FIELD OF THE DISCLOSURE
[0001] The present disclosure relates to respiratory and/or surgical humidifier
5 systems configured to supply humidified gases to a user (for example, a patient).
BACKGROUND
[0002] Respiratory apparatuses and surgical insufflators provide a flow of
pressurized gases through a conduit system to a patient. For a range of applications using these
and similar devices, it is beneficial to humidify gases the supplied gases. These applications
10 include where the gases are for breathing by the user and/or where the gases are being supplied
during surgery to a surgical site in a patient.
[0003] In the case of breathing gases in a noninvasive mode when the inspired
gases pass through the upper airway, such as when gases are delivered to the user via a face or
nasal mask, the humidity increases user comfort, improves the user's tolerance to the
15 noninvasive ventilation (NIV), and the humidified gases are less prone to drying out the tissues
(for example, the nasal mucosa) of the airway of the user. In the case of an invasive mode when
the gases delivered to the user bypass the upper airway, humidification of the gases has been
found to improve user comfort and provide physiological benefits, such as improved mucus
transport, can be necessary for user safety, such as for preventing airway obstruction due to
20 inspissation of airway secretion, disruption of the airway epithelium, and/or for improving
post-operative outcomes. In the case of surgical gases being delivered to a surgical site (for
example, an open surgery site) in the patient, humidification of the gases can also improve
post-operative outcomes. Humidification of surgical gases can also prevent or mitigate
desiccation of tissue, such as mesothelium.
25 [0004] In the case of high flow therapy, humidified gases are delivered to the user
at high flows through an unsealed patient interface. The user may be spontaneously breathing
during high flow therapy. In some situations, gases can also be delivered at a high flow rate to
a user who may be apneic, such as under anesthesia. A high flow system or high flow therapy
apparatus with a humidifier can be used to deliver high flow gases and the therapy apparatus
30 can control characteristics, such as for example characteristics of the gases flow, including the
flow rate, temperature, pressure, humidity, supplementary gases concentration, and the like.
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The use of high flow rate gases delivery can help to push the gases flow and hence oxygen
deeper into the patient's airways. A high flow rate of gases also helps flushing of the airways,
and flushing of carbon dioxide, which also can help to push oxygen/respiratory gases deeper
into the airways.
[0005] In the case of positive airway pressure therapy (PAP) therapy, a PAP
therapy apparatus that includes a blower and a humidifier can be used to provide pressure
therapy, for example, continuous positive airway pressure therapy (CPAP), to the user.
SUMMARY
[0006] A respiratory humidifier system can support an invasive mode and/or be
10 capable of delivering a higher humidity level to a user and/or receive a higher flow rate of
gases from a gases source (for example, the ventilator). A surgical humidifier system can
provide humidified surgical gases to a surgical site, for example, a peritoneal cavity, in a
patient. An increased heater plate power can be required in the respiratory and/or surgical
humidifier systems to support the higher humidity mode. In addition to being designed to keep
15 the condition of the gases delivered to the user at a desired humidity and/or temperature to
prevent condensation from forming within an inspiratory conduit, the systems disclosed herein
can also protect the user by reducing a risk of an undesirable, dangerous, and/or harmful level
of enthalpy, that is, an over-enthalpy scenario, from being delivered to the user. Enthalpy can
be defined as a thermodynamic quantity equivalent to the total heat content of a system. Non-
20 limiting factors that affect enthalpy of the delivered gases include temperature and/or humidity.
Enthalpy at or near the user should be kept below a predetermined level to prevent discomfort
or in some cases serious harm to the user. The enthalpy level can be of a greater concern at low
flow rates (for example, below about 7 L/min, or between about 4 L/min and about 7 L/min,
or otherwise) as the heat energy is more concentrated per unit of flow. When the flow rate is
25 higher, enthalpy can be less of or not a concern as the gases at a higher flow rate can sufficiently
remove the built-up energy from the respiratory and/or surgical systems.
