Aeration of the upper respiratory tract

Abstract

A respiratory support system comprises two gas sources each generating a respective flow of gases. The first gas source provides a first flow of gases to the lower respiratory tract of the patient via a first patient interface, for mechanical ventilation. The second gas source provides a second flow of gases to an upper respiratory tract of the patient via a second patient interface, for aeration. The first patient interface may be an invasive patient interface configured to isolate the lower respiratory tract from the upper respiratory tract of the patient. The second gas source may be controlled to provide the second flow of gases with a time-varying flow rate profile. The time-varying flow rate profile may have a predetermined frequency, or may be based on the first flow of gases provided by the first gas source.

Description

AERATION OF THE UPPER RESPIRATORY TRACT CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from United States Provisional Patent Application No. 63 / 774,055, filed March 18, 2025, the entire content of which is incorporated herein by reference.FIELD

[0002] The disclosure relates to respiratory support systems, devices, and methods. Particularly, though not exclusively, for aerating the upper respiratory tract of a patient during invasive ventilation.BACKGROUND

[0003] A mechanical ventilator is a medical device that may be used to provide respiratory support to a patient by moving air, oxygen, or a mixture of gases into and out of the lungs. Mechanical ventilators use positive pressure to push air into the lungs to partially or completely support the lung function of the patient. The ventilator may include one or more of a valve and a flow generator to provide a controlled flow of pressurized gases to the patient. Settings of the mechanical ventilator may be adjusted to meet the specific needs of the patient. The mechanical ventilator may:• provide gases to the lungs of the patient;• help remove expiratory gases, including carbon dioxide (CO2), from the lungs; and / or• provide positive pressure to keep the alveoli (air sacs) in the lungs from collapsing.

[0004] The gases may be delivered to the patient non-invasively or invasively.

[0005] In non-invasive ventilation, gases are supplied to one or more of the nose or mouth of the patient by a non-invasive patient interface. The non-invasive patient interface may be a total face mask, a full face mask, a nasal face mask, an oral face mask, a nasal pillows interface, or a nasal cannula, for example.

[0006] In invasive ventilation, the gases are supplied to the patient by an invasive patient interface inserted, at least in part, within the trachea or pharynx (e.g., laryngopharynx) of the patient. For example, by a medical or surgical procedure such as intubation or tracheotomy. The invasive patient interface, e.g., an endotracheal tube (ETT), may include a cuff which is inflated after insertion to isolate at least part of the lower respiratory tract of the patient from at least part of the upper respiratory tract and / or ambient air. The invasive patient interface therefore bypasses the upperrespiratory tract of the patient. The invasive patient interface may be an oral endotracheal tube inserted into the trachea or a laryngeal mask inserted into the pharynx through the patient's mouth (oral intubation), a nasal endotracheal tube inserted into the trachea through the patient's nose (nasal intubation), or a tracheostomy tube inserted into the patient's trachea through a stoma in the patient's neck (tracheotomy), for example.

[0007] In some circumstances, invasive ventilation may be preferred over non-invasive ventilation, or non-invasive ventilation may be unsuitable. For example, to ensure adequate ventilation and oxygenation of a patient that is in cardiac or respiratory arrest, experiencing severe respiratory failure, sedated, or undergoing a surgical procedure.

[0008] Invasive ventilation is a life-saving medical intervention used to assist or replace spontaneous breathing in patients who are unable to breathe adequately on their own. But invasive ventilation is associated with potential complications for the patient.SUMMARY

[0009] In a first aspect, a respiratory support system for providing respiratory support to a patient may comprise: a first gas source configured to provide a first flow of gases; a first patient interface configured to receive the first flow of gases from the first gas source for supply to at least part of a lower respiratory tract of the patient; a second gas source configured to provide a second flow of gases, the second gas source configured to control the second flow of gases to have a time-varying flow rate profile with a predetermined frequency; and a second patient interface configured to receive the second flow of gases from the second gas source for supply to at least part of an upper respiratory tract of the patient.

[0010] The time-varying flow rate profile may be independent of the first flow of gases and the first gas source.

[0011] In a second aspect, a respiratory support system for providing respiratory support to a patient may comprise: a first gas source configured to provide a first flow of gases; a first patient interface configured to receive the first flow of gases from the first gas source for supply to at least part of a lower respiratory tract of the patient; a second gas source configured to provide a second flow of gases, the second gas source configured to control the second flow of gases to have a time-varying flow rate profile independent of the first flow of gas and the first gas source; and a second patient interface configured to receive the second flow of gases from the second gas source for supply to at least part of an upper respiratory tract of the patient.

[0012] The time-varying flow rate profile may comprise a predetermined frequency. The predetermined frequency of the second gas source may be different to a frequency of the first gas source.

[0013] The first gas source and the second gas source may be configured to operate asynchronously.

[0014] The second gas source may be configured to operate without communicating with the first gas source.

[0015] The time-varying flow rate profile may comprise: a bi-level waveform, a rectangular waveform, a trapezoidal waveform, a square waveform, a triangular waveform, a sawtooth waveform, a curved waveform, a linear curved waveform, a sinusoidal waveform, a piecewise sinusoidal waveform, a non-linear curved waveform, a skewed waveform, an asymmetric waveform, or a normal breathing waveform.

[0016] In a third aspect, a respiratory support system for providing respiratory support to a patient may comprise: a first gas source configured to provide a first flow of gases; a first patient interface configured to receive the first flow of gases from the first gas source for supply to at least part of a lower respiratory tract of the patient; a second gas source configured to provide a second flow of gases, the second gas source configured to control the second flow of gases to have a time-varying flow rate profile based, at least in part, on the first flow of gases provided by the first gas source; and a second patient interface configured to receive the second flow of gases from the second gas source for supply to at least part of an upper respiratory tract of the patient.

[0017] The time-varying flow rate profile may comprise: a bi-level waveform, a matched waveform, a normal breathing waveform, a volume controlled ventilation waveform, a pressure controlled ventilation waveform, or a partially-matched waveform.

[0018] The second gas source may be configured to operate at the same frequency as the first gas source.

[0019] The second gas source may be configured to operate synchronously with the first gas source.

[0020] The second gas source may be configured to alternate between providing the second flow of gases at a first flow rate and a second flow rate, wherein the first flow rate is different to the second flow rate. The first flow rate may be greater than the second flow rate.

[0021] The second gas source may be configured to provide the second flow of gases at: the first flow rate for a portion of an inspiratory phase of the first gas source, and the second flow rate for: another portion of the inspiratory phase of the first gas source, and at least a portion of an expiratory phase of the first gas source.

[0022] The second gas source may be configured to provide the second flow of gases at the first flow rate for another portion of the expiratory phase of the first gas source.

[0023] The second gas source may be configured to provide the second flow of gases at the first flow rate to coincide with one or more of: a peak inspiratory flow rate of the first flow of gases, or a peak expiratory flow rate of the first flow of gases.

[0024] The second gas source may be configured to begin providing the second flow of gases at the first flow rate in advance of one or more of: the peak inspiratory flow rate of the first flow of gases, or the peak expiratory flow rate of the first flow of gases.

[0025] The second gas source may be configured to continue providing the second flow of gases at the first flow rate beyond one or more of: the peak inspiratory flow rate of the first flow of gases, or the peak expiratory flow rate of the first flow of gases.

[0026] The second gas source may be configured to provide the second flow of gases with a time-varying flow rate profile matching or approximating the first flow of gases for at least part of one or more of an inspiratory phase and an expiratory phase of the first gas source.

[0027] The first gas source may be configured to provide the first flow of gases as a bi-directional gas flow, and the second gas source configured to provide the second flow of gases as a uni-directional approximation of the first flow of gases.

[0028] The second gas source may be configured to communicate with the first gas source.

[0029] The respiratory support system may comprise a humidifier configured to heat and / or humidify the first flow of gases.

[0030] The second gas source may be configured to communicate with the humidifier.

[0031] In a fourth aspect, a respiratory support system for providing respiratory support to a patient may comprise: a first gas source configured to provide a first flow of gases; a first patient interface configured to receive the first flow of gases from the first gas source for supply to at least part of a lower respiratory tract of the patient; a pressure sensor configured to sense a pressure of the first flow of gases; a second gas source configured to: receive a pressure signal from the pressure sensor; determine abaseline pressure of the first flow of gases based on the pressure signal; determine a phase of the first gas source based on the pressure signal and the baseline pressure; and provide a second flow of gases comprising a time-varying flow rate profile synchronized with the first flow of gases; and a second patient interface configured to receive the second flow of gases from the second gas source for supply to at least part of an upper respiratory tract of the patient.

[0032] The second gas source may be configured to smooth the pressure signal by applying a moving average.

[0033] The second gas source may be configured to determine the baseline pressure based on an exponentially-weighted moving average of the pressure signal.

[0034] The second gas source may be configured to determine whether the first gas source is in: an inspiratory phase if the pressure signal is greater than the baseline pressure of the first flow of gases; and / or an expiratory phase if the pressure signal is less than the baseline pressure of the first flow of gases.

[0035] The second gas source may be configured to determine: a first threshold based on the baseline pressure; a second threshold based on the baseline pressure; whether the first gas source is in: an inspiratory phase if the pressure signal is greater than the first threshold; and / or an expiratory phase if the pressure signal is less than the baseline pressure.

[0036] The following optional features may apply to the respiratory support systems of any one of the first to fourth aspects.

[0037] The respiratory support system may comprise one or more of: a humidifier configured to heat and / or humidify the second flow of gases; and a heated conduit configured to heat the second flow of gases.

[0038] The humidifier and / or the heated conduit may be configured to periodically vary one or more of a temperature and / or a humidity of the second flow of gases.

[0039] The humidifier and / or the heated conduit may be configured to: alternate between heating the second flow of gases to a first temperature and a second temperature, wherein the second temperature is greater than the first temperature; and / or alternate between humidifying the second flow of gases to a first humidity and a second humidity, wherein the second humidity is greater than the first humidity.

[0040] The humidifier and / or the heated conduit may be configured to: heat the second flow of gases to the first temperature during at least part of an inspiratory phase of thefirst gas source; heat the second flow of gases to the second temperature during at least part of an expiratory phase of the first gas source; humidify the second flow of gases to the first humidity during at least part of the inspiratory phase of the first gas source; and / or humidify the second flow of gases to the second humidity during at least part of the expiratory phase of the first gas source.

[0041] The second gas source may be configured to periodically vary a composition of the second flow of gases.

[0042] The second gas source may be configured to periodically vary a proportion of oxygen in the second flow of gases.

[0043] The second gas source may be configured to periodically vary a proportion of carbon dioxide in the second flow of gases.

[0044] The second gas source may be configured to: alternate between providing the second flow of gases with a first proportion of oxygen and a second proportion of oxygen, wherein the first proportion of oxygen is greater than the second proportion of oxygen; and / or alternate between providing the second flow of gases with a first proportion of carbon dioxide and a second proportion of carbon dioxide, wherein the second proportion of carbon dioxide is greater than the first proportion of carbon dioxide.

[0045] The second gas source may be configured to: provide the second flow of gases with the first proportion of oxygen during at least part of an inspiratory phase of the first gas source; provide the second flow of gases with the second proportion of oxygen during at least part of an expiratory phase of the first gas source; provide the second flow of gases with the first proportion of carbon dioxide during at least part of the inspiratory phase of the first gas source; and / or provide the second flow of gases with the second proportion of carbon dioxide during at least part of the expiratory phase of the first gas source.

