

[0036] In some configurations of the first embodiment, the patient specific model is generated during the therapy session.

[0037] In some configurations of the first embodiment, the patient specific model is updated during the therapy session.

[0038] In some configurations of the first embodiment, the control phase is configured to be executed using a PID control based at least in part on the patient specific model.

[0039] In some configurations of the first embodiment, the patient specific model includes an oxygen efficiency of the patient.

[0040] In some configurations of the first embodiment, the oxygen efficiency is determined based at least in part on measured Sp02 and measured Fd02.

[0041] In some configurations of the first embodiment, the oxygen efficiency is determined based at least in part on measured Sp02 divided by measured Fd02.

[0042] In some configurations of the first embodiment, the oxygen efficiency is determined based at least in part on a non-linear relationship between measured Sp02 of the patient and measured Fd02.

[0043] In some configurations of the first embodiment, the controller is configured to predict the Sp02 of the patient based at least in part on the measured Fd02. [0044] In some configurations of the first embodiment, previous predictions of the Sp02 are compared with measured Sp02 to calculate model error.

[0045] In some configurations of the first embodiment, the model error is weighted by signal quality of the at least one sensor.

[0046] In some configurations of the first embodiment, the model error is used to correct the current Sp02 prediction.

[0047] In some configurations of the first embodiment, the predicted Sp02 is based at least in part on a Smith predictor.

[0048] In some configurations of the first embodiment, the controller is configured to receive input identifying characteristics of the patient.

[0049] In some configurations of the first embodiment, the patient characteristics include at least one of a patient type, age, weight, height, or gender.

[0050] In some configurations of the first embodiment, the patient type is one of normal, hypercapnic, or user-defined.

[0051] In some configurations of the first embodiment, the controller is further configured to record data corresponding to the measured Fd02 and the measured Sp02.

[0052] In some configurations of the first embodiment, the respiratory apparatus comprises a humidifier.

[0053] In some configurations of the first embodiment, the respiratory apparatus comprises an integrated blower and humidifier.

[0054] In some configurations of the first embodiment, the respiratory apparatus is configured to be portable.

[0055] In some configurations of the first embodiment, the respiratory apparatus is configured to have a controlled variable flow rate.

[0056] In some configurations of the first embodiment, the respiratory apparatus comprises a heated breathing tube.

[0057] In some configurations of the first embodiment, the ultrasonic sensor system comprises a first ultrasonic transducer and a second ultrasonic transducer.

[0058] In some configurations of the first embodiment, each of the first ultrasonic transducer and the second ultrasonic transducer is a receiver and a transmitter.

[0059] In some configurations of the first embodiment, the first ultrasonic transducer and the second ultrasonic transducer send pulses bidirectionally.

[0060] In some configurations of the first embodiment, the first ultrasonic transducer is a transmitter and the second ultrasonic transducer is a receiver.

[0061] In some configurations of the first embodiment, at least one of the first ultrasonic transducer or the second ultrasonic transducer send pulses along the gases flow

[0062] In some configurations of the first embodiment, at least one of the first ultrasonic transducer or the second ultrasonic transducer send pulses across the gases flow.

[0063] In some configurations of the first embodiment, the controller is configured to display a first oxygen efficiency characteristic on a display of the respiratory apparatus.

[0064] In some configurations of the first embodiment, the controller is configured to display a second oxygen efficiency characteristic on a display of the respiratory apparatus, and the second indication of oxygen efficiency is based at least in part on an oxygen efficiency and a measured respiration rate of the patient.

[0065] In some configurations of the first embodiment, the second oxygen efficiency characteristic is calculated by dividing measured Sp02 by measured Fd02, and dividing the resulting value by the measured respiratory rate.

[0066] In some configurations of the first embodiment, the controller is configured to display a graph or trend line indicating at least one of the first oxygen efficiency characteristic or the second oxygen efficiency characteristic over a defined period of time.

[0067] In accordance with certain features, aspects and advantages of a second embodiment disclosed herein, a respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising: a controller configured to control delivery of gases to the patient using closed loop control, the controller is configured to: control oxygen concentration (Fd02) of the gases flow to the patient; receive data from at least one patient sensor indicative of a measured oxygen saturation (Sp02) of the patient; receive data indicative of a measured Fd02 of the gases flow; receive a target Sp02 for the patient; and execute a step change to the Fd02 of the gases flow, a magnitude of the step change is based at least in part on the measured Sp02, the target Sp02 and an oxygen efficiency of the patient.

[0068] In some configurations of the second embodiment, the oxygen efficiency is determined based at least in part on measured Sp02 and measured Fd02.

[0069] In some configurations of the second embodiment, the oxygen efficiency is determined based at least in part on measured Sp02 divided by measured Fd02.

[0070] In some configurations of the second embodiment, the oxygen efficiency is determined based at least in part on a non-linear relationship between measured Sp02 of the patient and measured Fd02.

[0071] In some configurations of the second embodiment, the magnitude of the step change is based at least in part on recent changes to the target Fd02 prior to the step change.

[0072] In some configurations of the second embodiment, the magnitude of the step change is based at least in part on recent changes to the target Fd02 prior to the step change.

[0073] In some configurations of the second embodiment, a new target Fd02 is calculated based at least in part on the previous target Fd02.

[0074] In some configurations of the second embodiment, the controller is configured to execute a feed forward stage after the step change.

[0075] In some configurations of the second embodiment, the controller is further configured to maintain the target Fd02 immediately following the step change for a total duration of the feed forward stage.

[0076] In some configurations of the second embodiment, the feed forward stage ends if the measured Sp02 meets or exceeds the target Sp02.

[0077] In some configurations of the second embodiment, the feed forward stage ends if a maximum defined period of time is reached.

[0078] In some configurations of the second embodiment, the respiratory apparatus comprises a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

[0079] In some configurations of the second embodiment, the nasal cannula is a non-sealed nasal cannula.

[0080] In some configurations of the second embodiment, the respiratory apparatus is configured to deliver a nasal high flow (NHF) flow of gases to the patient.

[0081] In some configurations of the second embodiment, the at least one patient sensor is a pulse oximeter.

[0082] In some configurations of the second embodiment, the respiratory apparatus comprises a humidifier.

[0083] In some configurations of the second embodiment, the respiratory apparatus comprises a gases composition sensor configured to determine the measured Fd02 during operation of the respiratory apparatus, and the gases composition sensor is an ultrasonic transducer system.

[0084] In some configurations of the second embodiment, the controller is further configured to execute a control phase after the feed forward stage.

[0085] In some configurations of the second embodiment, in the control phase the controller is further configured to control Fd02 of the gases flow to achieve the target Fd02 using feedback control.

[0086] In some configurations of the second embodiment, the controller is further configured to receive an indication of signal quality of the at least one patient sensor, and apply a weighting to the control of the Fd02 based at least in part on the signal quality.

[0087] In some configurations of the second embodiment, the controller is further configured to execute the control phase using a predicted Sp02 of the patient.

[0088] In some configurations of the second embodiment, the respiratory apparatus is configured to be portable.

[0089] In some configurations of the second embodiment, the controller is configured to display a first oxygen efficiency characteristic on a display of the respiratory apparatus.

[0090] In some configurations of the second embodiment, the controller is configured to display a second oxygen efficiency characteristic on a display of the respiratory apparatus, and the second indication of oxygen efficiency is based at least in part on an oxygen efficiency and a measured respiration rate of the patient.

[0091] In some configurations of the second embodiment, the second oxygen efficiency characteristic is calculated by dividing measured Sp02 by measured Fd02, and dividing the resulting value by the measured respiratory rate.

[0092] In some configurations of the second embodiment, the controller is configured to display a graph or trend line indicating at least one of the first oxygen efficiency characteristic or the second oxygen efficiency characteristic over a defined period of time.

[0093] In accordance with certain features, aspects and advantages of a third embodiment disclosed herein, a respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising: a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to: receive device parameter data indicative of an oxygen concentration (Fd02) of the gases flow; receive patient parameter data from at least one sensor indicative of an oxygen saturation (Sp02) reading of the patient, wherein the Sp02 of the patient is affected by the Fd02 of the gases flow; receive an indication of signal quality of the at least one sensor; and apply a weighting to the control of the Fd02 based at least in part on the signal quality.

[0094] In some configurations of the third embodiment, the indication of signal quality corresponds to specific Sp02 readings.

[0095] In some configurations of the third embodiment, the respiratory apparatus comprises a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

[0096] In some configurations of the third embodiment, the nasal cannula is a non-sealed nasal cannula.

[0097] In some configurations of the third embodiment, the respiratory apparatus is configured to deliver a nasal high flow (NHF) flow of gases to the patient.

[0098] In some configurations of the third embodiment, the at least one sensor is a pulse oximeter.

[0099] In some configurations of the third embodiment, the controller is configured to receive input identifying characteristics of the patient.

[0100] In some configurations of the third embodiment, the controller is configured to control delivery of gases using a predicted Sp02 of the patient.

[0101] In some configurations of the third embodiment, the predicted Sp02 is based at least in part on a Smith predictor.

[0102] In some configurations of the third embodiment, the controller is configured to control delivery of gases using a patient specific model.

[0103] In some configurations of the third embodiment, the model is a patient specific model generated during a learning phase of a therapy session of the patient.

[0104] In some configurations of the third embodiment, the patient specific model is generated during the therapy session based at least in part on a default model.

[0105] In some configurations of the third embodiment, the patient specific model is updated during the therapy session.

[0106] In some configurations of the third embodiment, the model includes a delay time.

[0107] In some configurations of the third embodiment, the model includes an exponential decay.

[0108] In some configurations of the third embodiment, the model includes an oxygen efficiency of the patient.

[0109] In some configurations of the third embodiment, the oxygen efficiency is determined based at least in part on measured Sp02 and measured Fd02.

[0110] In some configurations of the third embodiment, the oxygen efficiency is determined based at least in part on measured Sp02 divided by measured Fd02.

[0111] In some configurations of the third embodiment, the oxygen efficiency is determined based at least in part on a non-linear relationship between measured Sp02 of the patient and measured Fd02.

[0112] In some configurations of the third embodiment, the respiratory apparatus is configured to be portable.

[0113] In accordance with certain features, aspects and advantages of a fourth embodiment disclosed herein, a respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising: a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to: control oxygen concentration (Fd02) of the gases flow to the patient; receive data from at least one patient sensor indicative of a measured oxygen saturation (Sp02) of the patient; receive data indicative of a measured Fd02 of the gases flow; receive a target Sp02 for the patient; and execute a wait stage, wherein during the wait stage the controller is configured to determine whether to execute a feed forward stage prior to transitioning to a control phase, wherein the target Fd02 of the gases flow is held constant during the wait stage; and execute a control phase wherein the Fd02 is controlled to achieve the target Sp02 using feedback control.

[0114] In some configurations of the fourth embodiment, the controller is further configured to determine whether to execute the feed forward stage based at least in part on the target Sp02 and the measured Sp02.

[0115] In some configurations of the fourth embodiment, the controller is further configured to determine whether to execute the feed forward stage based at least in part on an oxygen efficiency of the patient.

[0116] In some configurations of the fourth embodiment, the oxygen efficiency is determined based at least in part on measured Sp02 and measured Fd02.

[0117] In some configurations of the fourth embodiment, the oxygen efficiency is determined based at least in part on measured Sp02 divided by measured Fd02.

[0118] In some configurations of the fourth embodiment, the oxygen efficiency is determined based at least in part on a non-linear relationship between measured Sp02 of the patient and measured Fd02.

[0119] In some configurations of the fourth embodiment, if the controller determines to execute the feed forward stage, the controller executes the feed forward stage after the wait stage, and if the controller determines not to execute the feed forward stage, the controller executes the control phase after the wait phase.

[0120] In some configurations of the fourth embodiment, the controller is further configured to maintain a target Fd02 for a total duration of the feed forward stage.

[0121] In some configurations of the fourth embodiment, the feed forward stage ends if the measured Sp02 meets or exceeds the target Sp02.

[0122] In some configurations of the fourth embodiment, the feed forward stage ends if a maximum defined period of time is reached.

[0123] In some configurations of the fourth embodiment, the controller is further configured to execute the control phase after the feed forward stage.

[0124] In some configurations of the fourth embodiment, prior to execution of the feed forward stage, the controller is configured to determine whether to execute a step change to the Fd02 of the gases flow.

[0125] In some configurations of the fourth embodiment, the controller is further configured to determine whether to execute the step change based at least in part on recent changes to the target Fd02.

[0126] In some configurations of the fourth embodiment, the controller is further configured to determine whether to execute the step change based at least in part on the target Sp02 and the measured Sp02.

[0127] In some configurations of the fourth embodiment, the controller is further configured to determine whether to execute the step change based at least in part on an oxygen efficiency of the patient.

[0128] In some configurations of the fourth embodiment, a magnitude of the step change is based at least in part on the measured Sp02, the target Sp02 and an oxygen efficiency of the patient.

[0129] In some configurations of the fourth embodiment, the magnitude of the step change is based at least in part on recent changes to the target Fd02

[0130] In some configurations of the fourth embodiment, the respiratory apparatus comprises a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

[0131] In some configurations of the fourth embodiment, the nasal cannula is a non-sealed nasal cannula.

[0132] In some configurations of the fourth embodiment, the respiratory apparatus is configured to deliver a nasal high flow (NHF) flow of gases to the patient.

[0133] In some configurations of the fourth embodiment, the at least one patient sensor is a pulse oximeter.

[0134] In some configurations of the fourth embodiment, the respiratory apparatus comprises a humidifier.

[0135] In some configurations of the fourth embodiment, the respiratory apparatus comprises a gases composition sensor configured to determine a measured Fd02

during operation of the respiratory apparatus, and the gases composition sensor is an ultrasonic transducer system.

[0136] In some configurations of the fourth embodiment, the controller is further configured to receive an indication of signal quality of the at least one patient sensor, and apply a weighting to the control of the Fd02 based at least in part on the signal quality.

[0137] In some configurations of the fourth embodiment, the controller is further configured to apply the weighting during the control phase.

[0138] In some configurations of the fourth embodiment, the controller is further configured to execute the control phase using a predicted Sp02 of the patient.

[0139] In some configurations of the fourth embodiment, the respiratory apparatus is configured to be portable.

[0140] In accordance with certain features, aspects and advantages of a fifth embodiment disclosed herein, a respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising: a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to: deliver a nasal high flow (NHF) gases flow to the patient; receive data from at least one patient sensor indicative of a measured oxygen saturation (Sp02) of the patient; receive data indicative of a measured fraction of delivered oxygen (Fd02) of the gases flow; determine an oxygen efficiency of the patient; and generate a patient specific model based on measured Sp02 and measured Fd02, wherein the patient specific model uses the oxygen efficiency of the patient.

[0141] In some configurations of the fifth embodiment, the oxygen efficiency is determined based at least in part on measured Sp02 and measured Fd02.

[0142] In some configurations of the fifth embodiment, the oxygen efficiency is determined based at least in part on measured Sp02 divided by measured Fd02.