[0007] Enthalpy may become a problem when there is a significant change in the
operational state of the respiratory humidifier system. For example, when the respiratory
humidifier system is operating with a relatively high flow and transitions quickly to a relatively
30 low flow, there can be a significant increase in enthalpy. Measuring, predicting and controlling
enthalpy prevents a potentially dangerous increase in enthalpy. This can be done, for example,
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but using a wide range of sensors throughout the system to measure actual conditions, in
addition to a controller programmed to prevent over-enthalpy scenarios. Measuring, predicting
and controlling enthalpy becomes much more difficult when the respiratory humidifier system
has only a limited number of sensors. For example, if the respiratory humidifier system does
5 not have any sensors downstream from the humidification chamber, it is difficult to know how
much enthalpy is actually reaching the patient. Further, if the respiratory system only has
sensors in the flow generator (flow, motor speed or pressure) and/or in the humidifier (for
example heater plate temperature sensors), the determination of an over-enthalpy system may
also be difficult. Accordingly, the present Application provides configurations which protect
10 a patient from an over-enthalpy scenario. These configurations can be for systems with a wide
ranch of sensors throughout the entire respiratory humidification system, as well as specific
configurations for respiratory humidification systems with few or very limited sensors as will
be discussed below in more detail.
[0008] An example respiratory or surgical humidifier system configured to deliver
15 a flow of gases to a user can comprise a base unit comprising: a heater plate including one or
more heater plate heating elements; and a hardware controller configured to cause energization
of the one or more heating elements of the heater plate, the base unit configured to receive a
humidifier chamber including a thermally conductive base such that the thermally conductive
base contacts the heater plate, the humidifier chamber configured to hold a volume of water,
20 wherein the hardware controller is configured to be in electronic communication with a conduit
heating element in a conduit (for example a inspiratory or insufflation conduit) configured to
transport the gases from the humidifier chamber to a patient interface, the system configured
to determine and/or apply a power limit on the conduit heating element based at least in part
on one or more parameters of the heater plate.
25 [0009] Alternatively, in a configuration, the system can be configured to determine
and/or apply a power limit on the conduit heating element based at least in part on a water
temperature of the water held in the humidifier chamber.
[0010] In a configuration, the system can further comprise a heater plate
temperature sensor configured to measure a heater plate temperature and the system can be
30 configured to determine and/or apply the power limit based at least in part on the heater plate
temperature.
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[0011] In a configuration, the system can further comprise an ambient temperature
sensor configured to measure an ambient temperature and the system can be configured to
determine and/or apply a power limit on the conduit heating element based at least in part on
the ambient temperature.
[0012] In a configuration, the heater plate temperature sensor and/or the ambient
temperature sensor can comprise one or more thermistors.
[0013] In a configuration, the one or more thermistors can comprise at least one
negative temperature coefficient (NTC) thermistor.
[0014] In a configuration, the system can be configured to determine and/or apply
10 the power limit based at least in part on a heater plate power.
[0015]
non-binary.
[0016]
In a configuration, the power limit on the conduit heating element can be
In a configuration, the power limit can be configured to keep a user end
temperature of the gases under a first temperature limit.
15 [0017] In a configuration, the first temperature limit can be from 32°C to 45°C.
[0018]
[0019]
temperature limit.
In a configuration, the first temperature limit can be 40°C.
In a configuration, the first temperature limit can be a first dew point
[0020] In a configuration, the power limit can be configured to keep a user end
20 enthalpy of the gases under a first enthalpy limit on a specific enthalpy for dry air.
25
30
[0021] In a configuration, the first enthalpy limit can be from 122 kJ/m3 to 216
[0022] In a configuration, the first enthalpy limit can be from 195 kJ/m3 to 205
[0023] In a configuration, the system can be configured to determine and/or apply
the power limit independent of control of energization of the one or more heating elements of
the heater plate.
[0024] In a configuration, the system can be configured to determine and/or apply
the power limit using the hardware controller.
[0025] In a configuration, the hardware controller can comprise a central
processing unit (CPU).
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[0026] In a configuration, the system can be configured to determine and/or apply
the power limit based at least in part on a value indicative of a parameter indicative of a flow
rate of the flow of gases.
[0027] In a configuration, the power limit can be applied in response to the heater
5 plate temperature exceeds a heater plate temperature threshold.