[0046] The respiratory support system may comprise a nebulizer configured to dispense a nebulized substance into the second flow of gases.

[0047] The first gas source may comprise a mechanical ventilator.

[0048] The first patient interface may comprise an invasive patient interface. The invasive patient interface may comprise: an oral endotracheal tube, a nasal endotracheal tube, a tracheostomy tube, or a laryngeal mask.

[0049] The second gas source may comprise a nasal high flow device.

[0050] The second patient interface may comprise a nasal cannula. The nasal cannula may comprise: a symmetric dual-prong nasal cannula, an asymmetric dual-prong nasal cannula, or a single-prong nasal cannula.

[0051] The nasal cannula may comprise a dual-prong nasal cannula and the second gas source may comprise: a first blower configured to provide a first portion of the second flow of gases to the patient via a left nasal prong of the dual-prong nasal cannula; and a second blower configured to provide a second portion of the second flow of gases to the patient via a right nasal prong of the dual-prong nasal cannula.

[0052] The first blower and the second blower may be configured to provide the first portion of the second flow of gases and the second portion of the second flow of gases to the patient simultaneously.

[0053] The first blower and the second blower may be configured to provide the first portion of the second flow of gases and the second portion of the second flow of gases to the patient alternately.

[0054] The second gas source and / or the nasal cannula may be configured, or configurable, to alternate between: providing a majority or an entirety of the second flow of gases to the patient via a left naris of the patient, and providing the majority or the entirety of the second flow of gases to the patient via a right naris of the patient.

[0055] The nasal cannula may comprise a dual-prong nasal cannula and the second gas source may comprise: a first blower configured to provide a positive gas flow via a first nasal prong of the dual-prong nasal cannula; and a second blower configured to provide a negative gas flow via a second nasal prong of the dual-prong nasal cannula.

[0056] The second gas source may be pneumatically isolated from the first gas source.

[0057] The second gas source may be configured to intermittently provide an augmented cycle to the second flow of gases, the augmented cycle comprising one or more of a peak flow rate, a peak inspiratory flow rate, a peak expiratory flow rate, and a duration which is greater than that of one or more adjacent cycles of the second flow of gases.

[0058] In a fifth aspect, an aeration device may be configured to provide a secondary flow of gases for aerating at least part of an upper respiratory tract of a patient simultaneously receiving mechanical ventilation from a primary flow of gases provided by a ventilator. The aeration device may comprise: a flow generator configured to generate the secondary flow of gases, and a controller configured to control operationof the flow generator to generate the secondary flow of gases with a time-varying flow rate profile at a predetermined frequency.

[0059] The time-varying flow rate profile may be independent of the primary flow of gases and the ventilator.

[0060] The predetermined frequency of the aeration device may be different to a frequency of the ventilator.

[0061] The aeration device may be configured to operate asynchronously with the ventilator.

[0062] The aeration device may be configured to operate without communicating with the ventilator.

[0063] The time-varying flow rate profile may comprise: a bi-level waveform, a rectangular waveform, a trapezoidal waveform, a square waveform, a triangular waveform, a sawtooth waveform, a curved waveform, a linear curved waveform, a sinusoidal waveform, a piecewise sinusoidal waveform, a non-linear curved waveform, a skewed waveform, an asymmetric waveform, or a normal breathing waveform.

[0064] In a sixth aspect, an aeration device may be configured to provide a secondary flow of gases for aerating at least part of an upper respiratory tract of a patient simultaneously receiving mechanical ventilation from a primary flow of gases provided by a ventilator. The aeration device may comprise: a flow generator configured to generate the secondary flow of gases, and a controller configured to control operation of the flow generator to generate the secondary flow of gases with a time-varying flow rate profile based, at least in part, on the primary flow of gases provided by the ventilator.

[0065] The time-varying flow rate profile may comprise: a bi-level waveform, a matched waveform, a normal breathing waveform, a volume controlled ventilation waveform, a pressure controlled ventilation waveform, or a partially-matched waveform.

[0066] The aeration device may be configured to operate at the same frequency as the ventilator.

[0067] The aeration device may be configured to operate synchronously with the ventilator.

[0068] The aeration device may be configured to alternate between providing the secondary flow of gases at a first flow rate and a second flow rate, wherein the first flowrate is different to the second flow rate. The first flow rate may be greater than the second flow rate.

[0069] The aeration device may be configured to provide the secondary flow of gases at: the first flow rate for a portion of an inspiratory phase of the ventilator, and the second flow rate for: another portion of the inspiratory phase of the ventilator, and at least a portion of an expiratory phase of the ventilator.

[0070] The aeration device may be configured to provide the secondary flow of gases at the first flow rate for another portion of the expiratory phase of the ventilator.

[0071] The aeration device may be configured to provide the secondary flow of gases at the first flow rate to coincide with one or more of: a peak inspiratory flow rate of the primary flow of gases, or a peak expiratory flow rate of the primary flow of gases.

[0072] The aeration device may be configured to begin providing the secondary flow of gases at the first flow rate in advance of one or more of: the peak inspiratory flow rate of the primary flow of gases, or the peak expiratory flow rate of the primary flow of gases.

[0073] The aeration device may be configured to continue providing the secondary flow of gases at the first flow rate beyond one or more of: the peak inspiratory flow rate of the primary flow of gases, or the peak expiratory flow rate of the primary flow of gases.

[0074] The aeration device may be configured to provide the secondary flow of gases with a time-varying flow rate profile matching or approximating the primary flow of gases for at least part of one or more of an inspiratory phase and an expiratory phase of the ventilator.

[0075] The primary flow of gases may comprise a bi-directional gas flow, and the aeration device may be configured to provide the secondary flow of gases as a unidirectional approximation of the bi-directional gas flow.

[0076] The aeration device may be configured to communicate with the ventilator.

[0077] The aeration device may be configured to communicate with a humidifier configured to heat and / or humidify the primary flow of gases.

[0078] In a seventh aspect, an aeration device may be configured to provide a secondary flow of gases for aerating at least part of an upper respiratory tract of a patient simultaneously receiving mechanical ventilation from a primary flow of gases provided by a ventilator. The aeration device may comprise: a flow generator configured to generate the secondary flow of gases; a pressure sensor configured to sense apressure of the primary flow of gases; and a controller configured to: receive a pressure signal from the pressure sensor; determine a baseline pressure of the primary flow of gases based on the pressure signal; determine a phase of the ventilator based on the pressure signal and the baseline pressure; and control the flow generator to generate the secondary flow of gases with a time-varying flow rate profile synchronized with the primary flow of gases.

[0079] The controller may be configured to smooth the pressure signal by applying a moving average.

[0080] The controller may be configured to determine the baseline pressure based on an exponentially-weighted moving average of the pressure signal.

[0081] The controller may be configured to determine whether the ventilator is in: an inspiratory phase if the pressure signal is greater than the baseline pressure of the primary flow of gases; and / or an expiratory phase if the pressure signal is less than the baseline pressure of the primary flow of gases.

[0082] The controller may be configured to determine: a first threshold based on the baseline pressure; a second threshold based on the baseline pressure; whether the ventilator is in: an inspiratory phase if the pressure signal is greater than the first threshold; and / or an expiratory phase if the pressure signal is less than the baseline pressure.

[0083] The following optional features may apply to the aeration devices of any one of the fifth to seventh aspects.

[0084] The aeration device may comprise one or more of: a humidifier configured to heat and / or humidify the secondary flow of gases; and a heated conduit configured to heat the secondary flow of gases.

[0085] The humidifier and / or the heated conduit may be configured to periodically vary one or more of a temperature and / or a humidity of the secondary flow of gases.

[0086] The humidifier and / or the heated conduit may be configured to: alternate between heating the secondary flow of gases to a first temperature and a second temperature, wherein the second temperature is greater than the first temperature; and / or alternate between humidifying the secondary flow of gases to a first humidity and a second humidity, wherein the second humidity is greater than the first humidity.

[0087] The humidifier and / or the heated conduit may be configured to: heat the secondary flow of gases to the first temperature during at least part of an inspiratoryphase of the ventilator; heat the secondary flow of gases to the second temperature during at least part of an expiratory phase of the ventilator; humidify the secondary flow of gases to the first humidity during at least part of the inspiratory phase of the ventilator; and / or humidify the secondary flow of gases to the second humidity during at least part of the expiratory phase of the ventilator.

[0088] The controller may be configured to periodically vary a composition of the secondary flow of gases.

[0089] The controller may be configured to periodically vary a proportion of oxygen in the secondary flow of gases.

[0090] The controller may be configured to periodically vary a proportion of carbon dioxide in the secondary flow of gases.

[0091] The controller may be configured to: alternate between providing the secondary flow of gases with a first proportion of oxygen and a second proportion of oxygen, wherein the first proportion of oxygen is greater than the second proportion of oxygen; and / or alternate between providing the secondary flow of gases with a first proportion of carbon dioxide and a second proportion of carbon dioxide, wherein the second proportion of carbon dioxide is greater than the first proportion of carbon dioxide.

[0092] The controller may be configured to: provide the secondary flow of gases with the first proportion of oxygen during at least part of an inspiratory phase of the ventilator; provide the secondary flow of gases with the second proportion of oxygen during at least part of an expiratory phase of the ventilator; provide the secondary flow of gases with the first proportion of carbon dioxide during at least part of the inspiratory phase of the ventilator; and / or provide the secondary flow of gases with the second proportion of carbon dioxide during at least part of the expiratory phase of the ventilator.

[0093] The aeration device may comprise a nebulizer configured to dispense a nebulized substance into the secondary flow of gases.

[0094] The aeration device may be configured to supply the secondary flow of gases to the patient via a nasal cannula, the nasal cannula may comprise: a symmetric dualprong nasal cannula, an asymmetric dual-prong nasal cannula, or a single-prong nasal cannula.

[0095] The aeration device may comprise: a first blower configured to generate a first portion of the secondary flow of gases, and a second blower configured to generate a second portion of the secondary flow of gases.

[0096] The first blower and the second blower may be configured to generate the first portion of the secondary flow of gases and the second portion of the secondary flow of gases to the patient simultaneously.

[0097] The first blower and the second blower may be configured to generate the first portion of the secondary flow of gases and the second portion of the secondary flow of gases to the patient alternately.

[0098] The aeration device may be configured, or configurable, to alternate between: providing a majority or an entirety of the secondary flow of gases to the patient via a left naris of the patient, and providing the majority or the entirety of the secondary flow of gases to the patient via a right naris of the patient.

[0099] The first blower may be configured to generate a positive gas flow. The second blower may be configured to generate a negative gas flow.

[0100] The aeration device may be pneumatically isolated from the ventilator.

[0101] The controller may be configured to control operation of the flow generator to intermittently provide an augmented cycle to the secondary flow of gases, the augmented cycle comprising one or more of a peak flow rate, a peak inspiratory flow rate, a peak expiratory flow rate, and a duration which is greater than that of one or more adjacent cycles of the secondary flow of gases.

[0102] In an eighth aspect, a method is provided for aerating an upper respiratory tract of a patient receiving mechanical ventilation from a primary flow of gases provided by a ventilator. The method may comprise simultaneously providing a secondary flow of gases to an upper respiratory tract of the patient, the secondary flow of gases comprising a time-varying flow rate profile with a predetermined frequency.