[0143] In some configurations of the fifth embodiment, the oxygen efficiency is determined based at least in part on a non-linear relationship between measured Sp02 of the patient and measured Fd02.

[0144] In some configurations of the fifth embodiment, the patient specific model is generated based at least in part on a default model.

[0145] In some configurations of the fifth embodiment, the patient specific model is generated during a learning phase.

[0146] In some configurations of the fifth embodiment, the patient specific model is updated during a therapy session of the patient.

[0147] In some configurations of the fifth embodiment, the patient specific model models the magnitude of the change in Sp02 based at least in part on the change in Fd02.

[0148] In some configurations of the fifth embodiment, the patient specific model uses a flow rate of the gases flow.

[0149] In some configurations of the fifth embodiment, the patient specific model includes a delay time between a change in Fd02 and a change in Sp02 of the patient.

[0150] In some configurations of the fifth embodiment, the delay time is based at least in part on the flow rate of the gases flow.

[0151] In some configurations of the fifth embodiment, the patient specific model includes an exponential decay.

[0152] In some configurations of the fifth embodiment, the at least one patient sensor is a pulse oximeter.

[0153] In some configurations of the fifth embodiment, the respiratory apparatus comprises a humidifier.

[0154] In some configurations of the fifth embodiment, the Fd02 is measured using an ultrasonic transducer system.

[0155] In some configurations of the fifth embodiment, the ultrasonic transducer system comprises a first ultrasonic transducer and a second ultrasonic transducer.

[0156] In some configurations of the fifth embodiment, each of the first ultrasonic transducer and the second ultrasonic transducer is a receiver and a transmitter.

[0157] In some configurations of the fifth embodiment, the first ultrasonic transducer and the second ultrasonic transducer send pulses bidirectionally.

[0158] In some configurations of the fifth embodiment, the first ultrasonic transducer is a transmitter and the second ultrasonic transducer is a receiver.

[0159] In some configurations of the fifth embodiment, at least one of the first ultrasonic transducer or the second ultrasonic transducer send pulses along the gases flow. [0160] In some configurations of the fifth embodiment, at least one of the first ultrasonic transducer or the second ultrasonic transducer send pulses across the gases flow.

[0161] In some configurations of the fifth embodiment, the respiratory apparatus is configured to be portable.

[0162] In accordance with certain features, aspects and advantages of a sixth embodiment disclosed herein, a respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising: a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to: control oxygen concentration (Fd02) of the gases flow to the patient; receive data from at least one patient sensor indicative of a measured oxygen saturation (Sp02) of the patient; receive data indicative of a measured Fd02 of the gases flow; receive a target Sp02 for the patient; execute a step change to the Fd02 of the gases flow to a target Fd02; execute a feed forward stage; and execute a control phase wherein the Fd02 is controlled to achieve the target Sp02 using feedback control.

[0163] In some configurations of the sixth embodiment, a magnitude of the step change is based at least in part on the measured Sp02, the target Sp02, and an oxygen efficiency of the patient.

[0164] In some configurations of the sixth embodiment, the target Fd02 is based at least in part on recent changes to the target Fd02 prior to the step change.

[0165] In some configurations of the sixth embodiment, the controller is further configured to maintain the target Fd02 immediately following the step change for a total duration of the feed forward stage.

[0166] In some configurations of the sixth embodiment, the feed forward stage ends if a maximum defined period of time is reached.

[0167] In some configurations of the sixth embodiment, the feed forward stage ends if the measured Sp02 meets or exceeds the target Sp02.

[0168] In some configurations of the sixth embodiment, the controller is further configured to execute the control phase after the feed forward stage.

[0169] In some configurations of the sixth embodiment, the respiratory apparatus comprises a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

[0170] In some configurations of the sixth embodiment, the nasal cannula is a non-sealed nasal cannula.

[0171] In some configurations of the sixth embodiment, the respiratory apparatus is configured to deliver a nasal high flow (NHF) flow of gases to the patient.

[0172] In some configurations of the sixth embodiment, the at least one patient sensor is a pulse oximeter.

[0173] In some configurations of the sixth embodiment, the respiratory apparatus comprises a humidifier.

[0174] In some configurations of the sixth embodiment, the respiratory apparatus comprises a gases composition sensor configured to determine a measured Fd02 during operation of the respiratory apparatus, wherein the gases composition sensor is an ultrasonic transducer system.

[0175] In some configurations of the sixth embodiment, the controller is further configured to receive an indication of signal quality of the at least one patient sensor, and apply a weighting to the control of the Fd02 based at least in part on the signal quality.

[0176] In some configurations of the sixth embodiment, the controller is further configured to execute the control phase using a predicted Sp02 of the patient.

[0177] In some configurations of the sixth embodiment, the respiratory apparatus is configured to be portable.

[0178] In accordance with certain features, aspects and advantages of a seventh embodiment disclosed herein, a respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising: a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to: deliver the flow gases to the patient using nasal high flow (NHF); control an oxygen concentration (Fd02) of the gases flow to the patient; receive data from at least one patient sensor indicative of a measured oxygen saturation (Sp02) of the patient; receive a target Sp02 for the patient; and execute a step change to the Fd02 of the gases flow, wherein a magnitude of the step change is based at least in part on the measured Sp02 and the target Sp02 of the patient.

[0179] In some configurations of the seventh embodiment, the step change is further based at least in part on an oxygen efficiency of the patient.

[0180] In some configurations of the seventh embodiment, the oxygen efficiency is determined based at least in part on measured Sp02 and measured Fd02.

[0181] In some configurations of the seventh embodiment, the oxygen efficiency is determined based at least in part on measured Sp02 divided by measured Fd02.

[0182] In some configurations of the seventh embodiment, the oxygen efficiency is determined based at least in part on a non-linear relationship between measured Sp02 of the patient and measured Fd02.

[0183] In some configurations of the seventh embodiment, the magnitude of the step change is based at least in part on changes to the target Fd02 within a defined time period prior to the step change.

[0184] In some configurations of the seventh embodiment, a new target Fd02 is calculated based at least in part on the previous target Fd02.

[0185] In some configurations of the seventh embodiment, the controller is configured to execute a feed forward stage after the step change.

[0186] In some configurations of the seventh embodiment, the controller is further configured to maintain the Fd02 at the target Fd02 for a total duration of the feed forward stage.

[0187] In some configurations of the seventh embodiment, the feed forward stage ends if the measured Sp02 meets or exceeds the target Sp02.

[0188] In some configurations of the seventh embodiment, the feed forward stage ends if a maximum defined period of time is reached.

[0189] In some configurations of the seventh embodiment, the respiratory apparatus comprises a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

[0190] In some configurations of the seventh embodiment, the nasal cannula is a non-sealed nasal cannula.

[0191] In some configurations of the seventh embodiment, the at least one patient sensor is a pulse oximeter.

[0192] In some configurations of the seventh embodiment, the respiratory apparatus comprises a humidifier.

[0193] In some configurations of the seventh embodiment, the respiratory apparatus comprises a gases composition sensor configured to determine the measured Fd02 during operation of the respiratory apparatus, and the gases composition sensor is an ultrasonic transducer system.

[0194] In some configurations of the seventh embodiment, the controller is further configured to execute a control phase after the feed forward stage.

[0195] In some configurations of the seventh embodiment, in the control phase the controller is further configured to control Fd02 of the gases flow to achieve the target Fd02 using feedback control.

[0196] In some configurations of the seventh embodiment, the controller is further configured to receive an indication of signal quality of the at least one patient sensor, and apply a weighting to the control of the Fd02 based at least in part on the signal quality.

[0197] In some configurations of the seventh embodiment, the controller is further configured to execute the control phase using a predicted Sp02 of the patient.

[0198] In some configurations of the seventh embodiment, the respiratory apparatus is configured to be portable.

[0199] In some configurations of the seventh embodiment, the controller is configured to display a first oxygen efficiency characteristic on a display of the respiratory apparatus.

[0200] In some configurations of the seventh embodiment, the controller is configured to display a second oxygen efficiency characteristic on a display of the respiratory apparatus, and the second indication of oxygen efficiency is based at least in part on an oxygen efficiency and a measured respiration rate of the patient.

[0201] In some configurations of the seventh embodiment, the second oxygen efficiency characteristic is calculated by dividing measured Sp02 by measured Fd02, and dividing the resulting value by the measured respiratory rate.

[0202] In some configurations of the seventh embodiment, the controller is configured to display a graph or trend line indicating at least one of the first oxygen efficiency characteristic or the second oxygen efficiency characteristic over a defined period of time.

[0203] In accordance with certain features, aspects and advantages of at least one of the embodiments disclosed herein, a respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising: a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to: receive patient parameter data indicative of oxygen saturation (Sp02) of the patient from at least one sensor; and execute a control phase, wherein operation of the respiratory apparatus during a therapy session is based at least in part on the patient parameter data.

[0204] In some configurations, the apparatus comprises a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

[0205] In some configurations, the respiratory apparatus is configured to deliver a nasal high flow (NHF) flow of gases to the patient.

[0206] In some configurations, at least one sensor is a pulse oximeter.

[0207] In some configurations, the apparatus comprises an supplementary gas inlet valve.

[0208] In some configurations, the controller is configured to control operation of the supplementary gas inlet valve.

[0209] In some configurations, the supplementary gas inlet valve is a proportional valve.

[0210] In some configurations, the supplementary gas inlet valve is an oxygen inlet valve.

[0211] In some configurations, the apparatus comprises an ambient air inlet.

[0212] In some configurations, the oxygen inlet valve is in fluid communication with a filter module, wherein the respiratory apparatus is configured to entrain oxygen received from the oxygen inlet valve with ambient air from the ambient air inlet in the filter module.

[0213] In some configurations, the apparatus comprises a gases composition sensor configured to determine at least the oxygen content of gases flow during operation of the respiratory apparatus.

[0214] In some configurations, the gases composition sensor is an ultrasonic transducer system.

[0215] In some configurations, the gases composition sensor is positioned downstream of a blower module of the respiratory apparatus.

[0216] In some configurations, the filter module is positioned upstream of the blower module of the respiratory apparatus.

[0217] In some configurations, the closed loop control includes using a first closed loop control model configured to determine a target fraction of delivered oxygen (Fd02).

[0218] In some configurations, the target Fd02 is determined based at least in part on target Sp02 and patient Sp02.

[0219] In some configurations, the target Fd02 is further based at least in part on measured Fd02.

[0220] In some configurations, the closed loop control includes using a second closed loop control model configured to determine a control signal for an oxygen inlet valve.

[0221] In some configurations, the control signal for the oxygen valve is determined based at least in part on the target Fd02 and the measured Fd02.

[0222] In some configurations, the control signal for the oxygen valve is determined further based at least in part on a gases flow rate.

[0223] In some configurations, the controller is configured to transfer to a manual mode of operation when a signal quality of the at least one sensor is below a threshold.

[0224] In some configurations, the controller is configured to transfer to a manual mode of operation when the patient Sp02 is outside of defined limits.

[0225] In some configurations, the controller is configured to receive an indication of signal quality, and apply a weighting to the control of the Fd02 based at least in part on the signal quality.

[0226] In some configurations, the indication of signal quality corresponds to specific Sp02 readings.

[0227] In some configurations, the controller is configured to execute a plurality of phases during a therapy session of the respiratory apparatus, wherein the controller is configured to: execute a learning phase, wherein during the learning phase the controller is configured to generate a patient specific model; and execute the control phase based at least in part on the patient specific model.

[0228] In some configurations, during the learning phase the controller is configured to: receive device parameter data indicative of oxygen concentration of the gases flow provided to the patient; and receive patient parameter data indicative of oxygen saturation of the patient from at least one sensor.

[0229] In some configurations, the controller is configured to generate the patient specific model based at least in part on a relationship between the oxygen concentration of the gases flow and the oxygen saturation of the patient.

[0230] In some configurations, the learning phase has a maximum duration.

[0231] In some configurations, the learning phase is executed a plurality of times during the therapy session.

[0232] In some configurations, the controller is further configured to change the oxygen concentration during the learning phase.

[0233] In some configurations, the controller is further configured to change the oxygen concentration after the controller detects that the measured oxygen saturation of the patient parameter is stable.

[0234] In some configurations, the change is to increase the oxygen concentration.

[0235] In some configurations, the change is to decrease the oxygen concentration.

[0236] In some configurations, the patient specific model is based at least in part on signal quality data of the sensor recorded during the learning phase.

[0237] In some configurations, the patient specific model determines a delay time, wherein the delay time is a period of time between when a change in oxygen concentration of the gases flow occurs and a response in oxygen saturation of the patient.

[0238] In some configurations, the patient specific model calculates an exponential decay.

[0239] In some configurations, parameters of the patient specific model includes at least one of: delay time, rate of exponential decay, change in oxygen concentration, and change in blood oxygen saturation.

[0240] In some configurations, the controller is further configured to execute the control phase after the patient specific model satisfies defined characterization criteria.

[0241] In some configurations, the defined characterization criteria defines, for each of one or more of the parameters of the patient specific model, an acceptable value range for the parameter.

[0242] In some configurations, the control phase is configured to be executed using a PID control based at least in part on the patient specific model.

[0243] In some configurations, the controller is configured to receive device parameter data indicative of oxygen concentration of the gases flow.

[0244] In some configurations, the controller is configured to predict the oxygen saturation of the patient based at least in part on oxygen concentration of the gases flow.

[0245] In some configurations, the prediction is at least partially based on one or more patient parameter readings.

[0246] In some configurations, the previous predictions of the patient parameter are compared with measured patient parameter readings to calculate model error.

[0247] In some configurations, the model error is weighted by signal quality.

[0248] In some configurations, the model error is used to correct the current prediction.

[0249] In some configurations, the prediction is based on a model.

[0250] In some configurations, the model is patient specific.

[0251] In some configurations, the model is generated during a learning phase of the therapy session.

[0252] In some configurations, the control phase is configured to be executed using a predictive algorithm for predicting the oxygen saturation of the patient.

[0253] In some configurations, the predictive algorithm is a Smith predictor.

[0254] In some configurations, the output of the predictive algorithm is based at least in part on a patient specific model.

[0255] In some configurations, the controller is configured to receive input identifying characteristics of the patient.

[0256] In some configurations, the patient characteristics include at least one of a patient type, age, weight, height, or gender.

[0257] In some configurations, the patient type is one of normal, hypercapnic, or user-defined.

[0258] In some configurations, the controller is configured to execute a learning phase, wherein during the learning phase the controller is configured to: receive device parameter data indicative of oxygen concentration of the gases flow provided to the patient; receive patient parameter data indicative of oxygen saturation of the patient from at least one sensor; and calculate one or more model parameters for a patient specific model based on the device parameter data and the patient parameter data; determine that at least one of the one or more parameters does not satisfy patient characterization criteria for generation of a patient specific model; and execute the control phase, wherein operation of the respiratory apparatus during the therapy session is based at least in part on a default patient model.

[0259] In some configurations, the default patient model is selected from the plurality of default patient models based at least in part on one or more of the patient characteristics.