[0028] In a configuration, the system can be further configured to output a power
to the conduit heating element, the power substantially not exceeding the power limit.
[0029] In a configuration, the power limit can be a limit on a duty cycle of the
conduit heating element.
10 [0030] In a configuration, the system can be configured to determine and/or apply
the power limit without requiring an electrical current input of the conduit heating element.
[0031] In a configuration, the system can be configured to determine and/or apply
the power limit without requiring input from sensors in a gases flow pathway.
[0032] In a configuration, the system can be configured to determine and/or apply
15 the power limit without requiring input from sensors located at or near a chamber outlet and/or
a patient end.
[0033] In a configuration, the system may not comprise a sensor at or near the
chamber outlet and/or the patient end.
[0034] In a configuration, applying the power limit does not comprise turning off
20 the power to the conduit heating element and/or the one or more heater plate heating elements.
[0035] In a configuration, applying the power limit can further comprise turning
off the power to the conduit heating element.
[0036] In a configuration, the power limit can be further configured to keep the
user end enthalpy under a second enthalpy limit on the specific enthalpy for dry air, wherein
25 the second enthalpy limit can be higher than the first enthalpy limit.
[0037] In a configuration, the second enthalpy limit can be from 197 kJ/m3 to 441
[0038] In a configuration, the second enthalpy limit can be from 195 kJ/m3 to 205
kJ/m3
.
30 [0039] In a configuration, the second enthalpy limit can be for redundancy over the
first enthalpy limit.
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[0040] In a configuration, the second enthalpy limit can be configured to protect
the user from more significant harm than the first enthalpy limit.
[0041] In a configuration, the power limit can be further configured to keep the
user end temperature under a second temperature limit, wherein the second temperature limit
5 is higher than the first temperature limit.
[0042] In a configuration, the second temperature limit can be from 43°C to 63°C.
[0043]
[0044]
temperature limit.
In a configuration, the second temperature limit can be from 43°C to 45°C.
In a configuration, the second temperature limit can be a second dew point
10 [0045] In a configuration, the second temperature limit can be for redundancy over
the first temperature limit.
[0046] In a configuration, the second temperature limit can be configured to protect
the user from more significant enthalpy level than the first temperature limit.
[0047] In a configuration, the system can be configured to apply the power limit to
15 keep the user end temperature under the second temperature limit or the second enthalpy limit
using a CPU or electronic circuitry outside of the CPU.
[0048] In a configuration, applying the power limit to keep the user end
temperature or enthalpy under the second temperature limit or the second enthalpy limit can
comprise turning off the power to the conduit heating element.
20 [0049] In a configuration, the power limit to keep the user end temperature or
enthalpy under the second temperature limit or the second enthalpy limit can be applied based
at least in part on the heater plate temperature.
[0050] In a configuration, the power limit to keep the user end temperature or
enthalpy under the second temperature limit or the second enthalpy limit can be applied based
25 at least in part on the ambient temperature.
[0051] In a configuration, the power limit to keep the user end temperature or
enthalpy under the second temperature limit or the second enthalpy limit can decrease as the
ambient temperature increases.
[0052] In a configuration, the power limit configured to keep the user end
30 temperature or enthalpy under the second temperature limit or the second enthalpy limit can
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be applied only upon the heater plate temperature exceeding a second heater plate temperature
threshold.
[0053] In a configuration, the power limit configured to keep the user end
temperature or enthalpy under the second temperature limit or the second enthalpy limit can
5 be determined and/or applied based at least in part on the heater plate temperature when the
humidifier system is in steady state.
[0054] In a configuration, a heater plate power can be assumed to have a fixed
correlation to a difference between the heater plate temperature and a temperature of the
volume of water held in the humidifier chamber.
10 [0055] In a configuration, the power limit to keep the user end temperature or
enthalpy under the second temperature limit or the second enthalpy limit can be applied by
triggering a first protection circuit that comprises a comparator.
[0056] In a configuration, the power limit to keep the user end temperature or
enthalpy under the second temperature limit or the second enthalpy limit can be based in part
15 on a heater plate power.
[0057] In a configuration, the first protection circuit can apply the power limit
based in part on the heater plate power.