[0103] In a ninth aspect, a method is provided for aerating an upper respiratory tract of a patient receiving mechanical ventilation from a primary flow of gases provided by a ventilator. The method may comprise simultaneously providing a secondary flow of gases to an upper respiratory tract of the patient, the secondary flow of gases comprising a time-varying flow rate profile independent of the primary flow of gases.

[0104] In a tenth aspect, a method is provided for aerating an upper respiratory tract of a patient receiving mechanical ventilation from a primary flow of gases provided by a ventilator. The method may comprise simultaneously providing a secondary flow of gases to an upper respiratory tract of the patient, the secondary flow of gases comprising a time-varying flow rate profile based, at least in part, on the primary flow of gases provided by the ventilator.

[0105] In an eleventh aspect, a method is provided for aerating an upper respiratory tract of a patient receiving mechanical ventilation from a primary flow of gases provided by a ventilator. The method may comprise: sensing a pressure of the primary flow of gases; determining a phase of the ventilator based on the pressure of the primary flow of gases; and providing a secondary flow of gases to an upper respiratory tract of the patient with a time-varying flow rate profile synchronized with the primary flow of gases.

[0106] The following optional features may apply to the methods of any one of the eighth to eleventh aspects.

[0107] The methods may comprise fitting the patient with a nasal cannula configured to receive the secondary flow of gases for delivery to the upper respiratory tract of the patient.

[0108] The methods may comprise isolating the lower respiratory tract and the upper respiratory tract of the patient.

[0109] The methods may comprise alternating between providing the secondary flow of gases at a first flow rate and a second flow rate, wherein the first flow rate is different to the second flow rate.

[0110] The methods may comprise continuously varying a flow rate of the secondary flow of gases.

[0111] The methods may comprise periodically varying one or more of: a temperature of the secondary flow of gases, a humidity of the secondary flow of gases, and / or a composition of the secondary flow of gases.

[0112] The methods may comprise periodically alternating between providing the secondary flow of gases at: a first temperature and a second temperature, wherein the second temperature is greater than the first temperature; a first humidity and a second humidity, wherein the second humidity is greater than the first humidity; a first proportion of oxygen and second proportion of oxygen, wherein the first proportion of oxygen is greater than the second proportion of oxygen; and / or a first proportion of carbon dioxide and a second proportion of carbon dioxide, wherein the second proportion of carbon dioxide is greater than the first proportion of carbon dioxide.

[0113] The methods may comprise dispensing a nebulized substance into the secondary flow of gases.

[0114] The methods may comprise periodically alternating between: providing a majority or an entirety of the secondary flow of gases to a left naris of the patient, andproviding a majority or an entirety of the secondary flow of gases to a right naris of the patient.

[0115] The methods may comprise intermittently providing an augmented cycle to the secondary flow of gases, the augmented cycle comprising one or more of a peak flow rate, a peak inspiratory flow rate, a peak expiratory flow rate, and a duration which is greater than that of one or more adjacent cycles of the secondary flow of gases.

[0116] Further aspects and features of the present technology will be apparent from the following detailed description and the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0117] Non-limiting examples of the present technology will be described in detail below with reference to the accompanying drawings.

[0118] FIG. 1 illustrates a schematic diagram of a respiratory support system according to an example of the present technology, and gas flows within the ventilatory system during an expiratory phase.

[0119] FIG. 2 illustrates the gas flows within the respiratory support system of FIG. 1 during an inspiratory phase.

[0120] FIG. 3 illustrates the second flow of gases within the upper respiratory tract of the patient during the expiratory phase or inspiratory phase of the respiratory support system of FIG. 1.

[0121] FIG. 4 illustrates a time-varying flow rate profile of the second flow of gases according to a first example.

[0122] FIG. 5 illustrates a time-varying flow rate profile of the second flow of gases according to a second example.

[0123] FIG. 6 illustrates a time-varying flow rate profile of the second flow of gases according to a third example.

[0124] FIG. 7 illustrates a time-varying flow rate profile of the second flow of gases according to a fourth example.

[0125] FIG. 8 illustrates a time-varying flow rate profile of the second flow of gases according to a fifth example.

[0126] FIG. 9 illustrates a normal breathing waveform of a healthy human.

[0127] FIG. 10 illustrates a time-varying flow rate profile of the second flow of gases according to a sixth example.

[0128] FIG. 11 illustrates a time-varying flow rate profile of the second flow of gases according to a seventh example.

[0129] FIG. 12 illustrates a time-varying flow rate profile of the second flow of gases according to an eighth example.

[0130] FIG. 13 illustrates a time-varying flow rate profile of the second flow of gases according to a ninth example.

[0131] FIG. 14 illustrates a time-varying flow rate profile of the second flow of gases according to a tenth example.

[0132] FIG. 15 illustrates a time-varying flow rate profile of the second flow of gases according to an eleventh example.

[0133] FIG. 16 illustrates an example augmented cycle which may be provided by a respiratory support system according to examples of the present technology.

[0134] FIG. 17 illustrates a block diagram of an aeration system suitable for use in respiratory support systems of the present technology.

[0135] FIG. 18 illustrates an example inlet module of the aeration system of FIG. 17.

[0136] FIG. 19 illustrates an example control system for the aeration system of FIG.17.

[0137] FIG. 20 illustrates an isometric view of an example aeration device suitable for use in respiratory support systems of the present technology.

[0138] FIG. 21 illustrates a right side view of the aeration device of FIG. 20.

[0139] FIG. 22 illustrates a plan view of the aeration device of FIG. 20.

[0140] FIG. 23 illustrates a bottom view of the aeration device of FIG. 20.

[0141] FIG. 24 illustrates a reverse isometric view of the aeration device of FIG. 20.DETAILED DESCRIPTION OF THE DRAWINGS

[0142] Invasive ventilation is associated with a number of potential patient complications including, for example:• desiccation of the upper respiratory tract• accumulation of secretions• asynchrony• tracheitis• ventilator-associated pneumonia (VAP)• ventilator-associated sinusitis (VAS)• disruption to the nasal cycle,• ventilator-induced lung injury (VILI), and• ventilator-acquired brain injury (VABI).

[0143] Desiccation refers to the condition where the upper respiratory tract becomes abnormally dry. Desiccation may lead to mucosal damage, increased risk of infection, impaired mucociliary clearance, thickened secretions, or discomfort, for example.

[0144] Accumulation of secretions may promote bacterial overgrowth and colonization by pathogenic bacteria.

[0145] Asynchrony occurs when there are differences between the respiratory demands of a ventilated patient and the therapy provided by the mechanical ventilator. For example, when a patient commences expiration while the mechanical ventilator is in an inspiratory phase, or commences inspiration while the mechanical ventilator is in an expiratory phase.

[0146] Tracheitis is an inflammation of the trachea without the radiological signs of pneumonia.

[0147] Ventilator-associated pneumonia (VAP) has, in addition to what occurs with tracheitis, radiological evidence of pneumonia. VAP is part of a spectrum of infections of the patient's respiratory system following invasive ventilation, e.g., for at least 48 hours. The most common cause of VAP is bacterial infection.

[0148] Ventilator-associated sinusitis (VAS) is another infection associated with invasive ventilation. Infectious sinusitis is thought to affect about 27 % of mechanically ventilated patients. And the cause of undetermined fever in about 25 % of cases. The presence of VAS and VAP have been found to be associated.

[0149] The nasal cycle is a natural, physiological process in which an asymmetry of flow between the nasal passages varies over time. The predominant nasal airflow may alternate between the left and right nasal passages. This cycle typically occurs over a period of several hours and is a normal function of the nasal mucosa, the tissue lining the nasal cavities. Disruption to the nasal cycle may be a contributing factor to tracheitis, VAP, VAS, or other side effects of invasive ventilation.

[0150] Ventilator-induced lung injury (VILI) refers to lung damage that occurs as a result of mechanical ventilation. This condition can arise from several factors associated with mechanical ventilation, including one or more of excessive pressure (barotrauma), overdistension of the lung alveoli (volutrauma), repetitive opening and closing of lung units (atelectrauma), and inflammation caused by the mechanical forces (biotrauma).

[0151] Ventilator-acquired brain injury (VABI) refers to neurological damage or dysfunction that occurs in patients receiving mechanical ventilation. Mechanical ventilation may contribute to brain dysfunction in intensive care unit (ICU) patients without pre-existing neurological injury. This injury can result from various factors, such as one or more of altered cerebral blood flow, hypercapnia (elevated levels of carbon dioxide in the blood), hypoxia (insufficient oxygen supply), and inflammatory responses. Additionally, the use of sedatives and other medications during mechanical ventilation can contribute to cognitive impairment. VABI may manifest as one or more of delirium, sleep disruption, dyspnea, prolonged weaning, and a myriad of symptoms persistent past ICU discharge, e.g., long-term cognitive impairment with possible contributions to post-intensive care syndrome (PICS).

[0152] Complications such as one or more of the above may be at least in part caused by the upper respiratory tract of the patient being bypassed, e.g., by an endotracheal tube, resulting in a significantly reduced flow of gases and / or disruption to the normal physiological functions within the upper respiratory tract. Ordinarily, the upper respiratory tract of an invasively ventilated patient is given little attention other than occasional oral care, suctioning, or the like.

[0153] Aerating the upper respiratory tract may restore, to at least some extent, the normal physiological behaviors in the upper respiratory tract during invasive ventilation. The nasopharynx, oropharynx, and laryngopharynx of the upper respiratory tract, for example, play a role in respiratory function. In this area there are chemoreceptors, neuroreceptors, hairs and turbinates to filter air, mechanisms for the humidification and warming of inspired air, cells that produce immunoglobulins, and secretions for inhibiting or preventing infection. Aerating the upper respiratory tract with heated and / or humidified gases may further enhance physiological benefits for the patient. In some examples, the gases supplied to the upper respiratory tract of the patient may be heated and / or humidified to, or towards, the temperature and / or humidity typical within the upper respiratory tract of a healthy human adult. During inspiration, the gases within the upper respiratory tract of a healthy human adult may have a temperature and / or humidity about equal to that of ambient air. For example, between about 200Celsius (°C) and 24 °C and / or between about 20 % and about 60 % relative humidity in the controlled environment of a hospital with heating, ventilation, and air conditioning (HVAC) systems. During expiration, the gases within the upper respiratory tract of ahealthy human adult may have a temperature of between about 30 °C and 37 °C, between about 35 °C and 37 °C, or about 37 °C. And / or a relative humidity of between about 80% and 100%, between about 90% and 100%, or about 100% (i.e., saturation).

[0154] Nasal airflow in particular may activate mechanoreceptors located upon the olfactory neuroepithelium, producing a respiration-entrained signal in the olfactory bulb. This signal may then propagate downstream to cortical areas, e.g., one or more of the medial prefrontal cortex (mPFC) and hippocampus (HC). Activity in these regions of the brain may also be entrained to respiration (i.e., coordinated or synchronized with the patient's breathing cycle), and nasal respiration may contribute to cross-frequency coupling, modulating coherence and functional connectivity across brain networks. Many of the regions identified as displaying levels of nasal-respiratory influence are also recognized as within the default mode network (DMN). Sometimes referred to as the brain's 'task-negative' network, the DMN is considered a key integrator and processor of information, coordinating internal- and external-oriented cognition. The DMN supports attention, awareness and episodic memory. Its disturbance may relate to development of delirium, sleep disturbance, and long-term cognitive impairment— one or more of which may be manifestations of VABI. One or more of aeration of the upper respiratory tract, e.g., one or more of the nasal cavity and nasopharynx, and entrainment may contribute to maintaining functional connectivity of brain networks, e.g., the DMN, during mechanical ventilation.