[0260] In some configurations, the default patient model is selected from the plurality of default patient models based at least in part on the patient type.

[0261] In some configurations, the controller is further configured to record data corresponding to the measured oxygen concentration and the measured oxygen saturation.

[0262] In some configurations, the controller is further configured to stop recording data after a defined period of time.

[0263] In some configurations, the controller is further configured to stop recording data after the patient specific model satisfies defined characterization criteria.

[0264] In some configurations, the apparatus comprises a humidifier.

[0265] In some configurations, the apparatus comprises an integrated blower and humidifier.

[0266] In some configurations, the respiratory apparatus is configured to be portable.

[0267] In some configurations, the respiratory apparatus is configured to have a controlled variable flow rate.

[0268] In some configurations, the target Fd02 is further based at least in part on signal quality.

[0269] In some configurations, the respiratory apparatus is configured to vary flow rate by varying motor speed of the blower.

[0270] In accordance with certain features, aspects and advantages of at least one of the embodiments disclosed herein, a method of providing a flow of gases to a patient, the method comprising: by a controller of a respiratory apparatus, receiving patient parameter data indicative of oxygen saturation of the patient from at least one sensor; and controlling operation of the respiratory therapy apparatus using closed loop control during a control phase of the therapy session based at least in part on the patient parameter data.

[0271] In some configurations, the method comprises executing a learning phase during a therapy session, the learning phase including: receiving device parameter data indicative of oxygen concentration of the gases flow provided to the patient and patient parameter data indicative of oxygen saturation of the patient from at least one sensor; generating a patient specific model based at least in part on a relationship between the oxygen concentration of the gases flow and the oxygen saturation of the patient.

[0272] In some configurations, the method comprises controlling operation of the respiratory therapy apparatus during a control phase of the therapy session based at least in part on the patient specific model.

[0273] In some configurations, the method comprises recording data corresponding to the measured oxygen concentration and the measured oxygen saturation.

[0274] In some configurations, the method comprises stopping the recording data after a defined period of time.

[0275] In some configurations, the method comprises generating the patient specific model based at least in part on signal quality data of the at least one sensor recorded during the learning phase.

[0276] In some configurations, parameters of the patient specific model includes at least one of: delay time, rate of exponential decay, change in oxygen concentration, and change in blood oxygen saturation.

[0277] In some configurations, the method comprises executing the control phase after the patient specific model satisfies defined characterization criteria.

[0278] In some configurations, the defined characterization criteria defines, for each of one or more of the parameters of the patient specific model, an acceptable value range for the parameter.

[0279] In some configurations, the method comprises executing the control phase using a PID control based at least in part on the patient specific model.

[0280] In some configurations, the method comprises executing the control phase using a predictive algorithm for predicting the oxygen saturation of the patient.

[0281] In some configurations, the method comprises using the predicted oxygen saturation during the control phase.

[0282] In some configurations, the predictive algorithm is a Smith predictor.

[0283] In some configurations, the output of the predictive algorithm is based at least in part on the patient specific model.

[0284] In some configurations, the method comprises receiving input identifying characteristics of the patient.

[0285] In some configurations, the patient characteristics include at least one of a patient type, age, weight, height, or gender.

[0286] In some configurations, the method comprises changing the oxygen concentration during the learning phase.

[0287] In some configurations, the method comprises changing the oxygen concentration during the learning phase after detecting that the measured oxygen saturation of the patient parameter is stable.

[0288] In some configurations, the change is to increase the oxygen concentration.

[0289] In some configurations, the change is to decrease the oxygen concentration.

[0290] In some configurations, the method comprises executing the learning phase a plurality of times during the therapy session.

[0291] In some configurations, the method comprises transferring to a manual mode of operation when a signal quality of the at least one sensor is below a threshold. [0292] In some configurations, the method comprises transferring to a manual mode of operation when the patient Sp02 is outside of defined limits.

[0293] In some configurations, the method comprises determining a target Fd02 using a first closed control loop.

[0294] In some configurations, the target Fd02 is determined based at least in part on a target Sp02 and patient Sp02.

[0295] In some configurations, the target Fd02 is further based at least in part on measured Fd02.

[0296] In some configurations, the method comprises determining a control signal for an oxygen inlet valve using a second closed control loop.

[0297] In some configurations, the control signal is determined based at least in part on a the target Fd02 and the measured Fd02.

[0298] In some configurations, the control signal for the oxygen valve is further based at least in part on a gases flow rate.

[0299] In some configurations, the method comprises adjusting the oxygen inlet valve based on the control signal.

[0300] In some configurations, the method comprises entraining oxygen from the oxygen inlet valve with ambient air from an ambient air inlet within a filter module of the respiratory apparatus.

[0301] In some configurations, the method comprises receiving an indication of signal quality, and applying a weighting to the control of the Fd02 based at least in part on the signal quality.

[0302] In some configurations, the method comprises determining at least the oxygen content of gases flow during operation of the respiratory apparatus.

[0303] In some configurations, the target Fd02 is further based at least in part on signal quality.

[0304] In accordance with certain features, aspects and advantages of at least one of the embodiments disclosed herein, a respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising: a controller configured to control delivery of gases to the patient, wherein the controller is configured to: execute a learning phase, wherein during the learning phase the controller is configured to: receive device parameter data indicative of oxygen concentration of the gases flow provided to the patient; receive patient parameter data indicative of oxygen saturation of the patient from at least one sensor; and generate a patient specific model based at least in part on a relationship between the oxygen concentration of the gases flow and the oxygen saturation of the patient; and execute a control phase, wherein operation of the respiratory apparatus during a therapy session is based at least in part on the patient specific model.

[0305] In some configurations, the apparatus comprises patient interface is selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

[0306] In some configurations, the respiratory apparatus is an apparatus that delivers a nasal high flow (NHF) flow of gases.

[0307] In some configurations, the sensor is a pulse oximeter.

[0308] In some configurations, the controller is further configured to record data corresponding to the measured oxygen concentration and the measured oxygen saturation.

[0309] In some configurations, the controller is further configured to stop recording data after a defined period of time.

[0310] In some configurations, the patient specific model is based at least in part on signal quality data of the sensor recorded during the learning phase.

[0311] In some configurations, the patient specific model determines a delay time, wherein the delay time is a period of time between when a change in oxygen concentration of the gases flow and a response in oxygen saturation of the patient.

[0312] In some configurations, the patient specific model calculates an exponential decay.

[0313] In some configurations, parameters of the patient specific model includes at least one of: delay time, rate of exponential decay, change in oxygen concentration, and change in blood oxygen saturation.

[0314] In some configurations, the controller is further configured to execute the control phase after the patient specific model satisfies defined characterization criteria.

[0315] In some configurations, the defined characterization criteria defines, for each of one or more of the parameters of the patient specific model, an acceptable value range for the parameter.

[0316] In some configurations, the control phase is configured to be executed using closed loop control.

[0317] In some configurations, the control phase is configured to be executed using a PID control based at least in part on the patient specific model.

[0318] In some configurations, the control phase is configured to be executed using a predictive algorithm for predicting the oxygen saturation of the patient.

[0319] In some configurations, the controller is further configured to use the predicted oxygen saturation during the control phase.

[0320] In some configurations, the predictive algorithm is a Smith predictor.

[0321] In some configurations, the output of the predictive algorithm is based at least in part on the patient specific model.

[0322] In some configurations, the controller is configured to receive input identifying characteristics of the patient.

[0323] In some configurations, the patient characteristics include at least one of a patient type, age, weight, height, or gender.

[0324] In some configurations, the controller is further configured to change the oxygen concentration during the learning phase.

[0325] In some configurations, the controller is further configured to change the oxygen concentration after the controller detects that the measured oxygen saturation of the patient parameter is stable. In some configurations, the change is to increase the oxygen concentration. In some configurations, the change is to decrease the oxygen concentration.

[0326] In some configurations, the learning phase is executed a plurality of times during the therapy session.

[0327] Additionally, in accordance with certain features, aspects and advantages of at least one of the embodiments disclosed herein, a respiratory apparatus that provides a flow of gases to a patient, wherein the respiratory apparatus is configured to deliver a nasal high flow (NHF) flow of gases to the patient, the respiratory apparatus comprising: a controller configured to control operation of the respiratory apparatus and execute a plurality of phases during a therapy session of the respiratory apparatus, wherein the controller is configured to: execute a learning phase, wherein during the learning phase the controller is configured to generate a patient specific model; and execute a control phase, wherein

operation of the respiratory apparatus during the therapy session is based at least in part on the patient specific model.

[0328] In some configurations, during the learning phase, the controller is further configured to measure a property of the gases flow provided to the patient. In some configurations, the property is oxygen concentration of the gases flow.

[0329] In some configurations, during the learning phase, the controller is further configured to measure a physiological parameter of the patient using at least one sensor. In some configurations, the physiological parameter is oxygen saturation of the patient.

[0330] In some configurations, the controller is further configured to: receive device parameter data indicative of oxygen concentration of the gases flow provided to the patient; and receive patient parameter data indicative of oxygen saturation of the patient from at least one sensor. In some configurations, during the learning phase, the controller is further configured to generate a patient specific model based at least in part on a relationship between the oxygen concentration of the gases flow and the oxygen saturation of the patient.

[0331] In some configurations, the at least one sensor is a pulse oximeter.

[0332] In some configurations, the controller is further configured to change the oxygen concentration during the learning phase. In some configurations, the controller is further configured to change the oxygen concentration after the controller detects that the measured oxygen saturation of the patient parameter is stable. In some configurations, the change is to increase the oxygen concentration. In some configurations, the change is to decrease the oxygen concentration.

[0333] In some configurations, the controller is further configured to record data corresponding to the measured oxygen concentration and the measured oxygen saturation.

[0334] In some configurations, the controller is further configured to stop recording data after a defined period of time.

[0335] In some configurations, the controller is further configured to stop recording data after the patient specific model satisfies defined characterization criteria.

[0336] In some configurations, the patient specific model is based at least in part on signal quality data of the sensor recorded during the learning phase.

[0337] In some configurations, error values for sensor data can be weighted by the corresponding signal quality data.

[0338] In some configurations, the patient specific model determines a delay time, wherein the delay time is a period of time between when a change in oxygen concentration of the gases flow and a response in oxygen saturation of the patient.

[0339] In some configurations, the patient specific model calculates an exponential decay.

[0340] In some configurations, parameters of the patient specific model includes at least: delay time, rate of exponential decay, change in oxygen concentration, and change in blood oxygen saturation.

[0341] In some configurations, the control phase is configured to be executed using closed loop control.

[0342] In some configurations, the control phase is configured to be executed using a PID control based at least in part on the patient specific model.

[0343] In some configurations, the control phase is configured to be executed using a predictive algorithm for predicting the physiological parameter of the patient.

[0344] In some configurations, the controller is further configured to use the predicted oxygen saturation during the control phase.

[0345] In some configurations, the predictive algorithm is a Smith predictor.

[0346] In some configurations, the output of the predictive algorithm is based at least in part on the patient specific model.

[0347] In some configurations, the learning phase is executed a plurality of times during the therapy session.

[0348] In some configurations, the controller is configured to receive input identifying characteristics of the patient. In some configurations, the patient characteristics include at least one of a patient type, age, weight, height, or gender. In some configurations, the patient type is one of normal, hypercapnic, or user-defined.

[0349] Additionally, in accordance with certain features, aspects and advantages of at least one of the embodiments disclosed herein, a respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising: a controller configured to control delivery of gases to the patient, wherein the controller is configured to: receive device parameter data indicative of oxygen concentration of the gases flow; receive patient parameter data indicative of an oxygen saturation reading of the patient, wherein the oxygen saturation of the patient is affected by the oxygen concentration of the gases flow; and predict the oxygen saturation of the patient based at least in part on the oxygen concentration of the gases flow.

[0350] In some configurations, the apparatus comprises a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

[0351] In some configurations, the respiratory apparatus is an apparatus that delivers a nasal high flow (NHF) flow of gases.

[0352] In some configurations, the sensor is a pulse oximeter.

[0353] In some configurations, the prediction is at least partially based on one or more patient parameter readings. In some configurations, the previous predictions of the patient parameter are compared with measured patient parameter readings to calculate model error.

[0354] In some configurations, the model error is weighted by signal quality.

[0355] In some configurations, the model error is used to correct the current prediction.

[0356] In some configurations, the prediction is based on a model.

[0357] In some configurations, the model is patient specific.

[0358] In some configurations, the model is generated during a learning phase of the therapy session.

[0359] In some configurations, the patient specific model determines a delay time, wherein the delay time is a period of time between when a change in oxygen concentration of the gases flow and a response in oxygen saturation of the patient.

[0360] In some configurations, the patient specific model includes an exponential decay.

[0361] In some configurations, the controller is further configured to use the predicted oxygen saturation during the control phase.

[0362] In some configurations, the prediction is based on a Smith predictor.

[0363] In some configurations, the controller is configured to execute the control of the delivery of gases using closed loop control.

[0364] In some configurations, the model is based at least in part on signal quality data of the sensor recorded during the learning phase.

[0365] Additionally, in accordance with certain features, aspects and advantages of at least one of the embodiments disclosed herein, a respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising: a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to: receive device parameter data indicative of oxygen concentration of the gases flow; receive patient parameter data indicative of an oxygen saturation reading of the patient, wherein the oxygen saturation of the patient is affected by the oxygen concentration of the gases flow; receive an indication of signal quality; and apply a weighting to the control of the oxygen concentration based at least in part on the signal quality.

[0366] In some configurations, the indication of signal quality corresponds to specific oxygen saturation readings.

[0367] In some configurations, the apparatus comprises a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

[0368] In some configurations, the sensor is a pulse oximeter.

[0369] In some configurations, the controller is configured to control delivery of gases using a predictive algorithm for predicting the oxygen saturation of the patient. In some configurations, the output of the predictive algorithm is based at least in part on a model. In some configurations, the model is patient specific. In some configurations, the model is generated during a learning phase of the therapy session. In some configurations, the model includes a delay time. In some configurations, the model includes an exponential decay. In some configurations, the predictive algorithm is a Smith predictor.

[0370] In some configurations, the controller is configured to receive input identifying characteristics of the patient.

[0371] Additionally, in accordance with certain features, aspects and advantages of at least one of the embodiments disclosed herein, a respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising: a controller configured to control delivery of gases to the patient, wherein the controller is configured to: execute a learning phase, wherein during the learning phase the controller is configured to: receive device parameter data indicative of oxygen concentration of the gases flow provided to the patient; receive patient parameter data indicative of oxygen saturation of the patient from at least one sensor; and calculate one or more model parameters for a patient specific model based on the device parameter data and the patient parameter data; determine that at least one of the one or more parameters does not satisfy patient characterization criteria for generation of a patient specific model; and execute a control phase, wherein operation of the respiratory apparatus during a therapy session is based at least in part on a default patient model.

[0372] In some configurations, the apparatus comprises a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

[0373] In some configurations, the respiratory apparatus is an apparatus that delivers a nasal high flow (NHF) flow of gases.