[0058] In a configuration, the system can further comprise a second protection
circuit comprising a second comparator, the second protection circuit applying the power limit
20 based in part on the heater plate power.
[0059] In a configuration, a temperature of the volume of water held in the
humidifier chamber when the humidifier system is in transient state can be estimated based at
least in part on the heater plate power.
[0060] In a configuration, the temperature of the volume of water when the
25 humidifier system is in the transient state can be estimated further based in part on the heater
plate temperature.
[0061] In a configuration, the power limit to keep the user end temperature or
enthalpy under the second temperature limit or the second enthalpy limit can decrease when
the heater plate power decreases.
30 [0062] In a configuration, the system can further comprise the inspiratory conduit.
[0063] In a configuration, the system can further comprise an expiratory conduit.
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[0064] In a configuration, the power limit on the conduit heating element can be
triggered when the flow of gases is at below 7 L/min.
[0065] In a configuration, the power limit on the conduit heating element can be
triggered when the flow of gases is between 4 L/min and 7 L/min.
5 [0066] An example respiratory or surgical humidifier system configured to deliver
a flow of gases to a user can comprise a base unit comprising: a heater plate including one or
more heater plate heating elements; and a hardware controller configured to cause energization
of the one or more heating elements of the heater plate; the base unit configured to receive a
humidifier chamber including a thermally conductive base such that the thermally conductive
10 base contacts the heater plate, the humidifier chamber configured to hold a volume of water,
wherein the hardware controller can be in electronic communication with a conduit heating
element in an inspiratory conduit configured to transport gases from the humidifier chamber
to a patient interface, the hardware controller programmed to determine and/or apply a power
limit on the conduit heating element based at least in part on one or more parameters of the
15 heater plate that includes a parameter indicative of a flow rate of the flow of gases.
20
[0067] In a configuration, the system can further comprise a heater plate
temperature sensor configured to measure a heater plate temperature and the hardware
controller can be programmed to determine and/or apply the power limit based at least in part
on the heater plate temperature.
[0068] In a configuration, the system can further comprise an ambient temperature
sensor configured to measure an ambient temperature and the hardware controller programmed
to determine and/or apply a power limit on the conduit heating element based at least in part
on the ambient temperature.
[0069] In a configuration, the power limit can be configured to keep a user end
25 temperature of the gases under a temperature limit.
limit.
[0070] In a configuration, the temperature limit can be from 32°C to 45°C.
[0071]
[0072]
In a configuration, the temperature limit can be from 42°C to 45°C.
In a configuration, the temperature limit can be a dew point temperature
30 [0073] In a configuration, the power limit can be configured to keep a user end
enthalpy of the gases under a first enthalpy limit on a specific enthalpy for dry air.
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[0074] In a configuration, the first enthalpy limit can be from 122 kJ/m3 to 216
[0075] In a configuration, the first enthalpy limit can be from 195 kJ/m3 to 205
kJ/m3
.
5 [0076] In a configuration, the hardware controller can be programmed to determine
and/or apply the power limit independent of control of energization of the one or more heating
elements of the heater plate.
[0077] In a configuration, the hardware controller can be programmed to determine
and/or apply the power limit based at least in part on a heater plate power.
10 [0078] In a configuration, the hardware controller can be further programmed to
apply the power limit in response to the heater plate temperature exceeding a heater plate
temperature threshold.
[0079] In a configuration, the hardware controller can be further programmed to
output a power to the conduit heating element, the power substantially not exceeding the power
15 limit.
[0080] In a configuration, the power limit can be a limit on a duty cycle of the
conduit heating element.
[0081] In a configuration, the hardware controller can be programmed to determine
and/or apply the power limit without requiring a current input of the conduit heating element.
20 [0082] In a configuration, the system can be configured to determine and/or apply
the power limit without requiring input from sensors in a gases flow pathway.
[0083] In a configuration, the system can be configured to determine and/or apply
the power limit without requiring input from sensors located at or near a chamber outlet and/or
a patient end.
25 [0084] In a configuration, the system may not comprise a sensor at or near the
chamber outlet and/or the patient end.
[0085] In a configuration, applying the power limit does not comprise turning off
the power to the conduit heating element.