[0155] The flow of gases may assist in moving endogenous nitric oxide generated in the sinuses further down into the airways. This may aid in creating a more homeostatic environment within the upper airways.

[0156] FIG. 1 and FIG. 2 illustrate, in schematic form, an example respiratory support system 100 according to the present technology.

[0157] The respiratory support system 100 supplies gases to a patient 110. The patient 110 is represented schematically by the lower respiratory tract 112, e.g., the lungs, and the upper respiratory tract 114, e.g., the oral cavity and pharynx. Openings in the schematic upper respiratory tract 114 represent the nares 116 and the mouth 118 of the patient 110.

[0158] A first patient interface of the respiratory support system 100 may be an invasive patient interface. In this example, the invasive patient interface is an oral endotracheal tube 122. The oral endotracheal tube 122 passes through the upper respiratory tract 114 and into the lower respiratory tract 112. In other examples, the first patient interface may be a nasal endotracheal tube, a tracheostomy tube, or a laryngeal mask, for example.

[0159] The first patient interface, e.g., oral endotracheal tube 122, may include a cuff. The cuff 124 of the oral endotracheal tube 122 may be inflated to functionally separate, e.g., isolate, the lower respiratory tract 112 and the upper respiratory tract 114. In other examples, the first patient interface may not necessarily be configured to isolate the lower respiratory tract 112 from the upper respiratory tract 114. For example, an endotracheal tube for a neonatal patient may be uncuffed.

[0160] A distal end of the first patient interface, e.g., oral endotracheal tube 122, opens into the lower respiratory tract 112 of the patient 110. Gases may be supplied to, or received from, the lower respiratory tract 112 of the patient 110 through the invasive patient interface, e.g., oral endotracheal tube 122.

[0161] A second patient interface of the respiratory support system 100 may be a non-invasive patient interface. In this example, the non-invasive patient interface is a nasal cannula 142.

[0162] The non-invasive patient interface, e.g., nasal cannula 142, may be a nonsealing nasal cannula. The nasal prong 144 or nasal prongs 144 of the non-sealing nasal cannula may be configured so that they do not occlude the patient's naris or nares 116. Gases may vent from the patient's upper respiratory tract 114, around the nasal prongs 144, and out the patient's nares 116 to the ambient environment. In other examples, the nasal cannula 142 may be a sealing nasal cannula. The nasal prong or nasal prongs may seal within the nares 116. Or the non-invasive patient interface may be a nasal face mask or a nasal pillows interface, for example. Gases may vent from the patient's mouth 118, for example.

[0163] The nasal cannula 142 may be a dual-prong nasal cannula comprising a pair of nasal prongs 144. Each of the nasal prongs 144 may be configured to extend towards, or into, a respective one of the patient's nares 116. The nasal prongs 144 may deliver gases directly to the upper respiratory tract 114, e.g., the nasal cavity.

[0164] The dual-prong nasal cannula may be a symmetric dual-prong nasal cannula or an asymmetric dual-prong nasal cannula. A symmetric dual-prong nasal cannula comprises a pair of nasal prongs 144 with the same, or similar (e.g., ± 10 % or ± 5 %), dimensions (e.g., internal diameter) and resistance to flow. An asymmetric dual-prong nasal cannula comprises a pair of nasal prongs 144 which differ in dimensions (e.g., internal diameter) and resistance to flow.

[0165] In other examples, the nasal cannula may be a single-prong nasal cannula. The single-prong nasal cannula may have a single nasal prong 144 configured to extend towards, or into, one of the patient's nares 116. The other naris may be substantially unobstructed.

[0166] An asymmetric dual-prong nasal cannula providing relatively higher gas flow rates to the left naris may be referred to as a left asymmetric dual-prong nasal cannula. An asymmetric dual-prong nasal cannula providing relatively higher gas flow rates to the right naris may be referred to as a right asymmetric nasal cannula. A single-prong nasal cannula may be similarly referred to as a left single-prong nasal cannula or a right single-prong nasal cannula, respectively.

[0167] In some examples, the flow rate of the gases delivered to the nares 116 may be asymmetric, e.g., using an asymmetric dual-prong nasal cannula, a single-prong nasal cannula, or two separate flow generators supplying respective nasal prongs 144. In some examples, a majority of the flow of gases may be delivered to one naris. The flow rate to one naris may be between about 60 % and 90 % of the total volumetric flow rate of gases delivered to the nares. In other examples, the entirety of the flow of gases may be delivered to a single naris. At least part of the flow of gases, e.g., a majority of the flow of gases, may exit the other naris of the patient, e.g., if the patient's mouth is closed or sealed. In yet other examples, a positive flow of gases may be delivered to one naris, and a negative flow of gases may be drawn from the other naris as disclosed in further detail in International Patent Publication No. WO 2015 / 156690 Al, the entire content of which is incorporated herein by reference. The positive and negative flow of gases may be generated simultaneously.

[0168] Asymmetric gas flow may advantageously promote more laminar gas flow (i.e., less turbulence) and / or improved flushing of gases within the upper respiratory tract of the patient, when compared to a symmetric gas flow at the same flow rates.

[0169] The naris to which the majority of the gases, the entirety of the gases, or the positive flow of gases is delivered may change, e.g., alternate, over time. The naris may be alternated periodically, for example after between about 20 minutes (min) and 40 min, e.g., about every 30 min. If using an asymmetric dual-prong nasal cannula or a single-prong nasal cannula, the patient interface may be changed. For example, a left asymmetric dual-prong nasal cannula may be replaced by a right asymmetric dual-prong nasal cannula, or vice versa. Or a left single-prong nasal cannula may be replaced by a right single-prong nasal cannula, or vice versa. If using two separate flow generators each supplying a flow of gases to a respective naris, the same patient interface may remain on the patient. The flow generators may be controlled to change the naris to which the majority of the gases, the entirety of the gases, or the positive flow of gases is delivered. The change may occur automatically, e.g., after a predetermined period of time. Alternating between the nares may mimic or encourage nasal cycling.

[0170] In some examples, the nasal cannula may be an F&P Optiflow™ nasal cannula or an F&P Optiflow Duet™ asymmetric dual-prong nasal cannula available from Fisher & Paykel Healthcare of Auckland, New Zealand.

[0171] Stimulating the olfactory bulb may provide a therapeutic benefit by mimicking normal breathing of a healthy human. Using a nasal cannula to deliver the second flow of gases 170 may provide the best stimulation of the olfactory bulb.

[0172] The nasal cannula can remain on the patient as they transition off invasive ventilation onto a less intensive therapy such as nasal high flow therapy. The same nasal cannula can be used to provide this therapy, mitigating one or more of the time, cost, and disruption associated with changing the patient interface. The flow rate of the first flow of gases 160 may be gradually increased and / or the composition of the first flow of gases 160 may vary as the patient is weaned from invasive ventilation and ultimately extubated. For example, the oxygen content of the first flow of gases 160 may be increased as the patient is weaned from invasive ventilation. The cuff of the first patient interface may be deflated towards the end of the invasive therapy to acclimatize the patient to breathing with assistance from nasal high flow therapy.

[0173] In other examples, the first patient interface may comprise a tracheostomy interface configured to provide the first flow of gases 160 to the upper respiratory tract 114. The first flow of gases 160 may exit the upper respiratory tract through one or more of the nares 116, the mouth 118, or the tracheostomy interface.

[0174] In the example respiratory support system 100, a first gas source 126 is configured to provide a first flow of gases 160 to the lower respiratory tract 112 of the patient 110. In other examples or contexts, the first gas source may be referred to as a primary gas source or ventilation gas source, for example.

[0175] In some examples, the first gas source 126 may be configured to control the first flow of gases 160, e.g., a phase of the first flow of gases 160, based at least in part on one or more of a volume of the first flow of gases 160, a pressure of the first flow of gases 160, or spontaneous breathing of the patient. In some examples, the first gas source 126 may control the breathing cycle of the patient 110. The first gas source 126 may be a mechanical ventilator, for example. The first gas source 126 may be configured to provide a bi-directional gas flow to and from the patient 110.

[0176] In various examples, the first flow of gases 160 may include any one, or a combination of any two or more, of air, oxygen, or heliox.

[0177] The first gas source 126 may be pneumatically coupled with the first patient interface, e.g., by a first breathing circuit 130.

[0178] The first breathing circuit 130 may include one or more of an inspiratory limb 132, an expiratory limb 134, or a first interface conduit 136. The first breathing circuit 130 in the illustrated example is a dual-limb breathing circuit.

[0179] As illustrated in FIG. 1, the expiratory limb 134 may be configured, e.g., during an expiratory phase, to convey the first flow of gases 160 from the first patient interface, e.g., oral endotracheal tube 122, to the first gas source 126, e.g., a gases return inlet of the first gas source 126. In some examples, via the first interface conduit 136 as illustrated.

[0180] As illustrated in FIG. 2, the inspiratory limb 132 may be configured, e.g., during an inspiratory phase, to convey the first flow of gases 160 from the first gas source 126, e.g., a gases outlet of the first gas source 126, to the first patient interface, e.g., oral endotracheal tube 122. In some examples, via the first interface conduit 136 as illustrated.

[0181] In other examples, one or more of the inspiratory limb 132 or the expiratory limb 134 may be coupled directly with the first patient interface, e.g., oral endotracheal tube 122, or a Y-piece coupled with the first patient interface, optionally omitting the first interface conduit 136.

[0182] One or more of the inspiratory limb 132, expiratory limb 134, or first interface conduit 136 may be heated, e.g., include a heated conduit. Heating a conduit may advantageously inhibit or prevent the formation of condensate in the conduit or downstream components of the respiratory support system 100, or dissipate condensate or other liquids within the conduit. In some examples, a heating wire may be provided within a lumen of the conduit, embedded in a wall of the conduit, or wrapped around the conduit. The first gas source 126 may be configured to control heating of the heated conduit, e.g., by controlling power supplied to the heating wire.

[0183] The first breathing circuit 130 may include a Y-piece (not shown). The Y-piece may couple, e.g., removably couple, together the inspiratory limb 132, the expiratory limb 134, and the first interface conduit 136 (or, in some cases, the first patient interface).

[0184] The first breathing circuit 130 may include a filter (not shown). The filter may be configured to inhibit or prevent the ingress of pathogens into the first gas source 126, for example. The filter may be located between the expiratory limb 134 and the gases return inlet of the first gas source 126, for example.

[0185] The respiratory support system 100 may include a first humidifier (not shown). The first humidifier may be configured to heat and humidify the first flow of gases 160.The first humidifier may include a heat source configured to heat a volume of water, or other humidifying liquid, contained within a humidifier chamber. The humidifier chamber may include chamber inlet configured to receive the first flow of gases 160 from the first gas source 126, e.g., via a humidifier supply conduit, and a chamber outlet configured to provide the heated and humidified first flow of gases 160 to the first patient interface, e.g., via one or more of the inspiratory limb 132, Y-piece, and / or first interface conduit 136. The humidifier chamber may be regarded as part of the first breathing circuit 130, e.g., the inspiratory limb 132.