[0374] In some configurations, the sensor is a pulse oximeter.

[0375] In some configurations, the controller is further configured to record data corresponding to measured oxygen concentration and measured oxygen saturation.

[0376] In some configurations, the one or more mode parameters include at least one of: delay time, rate of exponential decay, change in oxygen concentration, or change in blood oxygen saturation.

[0377] In some configurations, the default patient model is selected from one of a plurality of default patient models.

[0378] In some configurations, the controller is configured to receive input one or more patient characteristics. In some configurations, the patient characteristics include at least one of a patient type, age, weight, height, or gender. In some configurations, the patient type is one of normal, hypercapnic, or user-defined. In some configurations, the default patient model is selected from the plurality of default patient models based at least in part on the one or more patient characteristics. In some configurations, the default patient model is selected from the plurality of default patient models based at least in part on the patient type.

[0379] In some configurations, the control phase is configured to be executed using closed loop control.

[0380] In some configurations, the control phase is configured to be executed using a PID control based at least in part on the default patient model.

[0381] In some configurations, the control phase is configured to be executed using a predictive algorithm for predicting the oxygen saturation of the patient.

[0382] In some configurations, the controller is further configured to use the predicted oxygen saturation during the control phase to control delivery of gases to the patient.

[0383] In some configurations, the predictive algorithm is a Smith predictor.

[0384] In some configurations, the output of the predictive algorithm is based at least in part on the default patient model.

[0385] Additionally, in accordance with certain features, aspects and advantages of at least one of the embodiments disclosed herein, a method of providing a flow of gases to a patient, the method comprising: by a controller of a respiratory therapy apparatus, executing a learning phase during a therapy session, the learning phase including: receiving device parameter data indicative of oxygen concentration of the gases flow provided to the patient; receiving patient parameter data indicative of oxygen saturation of the patient from at least one sensor; and generating a patient specific model based at least in part on a relationship between the oxygen concentration of the gases flow and the oxygen saturation of the patient; and controlling operation of the respiratory therapy apparatus during a control phase of the therapy session based at least in part on the patient specific model.

[0386] The method can include recording data corresponding to the measured oxygen concentration and the measured oxygen saturation.

[0387] The method can include stopping the recording data after a defined period of time.

[0388] The method can include generating the patient specific model based at least in part on signal quality data of the at least one sensor recorded during the learning phase.

[0389] The parameters of the patient specific model includes at least one of: delay time, rate of exponential decay, change in oxygen concentration, and change in blood oxygen saturation.

[0390] The method can include executing the control phase after the patient specific model satisfies defined characterization criteria. The defined characterization criteria can define, for each of one or more of the parameters of the patient specific model, an acceptable value range for the parameter.

[0391] The method can include executing the control phase using a PID control based at least in part on the patient specific model.

[0392] The method can include executing the control phase using a predictive algorithm for predicting the oxygen saturation of the patient. The method can include using the predicted oxygen saturation during the control phase. The predictive algorithm can be a Smith predictor. The output of the predictive algorithm can be based at least in part on the patient specific model.

[0393] The method can include receiving input identifying characteristics of the patient. The patient characteristics can include at least one of a patient type, age, weight, height, or gender.

[0394] The method can include changing the oxygen concentration during the learning phase. The method can include changing the oxygen concentration during the learning phase after detecting that the measured oxygen saturation of the patient parameter is stable. The change can increase the oxygen concentration. The change can decrease the oxygen concentration.

[0395] The method can include executing the learning phase a plurality of times during the therapy session.

[0396] Features from one or more embodiments or configurations may be combined with features of one or more other embodiments or configurations. Additionally, more than one embodiment may be used together during a process of respiratory support of a patient.

[0397] The term 'comprising' as used in this specification means 'consisting at least in part of . When interpreting each statement in this specification that includes the term 'comprising', features other than that or those prefaced by the term may also be present. Related terms such as 'comprise' and 'comprises' are to be interpreted in the same manner.

[0398] It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.

[0399] It should be understood that alternative embodiments or configurations may comprise any or all combinations of two or more of the parts, elements or features illustrated, described or referred to in this specification.

[0400] This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features.

[0401] To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting. Where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

BRIEF DESCRIPTION OF THE DRAWINGS

[0402] Figure 1 A shows in diagrammatic form a flow therapy apparatus.

[0403] Figure IB illustrates a sensing circuit board including a flow rate sensor that may be used in a flow therapy apparatus.

[0404] Figures 1C-1D illustrate schematic diagrams of various ultrasonic transducer configurations for the sensor system using cross-flow beams.

[0405] Figures IE- IF illustrate schematic diagrams of various ultrasonic transducer configurations for the sensor system using along-flow beams.

[0406] Figure 2 illustrates graphs showing phases of operation of a flow therapy apparatus.

[0407] Figure 3 illustrates graphs showing a fitted trend line for a patient model.

[0408] Figure 4 illustrates a graph showing iterations of a trend line for a patient model.

[0409] Figure 5 illustrates a graph showing signal lag between predicted Sp02 values and actual Sp02 values.

[0410] Figure 6 illustrates a Smith predictor being utilized with the PID controller.

[0411] Figure 7 illustrates a graph of predicted Sp02 values with the delay time.

[0412] Figure 8 illustrates graphs showing outputs of different computational models for PID controllers.

[0413] Figure 9A illustrates a flowchart of a process for a method of controlling operation of a flow therapy apparatus during a flow therapy session.

[0414] Figure 9B illustrates a flowchart of a subprocess for a learning phase of the flow therapy session.

[0415] Figure 9C illustrates a flowchart of a subprocess for a control phase of the flow therapy session.

[0416] Figure 10 is a schematic diagram of a closed loop control system.

[0417] Figure 11 illustrates a process for calculating oxygen efficiency for a patient.

[0418] Figure 12 illustrates graphs showing phases of operation of a flow therapy apparatus.

[0419] Figure 13A illustrates a flowchart of a process for a method of controlling operation of a flow therapy apparatus during a flow therapy session.

[0420] Figure 13B illustrates a flowchart of a subprocess for a setup phase of the flow therapy session.

[0421] Figure 13C illustrates a flowchart of a subprocess for a control phase of the flow therapy session.

[0422] Figure 14 is a first underside perspective view of the main housing of the flow therapy apparatus showing a recess inside the housing for the motor and/or sensor module sub-assembly.

[0423] Figure 15 is a second underside perspective view of the main housing of the flow therapy apparatus showing the recess for the motor and/or sensor module subassembly.

[0424] Figure 16 is a perspective view of the motor and/or sensor subassembly, underside of the main housing, and fixed elbow of the flow therapy apparatus.

[0425] Figure 17 is an exploded perspective view of components of the motor and/or sensor sub-assembly schematically showing by way of an arrow the gas flow path through the sub-assembly.

[0426] Figure 18 is an underside view of a cover and sensing PCB of the motor and/or sensor sub-assembly showing the position of sensors.

[0427] Figure 19 is a rear perspective view of the flow therapy apparatus sectioned adjacent the rear edge of the apparatus, showing the arrangement of a portion of the main housing that provides the recess for receipt of the motor and/or sensor sub-assembly.

[0428] Figure 20 is a left front perspective view of the flow therapy apparatus.

[0429] Figure 21 is a left front perspective view of the flow therapy apparatus.

[0430] Figure 22 is a left front perspective partial cutaway view showing the valve module and the filter module.

[0431] Figure 23 is a schematic gas flow path diagram for the filter module and the valve module, with the solid line arrows representing the flow of oxygen (or another gas), and the dashed line arrows representing the flow of ambient air.

[0432] Figure 24 is a sectional view showing the gas flow path through the filter module and the valve module.

[0433] Figure 25 is a rear side overhead perspective view of a first configuration valve module.

[0434] Figure 26 is a rear side overhead perspective view showing the gas flow paths through the first configuration valve module, with the solid line arrows representing the flow of oxygen (or another gas), and the dashed line arrow representing the flow of ambient air.

[0435] Figure 27 is a sectional view through the first configuration valve module.

[0436] Figure 28 is a sectional view showing the coupling of, and gas flow path through, the valve and valve manifold of the first configuration valve module.

DETAILED DESCRIPTION

[0437] Patients suffering from various health conditions and diseases can benefit from oxygen therapy. For example, patients suffering from chronic obstructive pulmonary disease (COPD), pneumonia, asthma, bronchopulmonary dysplasia, heart failure, cystic fibrosis, sleep apnea, lung disease, trauma to the respiratory system, acute respiratory distress, receiving pre- and post- operative oxygen delivery, and other conditions or diseases can benefit from oxygen therapy. A common way of treating such problems is by supplying the patients with supplemental oxygen to prevent their blood oxygen saturation (Sp02) from dropping too low (e.g., below about 90%). However, supplying the patient with too much oxygen can over oxygenate their blood, and is also considered dangerous. Generally, the patient's Sp02 is kept in a range from about 80% to about 99%, and preferably about 92% to about 96%, although these ranges may differ due to patient conditions. Due to various factors such as respiratory rate, lung tidal volume, heart rate, activity levels, height, weight, age, gender, and other factors, there is no one prescribed level of supplemental oxygen that can consistently achieve an Sp02 response in the targeted range for each patient. Individual patients will regularly need their fraction of oxygen delivered to the patient (Fd02) monitored and adjusted to ensure they are receiving the correct Fd02 to achieve the targeted Sp02. Achieving a correct and consistent Sp02 is an important factor in treating patients with various health conditions or diseases. Additionally, patients suffering from these health problems may find benefit from a system that automatically controls oxygen saturation. The present disclosure is applicable to a wide range of patients that require fast and accurate oxygen saturation control.

[0438] The fraction of oxygen delivered to a patient (Fd02) may be controlled manually. A clinician can manually adjust an oxygen supply valve to change the flow rate or fraction of oxygen being delivered to the patient. The clinician can determine Sp02 levels of the patient using a patient monitor, such as a pulse oximeter. The clinician can continue to manually adjust the amount of oxygen being delivered to the patient until the Sp02 level of the patient reaches a determined level.

[0439] One problem with current methods is that when the clinician is trying to achieve a specific Sp02 level they would need to alter the Fd02, wait for the Sp02 reading to settle, and then apply further changes to the Fd02 until the Sp02 is at the required level.

The repetitive process of altering the Fd02 and waiting for the Sp02 to settle can be a very time consuming process, particularly if multiple patients are requiring the same treatment.

[0440] Another problem is the accuracy of the Sp02 that can be achieved. Accuracy of the Sp02 control can be dependent on how fine the increments are for displayed Sp02 and selectable Fd02. The accuracy may be hampered by the increased amount of time required to get increasingly accurate values, as a clinician may get close to the ideal Sp02 and decide not to alter the Fd02 any further.

[0441] Another problem is that other factors may cause the patient's Sp02 levels to change over time without any change in Fd02. Patients would need to be regularly checked on and have their Fd02 adjusted in order to maintain their Sp02 at the correct value. This process can be quite time consuming for the clinician. Additionally, if the time between adjustments is too long, the patient can be at risk of their Sp02 drifting too far from the targeted level.

[0442] While some systems exist that attempt something similar, many of them are plagued by further problems stemming from difficulties in measuring patient oxygen saturation. Pulse oximeters and similar devices generate a signal that lags far behind the corresponding change in oxygen fraction delivered. Additionally, oxygen saturation readings can become inaccurate due to various factors.

[0443] The present disclosure provides for closed loop control of a flow therapy apparatus that allows a patient or clinician to set a target Sp02 instead of a target Fd02. The flow therapy apparatus can automatically alter the Fd02 of the flow therapy apparatus to achieve the targeted Sp02 based on values of target Sp02, current Sp02, and current Fd02. Automatically controlling the Fd02 can help to quickly and accurately adjust the Fd02 until a target Sp02 is achieved. In some configurations, the system can generate a patient specific model for each patient at the initiation of a therapy session. The flow therapy apparatus can have greater precision in achieving the targeted Sp02 by adjusting the Fd02, as needed, to stay within the targeted Sp02 range, without being constantly monitored by a clinician.

[0444] The present disclosure provides for a flow therapy apparatus that can implement one or more closed loop control systems. Features of the closed loop control system may be combined with features of one or more configurations disclosed herein.

[0445] The flow therapy apparatus may operate in automatic mode or manual mode. In automatic mode, the controller can automatically control the Fd02 based on a target Fd02 determined based on the target Sp02 and/or measured Sp02. A valve at the oxygen inlet may be connected to the controller that can control the oxygen concentration in gases flow based on a target Fd02. The controller can execute a control algorithm that can measure Fd02 output by the flow therapy apparatus. The Fd02 measurement may be taken periodically at a defined frequency, such as a maximum sample rate of the gases concentration sensors or at a lower frequency, or the measurement may be taken aperiodically. The controller can continue to adjust the valve at the oxygen inlet until the measured Fd02 arrives at the target Fd02. The measured Fd02 may be determined by a gases composition sensor.

[0446] In manual mode, the controller can receive a target Fd02 from a clinician or patient, such as via a user interface. The controller can automatically control the Fd02 based on the received target Fd02. The controller can control the oxygen concentration in gases flow by controlling the oxygen inlet valve based on a target Fd02. The controller can execute a control algorithm that can use a measured Fd02 output by the flow therapy apparatus (for example, by a gases composition sensor of the flow therapy apparatus) as an input to the controller. The Fd02 measurement may be taken periodically at a defined frequency, such as a maximum sample rate of the gases concentration sensors or at a lower frequency, or the measurement may be taken aperiodically. The controller can continue to adjust the valve at the oxygen inlet to drive the measured Fd02 towards the target Fd02. The measured Fd02 may be determined by a gases composition sensor.

[0447] The flow therapy apparatus may be configured to change from automatic mode to manual mode when the Sp02 of the patient is not within an acceptable patient range. In some instances, the flow therapy apparatus reverts to manual mode when the Sp02 of the patient is outside of the patient limits (above or below) or if the patient's Sp02 did not move within the limits within a defined period of time after the start of the therapy session. The flow therapy apparatus may revert to manual mode when the signal quality of the patient sensor is below a threshold level for a defined period of time. In some configurations, the flow therapy apparatus may trigger an alarm when it switches from automatic mode to manual mode. In some configurations, the flow therapy apparatus may trigger an alarm when the signal quality of the patient sensor is below a threshold level for a defined period of time. The flow therapy apparatus may continue to function in automatic mode after the alarm is triggered. The flow therapy apparatus may provide the user, through a graphical user interface, with an option to disable the alarm or to exit automatic mode.

[0448] In automatic mode, the controller may utilize two control loops. The first control loop can determine a target Fd02 based on the target Sp02. The second control loop can use the target Fd02 output by the first control loop and measured Fd02 to output an oxygen inlet valve control signal. In manual mode the controller may only use the second the control loop, the second control loop can receive a target Fd02 output from user input or a default value.

