BACKGROUND
[002] Respiratory support apparatuses are used in various environments, such as hospitals or
other medical facilities, to deliver a flow of breathing gases to a patient. The gases flow is
typically heated and humidified to aid patient comfort and mitigate drying of the airway. The
gases flow is delivered to the patient via an inspiratory conduit and a patient interface. Examples
of such respiratory support apparatus include Non-Invasive Ventilation (NIV) apparatus such as
CPAP, PEEP, Bi-Level apparatus, and High Flow apparatus.
[003] The patient interface, included in a high flow respiratory support apparatus, typically
comprises a nasal cannula. The nasal cannula may comprise one or more prongs that are
configured to be received in the nares of the patient. The prongs may be configured to not seal
against the nares so that gases (including exhalation gases) can leak around the prongs. The
therapy provided by a high flow respiratory support apparatus with a nasal cannula is often
referred to as nasal high flow respiratory support or nasal high flow (NHF) therapy.
[004] During NHF therapy, the flow is usually maintained at a set rate within a range (for
example, 10 to 100 L/min for adults or 1 to 25 L/min for neonates or children). The gases flow
may consist of air, or air supplemented with additional oxygen. During NHF therapy, the
temperature of the breathing gas, at the patient interface, can usually be selected from a series of
pre-set values (for example, 31 °C, 34 °C, or 37 °C).
[005] Another example of a respiratory support apparatus is aN on-Invasive Ventilation (NIV)
apparatus. Non-Invasive Ventilation apparatus may be flow-controlled apparatus (that control to
a set flow rate), or pressure-controlled apparatus (that control to a set pressure). Pressure-
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controlled NIV apparatus may control to a constant pressure (as in CP AP therapy) or to a variable
pressure (as in Bi-Level therapy). In Bi-Level NIV therapy, the set pressure during inspiration
may be different to the set pressure during expiration.
[006] The patient interface used with a NIV apparatus typically comprises a patient interface
that seals, at least partially, against the user's face. Examples of a sealing patient interface include
an oral, nasal, or full-face mask comprising a sealing cushion that seals against the patient's face.
SUMMARY OF DISCLOSURE
[007] The present disclosure stems from some work in trying to provide a respiratory support
apparatus that can be used to improve the treatment of patients, and, in some cases, to improve
the treatment of patients infected with viruses, such as Human Rhinovirus (HRV) for example.
[008] An apparatus in accordance with this disclosure may improve the treatment of patients
having upper respiratory tract viral infections or bacterial infections, for example the human
rhinovirus (HRV) or the influenza virus, or other viruses that cause upper respiratory tract
infections.
[009] One aspect of the present disclosure is to provide a respiratory support apparatus that is
controlled to deliver a high gases flow at relatively high temperature, for example temperatures
above 40 °C, and in some cases between 43 and 4 7 oc.
[0010] One aspect of the present disclosure is to provide a respiratory support apparatus that is
controlled to deliver a gases flow with a high energy (relative to the energy of gases flows
delivered by known respiratory support apparatus). This high energy gases flow may consist of a
high temperature gases flow or a high dew-point gases flow (i.e. a gases flow with a high
temperature and a high humidity). For example, the temperature of the gases flow may be above
40 °C, and in some cases between 43 and 47 oc. In this example, or another example, the dewpoint
of the gases flow may be above 40 °C, and in some cases 43 to 47 °C."
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[0011] Other aspects of this disclosure are to provide a high flow apparatus that is controlled to
manage the enthalpy and/or dew-point of the gases flow to help the patient remain safe from
excessive enthalpy exposure and thermal injury during and immediately after being exposed to a
high flow of high-temperature gases. The enthalpy and/or dew-point can be measured at the
patient interface or calculated from measurements made elsewhere in the gases flow path between
the flow generator and the patient interface.
[0012] Aspects of this disclosure are to providing an apparatus that is operative according to a
normal mode, and according to a high-temperature mode in which respiratory gases are delivered
to the patient at relatively high temperatures, the apparatus being further operative according to
one or more safety algorithms. The safety algorithm(s) may be configured to control one or more
properties of the respiratory gases to be within safe levels during the high-temperature mode.
The safety algorithm(s) may be configured to control one or more properties of the respiratory
gases to be within safe levels after the high-temperature mode has terminated, but before the
normal mode resumes.
[0013] The present disclosure provides an apparatus that is controlled to deliver a gases flow at
a relative high temperature so as to increase the temperature of the gases supplied to the patient,
and/or to increase the dew-point of the gases supplied to the patient. The dew-point of the gases
supplied to the patient will vary in dependence upon the humidity of the gases. The apparatus
may be controlled to operate in a high temperature mode, in which either the temperature of the
gases supplied to the patient is relatively high, or both the temperature and the dew-point of the
gases supplied to the patient are relatively high.
[0014] In an apparatus in accordance with this disclosure, the gases temperature and/or dewpoint
refers to the temperature and/or dew-point of the gases as supplied to the patient (i.e. at or
in the patient interface). The temperature at the patient could be measured using one or more
sensors at the patient. For example, these one or more sensors could be at the patient end of an
inspiratory conduit, or at or in the patient interface itself Alternatively, the temperature could be
measured elsewhere in the apparatus. For example, the temperature could be measured at the
humidifier, at the humidifier outlet, or at some other point between the humidifier and the patient.