[0186] In some cases, the first patient interface, e.g., the oral endotracheal tube 122, may also be regarded as part of the first breathing circuit 130.

[0187] One or more components of the first breathing circuit 130 may be disposable to reduce the risk of cross-infection between different patients. One or more components of the first breathing circuit 130 may be configured to be reprocessed for extended use by the same patient, or for use with two or more different patients. The reprocessing may include chemical disinfection or autoclaving, e.g., exposure to one or more of an elevated temperature or pressure for a predetermined period of time sufficient to sterilize the component. For example, a temperature of about 120 °C at a pressure of about 2 standard atmospheres (atm) for a period of between about 30 minutes (min) and 60 min. The components may be configured to withstand multiple reprocessing cycles, e.g., at least five, or at least ten, reprocessing cycles.

[0188] Any two or more components of the first breathing circuit 130 may be supplied together as a breathing circuit kit. The components may be packaged together, e.g., in sterile sealed packaging. Any two or more of the components of the breathing circuit kit may be pre-assembled. Pre-assembly may improve ease or efficiency in setting up the respiratory support system 100, and / or mitigate the risk of misconnections.

[0189] Together, the first gas source 126, first breathing circuit 130, and first patient interface, e.g., oral endotracheal tube 122, may be regarded as forming a ventilation system 120, or sub-system, of the respiratory support system 100.

[0190] In the example respiratory support system 100, a second gas source 146 is configured to provide a second flow of gases 170 to the upper respiratory tract 114 of the patient 110. In other examples or contexts, the second gas source may be referred to as a secondary gas source, aeration device, nasal high flow device, or supplementary gas source, for example.

[0191] The second flow of gases 170 may include any one, or a combination of any two or more, of air, oxygen (O2), carbon dioxide (CO2), or heliox, for example. In some examples, the composition of the second flow of gases 170 may be different to thecomposition of the first flow of gases 160. In other examples, the composition of the first flow of gases 160 and the second flow of gases 170 may be the same.

[0192] The second gas source 146 may be configured to control a flow rate of the second flow of gases 170. The second gas source 146 may be configured to provide a time-varying flow rate profile during at least part, or an entirety, of one or more of the inspiratory phase, expiratory phase, or breathing cycle, as described in further detail below with reference to FIG. 4 to FIG. 15. The second gas source 146 may be configured to provide a flow rate of at least about 8 liters per minute (l / min), or at least about 15 l / min, e.g., about 30 l / min. In some examples, the second gas source 146 may be a nasal high flow device.

[0193] The second gas source 146 may be configured to determine a phase of the breathing cycle. The second gas source 146 may determine the breathing cycle by wired or wireless communication with the first gas source 126. Alternatively, or additionally, the second gas source 146 may be configured to determine the phase of the breathing cycle by sensing one or more properties of one or more of the first gas source 126, the first flow of gases 160, or the patient. For example, the second gas source 146 may include, or communicate with, a sensor, e.g., one or more of a flow rate sensor or a pressure sensor in the flow path of the first flow of gases. In some examples, the second gas source 146 may communicate with the first gas source 126. In some examples, the second gas source 146 may communicate with the first humidifier configured to humidify the first flow of gases provided by the first gas source 126. The first humidifier may have a pressure and / or flow sensor configured to determine a flow rate and / or pressure of the first flow of gases. The second gas source 146 may receive flow rate and / or pressure data from the first gas source 126 and / or the first humidifier, e.g., in realtime. The second gas source 146 may use the flow rate and / or pressure data to determine a phase of the breathing cycle of the first gas source 126.

[0194] In some examples, the second gas source 146 may include a pressure sensor (not shown). The pressure sensor may be connected to the first breathing circuit 130 via a pressure line (not shown). For example, the pressure line may interface with a pressure port on a Y-piece of the first breathing circuit 130. The Y-piece may be connected with the first patient interface, e.g., oral endotracheal tube 122. This arrangement enables the second gas source 146 to continuously monitor the pressure of the first flow of gases 160 within the first breathing circuit 130.

[0195] The second gas source 146, e.g., the controller 1728 described below with reference to FIG. 17, may receive a pressure signal from the pressure sensor. The pressure signal may comprise a series of instantaneous pressure readings. The pressure signal may be digital or analog.

[0196] The second gas source 146, e.g., the controller 1728, may optionally smooth the pressure signal by applying a moving average. For example, a moving average with a period of approximately 50 milliseconds. The second gas source 146, e.g., the controller 1728, may determine a baseline pressure of the first flow of gases 160. The baseline pressure may comprise a measure of a central tendency of the pressure of the first flow of gases 160 such as an average, a weighted average, a mean, or a median of the pressure signal, for example. In one example, the second gas source 146 may determine the baseline pressure using an exponentially-weighted moving average (EWMA) filter on the smoothed pressure signal. Thus, the baseline pressure may represent a continuously updated average of the pressure of the first flow of gases 160. The EWMA filter may initially respond more rapidly, within the first 500 milliseconds of therapy, to quickly approximate the average pressure, before transitioning to a slower response for the remainder of the therapy.

[0197] An instantaneous pressure (e.g., the pressure signal or the smoothed pressure signal) greater than the baseline pressure may indicate that the first gas source 126 is in an inspiratory phase. An instantaneous pressure (e.g., the pressure signal or the smoothed pressure signal) less than the baseline pressure may indicate that the first gas source 126 is in an expiratory phase.

[0198] This method enables the second gas source to automatically identify the phase of the first gas source. Because the baseline pressure is continuously updated, the second gas source 146 may adapt to any changes in the settings of the first gas source 126 over time.

[0199] In another example, the second gas source 146 may determine a mean pressure over several breaths at the start of therapy. The inspiratory phase and expiratory phase of the first gas source 126 may be determined using a first threshold and a second threshold. The first threshold may be greater than the second threshold. The first threshold may be an upper threshold. The second threshold may be a lower threshold. The first threshold and the second threshold may be offset from the mean pressure. For example, the first threshold and the second threshold may be set at ± 1 cmH20 from the mean pressure. Or a proportion of the mean pressure, e.g., ± 10 % (90 % and 110 %) of the mean pressure, for example. An instantaneous pressure (e.g., the pressure signal or the smoothed pressure signal) greater than the first threshold may indicate that the first gas source 126 is in an inspiratory phase. An instantaneous pressure (e.g., the pressure signal or the smoothed pressure signal) less than the second threshold may indicate that the first gas source 126 is in an expiratory phase. The mean pressure may be periodically updated to accommodate changes in the therapy settings of the first gas source 126.

[0200] In another configuration, the mean pressure and / or the upper and lower thresholds may be manually input into the second gas source 146, e.g., by medical personnel via a user interface of the second gas source 146.

[0201] Further details of a device suitable for use as the second gas source 146 are described below with reference to FIG. 17 to FIG. 24.

[0202] The second gas source 146 in some examples may be configured to provide the second flow of gases 170 as a uni-directional gas flow. For example, the second gas source 146 may include a centrifugal blower configured to generate a pressurized flow of gases from ambient air. In some examples, as described below, the aeration system 140 may comprise a pair of second gas sources 146, or a single second gas source 146 with a pair of blowers, each configured to provide a portion of the second flow of gases 170 to respective nares of the patient 110. The second gas sources 146 or blowers may be controlled independently of each other.

[0203] In some examples, as illustrated in FIG. 1 and FIG. 2, the second gas source 146 may be physically and / or pneumatically isolated from the first gas source 126.

[0204] The second gas source 146 may be pneumatically coupled with the second patient interface, e.g., by a second breathing circuit 150.

[0205] The second breathing circuit 150 in this example is a single-limb breathing circuit. The single-limb breathing circuit includes a delivery conduit 152. The delivery conduit 152 may be configured to be removably coupled with the nasal cannula 142. In some examples, the second patient interface, e.g., nasal cannula 142, may include a second interface conduit, e.g., a cannula conduit. The second interface conduit may have a smaller internal diameter and / or external diameter than the delivery conduit 152. The second interface conduit may be relatively flexible, e.g., more flexible than the delivery conduit 152. The relatively flexible second interface conduit may be configured to be routed at least partially over or around the patient's head for convenience or comfort without unduly disrupting the fitting of the first patient interface and / or the second patient interface to the patient, for example. The relatively flexible second interface conduit may decouple tube drag forces between the delivery conduit 152 and the nasal cannula 142. In some examples, the second interface conduit may be formed, at least in part, from a breathable material. The breathable material may advantageously mitigate formation or accumulation of condensate or other liquids within the second interface conduit and / or other portions of the nasal cannula 142, and / or dissipate any accumulated condensate or other liquids within the second interface conduit.

[0206] One or more of the delivery conduit 152 and / or second interface conduit may be heated, as described above with respect to the first breathing circuit 130. Heating may be controlled by the second gas source 146.

[0207] The respiratory support system 100 may include a second humidifier (not shown) configured to heat and humidify the second flow of gases 170. The second humidifier may be integrated with the second gas source. The humidifier chamber of the second humidifier may be regarded as part of the second breathing circuit 150. The second humidifier may otherwise be similar in configuration and function to the first humidifier described above.

[0208] Replicating the homeostatic conditions of the upper airways may provide a therapeutic benefit. Air that is breathed in normally is at ambient conditions. Hence, in some examples it may be beneficial to provide the second flow of gases 170 at a relatively low temperature, for example about 21 °C, and / or a relatively low humidity, for example about 50 % relative humidity. Air that is exhaled is normally at a relatively higher temperature and humidity. Hence, in some examples it may be beneficial to provide the second flow of gases 170 at a relatively high temperature and / or humidity, for example about 31 °C and 80 % relative humidity, or about 37 °C and 100 % relative humidity.

[0209] In some examples, the second flow of gases 170 may be provided at a relatively higher temperature and / or humidity during the expiratory phases than during the inspiratory phases of the first gas source 126. In other examples, the temperature and / or humidity may be varied over longer time periods. For example, oscillating between two levels with a period of between about 15 min and 2 hours.

[0210] In some cases, the second patient interface, e.g., the nasal cannula 142, may be regarded as part of the second breathing circuit 150.

[0211] One or more components of the second breathing circuit 150 may be disposable to reduce the risk of cross-infection between different patients. In some examples, all components of the second breathing circuit 150 may be disposable. One or more components of the second breathing circuit 150 may be reusable, e.g., configured to be reprocessed for extended use by the same patient, or for use with two or more different patients. In some examples, all components of the second breathing circuit 150 may be reusable. The reprocessing may include chemical disinfection or autoclaving, e.g., exposure to one or more of an elevated temperature or pressure for a predetermined period of time sufficient to sterilize the component. For example, a temperature of about 120 °C at a pressure of about 2 standard atmospheres (atm) for a period of between about 30 minutes (min) and 60 min. The components may be configured towithstand multiple reprocessing cycles, e.g., at least five, or at least ten, reprocessing cycles.

[0212] Any two or more components of the second breathing circuit 150 may be supplied together as a breathing circuit kit. For example, nasal cannula 142 and the delivery conduit 152, the delivery conduit 152 and the humidifier chamber, or the nasal cannula 142, delivery conduit 152, and the humidifier chamber. The components may be packaged together, e.g., in sterile sealed packaging. Any two or more of the components of the breathing circuit kit may be pre-assembled. Pre-assembly may improve ease or efficiency in setting up the respiratory support system 100, and / or mitigate the risk of misconnections.