[0449] During a high flow therapy session, the oxygen concentration measured in the device, fraction of delivered oxygen (Fd02), can be substantially the same as the oxygen concentration the user is breathing, fraction of inspired oxygen (Fi02), when the flow rate of gas delivered meets or exceeds the peak inspiratory demand of the patient. This means that the volume of gas delivered by the device to the patient during inspiration meets, or is in excess of, the volume of gas inspired by the patient during inspiration. High flow therapy helps to prevent entrainment of ambient air when the patient breathes in, as well as flushing the patient's airways of expired gas. So long as the flow rate of delivered gas meets or exceeds peak inspiratory demand of the patient, entrainment of ambient air is prevented and the gas delivered by the device, Fd02, is substantially the same as the gas the patient breathes in, Fi02.

Flow Therapy Apparatus

[0450] A flow therapy apparatus 10 is shown in Figure 1A. The apparatus 10 can comprise a main housing 100 that contains a flow generator 11 in the form of a motor/impeller arrangement (for example, a blower), an optional humidifier 12, a controller 13, and a user interface 14 (comprising, for example, a display and input device(s) such as button(s), a touch screen, or the like). The controller 13 can be configured or programmed to control the operation of the apparatus. For example, the controller can control components of the apparatus, including but not limited to: operating the flow generator 11 to create a flow of gas (gases flow) for delivery to a patient, operating the humidifier 12 (if present) to humidify and/or heat the generated gases flow, control a flow of oxygen into the flow generator blower, receiving user input from the user interface 14 for reconfiguration and/or user-defined operation of the apparatus 10, and outputting information (for example on the display) to the user. The user can be a patient, healthcare professional, or anyone else interested in using the apparatus. As used herein, a "gases flow" can refer to any flow of gases that may be used in the breathing assistance or respiratory device, such as a flow of ambient air, a flow comprising substantially 100% oxygen, a flow comprising some combination of ambient air and oxygen, and/or the like.

[0451] A patient breathing conduit 16 is coupled at one end to a gases flow outlet 21 in the housing 100 of the flow therapy apparatus 10. The patient breathing conduit 16 is coupled at another end to a patient interface 17 such as a non-sealed nasal cannula with a manifold 19 and nasal prongs 18. Additionally, or alternatively, the patient breathing conduit 16 can be coupled to a face mask, a nasal mask, a nasal pillows mask, an endotracheal tube, a tracheostomy interface, and/or the like. The gases flow that is generated by the flow therapy apparatus 10 may be humidified, and delivered to the patient via the patient conduit 16 through the cannula 17. The patient conduit 16 can have a heater wire 16a to heat gases flow passing through to the patient. The heater wire 16a can be under the control of the controller 13. The patient conduit 16 and/or patient interface 17 can be considered part of the flow therapy apparatus 10, or alternatively peripheral to it. The flow therapy apparatus 10, breathing conduit 16, and patient interface 17 together can form a flow therapy system.

[0452] The controller 13 can control the flow generator 11 to generate a gases flow of the desired flow rate. The controller 13 can also control a supplemental oxygen inlet to allow for delivery of supplemental oxygen, the humidifier 12 (if present) can humidify the gases flow and/or heat the gases flow to an appropriate level, and/or the like. The gases flow is directed out through the patient conduit 16 and cannula 17 to the patient. The controller 13 can also control a heating element in the humidifier 12 and/or the heating element 16a in the patient conduit 16 to heat the gas to a desired temperature for a desired level of therapy and/or level of comfort for the patient. The controller 13 can be programmed with or can determine a suitable target temperature of the gases flow.

[0453] The oxygen inlet port 28 can include a valve through which a pressurized gas may enter the flow generator or blower. The valve can control a flow of oxygen into the flow generator blower. The valve can be any type of valve, including a proportional valve or a binary valve. The source of oxygen can be an oxygen tank or a hospital oxygen supply. Medical grade oxygen is typically between 95% and 100% purity. Oxygen sources of lower purity can also be used. Examples of valve modules and filters are disclosed in U.S. Provisional Application No. 62/409,543, titled "Valve Modules and Filter", filed on October 18, 2016, and U.S. Provisional Application No. 62/488,841, titled "Valve Modules and Filter", filed on April 23, 2017, which are hereby incorporated by reference in their entireties. Valve modules and filters are discussed in further detail below with relation to Figures 17-25.

[0454] The flow therapy apparatus 10 can measure and control the oxygen content of the gas being delivered to the patient, and therefore the oxygen content of the gas inspired by the patient. During high flow therapy, the high flow rate of gas delivered meets or exceeds the peak inspiratory demand of the patient. This means that the volume of gas delivered by the device to the patient during inspiration meets, or is in excess of, the volume of gas inspired by the patient during inspiration. High flow therapy therefore helps to prevent entrainment of ambient air when the patient breathes in, as well as flushing the patient's airways of expired gas. So long as the flow rate of delivered gas meets or exceeds peak inspiratory demand of the patient, entrainment of ambient air is prevented, and the gas delivered by the device is substantially the same as the gas the patient breathes in. As such, the oxygen concentration measured in the device, fraction of delivered oxygen, (Fd02) would be substantially the same as the oxygen concentration the user is breathing, fraction of inspired oxygen (Fi02), and as such the terms may can be seen as equivalent.

[0455] Operation sensors 3a, 3b, 3c, such as flow, temperature, humidity, and/or pressure sensors can be placed in various locations in the flow therapy apparatus 10. Additional sensors (for example, sensors 20, 25) may be placed in various locations on the patient conduit 16 and/or cannula 17 (for example, there may be a temperature sensor 29 at or near the end of the inspiratory tube). Output from the sensors can be received by the controller 13, to assist the controller in operating the flow therapy apparatus 10 in a manner that provides suitable therapy. In some configurations, providing suitable therapy includes meeting a patient's peak inspiratory demand. The apparatus 10 may have a transmitter and/or receiver 15 to enable the controller 13 to receive signals 8 from the sensors and/or to control the various components of the flow therapy apparatus 10, including but not limited to the flow generator 11, humidifier 12, and heater wire 16a, or accessories or peripherals associated with the flow therapy apparatus 10. Additionally, or alternatively, the transmitter and/or receiver 15 may deliver data to a remote server or enable remote control of the apparatus 10.

[0456] Oxygen may be measured by placing one or more gas composition sensors (such as an ultrasonic transducer system, also referred to as an ultrasonic sensor system) after the oxygen and ambient air have finished mixing. The measurement can be taken within the device, the delivery conduit, the patient interface, or at any other suitable location.

[0457] Oxygen concentration may also be measured by using flow rate sensors on at least two of the ambient air inlet conduit, the oxygen inlet conduit, and the final delivery conduit to determine the flow rate of at least two gases. By determining the flow rate of both inlet gases or one inlet gas and one total flow rate, along with the assumed or measured oxygen concentrations of the inlet gases (about 20.9% for ambient air, about 100% for oxygen), the oxygen concentration of the final gas composition can be calculated. Alternatively, flow rate sensors can be placed at all three of the ambient air inlet conduit, the oxygen inlet conduit, and the final delivery conduit to allow for redundancy and testing that each sensor is working correctly by checking for consistency of readings. Other methods of measuring the oxygen concentration delivered by the flow therapy apparatus 10 can also be used.

[0458] The flow therapy apparatus 10 can include a patient sensor 26, such as a pulse oximeter or a patient monitoring system, to measure one or more physiological parameters of the patient, such as a patient's blood oxygen saturation (Sp02), heart rate, respiratory rate, perfusion index, and provide a measure of signal quality. The sensor 26 can communicate with the controller 13 through a wired connection or by communication through a wireless transmitter on the sensor 26. The sensor 26 may be a disposable adhesive sensor designed to be connected to a patient's finger. The sensor 26 may be a non-disposable sensor. Sensors are available that are designed for different age groups and to be connected to different locations on the patient, which can be used with the flow therapy apparatus. The pulse oximeter would be attached to the user, typically at their finger, although other places such as an earlobe are also an option. The pulse oximeter would be connected to a processor in the device and would constantly provide signals indicative of the patient's blood oxygen saturation. The patient sensor 26 can be a hot swappable device, which can be attached or interchanged during operation of the flow therapy apparatus 10. For example, the patient sensor 26 may connect to the flow therapy apparatus 10 using a USB interface or using wireless communication protocols (such as, for example, near field communication, WiFi or Bluetooth®). When the patient sensor 26 is disconnected during operation, the flow therapy apparatus 10 may continue to operate in its previous state of operation for a defined time period. After the defined time period, the flow therapy apparatus 10 may trigger an alarm, transition from automatic mode to manual mode, and/or exit control mode (e.g., automatic mode or manual mode) entirely. The patient sensor 26 may be a bedside monitoring system or other patient monitoring system that communicates with the flow therapy apparatus 10 through a physical or wireless interface.

[0459] The flow therapy apparatus 10 may comprise a high flow therapy apparatus. As used herein, "high flow" therapy refers to administration of gas to the airways of a patient at a relatively high flow rate that meets or exceeds the peak inspiratory demand of the patient. The flow rates used to achieve "high flow" may be any of the flow rates listed below. For example, in some configurations, for an adult patient 'high flow therapy' may refer to the delivery of gases to a patient at a flow rate of greater than or equal to about 10 litres per minute (10 LPM), such as between about 10 LPM and about 100 LPM, or between about 15 LPM and about 95 LPM, or between about 20 LPM and about 90 LPM, or between 25 LPM and 75 LPM, or between about 25 LPM and about 85 LPM, or between about 30 LPM and about 80 LPM, or between about 35 LPM and about 75 LPM, or between about 40 LPM and about 70 LPM, or between about 45 LPM and about 65 LPM, or between about 50 LPM and about 60 LPM. In some configurations, for a neonatal, infant, or child patient 'high flow therapy' may refer to the delivery of gases to a patient at a flow rate of greater than 1 LPM, such as between about 1 LPM and about 25 LPM, or between about 2 LPM and about 25 LPM, or between about 2 LPM and about 5 LPM, or between about 5 LPM and about 25 LPM, or between about 5 LPM and about 10 LPM, or between about 10 LPM and about 25 LPM, or between about 10 LPM and about 20 LPM, or between about 10 LPM and 15 LPM, or between about 20 LPM and 25 LPM. A high flow therapy apparatus with an adult patient, a neonatal, infant, or child patient, may deliver gases to the patient at a flow rate of between about 1 LPM and about 100 LPM, or at a flow rate in any of the sub-ranges outlined above.

The flow therapy apparatus 10 can deliver any concentration of oxygen (e.g., Fd02), up to 100%, at any flowrate between about 1 LPM and about 100 LPM. In some configurations, any of the flowrates can be in combination with oxygen concentrations (Fd02s) of about 20%-30%, 2196-30%, 21 %-40%, 30%-40%, 40%-50%, 50%-60%, 60%-70%, 70%-80%, 80%-90%, and 90%-100%. In some combinations, the flow rate can be between about 25 LPM and 75 LPM in combination with an oxygen concentration (Fd02) of about 20%-30%, 21%-30%, 21%-40%, 30%-40%, 40%-50%, 50%-60%, 60%-70%, 70%-80%, 80%-90%, and 90%- 100%. In some configurations, the flow therapy apparatus 10 may include safety thresholds when operating in manual mode that prevent a user from delivering to much oxygen to the patient.

[0460] High flow therapy may be administered to the nares of a user and/or orally, or via a tracheostomy interface. High flow therapy may deliver gases to a user at a flow rate at or exceeding the intended user's peak inspiratory flow requirements. The high flow therapy may generate a flushing effect in the nasopharynx such that the anatomical dead space of the upper airways is flushed by the high incoming gases flow. This can create a reservoir of fresh gas available for each and every breath, while minimizing re -breathing of nitrogen and carbon dioxide. Meeting inspiratory demand and flushing the airways is additionally important when trying to control the patient's Fd02. High flow therapy can be delivered with a non-sealing patient interface such as, for example, a nasal cannula. The nasal cannula may be configured to deliver breathing gases to the nares of a user at a flow rate exceeding the intended user's peak inspiratory flow requirements.

[0461] The term "non-sealing patient interface" as used herein can refer to an interface providing a pneumatic link between an airway of a patient and a gases flow source (such as from flow generator 11) that does not completely occlude the airway of the patient. Non-sealed pneumatic link can comprise an occlusion of less than about 95% of the airway of the patient. The non-sealed pneumatic link can comprise an occlusion of less than about 90% of the airway of the patient. The non-sealed pneumatic link can comprise an occlusion of between about 40% and about 80% of the airway of the patient. The airway can include one or more of a nare or mouth of the patient. For a nasal cannula the airway is through the nares.

[0462] The flow generator or blower 11 can include an ambient air inlet port 27 to entrain ambient room air into the blower. The flow therapy apparatus 10 may also include an oxygen inlet port 28 leading to a valve through which a pressurized gas may enter the flow generator or blower 1 1. The valve can control a flow of oxygen into the flow generator blower 11. The valve can be any type of valve, including a proportional valve or a binary valve.

[0463] The blower can operate at a motor speed of greater than about 1 ,000 RPM and less than about 30,000 RPM, greater than about 2,000 RPM and less than about 21 ,000 RPM, or between any of the foregoing values. Operation of the blower can mix the gases entering the blower through the inlet ports. Using the blower as the mixer can decrease the pressure drop that would otherwise occur in a system with a separate mixer, such as a static mixer comprising baffles, because mixing requires energy.

[0464] With additional reference to Figure IB, a sensing circuit board 2200 is shown that can be implemented in the flow therapy apparatus 10. The sensing circuit board 2200 can be positioned in a sensor chamber such that the sensing circuit board 2200 is at least partially immersed in the flow of gases. The flow of gases may exit the blower 11 through a conduit and enter a flow path in the sensor chamber. At least some of the sensors on the sensing circuit board 2200 can be positioned within the flow of gases to measure gas properties within the flow. After passing through the flow path in the sensor chamber, the gases can exit to the humidifier 12 described above.

[0465] The sensing circuit board 2200 can be a printed sensing circuit board (PCB). Alternatively, the circuit on the board 2200 can be built with electrical wires connecting the electronic components instead of being printed on a circuit board. At least a portion of the sensing circuit board 2200 can be mounted outside of a flow of gases. The flow of gases can be generated by the flow generator 1 1 described above. The sensing circuit board 2200 can comprise ultrasonic transducers 2204. The sensing circuit board 2200 can comprise one or more of thermistors 2205. The thermistors 2205 can be configured to measure a temperature of the gases flow. The sensing circuit board 2200 can comprise a thermistor flow rate sensor 2206. The sensing circuit board 2200 can comprise other types of sensors, such as humidity sensors including humidity only sensors to be used with a separate temperature sensor and combined humidity and temperature sensors, sensors for measuring barometric pressure, sensors for measuring differential pressure, and/or sensors for measuring gauge pressure. The thermistor flow rate sensor 2206 can comprise hot wire anemometer, such as a platinum wire, and/or a thermistor, such as a negative temperature coefficient (NTC) or positive temperature coefficient (PTC) thermistor. Other non-limiting examples of the heated temperature sensing element include glass or epoxy-encapsulated or non-encapsulated thermistors. The thermistor flow rate sensor 2206 can be configured to measure flow rate of the gases by being supplied with a constant power, or be maintained at a constant sensor temperature or a constant temperature difference between the sensor and the flow of gases.