If the temperature is measured distal from the patient (at a humidifier outlet for example), a
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controller of the apparatus may be configured to calculate how the temperature might change
between the point of measurement and the patient. The controller may be configured to control
a heater of a heated inspiratory conduit to try to maintain the temperature of the gases before the
gases reach the patient. In other words, the controller may control the conduit heater to
compensate for any calculated temperature drop along the inspiratory conduit.
[0015] The controller may control the conduit heater based on feedback from one or more patient
end sensors, such as a temperature sensor and/or humidity sensor, at a patient end of the conduit.
The patient end sensor(s) may be located at the patient end of the conduit, for example in a cuff
or connector at the end of the conduit. The patient end sensor( s) may be located in the patient
interface. The controller may be configured to determine a temperature drop from the end of the
inspiratory conduit to the patient, for example a 3°C drop.
[0016] Apparatus in accordance with this disclosure may be controlled to deliver a gases flow
with a high temperature and a high dew-point (i.e. a gases flow with a high temperature and a
relative humidity sufficiently high for the gases flow to have a high dew-point).
[0017] In one example the high dew-point comprises a temperature above 40°C and humidity
of over 80%.
[0018] Apparatus in accordance with this disclosure can be operative according to a hightemperature
mode wherein the gases flow has a higher peak temperature and/or a higher dewpoint
than when in a normal mode. The normal mode is a therapy mode in which respiratory
gases are delivered to the patient, but not at high temperature or high dew-point.

WHAT IS CLAIMED IS:
1. A respiratory support apparatus configured to provide a gases flow to a patient, the
respiratory support apparatus comprising:
a flow generator configured to generate the gases flow;
a humidifier configured to humidify the gases flow;
a controller, the apparatus being controlled by the controller to function in at least
two modes, being a normal mode and a high-temperature mode, wherein when in the hightemperature
mode, the peak temperature of gases delivered to the patient is higher than
the peak temperature of gases delivered to the patient when in the normal mode;
wherein in the normal mode the controller controls the flow generator to generate
the gases flow at a flow rate within a first flow rate range that is limited by a first peak
flow rate; and
wherein in the high-temperature mode, the controller controls the flow generator
to generate the gases flow at a flow rate within a second flow rate range that is limited by
a second peak flow rate, the second peak flow rate being lower than the first peak flow
rate of the normal mode.
2. The apparatus of claim 1 wherein the first flow rate range is limited by a first minimum
flow rate, and the second flow rate range is limited by a second minimum flow rate, the
second minimum flow rate being higher than the first minimum flow rate.
3. The apparatus of any one of the preceding claims wherein the magnitude of a change of flow
rate range between high-temperature mode and normal mode is controlled so as to be below
a predetermined threshold.
4. The apparatus of claim 2 wherein the minimum flow rate of the second flow rate range, is
equal to or less than the minimum flow rate of the first flow rate range.
5. The apparatus of any one of the preceding claims wherein the second flow rate range is
narrower than the first flow rate range.
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6. The apparatus of any one of the preceding claims wherein the second flow rate range is
narrower than the first flow rate range by between 1 and 70 L/min, preferably between 5
and 60 L/min and more preferably between 10 and 60 L/min.
7. The apparatus of any one of the preceding claims wherein when in the high-temperature
mode the gases flow to the patient is controlled to a temperature range of 41 to 50 °C,
preferably 43 to 47 oc.
8. The apparatus of any one of the preceding claims wherein the controller limits the duration
of the high-temperature mode to a set duration.
9. The apparatus of any one of the preceding claims and configured to be controlled by the
controller in a further mode, being a cool-down mode, the cool-down mode being operative
after the high-temperature mode, such that when in the cool-down mode, any one or more
of:
a. the flow rate is controlled to a flow-rate set point, wherein the rate of change
of the flow rate from the flow rate used during high-temperature mode to the
flow rate set point is controlled to be below a predetermined threshold;
b. the electrical power supplied to the humidifier heater is reduced from that
used during normal mode and/or high-temperature mode; and/or
c. a temperature set point of the gases flow delivered to the patient is reduced
from that during high-temperature mode.
10. A respiratory support apparatus configured to provide a gases flow to a patient, the
respiratory support apparatus comprising:
a flow generator configured to generate the gases flow;
a humidifier configured to humidify the gases flow;
a controller, the apparatus being controlled by the controller to function in at least
two modes, being a normal mode and a high-temperature mode, wherein when in the hightemperature
mode, the temperature of gases delivered to the patient is higher than the
temperature of gases delivered to the patient in normal mode;
wherein in the high-temperature mode the controller limits the duration of the hightemperature
mode to a maximum duration.
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11. The apparatus of claim 10 wherein the controller limits the duration of the high-temperature
mode using a signal generated by a timer.
12. The apparatus of claim 11 wherein the set duration is between 15 and 180 minutes, preferably
20 and 120 minutes, and more preferably between 30 and 90 minutes.
13. The apparatus of claim 10 wherein the controller limits the duration of the high-temperature
mode using a signal generated by a counter.
14. The apparatus of any one of claims 11 to 13 wherein the apparatus generates the signal.
15. The apparatus of claim 14 wherein the apparatus comprises a further controller, configured
to generate the signal.
16. The apparatus of any one of claims 11 to 13 wherein the apparatus receives the signal from
a remote device.
17. The apparatus of any one of claims 12 to 15 wherein the apparatus is configured to be
controlled by the controller in a further mode, being a cool-down mode, the cool-down
mode being operative after the high-temperature mode ends.