[0213] Together, the second gas source 146, second breathing circuit 150, and second patient interface may be regarded as forming an aeration system, or sub-system, of the respiratory support system 100.

[0214] In some examples, any two or more components of the first breathing circuit 130 and the second breathing circuit 150 may be supplied together as kit. The first breathing circuit 130 and the second breathing circuit 150 may be packaged together, e.g., in sterile sealed packaging.

[0215] The arrows in FIG. 1 represent potential gas flows within the respiratory support system 100 during at least part of an expiratory phase of a breathing cycle.

[0216] The phase of the breathing cycle in this example may refer to the phase of the first gas source 126. The respiratory phase of the patient may be controlled by the first gas source 126.

[0217] During at least part of the expiratory phase, the first gas source 126 receives the first flow of gases 160 from the lower respiratory tract 112 of the patient 110. In this example, through the invasive patient interface, e.g., oral endotracheal tube 122, first interface conduit 136, and expiratory limb 134.

[0218] Meanwhile, the second gas source 146 may provide the second flow of gases 170 to the upper respiratory tract 114 of the patient 110. In this example, through the delivery conduit 152 and non-invasive patient interface, e.g., nasal cannula 142. The second flow of gases 170 may circulate within at least part of the upper respiratory tract 114 of the patient 110, e.g., one or more of the nasal cavity, pharynx, or oral cavity, before being vented from the upper respiratory tract 114 through the patient's mouth 118 and / or nares 116.

[0219] In other examples, the second gas source 146 may cease providing the second flow of gases 170 during at least part of the expiratory phase, as described in further detail below.

[0220] The arrows in FIG. 2 represent potential gas flows within the respiratory support system 100 during at least part of an inspiratory phase of the breathing cycle.

[0221] During at least part of the inspiratory phase, the first gas source 126 supplies the first flow of gases 160 to the lower respiratory tract 112 of the patient 110. In this example, through the inspiratory limb 132, first interface conduit 136, and invasive patient interface, e.g., oral endotracheal tube 122.

[0222] Meanwhile, the second gas source 146 may provide the second flow of gases 170 to the upper respiratory tract 114 of the patient 110. In this example, through the delivery conduit 152 and non-invasive patient interface, e.g., nasal cannula 142. The second flow of gases 170 may circulate within at least part of the upper respiratory tract 114 of the patient 110, e.g., one or more of the nasal cavity, pharynx, or oral cavity, before being vented from the upper respiratory tract 114 through the patient's mouth 118 and / or nares 116.

[0223] In other examples, the second gas source 146 may cease providing the second flow of gases 170 during at least part of the inspiratory phase, as described in further detail below.

[0224] The respiratory support system 100 thus aerates the upper respiratory tract 114 of the patient during at least part of one or more of the expiratory phase or the inspiratory phase of ventilation of the lower respiratory tract 112. Aeration may mitigate or avoid the stagnancy within the upper respiratory tract 114 which is associated with invasive ventilation bypassing the upper respiratory tract 114. Pneumatic isolation of the first gas source 126 and second gas source 146 may advantageously permit greater flexibility in one or more of the composition or control of the gases supplied to the upper respiratory tract 114. For example, while the first flow of gases 160 is bi-directional, the second flow of gases 170 may be uni-directional, the second flow of gases 170 may consist of ambient air and / or include a higher proportion of carbon dioxide than the first flow of gases 160, and / or the first flow of gases 160 may be controlled based on a pressure or volume while the second flow of gases 170 may be controlled based on a flow rate.

[0225] FIG. 3 schematically illustrates the second flow of gases 170 within the upper respiratory tract 114 of the patient 110 during one or more of the expiratory phase or the inspiratory phase of the respiratory support system 100 as shown in FIG. 1 and FIG.2, respectively.

[0226] For clarity, the first flow of gases is omitted from FIG. 3. But it will be appreciated that the first flow of gases may simultaneously flow through the oral endotracheal tube 122, from or to the lower respiratory tract.

[0227] During one or more of the expiratory phase or the inspiratory phase, the second gas source 146 (shown in FIG. 1 and FIG. 2) supplies the second flow of gases 170 to the upper respiratory tract 114 of the patient 110. The second flow of gases exits the nasal prongs 144 of the nasal cannula 142 into the nasal cavity 302. The second flow of gases 170 may flow through, or circulate within, at least part of the upper respiratory tract 114 before being vented from one or more of the mouth 118 or nares 116 of the patient 110.

[0228] In one example, as illustrated in FIG. 3, the second flow of gases 170 may flow through the nasal cavity 302, nasopharynx 306, oropharynx 308, laryngopharynx 310, the upper part of the trachea 312 above the cuff 124 of the first patient interface, e.g., oral endotracheal tube 122, and the oral cavity 304 before being vented from the patient's mouth 118.

[0229] As disclosed above, the second gas source 146 may be configured to provide the second flow of gas with a time-varying flow rate profile. Various illustrative and non-limiting examples of different time-varying flow rate profiles are described below with reference to FIG. 4 to FIG. 15.

[0230] In some examples, the time-varying flow rate profile may be a periodic waveform.

[0231] In some examples, the periodic waveform may have a predetermined frequency. The predetermined frequency may be fixed or selected by a user of the second gas source 146, e.g., a clinician. Or the frequency may be determined and / or varied dynamically, e.g., in real-time. The frequency may be based at least in part on inputs from one or more sensors. The frequency (and / or amplitude) may be based at least in part on one or more patient properties. For example, body weight or ideal body weight (IBW), which may correlate with the patient's lung capacity.

[0232] In other examples, the frequency of the second flow of gas may vary. The frequency may depend on one or more of a sedation level or wakefulness of the patient. A relatively lower frequency may be used for patients that are fully sedated and unconscious. A relatively higher frequency may be used for patients who are awake and conscious, or being weaned from invasive ventilation. The controller of the second gas source 146 may be configured to receive or determine a measure of one or more of the sedation or wakefulness of the patient, and vary the frequency based on the measure. The measure may be obtained from the first gas source 126, from a sensor,or be manually input by medical personnel. Medical personnel may manually input different frequencies as the patient is weaned. The measure may be a measure of respiratory effort of the patient, with higher effort corresponding to lower sedation or increased wakefulness. The measure may be based on a physiological parameter such as an electroencephalography (EEG) signal or a Richmond Agitation-Sedation Scale (RASS) score. Alternatively, or additionally, the controller may receive or determine a mode of the first gas source 126, which may switch from a timed breath mode during deep sedation to a spontaneously triggered breath mode during weaning or lighter sedation. The controller may change the frequency based on the mode of the first gas source 126.

[0233] The frequency may alternatively, or additionally, be varied based on one or more of the time of day or the patient's circadian rhythm. During nighttime, or whenever the patient is usually asleep, a lower frequency may be used. During daytime, or whenever the patient is usually awake, a higher frequency may be used.

[0234] In some examples, not shown in the drawings, an oscillation may be superimposed on the time-varying flow rate profile. The oscillation may be at a higher frequency than the predetermined frequency of the time-varying flow rate profile. For example, between about 2 Hz and 250 Hz. The higher-frequency oscillation may stimulate receptors and brain activity at a different frequency. An amplitude of the oscillation may be less than an amplitude of the time-varying flow rate profile. For example, less than about half, less than about a quarter, or less than about a tenth of the amplitude of the time-varying flow rate profile.

[0235] In some examples, the time-varying flow rate profile may be independent of the first flow of gas provided by the first gas source 126, as shown in FIG. 4 to FIG. 8. For example, the frequency of the second gas source 146 may be different to a frequency of the first gas source 126, or the first gas source 126 and the second gas source 146 may be asynchronous. In other examples, the time-varying flow rate profile may be dependent on the first flow of gas and / or the first gas source, as described below with particular reference to FIG. 10 to FIG. 15. For example, the frequency of the second gas source 146 may be about the same as the frequency of the first gas source 126, e.g., ± 10 % or ± 5 %, and / or the second gas source 146 may be synchronized with the first gas source 126.

[0236] In some examples, the time-varying flow rate profile may comprise one or more, e.g., two, different constant flow rates, as shown in FIG. 4, FIG. 10, and FIG. 11. In some examples, the time-varying flow rate profile may comprise a continuously-varying flow rate, as shown in FIG. 6 to FIG. 9, FIG. 12, and FIG. 13. In some examples,the time-varying flow rate profile may comprise a combination of one or more constant flow rates and one or more continuously-varying flow rates, as shown in FIG. 14.

[0237] Referring in particular to FIG. 4, a first example of a time-varying flow rate profile is illustrated in the form of a rectangular waveform 400.

[0238] The second gas source 146 may be configured to alternate between providing the second flow of gases 170 at a first flow rate 402 and a second flow rate 404. The first flow rate 402 may be higher than the second flow rate 404. The first flow rate 402 and the second flow rate 404 may be predetermined. For example, selected or adjusted by medical personnel via a user interface of the second gas source 146.

[0239] In some examples, as shown in FIG. 4, a first interval 406 of the first flow rate 402, e.g., the period between Toand Ti, may be about equal to a second interval 408 of the second flow rate 404, e.g., the period between Ti and T2. In that case, the rectangular waveform may be a square waveform, i.e., have a duty cycle of 50%.

[0240] In other examples, the first interval 406 and the second interval 408 may differ. The rectangular waveform may have a duty cycle of less than 50% or more than 50%.

[0241] In some examples, the period 410 of the rectangular waveform 400, e.g., the period between Toand T2, may be about equal to the period of a breathing cycle of a healthy human. For example, a period of between about 3 seconds (s) and 5 s (equivalent to a respiratory rate of between about 12 breaths per minute (bpm) and 20 bpm, or a frequency of between about 0.2 Hertz (Hz) and 0.3 Hz), or between about 3 s and 4 s.

[0242] In other examples, the period 410 of the rectangular waveform 400 may be greater than the period of a breathing cycle of a healthy human. For example, a period of between about 5 s and 15 s, or about 12 s (equivalent to a frequency of about 0.08 Hz).

[0243] In yet other examples, the period 410 of the rectangular waveform 400, may be less than the period of a breathing cycle of a healthy human. For example, a period of between about 200 milliseconds (ms) and 500 ms (equivalent to a frequency of between about 2 Hz and 10 Hz). Such periods are thought to help improve cognitive function and brain activity, potentially mitigating one or more of delirium and cognitive decline associated with invasive ventilation.

[0244] A duration of one or more of the first interval 406, the second interval 408, or the period 410, may be predetermined. For example, selected or adjusted by medical personnel via a user interface of the second gas source 146.

[0245] In yet other examples, the waveform may comprise a relatively higher-frequency waveform superimposed on a relatively lower-frequency periodic waveform. The relatively higher-frequency waveform and the relatively lower-frequency periodic waveform may be alike (e.g., both sinusoidal waveforms) or different (e.g., the relatively higher-frequency waveform may be a sinusoidal waveform and the relatively lower-frequency periodic waveform may be a rectangular waveform).

[0246] In some examples, the first flow rate 402 of the rectangular waveform 400 may be between about 30 liters per minute (L / min) and 60 L / min. In some examples, the second flow rate 404 of the rectangular waveform 400 may be between about 0 L / min and 15 L / min. In some examples, the second flow rate 404 may be non-zero, e.g., between about 0 L / min and 5 L / min. A non-zero second flow rate 404 may mitigate condensation within the delivery conduit 152, or other issues that may be associated with low or zero flow. In one example, the first flow rate 402 may be about 30 L / min and the second flow rate 404 may be about 1 L / min.