[0466] The sensing circuit board 2200 can comprise a first portion 2201 and a second portion 2202. The first portion 2201 can be positioned to be within the flow path of the gases, whereas the second portion 2202 can be positioned to be outside the flow path of the gases. The direction of the flow of gases is indicated in Figure IB by the arrow 2203. The direction of the flow of gases can be a straight line, or curved in shown in Figure IB.

[0467] Positioning the one or more of thermistors 2205 and/or the thermistor flow rate sensor 2206 downstream of the combined blower and mixer can take into account heat supplied to the gases flow from the blower. Also, immersing the temperature-based flow rate sensors in the flow path can increase the accuracy of measurements because the sensors being immersed in the flow can more likely to be subject to the same conditions, such as temperature, as the gases flow and therefore provide a better representation of the gases characteristics.

[0468] The sensing circuit board 2200 can comprise ultrasonic transducers, transceivers, or sensors of the sensing circuit board to measure gases properties of the gases flow, such as gas composition or concentration of one or more gases within the gases stream. Any suitable transducer, transceiver, or sensor may be mounted to the sensing circuit board 2200 as will be appreciated. In this configuration, the sensing circuit board includes an ultrasonic transducer system (also referred to as an ultrasonic sensor system) that employs ultrasonic or acoustic waves for determining gas concentrations. Various sensor configurations are described below with respect to Figures 1C-1F.

[0469] The ultrasonic transducer system may determine the relative gas concentrations of two or more gases in the gases flow. The ultrasonic transducer system may be configured to measure the oxygen fraction in the bulk gases stream flow, which consists of atmospheric air augmented with supplemental oxygen, which is essentially a binary gas mixture of nitrogen (N2) and oxygen (02). It will also be appreciated that the ultrasonic transducer system may be configured to measure the gas concentrations of other augmentation gases that have blended with atmospheric air in the gases stream, including nitrogen (N2) and carbon dioxide (C02). The ultrasonic transducers can determine the gas concentration of gases in the gases flow at a relatively high frequency. For example, the ultrasonic transducers can output a measured Fd02 value at a maximum sample rate of the sensors or at a lower frequency than the maximum sample rate, such as between about 1 Hz and 200 Hz, about 1 Hz and 100 Hz, about 1 Hz and 50 Hz, and about 1 Hz and 25 Hz.

[0470] In some configurations, sensing circuit board 2200 includes a pair of ultrasonic transducers that are provided on opposite sides of the sensing circuit board. Various alternative configurations of the ultrasonic transducers can be used for sensing the characteristics of the gases stream by the transmission and reception of ultrasonic beams or pulses.

[0471] The distance between the ultrasonic transducers 2204 on opposite ends of the sensing circuit board 2200 can affect measurement resolution. An increased distance between each of the ultrasonic transducers 2204 can reduce the proportional or fractional error, since in general a measured length will have a certain amount of error, and if the length is increased, the proportion of error generated during measurement is less than for a shorter length. Thus, the overall uncertainty of the measurement decreases. An increased distance can also increase measurement resolution and accuracy, since it allows for a longer time period for acoustic signals between the ultrasonic transducers 2204. However, an increased distance can lead to a weaker signal.

[0472] The ultrasonic transducers 2204 can be positioned such that the space between the ultrasonic transducers 2204 at least partially coincides with the flow path. In some configurations, the ultrasonic transducers are positioned on opposing ends of the sensing circuit board. Because the whole face of the flow path is exposed to the acoustic path, the sound waves propagate through all of the gases in the flow path. Averaging of the waves can occur across the entire flow path rather than a section of the flow path. Averaging over a longer distance reduces error and reduces the dependence of air-oxygen mixing. The

ultrasonic transducers can be configured to measure the gases characteristics from any angle relative to the flow path.

[0473] Positioning sensors in the flow path or module, instead of outside the flow path or module, allows the transducers 2204 to both operate within a smaller temperature range relative to one another, or both substantially at one temperature (namely, the temperature of the gas flow). Having them at a substantially homogenous temperature increases accuracy as the transducers are sensitive to temperature. Further, positioning sensors along the flow path allows for measurements and calculations that account for the influence of the gas velocity so that the effect of gas velocity can be removed from the sensor measurement.

[0474] The ultrasonic transducer system is configured as an ultrasound binary gas sensing system. Binary gas analysis using ultrasound is based on sensing the speed of an acoustic pulse through the gas sample, which in this case is the bulk or primary flow of the gases stream flowing through sensing passage of the sensor housing. The speed of sound is a function of gas mean molecular weight and temperature. The system can receive a sensor signal indicative of the temperature of the gases flowing between the beam path between ultrasonic transducers. With knowledge of sensed speed of sound and sensed temperature, the gas composition in the gases stream may be determined or calculated. In particular, measurements of the speed of sound across the sensing passage may be used to infer the ratios of two known gases by reference to empirical relationships, standard algorithms, or data stored in the form of look-up tables, as is known in the art of binary gas analysis with ultrasound. It will be appreciated that alternatively an estimate of the temperature of the gases stream in the beam path of the ultrasound transducers may be used in the binary gas analysis calculations if a temperature sensor is not employed. In such alternative embodiments, the temperature of the gases stream may be conditioned or controlled to within a narrow temperature band to enable an estimate of temperature of the gases stream in the beam path to be used.

[0475] In some configurations, the flow therapy apparatus may also be provided with a humidity sensor that is located in the flow path and which is configured to generate a humidity signal indicative of the humidity of the gases stream flowing through the sensor assembly. In such embodiments, the gas composition may be determined by the sensed

speed of sound, and the sensed temperature and/or sensed humidity. The humidity sensor may be a relative humidity sensor or an absolute humidity sensor. In some embodiments, the gas composition may be determined based on the sensed speed of sound and the sensed humidity, without the need for a temperature sensor.

[0476] The ultrasonic transducer system may be used to measure respective ratios of any two known gases in a gas composition. The ultrasonic transducer system can determine the relative gas concentration in a mixture of air blended with supplementary oxygen, which is substantially equivalent to a nitrogen/oxygen mixture. In such a binary gas mixture, by monitoring the speed of sound and taking the temperature into account, the mean molecular weight of the gas can be determined, and thus, the relative concentrations of the two gases may be determined. From this ratio, the oxygen fraction or nitrogen fraction of the gases stream may be extracted.

[0477] Referring to Figures 1C-1F, various configurations of the ultrasonic transducers will be described for the gas composition sensing system for sensing the speed of sound through the gases stream by the transmission and reception of ultrasonic beams or pulses. Like reference numerals, represent like components.

[0478] Referring to Figure 1C, the transducer configuration 2300 provides an arrangement in which there is a pair of transducers 2302, 2304 opposing each other and positioned on opposite sides of the sensing passage 2306, with the gases flow path direction indicated generally by 2308. In this configuration, each of the transducers 2302, 2304 is driven as either a dedicated transmitter or receiver, such that ultrasonic pulses 2310 are transmitted uni-directionally across the gases flow path from the transmitter to the receiver transducer. As shown, the transducer pair is aligned (i.e. not-displaced upstream or downstream from each other) relative to the air flow path direction 2308 and is configured to transmit cross-flow pulses that are substantially perpendicular to the gases flow path direction.

[0479] Referring to Figure ID, an alternative transducer configuration 2320 is illustrated in which a pair of transducers 2322, 2324 is provided opposing each other on opposite sides of the sensing passage, but wherein each transducer may operate as both a transmitter and receiver (i.e., the transducer is an ultrasonic transmitter-receiver or transceiver). In this configuration, bi-directional ultrasonic pulses 2326 may be sent between the transducer pair 2322, 2324. For example, pulses may be sent back and forth alternately between the transducers or in any other sequence or pattern. Again, the transducer pair is aligned relative to the gases flow path direction and are configured to transmit cross-flow pulses that are substantially perpendicular to the gases flow path direction.

[0480] Referring to Figure IE, an alternative transducer configuration 2360 is illustrated in which there is a pair of transducers 2362, 2364 opposing each other from opposite ends of the sensing passage 2306, with the gases flow path direction or axis indicated generally by 2308. In this configuration 2360, each of the transducers 2362, 2364 is driven as either a dedicated transmitter or receiver, such that along-flow ultrasonic pulses 2366 are transmitted uni-directionally in a beam path between the transmitter and receiver that is substantially aligned or parallel with the gases flow path axis 2308 in the sensing passage 2306. In the embodiment shown, the transmitter is upstream of the receiver, but it will be appreciated that the opposite arrangement could be employed. With this configuration, a flow rate sensor is provided in the sensing passage to provide a flow rate signal indicative of the flow rate of the gases stream in the sensing passage. It will be appreciated that the speed of sound in the sensing passage can be derived or determined in a similar manner to that previously described, and that the flow rate signal is utilized in the signal processing to remove or compensate for the gases flow rate in the calculated speed of sound signal.

[0481] Referring to Figure IF, an alternative transducer configuration 2370 is illustrated in which a pair of transducers 2372, 2374 is provided opposing each other from opposite ends of the sensing passage like in Figure IE, but wherein each transducer may operate as both a transmitter and receiver, i.e. is an ultrasonic transmitter-receiver or transceiver. In this configuration, bi-directional along-flow ultrasonic pulses 2376 may be sent between the transducer pair 2372, 2374. For example, pulses may be sent back and forth alternately between the transducers or in any other sequence or pattern. Again, the transducer pair are aligned with the gases flow path axis 2308 and are configured to transmit along-flow pulses in a beam path or paths that are substantially aligned or parallel to the gases flow path axis 2308 in the sensing passage 2306. With this configuration, a separate flow rate sensor need not necessarily be provided, as the flow rate component of the speed of sound signal can be directly derived or determined from processing of the transmitted and received acoustic pulses.

[0482] Some examples of flow therapy apparatuses are disclosed in International Application No. PCT/NZ2016/050193, titled "Flow Path Sensing for Flow Therapy Apparatus", filed on December 2, 2016, and International Application No. PCT/IB2016/053761, titled "Breathing Assistance Apparatus", filed on June 24, 2016, which are hereby incorporated by reference in their entireties. Examples of configurations of flow therapy apparatuses that can be used with aspects of the present disclosure are discussed in further detail below with relation to Figures 11-16.

Control System

[0483] With reference again to Figure 1A, the controller 13 can be programmed with or configured to execute a closed loop control system for controlling the operation of the flow therapy apparatus. The closed loop control system can be configured to ensure the patient's Sp02 reaches a target level and consistently remains at or near this level.

[0484] The controller 13 can receive input(s) from a user that can be used by the controller 13 to execute the closed loop control system. The target Sp02 value can be a single value or a range of values. The value(s) could be pre-set, chosen by a clinician, or determined based on the type of patient, where type of patient could refer to current affliction, and/or information about the patient such as age, weight, height, gender, and other patient characteristics. Similarly, the target Sp02 could be two values, each selected in any way described above. The two values would represent a range of acceptable values for the patient's Sp02. The controller can target a value within said range. The targeted value could be the middle value of the range, or any other value within the range, which could be pre-set or selected by a user. Alternatively, the range could be automatically set based on the targeted value of Sp02. The controller can be configured to have one or more set responses when the patient's Sp02 value moves outside of the range. The responses may include alarming, changing to manual control of Fd02, changing the Fd02 to a specific value, and/or other responses. The controller can have one or more ranges, where one or more different responses occur as it moves outside of each range.

[0485] The graphical user interface of the flow therapy apparatus may be configured to prompt the user to input a patient type, and the Sp02 limits would be determined based on what the user selects. Additionally, the user interface may include a custom option, where the user can define the limits.

[0486] Generally, Sp02 would be controlled between about 80% and about 100%, or about 80% and about 90%, or about 88% and about 92%, or about 90% and about 99%, or about 92% and about 96%. The Sp02 could be controlled between any two suitable values from any two of the aforementioned ranges. The target Sp02 could be between about 80% and about 100%, or between about 80% and about 90%, or between about 88% and about 92%, or between about 90% and about 99%, or between about 92% and about 96%, or about 94%, or 94% or about 90%, or 90%, or about 85%, or 85%. The Sp02 target could be any value between any two suitable values from any two of the aforementioned ranges. The Sp02 target can correspond to the middle of the Sp02 for a defined range.

[0487] The Fd02 can be configured to be controlled within a range. As discussed previously, the oxygen concentration measured in the apparatus (Fd02) would be substantially the same as the oxygen concentration the patient is breathing (Fi02) so long as the flow rate meets or exceeds the peak inspiratory demand of the patient, and as such the terms may can be seen as equivalent. Each of the limits of the range could be pre-set, selected by a user, or determined based on the type of patient, where the type of patient could refer to current affliction, and/or information about the patient such as age, weight, height, gender, and/or other patient characteristic. Alternatively, a single value for Fd02 could be selected, and the range could be determined at least partially based on this value. For example, the range could be a set amount above and below the selected Fd02. The selected Fd02 could be used as the starting point for the controller. The system could have one or more responses if the controller tries to move the Fd02 outside of the range. These responses could include alarming, preventing the Fd02 moving outside of the range, switching to manual control of Fd02, and/or switching to a specific Fd02. The device could have one or more ranges where one or more different responses occur as it reaches the limit of each range.

[0488] Fd02 can be controlled between about 21% and about 100%, or about 21% and about 90%, or about 21% and about 80%, or about 21% and about 70%, or about

21% and about 60%, or about 21% and about 50%, or about 25% and about 45%. The Fd02 could be controlled between any two suitable values from any two ranges described. The Fd02 target could be between any two suitable values from any two ranges described. If the range is based on the single value, the upper and lower limits could be decided by adding/subtracting a fixed amount from the selected value. The amount added or subtracted could be about 1%, or about 5%, or 10 %, or about 15%, or about 20%, or about 30%, or about 50%, or about 100%. The amount added/subtracted could change relative to the selected value. For example, the upper limit could be 20% higher than the selected value, so a selected value of 50% Fd02 would have an upper limit of 60% for the range of control. The percentage used for the range could be about 1 %, or about 5%, or 10 %, or about 15%, or about 20%, or about 30%, or about 50%, or about 100%. The method for calculating the lower limit and the upper would not necessarily need to be the same. If a single value is used, the value could be between about 21% and about 100%, or about 25% and about 90%, or about 25% and about 80%, or about 25% and about 70%, or about 25% and about 60%, or about 25% and about 50%, or about 25% and about 45%.

[0489] The graphical user interface 14 (GUI) can be configured to display the range of values between which Fd02 and/or Sp02 are being controlled. The range could be displayed by having the two limits set apart from each other on the GUI, with an indicator appearing within the range to graphically represent the position of the current value with respect to the limits of the range.

[0490] The GUI can display graphs of recent Fd02 and/or Sp02 data. The GUI can display the level of each parameter on the same or different graphs over a defined period of time, such as one or more hours. The length of time over which data is displayed could match the length of the time for which data is currently available.