[0247] In some examples, the difference between the first flow rate 402 and the second flow rate 404 of the rectangular waveform 400, flow delta 412, may be between about 15 L / min and 30 L / min. For example, the first flow rate 402 and the second flow rate 404 may be 30 L / min and 0 L / min, 30 L / min and 15 L / min, or 60 L / min and 30 L / min, respectively.

[0248] One or more of the first flow rate 402, second flow rate 404, and flow delta 412 may be predetermined, e.g., selected or adjusted by a user of the second gas source 146.

[0249] FIG. 5 illustrates a second example of a time-varying flow rate profile in the form of a trapezoidal waveform 500.

[0250] Although the rectangular waveform 400 of FIG. 4 is illustrated as transitioning between the first flow rate 402 and the second flow rate 404 substantially instantaneously, in other examples the transition may occur over a period of time, e.g., a ramp period 514, whether intentionally or due to mechanical limitations.

[0251] During an initial portion of the first interval 506, the second gas source 146 may ramp the flow rate up from the lower second flow rate 504 to the higher first flow rate 402. During an initial portion of the second interval 508, the second gas source 146 may ramp the flow rate down from the first flow rate 502 to the second flow rate 504. In some examples, the ramp period 514 may be the same during both the first interval 506 and the second interval 508. In other examples, a rising ramp period may differ from a falling ramp period. In some examples, the ramp periods 514 may beconstant. In other examples, the ramp period may vary from one ramp period to the next.

[0252] Although the ramp periods 514 occur during an initial portion of the first interval 506 and second interval 508 in FIG. 5, in other examples, the ramp period may alternatively occur, or commence, in a final portion of the interval.

[0253] In some examples, as shown in FIG. 5, the flow rate may be continuously varied during the ramp period 514. In other examples, the flow rate may be varied in a number of discrete increments, e.g., ten or more increments, to approximate a trapezoidal waveform.

[0254] FIG. 6 illustrates a third example of a time-varying flow rate profile in the form of a triangular waveform 600.

[0255] During a first interval 602, e.g., the period between Toand Ti, the second gas source 146 may be configured to gradually increase the flow rate of the second flow of gases 170 towards a first flow rate 608. During a second interval 604, e.g., the period between Ti and T2, the second gas source 146 may be configured to gradually decrease the flow rate of the second flow of gases 170 towards a second flow rate 610. The first flow rate 608 may be higher than the second flow rate 610.

[0256] In some examples, as shown in FIG. 6, the first interval 602 may be about equal to the second interval 604. In that case, a period of the triangular waveform may form an isosceles triangle.

[0257] In other examples, the first interval 602 and the second interval 604 may differ. In that case, a period of the triangular waveform may form an acute triangle or a right triangle. For example, the triangular waveform may be a sawtooth waveform.

[0258] The periods, flow rates, and flow delta of the triangular waveform 600 may be similar to those of the rectangular waveform 400 and variants as described above with reference to FIG. 4.

[0259] In some examples, as shown in FIG. 6, the flow rate may be continuously varied. In other examples, the flow rate may be varied in a number of discrete increments, e.g., ten or more increments, to approximate a triangular waveform.

[0260] FIG. 7 illustrates a fourth example of a time-varying flow rate profile in the form of a curved waveform 700. As shown in FIG. 7, the curved waveform 700 may be a sinusoidal waveform, for example.

[0261] During a first interval 706, e.g., the period between To and Ti, the second gas source 146 may be configured to increase the flow rate of the second flow of gases 170 towards a first flow rate 702. During a second interval 708, e.g., the period between Ti and T2, the second gas source 146 may be configured to gradually decrease the flow rate of the second flow of gases 170 towards a second flow rate 704. The first flow rate 702 may be higher than the second flow rate 704. A first differential of the flow rate may vary continuously throughout the first interval 706 and / or the second interval 708.

[0262] In some examples, as shown in FIG. 7, the first interval 706 may be about equal to the second interval 708. In that case, the curved waveform 700 may form a linear curved waveform, e.g., a sinusoidal waveform.

[0263] In other examples, the first interval 706 may differ from the second interval 708. In that case, the curved waveform 700 may form a non-linear curved waveform, e.g., a skewed waveform or an asymmetric waveform.

[0264] The periods, flow rates, and flow delta of the curved waveform 700 may be similar to those of the rectangular waveform 400 and variants as described above with reference to FIG. 4.

[0265] In some examples, as shown in FIG. 7, the flow rate may be continuously varied. In other examples, the flow rate may be varied in a number of discrete increments, e.g., ten or more increments, to approximate a curved waveform.

[0266] Because the second gas source 146 and the second flow of gases 170 are configured to aerate the upper respiratory tract of the patient while the patient is invasively ventilated by the first gas source and the first flow of gases 160, the timevarying flow rate profile does not necessarily have to be coordinated, e.g., synchronized, with the breathing cycle of the first gas source 126 and / or the patient. This decoupling may advantageously simplify one or more of the sensing, control, and communications systems of the second gas source. Alternatively, or additionally, the decoupling may advantageously permit the second gas source 146 to provide a time-varying flow rate profile with a different frequency to that of the first gas source 126, e.g., a higher frequency. The frequency of the time-varying flow rate profile of the second flow of gases 170 may be selected to optimize the therapeutic benefits to the upper respiratory tract 114 of the patient, without impacting ventilation and gas-exchange of the patient.

[0267] In other examples, as described below, it may be beneficial to coordinate, e.g., synchronize, operation of the first gas source 126 and the second gas source 146. Gas flows within the upper respiratory tract which approximate, to at least some degree, those of a typical healthy human adult and / or provided to the lower respiratory tractmay provide additional and / or alternative therapeutic benefits, such as facilitating weaning from invasive ventilation.

[0268] FIG. 8 illustrates a fifth example of a time-varying flow rate profile in the form of another curved waveform. As shown in FIG. 8, the curved waveform may comprise a piecewise sinusoidal waveform 800.

[0269] During a first interval 802, the piecewise sinusoidal waveform 800 may have a first profile. The first profile may have a first amplitude 808.

[0270] During a second interval 804 of the period 806, the piecewise sinusoidal waveform 800 may have a second profile. The second profile may have a second amplitude 810.

[0271] The first profile and / or the second profile may be sinusoidal or parabolic.

[0272] The first profile and / or the second profile may have different intervals, as shown in FIG. 8. In other examples, the first interval 802 and the second interval 804 may be about equal.

[0273] The first profile and / or the second profile may have different amplitudes, as shown in FIG. 8. In other examples, the first amplitude 808 and the second amplitude 810 may be about equal.

[0274] In some examples, as shown in FIG. 8, both the intervals 802, 804 and the amplitudes 808, 810 may differ.

[0275] A second flow of gases 170 having the waveform of any of FIG. 4 to FIG. 8, for example, may be provided by the second gas source 146 independently from the first flow of gases 160 and the first gas source 126. That is, the first flow of gases 160 and the second flow of gases 170, and the first gas source 126 and the second gas source 146, may be asynchronous. In other examples, the second flow of gases 170 may be provided so that the first interval, coincides with an inspiratory phase of the first gas source 126, and / or the second interval coincides with an expiratory phase of the second gas source 146.

[0276] For the purpose of describing the example time-varying flow rate profiles of FIG. 10 to FIG. 15, FIG. 9 illustrates the flow profile of a normal breathing waveform of a typical healthy human for a single breathing cycle.

[0277] In each of the inspiratory phase and the expiratory phase there may be a period of relatively higher magnitude flow.

[0278] During the inspiratory phase 902, contraction of the diaphragm and intercostal muscles expands the thoracic cavity, decreasing air pressure within the lungs with respect to the pressure of ambient air, which in turn draws air into the lungs.

[0279] The flow rate of the air during an initial portion 910 of the inspiratory phase 902 may increase from zero towards a peak inspiratory flow rate 908. The flow rate of the air during an end portion 912 of the inspiratory phase 902 may decrease towards zero.

[0280] As shown in FIG. 9, the periods of the initial portion and the end portion of the inspiratory phase 902 may be about equal. The waveform during the inspiratory phase 902 may be curved and / or relatively symmetric, e.g., parabolic.

[0281] During the expiratory phase 904, relaxation of the diaphragm and intercostal muscles and elastic recovery of the lungs and chest wall increases air pressure within the lungs with respect to the pressure of ambient air, expelling the air out of the lungs. Additional muscles, e.g., abdominal muscles, may be engaged to expel the air more forcefully.

[0282] The intervals of the inspiratory phase 902 and expiratory phase 904 may differ. As shown in FIG. 9, the expiratory phase 904 may be longer than the inspiratory phase 902. The relationship between the intervals of the inspiratory phase 902 and the expiratory phase 904 may be expressed as an inspiratory: expiratory ratio (I: E ratio).

[0283] The flow rate of the air during an initial portion 914 of the expiratory phase 904 increases (in magnitude) from zero towards a peak expiratory flow rate 918. The flow rate of the air during an end portion 916 of the expiratory phase 904 may decrease (in magnitude) to zero relatively slowly.

[0284] The waveform during the expiratory phase 904 may be relatively asymmetric. The flow rate of the air during the end portion 916 of the expiratory phase 904 may initially decrease (in magnitude) relatively rapidly before slowing. For example, the decrease may be an exponential decay.

[0285] The period of the end portion 916 of the expiratory phase 904 may be greater than the period of one or more of the initial portion 910 or the end portion 912 of the inspiratory phase 902, the initial portion 914 of the expiratory phase. In some examples, as shown in FIG. 9, the period of the end portion 916 of the expiratory phase 904 may be greater than the period of all three of the initial portion 910 and end portion 912 of the inspiratory phase 902 and the initial portion 914 of the expiratory phase 904 combined.

[0286] As shown in FIG. 9, the typical flow profile for each breathing cycle of a healthy human adult may be a non-linear curved waveform deviating from a sinusoidal shape, e.g., a skewed waveform and / or an asymmetric waveform.

[0287] In the case of an invasively ventilated patient, the waveform of the first flow of gases 160 provided to the patient is determined, at least in part, by the first gas source. The first flow of gases 160 may or may not resemble the normal breathing waveform to varying degrees. Depending, for example, on the operating mode of the first gas source. By way of example, the operating mode of the first gas source may be selected from one or more of:• volume control ventilation (VCV)• pressure control ventilation (PCV)• pressure support ventilation (PSV)• synchronized intermitted mandatory ventilation (SIMV)• assist-control ventilation (ACV)• continuous positive airway pressure (CPAP)• bi-level positive airway pressure (BPAP)• adaptive support ventilation (ASV), or• high-frequency oscillatory ventilation (HFOV).

[0288] In some examples, the first flow of gases 160 provided by the first gas source 126 may match, or at least approximate, one or more of the period of the breathing cycle 906, the period of the inspiratory phase 902, the period of the expiratory phase 904, the peak inspiratory flow rate 908, the inspiratory:expiratory ratio, the peak expiratory flow rate 918, and the profile of a normal breathing waveform in one or more of the inspiratory phase 902 and expiratory phase 904.