[0491] Fd02 data displayed can be at least one of the target Fd02 or the measured Fd02. The Sp02 data can include a line indicating target Sp02. Additionally, or alternatively, Sp02 and/or Fd02 data can include one or more lines or shaded areas indicating their respective control limits.

[0492] The graphs can be displayed on the default display. Alternatively, the graphs can be hidden with only current data values being shown. The graph can become

available through interaction with the GUI, such as by selecting to view a graph for a defined parameter.

Closed Loop Control

[0493] With reference to Figure 10 a schematic diagram of the closed loop control system 1000 is illustrated. The closed loop control system may utilize two control loops. The first control loop may be implemented by the Sp02 controller. The Sp02 controller can determine a target Fd02 based in part on the target Sp02 and/or the measured Sp02. As discussed above, the target Sp02 value can be a single value or a range of acceptable values. The value(s) could be pre-set, chosen by a clinician, or determined automatically based on client characteristics. Generally, target Sp02 values are received or determined before or at the beginning of a therapy session, though target Sp02 values may be received at any time during the therapy session. During a therapy session, the Sp02 controller can also receive as inputs: measured Fd02 reading(s) from a gases composition sensor, and measured Sp02 reading(s) and a signal quality reading(s) from the patient sensor. In some configurations, the Sp02 controller can receive target Fd02 as an input, in such a case, the output of the Sp02 controller may be provided directly back to the Sp02 controller as the input. Based at least in part on the inputs, the Sp02 controller can output a target Fd02 to the second control loop.

[0494] The second control loop may be implemented by the Fd02 controller. The Fd02 controller can receive inputs of measured Fd02 and target Fd02. The Fd02 controller can then output an oxygen inlet valve control signal to control the operation of the oxygen valve based on a difference between these measured Fd02 and target Fd02 values. The Fd02 controller may receive the target Fd02 value that is output from the first control loop when the flow therapy apparatus is operating in automatic mode. The Fd02 controller may also receive additional parameters such as flow rate values, gas properties, and/or measured Fd02. The gas properties may include the temperature of the gas at the 02 inlet and/or the oxygen content of the supply source. The gases supply source connected to the oxygen inlet valve may be an enriched oxygen gasflow where the oxygen content of the supply source may be less than pure oxygen (i.e., 100%). For example, the oxygen supply source may be an oxygen enriched gasflow having an oxygen content of less than 100% and greater than 21%.

[0495] From at least some of the inputs, the Fd02 controller can determine an oxygen flow rate that would be required to achieve the target Fd02. The Fd02 controller can use the flow rate input in order to alter the valve control signal. If the flow rate changes, the Fd02 controller can automatically calculate a new required oxygen flow rate required to maintain the target Fd02 at the new flow rate without having to wait for feedback from the gas concentration sensor, such as the measured Fd02 value. The Fd02 controller can then output the altered valve control signal to control the valve based on the new flow rate. In some configurations, the control signal of the Fd02 controller may set the current of the oxygen valve in order to control operation of the oxygen valve. Additionally, or alternatively, the Fd02 controller could detect changes to the measured Fd02 and alter the position of the valve accordingly. During manual mode, the second control loop can operate independently without receiving the target Fd02 from the first control loop. Rather, the target Fd02 can be received from user input or a default value.

[0496] During the therapy session, the Sp02 and Fd02 controllers can continue to automatically control the operation of the flow therapy apparatus until the therapy session ends or an event triggers a change from the automatic mode to manual mode.

Closed Loop Control using Patient Model

[0497] Figure 2 provides graphs 200 for Sp02 and Fd02 illustrating the phases of the operation of the flow therapy apparatus during a therapy session. Although Fd02 (oxygen fraction delivered) is used in the graphs, as previously discussed earlier, the Fd02 is substantially the same as Fi02 so long as the flow rate meets or exceeds the peak inspiratory demand of the patient. The phases of operation include a learning phase 210 and a control phase 220. During the learning phase, the controller generates a patient specific model. Due to differences between individual patients, there can be variation in the way in which each patient's Sp02 responds to a change in Fd02. As a result, patient specific model can be generated to provide better control of the patient's Sp02. The learning phase 210, also referred to as a model building phase, can include a wait stage 212, a feed forward stage 214, and a model generation or patient characterization stage 216. The patient characterization stage occurs simultaneously with at least a portion of the feed forward stage 214. During the patient characterization phase, the patient specific model can be iteratively developed as data is gathered during the feed forward stage 214. The learning phase concludes after generation of the patient specific model. After the learning phase, the flow therapy apparatus operates in the control phase until the end of the therapy session. As described below, the flow therapy apparatus may be configured to transition back to the learning phase during a therapy session. In some configurations, the learning phase is optional and a patient specific model can be generated without a defined learning phase. For example, in such configurations, a default model may be used initially. The default model can then be updated during the therapy session to a patient specific model. The patient specific model may be updated at defined intervals, defined events, periodically, aperiodically, and/or continuously during a therapy session.

WHAT IS CLAIMED IS:

1. A respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising:

a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to:

receive patient parameter data indicative of oxygen saturation (Sp02) of the patient from at least one sensor;

execute a control phase, wherein operation of the respiratory apparatus during a therapy session is based at least in part on the patient parameter data; and

a gases composition sensor configured to determine at least oxygen content (Fd02) of gases flow during operation of the respiratory apparatus, wherein the gases composition sensor is an ultrasonic sensor system.

2. The respiratory apparatus of claim 1 further comprising a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

3. The respiratory apparatus of claim 2, wherein the nasal cannula is a non-sealed nasal cannula.

4. The respiratory apparatus of any of Claims 1-3 wherein the respiratory apparatus is configured to deliver a nasal high flow (NHF) flow of gases to the patient.

5. The respiratory apparatus of any of claims 1-4 wherein the at least one sensor is a pulse oximeter.

6. The respiratory apparatus of any of Claims 1-5, wherein the controller is configured to receive device parameter data indicative of an oxygen concentration of the gases flow.

7. The respiratory apparatus of any of Claims 1-6 further comprising a supplementary gas inlet valve.

8. The respiratory apparatus of Claim 7, wherein the controller is configured to control operation of the supplementary gas inlet valve.

9. The respiratory apparatus of any of Claims 7-8, wherein the supplementary gas inlet valve is a proportional valve.

10. The respiratory apparatus of any of Claims 7-9, wherein the supplementary gas inlet valve is an oxygen inlet valve.

11. The respiratory apparatus of any of Claims 7-10, wherein the supplementary gas inlet valve comprises a swivel connector.

12. The respiratory apparatus of any of Claims 1-11 further comprising an ambient air inlet.

13. The respiratory apparatus of Claim 12 when dependent on claim 10, wherein the oxygen inlet valve is in fluid communication with a filter module, wherein the respiratory apparatus is configured to entrain oxygen received from the oxygen inlet valve with ambient air from the ambient air inlet in the filter module.

14. The respiratory apparatus of Claim 1-13, wherein the gases composition sensor is positioned downstream of a blower module of the respiratory apparatus.

15. The respiratory apparatus of Claim 14 when dependent on claim 13, wherein the filter module is positioned upstream of the blower module of the respiratory apparatus.

16. The respiratory apparatus of any of Claims 14-15, wherein the blower module mixes ambient air and oxygen.

17. The respiratory apparatus of any of Claims 1-16, wherein the closed loop control includes using a first closed loop control model configured to determine a target fraction of delivered oxygen (Fd02).

18. The respiratory apparatus of Claim 17, wherein the target Fd02 is determined based at least in part on a target Sp02 and measured Sp02.

19. The respiratory apparatus of Claim 18, wherein the target Fd02 is further based at least in part on measured Fd02.

20. The respiratory apparatus of any of Claims 18-19, wherein the target Fd02 is further based at least in part on a previous target Fd02.

21. The respiratory apparatus of any of Claims 1-20, wherein the closed loop control includes using a second closed loop control model configured to determine a control signal for an oxygen inlet valve based at least in part on a difference between the target Fd02 and the measured Fd02.

22. The respiratory apparatus of Claim 21, wherein the control signal for the oxygen valve is determined based at least in part on the target Fd02 and the measured Fd02.

23. The respiratory apparatus of Claim 22, wherein the control signal for the oxygen valve is determined further based at least in part on a gases flow rate.

24. The respiratory apparatus of Claim 23, wherein the gases flow rate is the total gases flow rate.

25. The respiratory apparatus of any of Claims 1-24, wherein the controller is configured to transfer to a manual mode of operation when a signal quality of the at least one sensor is below a threshold.

26. The respiratory apparatus of any of Claims 1-25, wherein the controller is configured to transfer to a manual mode of operation when the patient Sp02 is outside of defined limits.

27. The respiratory apparatus of Claim 1 -26, wherein the controller is configured to trigger an alarm when the patient Sp02 is outside of the defined limits.

28. The respiratory apparatus of any of Claims 1-27, wherein control of the delivery of gases includes control of Fd02 of the gases flow, wherein the controller is configured to receive an indication of signal quality of the at least one sensor, and apply a weighting to the control of the Fd02 based at least in part on the signal quality.

29. The respiratory apparatus of Claim 28, wherein the indication of signal quality corresponds to specific Sp02 readings.

30. The respiratory apparatus of any of Claims 1-29, wherein the control phase is configured to be executed using a patient specific model

31. The respiratory apparatus of Claim 30, wherein the patient specific model is generated during a learning phase of the therapy session.

32. The respiratory apparatus of Claim 30, wherein the patient specific model is generated during the therapy session.

33. The respiratory apparatus of any of Claims 30-32, wherein the patient specific model is updated during the therapy session.

34. The respiratory apparatus of any of Claims 30-33 wherein the control phase is configured to be executed using a PID control based at least in part on the patient specific model.

35. The respiratory apparatus of any of Claims 30-34, wherein the patient specific model includes an oxygen efficiency of the patient.

36. The respiratory apparatus of Claim 35, wherein the oxygen efficiency is determined based at least in part on measured Sp02 and measured Fd02.

37. The respiratory apparatus of any of Claims 35-36, wherein the oxygen efficiency is determined based at least in part on measured Sp02 divided by measured Fd02.

38. The respiratory apparatus of any of Claims 35-36, wherein the oxygen efficiency is determined based at least in part on a non-linear relationship between measured Sp02 of the patient and measured Fd02.

39. The respiratory apparatus of Claim 1-38, wherein the controller is configured to predict the Sp02 of the patient based at least in part on the measured Fd02.

40. The respiratory apparatus of Claim 39, wherein previous predictions of the Sp02 are compared with measured Sp02 to calculate model error.

41. The respiratory apparatus of Claim 40, wherein the model error is weighted by signal quality of the at least one sensor.

42. The respiratory apparatus of any of Claims 40-41, wherein the model error is used to correct the current Sp02 prediction.

43. The respiratory apparatus of any of Claims 39-42, wherein the predicted Sp02 is based at least in part on a Smith predictor.

44. The respiratory apparatus of any of Claims 1-43, wherein the controller is configured to receive input identifying characteristics of the patient.

45. The respiratory apparatus of Claim 44, wherein the patient characteristics include at least one of a patient type, age, weight, height, or gender.

46. The respiratory apparatus of Claim 45, wherein the patient type is one of normal, hypercapnic, or user-defined.

47. The respiratory apparatus of any of Claims 1-46, wherein the controller is further configured to record data corresponding to the measured Fd02 and the measured Sp02.

48. The respiratory apparatus of any of Claims 1-47 further comprising a humidifier.

49. The respiratory apparatus of any of Claims 1 -48 further comprising an integrated blower and humidifier.

50. The respiratory apparatus of any of Claims 1-49, wherein the respiratory apparatus is configured to be portable.

51. The respiratory apparatus of any of Claims 1-50, wherein the respiratory apparatus is configured to have a controlled variable flow rate.

52. The respiratory apparatus of any of Claims 1-51 further comprising a heated breathing tube.

53. The respiratory apparatus of any of Claims 1-52 wherein the ultrasonic sensor system comprises a first ultrasonic transducer and a second ultrasonic transducer.

54. The respiratory apparatus of Claim 53 wherein each of the first ultrasonic transducer and the second ultrasonic transducer is a receiver and a transmitter.

55. The respiratory apparatus of Claim 54 wherein the first ultrasonic transducer and the second ultrasonic transducer send pulses bidirectionally.

56. The respiratory apparatus of Claim 55 wherein the first ultrasonic transducer is a transmitter and the second ultrasonic transducer is a receiver.

57. The respiratory apparatus of any of Claims 53-56 wherein at least one of the first ultrasonic transducer or the second ultrasonic transducer send pulses along the gases flow

58. The respiratory apparatus of any of Claims 53-56 wherein at least one of the first ultrasonic transducer or the second ultrasonic transducer send pulses across the gases flow.

59. The respiratory apparatus of any of Claims 1-58, wherein the controller is configured to display a first oxygen efficiency characteristic on a display of the respiratory apparatus.

60. The respiratory apparatus of any of Claims 1-59, wherein the controller is configured to display a second oxygen efficiency characteristic on a display of the respiratory apparatus, wherein the second indication of oxygen efficiency is based at least in part on an oxygen efficiency and a measured respiration rate of the patient.

61. The respiratory apparatus of Claim 60, wherein the second oxygen efficiency characteristic is calculated by dividing measured Sp02 by measured Fd02, and dividing the resulting value by the measured respiratory rate.

62. The respiratory apparatus of any of Claims 60-61, wherein the controller is configured to display a graph or trend line indicating at least one of the first oxygen efficiency characteristic or the second oxygen efficiency characteristic over a defined period of time.

63. A respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising:

a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to:

control oxygen concentration (Fd02) of the gases flow to the patient; receive data from at least one patient sensor indicative of a measured oxygen saturation (Sp02) of the patient;

receive data indicative of a measured Fd02 of the gases flow;

receive a target Sp02 for the patient; and

execute a step change to the Fd02 of the gases flow, wherein a magnitude of the step change is based at least in part on the measured Sp02, the target Sp02 and an oxygen efficiency of the patient.

64. The respiratory apparatus of Claim 63, wherein the oxygen efficiency is determined based at least in part on measured Sp02 and measured Fd02.

65. The respiratory apparatus of any of Claims 63-64, wherein the oxygen efficiency is determined based at least in part on measured Sp02 divided by measured Fd02.

66. The respiratory apparatus of any of Claims 63-64, wherein the oxygen efficiency is determined based at least in part on a non-linear relationship between measured Sp02 of the patient and measured Fd02.

67. The respiratory apparatus of any of Claims 63-66, wherein the magnitude of the step change is based at least in part on recent changes to the target Fd02 prior to the step change.

68. The respiratory apparatus of Claim 67, wherein a new target Fd02 is calculated based at least in part on the previous target Fd02.

69. The respiratory apparatus of any of Claims 63-68, wherein the controller is configured to execute a feed forward stage after the step change.

70. The respiratory apparatus of Claim 69, wherein the controller is further configured to maintain the target Fd02 immediately following the step change for a total duration of the feed forward stage.

71. The respiratory apparatus of any of Claims 69-70, wherein the feed forward stage ends if the measured Sp02 meets or exceeds the target Sp02.

72. The respiratory apparatus of any of Claims 69-71 , wherein the feed forward stage ends if a maximum defined period of time is reached.

73. The respiratory apparatus of any of Claims 63-72, further comprising a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

74. The respiratory apparatus of claim 73, wherein the nasal cannula is a non-sealed nasal cannula.

75. The respiratory apparatus of any of Claims 63-74, wherein the respiratory apparatus is configured to deliver a nasal high flow (NHF) flow of gases to the patient.

76. The respiratory apparatus of any of Claims 63-75, wherein the at least one patient sensor is a pulse oximeter.

77. The respiratory apparatus of any of Claims 63-76 further comprising a humidifier.

78. The respiratory apparatus of any of Claims 63-77 further comprising a gases composition sensor configured to determine the measured Fd02 during operation of the respiratory apparatus, wherein the gases composition sensor is an ultrasonic transducer system.

79. The respiratory apparatus of any of Claims 63-78, wherein the controller is further configured to execute a control phase after the feed forward stage.

80. The respiratory apparatus of Claim 79, wherein in the control phase the controller is further configured to control Fd02 of the gases flow to achieve the target Fd02 using feedback control.

81. The respiratory apparatus of any of Claims 80, wherein the controller is further configured to receive an indication of signal quality of the at least one patient sensor, and apply a weighting to the control of the Fd02 based at least in part on the signal quality.

82. The respiratory apparatus of any of Claims 79-81, wherein the controller is further configured to execute the control phase using a predicted Sp02 of the patient.

83. The respiratory apparatus of any of Claims 63-82, wherein the respiratory apparatus is configured to be portable.

84. The respiratory apparatus of any of Claims 63-83, wherein the controller is configured to display a first oxygen efficiency characteristic on a display of the respiratory apparatus.

85. The respiratory apparatus of any of Claims 63-84, wherein the controller is configured to display a second oxygen efficiency characteristic on a display of the respiratory apparatus, wherein the second indication of oxygen efficiency is based at least in part on an oxygen efficiency and a measured respiration rate of the patient.

86. The respiratory apparatus of Claim 85, wherein the second oxygen efficiency characteristic is calculated by dividing measured Sp02 by measured Fd02, and dividing the resulting value by the measured respiratory rate.

87. The respiratory apparatus of any of Claims 85-86, wherein the controller is configured to display a graph or trend line indicating at least one of the first oxygen efficiency characteristic or the second oxygen efficiency characteristic over a defined period of time.

88. A respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising:

a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to:

receive device parameter data indicative of an oxygen concentration (Fd02) of the gases flow;

receive patient parameter data from at least one sensor indicative of an oxygen saturation (Sp02) reading of the patient, wherein the Sp02 of the patient is affected by the Fd02 of the gases flow;

receive an indication of signal quality of the at least one sensor; and apply a weighting to the control of the Fd02 based at least in part on the signal quality.

89. The respiratory apparatus of Claim 88, wherein the indication of signal quality corresponds to specific Sp02 readings.

90. The respiratory apparatus of any of Claims 88-89, further comprising a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

91. The respiratory apparatus of claim 90, wherein the nasal cannula is a non-sealed nasal cannula.

92. The respiratory apparatus of any of Claims 88-91 , wherein the respiratory apparatus is configured to deliver a nasal high flow (NHF) flow of gases to the patient.

93. The respiratory apparatus of any of Claims 88-92, wherein the at least one sensor is a pulse oximeter.

94. The respiratory apparatus of any of Claims 88-93, wherein the controller is configured to receive input identifying characteristics of the patient.

95. The respiratory apparatus of any of Claims 88-94, wherein the controller is configured to control delivery of gases using a predicted Sp02 of the patient.

96. The respiratory apparatus of any of Claims 95, wherein the predicted Sp02 is based at least in part on a Smith predictor.

97. The respiratory apparatus of any of Claims 88-96, wherein the controller is configured to control delivery of gases using a patient specific model.

98. The respiratory apparatus of Claim 97, wherein the model is a patient specific model generated during a learning phase of a therapy session of the patient.

99. The respiratory apparatus of Claim 97, wherein the patient specific model is generated during the therapy session based at least in part on a default model.

100. The respiratory apparatus of any of Claims 97-99, wherein the patient specific model is updated during the therapy session.

101. The respiratory apparatus of any of Claims 97-100, wherein the model includes a delay time.

102. The respiratory apparatus of any of Claims 97-101 , wherein the model includes an exponential decay.

103. The respiratory apparatus of any of Claims 97-102, wherein the model includes an oxygen efficiency of the patient.

104. The respiratory apparatus of Claim 103, wherein the oxygen efficiency is determined based at least in part on measured Sp02 and measured Fd02.

105. The respiratory apparatus of any of Claims 103-104, wherein the oxygen efficiency is determined based at least in part on measured Sp02 divided by measured Fd02.

106. The respiratory apparatus of any of Claims 103-104, wherein the oxygen efficiency is determined based at least in part on a non-linear relationship between measured Sp02 of the patient and measured Fd02.

107. The respiratory apparatus of any of Claims 88-106, wherein the respiratory apparatus is configured to be portable.

108. A respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising:

a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to:

control oxygen concentration (Fd02) of the gases flow to the patient; receive data from at least one patient sensor indicative of a measured oxygen saturation (Sp02) of the patient;

receive data indicative of a measured Fd02 of the gases flow;

receive a target Sp02 for the patient; and

execute a wait stage, wherein during the wait stage the controller is configured to determine whether to execute a feed forward stage prior to transitioning to a control phase, wherein the target Fd02 of the gases flow is held constant during the wait stage; and

execute a control phase wherein the Fd02 is controlled to achieve the target Sp02 using feedback control.

109. The respiratory apparatus of Claim 108, wherein the controller is further configured to determine whether to execute the feed forward stage based at least in part on the target Sp02 and the measured Sp02.

110. The respiratory apparatus of any of Claims 108-109 wherein if the controller determines to execute the feed forward stage, the controller executes the feed forward stage after the wait stage, and if the controller determines not to execute the feed forward stage, the controller executes the control phase after the wait phase.

111. The respiratory apparatus of any of Claims 108-110, wherein the controller is further configured to maintain a target Fd02 for a total duration of the feed forward stage.

112. The respiratory apparatus of any of Claims 108-111 , wherein the feed forward stage ends if the measured Sp02 meets or exceeds the target Sp02.

113. The respiratory apparatus of any of Claims 108-112, wherein the feed forward stage ends if a maximum defined period of time is reached.

114. The respiratory apparatus of any of Claims 108-113, wherein the controller is further configured to execute the control phase after the feed forward stage.

115. The respiratory apparatus any of Claims 108-114, wherein, prior to execution of the feed forward stage, the controller is configured to determine whether to execute a step change to the Fd02 of the gases flow.

116. The respiratory apparatus of Claim 115 wherein the controller is further configured to determine whether to execute the step change based at least in part on recent changes to the target Fd02.

117. The respiratory apparatus of any of claims Claim 1 15-116, wherein the controller is further configured to determine whether to execute the step change based at least in part on the target Sp02 and the measured Sp02.

118. The respiratory apparatus of any of Claims 115-117, wherein the controller is further configured to determine whether to execute the step change based at least in part on an oxygen efficiency of the patient.

119. The respiratory apparatus of any of Claims 115-118, wherein a magnitude of the step change is based at least in part on the measured Sp02, the target Sp02 and an oxygen efficiency of the patient.

120. The respiratory apparatus of any of Claims 1 18-119, wherein the oxygen efficiency is determined based at least in part on measured Sp02 and measured Fd02.

121. The respiratory apparatus of any of Claims 1 18-120, wherein the oxygen efficiency is determined based at least in part on measured Sp02 divided by measured Fd02.

122. The respiratory apparatus of any of Claims 1 18-121, wherein the oxygen efficiency is determined based at least in part on a non-linear relationship between measured Sp02 of the patient and measured Fd02.

123. The respiratory apparatus of any of Claims 119-122, wherein the magnitude of the step change is based at least in part on recent changes to the target Fd02.

124. The respiratory apparatus of any of Claims 108-123, further comprising a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

125. The respiratory apparatus of claim 124, wherein the nasal cannula is a non-sealed nasal cannula.

126. The respiratory apparatus of any of Claims 108-125 wherein the respiratory apparatus is configured to deliver a nasal high flow (NHF) flow of gases to the patient.

127. The respiratory apparatus of any of Claims 108-126, wherein the at least one patient sensor is a pulse oximeter.

128. The respiratory apparatus of any of Claims 108-127 further comprising a humidifier.

129. The respiratory apparatus of any of Claims 108-128 further comprising a gases composition sensor configured to determine a measured Fd02 during operation of the respiratory apparatus, wherein the gases composition sensor is an ultrasonic transducer system.

130. The respiratory apparatus of any of Claims 108-129, wherein the controller is further configured to receive an indication of signal quality of the at least one patient sensor, and apply a weighting to the control of the Fd02 based at least in part on the signal quality.

131. The respiratory apparatus of any of Claims 108-130, wherein the controller is further configured to apply the weighting during the control phase.

132. The respiratory apparatus of any of Claims 108-131 , wherein the controller is further configured to execute the control phase using a predicted Sp02 of the patient.

133. The respiratory apparatus of any of Claims 108-132, wherein the respiratory apparatus is configured to be portable.

134. A respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising:

a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to:

deliver a nasal high flow (NHF) gases flow to the patient;

receive data from at least one patient sensor indicative of a measured oxygen saturation (Sp02) of the patient;

receive data indicative of a measured fraction of delivered oxygen (Fd02) of the gases flow;

determine an oxygen efficiency of the patient; and

generate a patient specific model, wherein the patient specific model uses the oxygen efficiency of the patient.

135. The respiratory apparatus of Claim 134, wherein the oxygen efficiency is determined based at least in part on measured Sp02 and measured Fd02.

136. The respiratory apparatus of any of Claims 134-135, wherein the oxygen efficiency is determined based at least in part on measured Sp02 divided by measured Fd02.

137. The respiratory apparatus of any of Claims 134-135, wherein the oxygen efficiency is determined based at least in part on a non-linear relationship between measured Sp02 of the patient and measured Fd02.

138. The respiratory apparatus of any of Claims 134, wherein the patient specific model is generated based at least in part on a default model.

139. The respiratory apparatus of any of Claims 134, wherein the patient specific model is generated during a learning phase.

140. The respiratory apparatus of any of claims Claim 134, wherein the patient specific model is updated during a therapy session of the patient.

141. The respiratory apparatus of any of Claims 134-140, wherein the patient specific model models the magnitude of the change in Sp02 based at least in part on the change in Fd02.

142. The respiratory apparatus of any of Claims 134-141 , wherein the patient specific model uses a flow rate of the gases flow.

143. The respiratory apparatus of any of Claims 134-142, wherein the patient specific model includes a delay time between a change in Fd02 and a change in Sp02 of the patient.

144. The respiratory apparatus of Claim 143, wherein the delay time is based at least in part on the flow rate of the gases flow.

145. The respiratory apparatus of any of Claims 134-144, wherein the patient specific model includes an exponential decay.

146. The respiratory apparatus of any of Claims 134-145, wherein the at least one patient sensor is a pulse oximeter.

147. The respiratory apparatus of any of Claims 134-146 further comprising a humidifier.

148. The respiratory apparatus of any of Claims 134-147, wherein the Fd02 is measured using an ultrasonic transducer system.

149. The respiratory apparatus of Claim 148, wherein the ultrasonic transducer system comprises a first ultrasonic transducer and a second ultrasonic transducer.

150. The respiratory apparatus of Claim 149, wherein each of the first ultrasonic transducer and the second ultrasonic transducer is a receiver and a transmitter.

151. The respiratory apparatus of Claim 150, wherein the first ultrasonic transducer and the second ultrasonic transducer send pulses bidirectionally.

152. The respiratory apparatus of Claim 148, wherein the first ultrasonic transducer is a transmitter and the second ultrasonic transducer is a receiver.

153. The respiratory apparatus of any of Claims 149- 151, wherein at least one of the first ultrasonic transducer or the second ultrasonic transducer send pulses along the gases flow.

154. The respiratory apparatus of any of Claims 149- 151, wherein at least one of the first ultrasonic transducer or the second ultrasonic transducer send pulses across the gases flow.

155. The respiratory apparatus of any of Claims 134-154, wherein the respiratory apparatus is configured to be portable.

156. A respiratory apparatus that provides a flow of gases to a patient, the respiratory apparatus comprising:

a controller configured to control delivery of gases to the patient using closed loop control, wherein the controller is configured to:

control oxygen concentration (Fd02) of the gases flow to the patient; receive data from at least one patient sensor indicative of a measured oxygen saturation (Sp02) of the patient;

receive data indicative of a measured Fd02 of the gases flow;

receive a target Sp02 for the patient;

execute a step change to the Fd02 of the gases flow to a target Fd02; execute a feed forward stage; and

execute a control phase wherein the Fd02 is controlled to achieve the target Sp02 using feedback control.

157. The respiratory apparatus of Claim 156, wherein a magnitude of the step change is based at least in part on the measured Sp02, the target Sp02, and an oxygen efficiency of the patient.

158. The respiratory apparatus of Claim 157, wherein the target Fd02 is based at least in part on recent changes to the target Fd02 prior to the step change.

159. The respiratory apparatus of any of Claims 156-158, wherein the controller is further configured to maintain the target Fd02 immediately following the step change for a total duration of the feed forward stage.

160. The respiratory apparatus of any of Claims 156-159, wherein the feed forward stage ends if a maximum defined period of time is reached.

161. The respiratory apparatus of any of Claims 156-160, wherein the feed forward stage ends if the measured Sp02 meets or exceeds the target Sp02.

162. The respiratory apparatus of any of Claims 156-161, wherein the controller is further configured to execute the control phase after the feed forward stage.

163. The respiratory apparatus of any of Claims 156-162, further comprising a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillows mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

164. The respiratory apparatus of claim 163, wherein the nasal cannula is a non-sealed nasal cannula.

165. The respiratory apparatus of any of Claims 156-164 wherein the respiratory apparatus is configured to deliver a nasal high flow (NHF) flow of gases to the patient.

166. The respiratory apparatus of any of Claims 156-165, wherein the at least one patient sensor is a pulse oximeter.

167. The respiratory apparatus of any of Claims 156-166 further comprising a humidifier.

168. The respiratory apparatus of any of Claims 156-167 further comprising a gases composition sensor configured to determine a measured Fd02 during operation of the respiratory apparatus, wherein the gases composition sensor is an ultrasonic transducer system.

169. The respiratory apparatus of any of Claims 156-168, wherein the controller is further configured to receive an indication of signal quality of the at least one patient sensor, and apply a weighting to the control of the Fd02 based at least in part on the signal quality.

170. The respiratory apparatus of any of Claims 156-169, wherein the controller is further configured to execute the control phase using a predicted Sp02 of the patient.

171. The respiratory apparatus of any of Claims 156-170, wherein the respiratory apparatus is configured to be portable.