[0289] FIG. 10 illustrates a sixth example of a time-varying flow rate profile in the form of a bi-level waveform 1000.

[0290] The second gas source 146 may be configured to switch between providing the second flow of gases 170 at a first flow rate 1002 and a second flow rate 1004. The first flow rate 1002 may be greater than the second flow rate 1004.

[0291] The second gas source 146 may be configured to provide the second flow of gases 170 at the first flow rate 1002 during part of the inspiratory phase 902 and again during part of the expiratory phase 904. The first flow rate 1002 of the second flow of gases 170 may coincide with one or more of the peak inspiratory flow rate 908 and peak expiratory flow rate 918 of the first flow of gases 160.

[0292] In some examples, as shown in FIG. 10, the second gas source 146 may be configured to commence the first flow rate 1002 in advance of one or more of the peak inspiratory flow rate 908 and the peak expiratory flow rate 918, e.g., by a lead period.

[0293] In some examples, as shown in FIG. 10, the second gas source 146 may be configured to maintain the first flow rate 1002 beyond one or more of the peak inspiratory flow rate 908 and the peak expiratory flow rate 918, e.g., by a lag period.

[0294] In some examples, as shown in FIG. 10, the lag period may be about equal to the lead period. In such cases, the peak inspiratory flow rate 908 of the first flow of gases 160 may coincide with a mid-point of the first flow rate 1002. In other examples, the lead period and the lag period may differ.

[0295] In some examples, one or more of the lead period and the lag period may be about the same for both the inspiratory phase 902 and the expiratory phase 904. In other examples, one or more of the lead periods and the lag periods may differ between the inspiratory phase 902 and the expiratory phase 904.

[0296] The second gas source 146 may be configured to provide the second flow rate 1004 for at least part of one or more of the inspiratory phase 902 and expiratory phase 904.

[0297] In some examples, the second flow rate 1004 may be provided for between about 20 % and 80 %, between about 40 % and 60 %, or about 50 %, of the period of the inspiratory phase 902. The second flow rate 1004 may be provided for between about 25% and about 95%, between about 50 % and 90 %, between about 60 % and 85 %, or about 80% of the period of the expiratory phase 904.

[0298] In some examples, one or more of the first flow rate 1002, second flow rate 1004, or a flow delta (the difference between the first flow rate 1002 and the second flow rate 1004) of the bi-level waveform 1000 may be predetermined, e.g., selected or adjusted by a user of the second gas source 146. In other examples, one or more of the first flow rate 1002 and the second flow rate 1004 may depend on the first flow of gases 160. For example, as shown in FIG. 10, the first flow rate 1002 may be related to, e.g., about the same as, the peak inspiratory flow rate 908.

[0299] Except as described above or otherwise apparent from the drawings, the bilevel waveform 1000 may be similar to the rectangular waveform 400, and variants, as described above with reference to FIG. 4. Particularly, but not exclusively, in relation to the flow rates, flow delta, and ramp period.

[0300] In some examples, as shown in FIG. 10 and the following examples, the first interval of waveform may be configured to coincide with the inspiratory phase 902 of the first gas source 126. The second interval of the waveform may be configured to coincide with the expiratory phase 904 of the first gas source 126. That is, the timing and duration of the first interval and the second interval may be controlled based on detecting a change in phase of the first flow of gases 160. In other examples, a duration of one or more of the first interval or the second interval may be predetermined, e.g., selected or adjusted by medical personnel. In such examples, the bi-level waveform 1000 as a whole may be triggered by detection of an event in the first flow of gases 160. The event may comprise one or more of commencement of the inspiratory phase, commencement of the expiratory phase, peak inspiratory flow rate, and peak expiratory flow rate, for example.

[0301] FIG. 11 illustrates a seventh example of a time-varying flow rate profile in the form of another bi-level waveform 1100.

[0302] The bi-level waveform 1100 provides the second flow of gases 170 at a higher flow rate only during part of the inspiratory phase. The second flow of gases 170 may be provided at a lower flow rate during part of the inspiratory phase, and an entirety of the expiratory phase.

[0303] The bi-level waveform 1100 otherwise may be similar to the bi-level waveform 1000, and variants, as described above with reference to FIG. 10.

[0304] FIG. 12 illustrates an eighth example of a time-varying flow rate profile in the form of a matched waveform 1200.

[0305] The second gas source 146 in this example may be configured to match, or at least approximate, a normal breathing waveform, e.g., as shown in FIG. 9. The matched waveform 1200 may match, or approximate, one or more (or, as shown in FIG. 12, all) of the period of the breathing cycle, the period of the inspiratory phase, the period of the expiratory phase, the peak inspiratory flow rate 908, the inspiratory: expiratory ratio, the peak expiratory flow rate 918, and the profile of the curved waveform 700 in one or more of the inspiratory phase 902 and expiratory phase 904.

[0306] The matched waveform 1200 of FIG. 12 may be produced by a second gas source 146 configured for uni-directional gas flow. Such a second gas source 146 may match or approximate the magnitude, if not the direction, of the first flow of gases. Hence the second flow of gases 170 in this example is an inversion of the first flow of gases 160 during the expiratory phase. For example, akin to a full-wave rectified form of an alternating current (AC) sine wave in the field of electrical and electronics engineering. Such a waveform may be referred to as a uni-directional approximation ofa bi-directional gas flow. In other examples, the second gas source 146 may be configured for bi-directional gas flow and may match or approximate both the magnitude and direction of the first flow of gases 160. In such examples, the waveform of the second flow of gases 170 may resemble the normal breathing waveform of FIG. 9.

[0307] FIG. 13 illustrates a ninth example of a time-varying flow rate profile in the form of a partially-matched waveform 1300.

[0308] The second gas source 146 in this example may be configured to match, or at least approximate, the waveform of the first flow of gases during the inspiratory phase only. The flow rate of the second flow of gases 170 may be zero, or a constant nonzero flow rate, throughout the expiratory phase.

[0309] In other examples, the second gas source 146 may be configured to match, or at least approximate, the waveform of the first flow of gases during the expiratory phase only. The flow rate of the second flow of gases 170 may be zero, or a constant nonzero flow rate, throughout the inspiratory phase.

[0310] As noted above, the waveform of the first flow of gases 160 may be determined by the first gas source 126, and won't necessarily resemble the normal breathing waveform of FIG. 9. To illustrate this, FIG. 13 and FIG. 14 illustrate alternative flow rate waveforms which may be provided by the first gas source 126 and a second gas source configured to provide a matched waveform.

[0311] FIG. 14 illustrates the flow waveform of the first flow of gases 160 provided by a first gas source 126 operating in volume control ventilation (VCV) mode, and the corresponding matched waveform 1400 of the second flow of gases 170 provided by the second gas source 146. As in FIG. 12, the second flow of gases 170 may be a unidirectional approximation of the bi-directional first flow of gases 160.

[0312] As shown in FIG. 14, the matched waveform 1400 may comprise a first flow rate during the inspiratory phase and a variable flow rate 1404 during the expiratory phase. The first flow rate may be constant or near-constant throughout the inspiratory phase. The variable flow rate 1404 may decrease throughout the expiratory phase, e.g., in an exponential decay. The flow rate of the second flow of gases 170 may increase rapidly between the inspiratory phase and the expiratory phase, and / or between the expiratory phase and the inspiratory phase.

[0313] The matched waveform 1400 may alternatively be referred to as a volume controlled ventilation waveform.

[0314] FIG. 15 illustrates the flow waveform of the first flow of gases 160 provided by a first gas source 126 operating in pressure control ventilation (PCV) mode, and the corresponding matched waveform 1500 of the second flow of gases 170 provided by the second gas source 146. As in FIG. 12 and FIG. 14, the second flow of gases 170 may be a uni-directional approximation of the bi-directional first flow of gases 160.

[0315] As shown in FIG. 15, the matched waveform 1500 may comprise a first variable flow rate 1502 during the inspiratory phase and a second variable flow rate 1504 during the expiratory phase. The first variable flow rate 1502 may be curved, increasing towards a peak inspiratory flow rate, then decreasing towards zero. At least part of the first variable flow rate 1502 may be approximately parabolic. An end portion of the first variable flow rate 1502 may decrease gradually, e.g., in an exponential decay. The second variable flow rate 1504 may decrease throughout the expiratory phase, e.g., in an exponential decay. The flow rate of the second flow of gases 170 may increase rapidly between the inspiratory phase and the expiratory phase.

[0316] The matched waveform 1500 may alternatively be referred to as a pressure controlled ventilation waveform.

[0317] In respiratory support systems in which the second flow of gases 170 is controlled based at least in part upon the first flow of gases 160, e.g., as described above with reference to FIG. 10 to FIG. 12, the second gas source 146 may communicate with the first gas source 126. In some examples, the second gas source 146 may receive an indication of the mode of operation of the first gas source 126. For example, VCV, PCV, PSV, SIMV, ACV, CPAP, BPAP, ASV, or HFOV. The second gas source 146 may select a flow profile appropriate for that mode of operation.

[0318] In some examples, the second gas source 146 may alternatively or additionally receive more information on the first flow of gases 160 from the first gas source 126, such as one or more of the flow rate, pressure, interval, period, frequency, respiratory rate, amplitude, inspiratory: expiratory ratio, and / or inspiration trigger.

[0319] In some examples, the second gas source 146 may alternatively or additionally receive information on the first flow of gases 160 from one or more sensors external to the first gas source 126 and / or the second gas source 146. For example, from one or more of:• a pressure and / or flow sensor of the first humidifier,• a pressure and / or flow sensor of the first breathing circuit 130 (e.g., the inspiratory limb 132, expiratory limb 134, first interface conduit 136, catheter mount, or first patient interface),• a patient sensor, e.g. :o a diaphragm electrical activity (Edi) sensor,o an electrical impedance tomography (EIT) sensor,o an impedance pneumography sensor,o a respiratory inductive plethysmography (RIP) sensor,o a capnography sensor,o a respiratory inductance band,o an accelerometer,o a bed or under-mattress sensor,o an ultrasound sensor, oro an optical sensor.

[0320] The information on the first flow of gases 160 may permit the second gas source 146 to control the second flow of gases 170 to match or approximate the first flow of gases 160. The flow rate of the second flow of gases 170 may be proportional to that of the first flow of gases 160. In some examples, the flow rate of the second flow of gases 170 may be controlled to be between about 50% and 200%, e.g., about 100%, of the flow rate of the first flow of gases 160.

[0321] In one example, the second gas source 146 may initially receive information on the ventilator mode, e.g. from communication with the ventilator or input by a clinician. Information from a pressure sensor may then be used to determine when the breathing cycle changes between the inspiratory phase and the expiratory phase.

[0322] The temperature of the second flow of gases 170 may controlled by one or more of the optional heated delivery conduit, heated second interface conduit, and second humidifier as described above with reference to FIG. 1. The humidity of the second flow of gases 170 may be controlled by at least the optional second humidifier.

[0323] In some examples, the temperature may be independent of the first flow of gases and the time-varying flow rate profile of the second flow of gases. The temperature may be controlled to be constant. For example, a constant temperature within the range of between about 20 degrees Celsius (°C) and 27 °C, between about 21 °C and 34 °C, between about 27 °C and 31 °C, between about 27 °C and 31 °C, or between about 34 °C and 37 °C.

[0324] In other examples, the temperature may vary, e.g., dependent on the first flow of gases or the second flow of gases. For example, based on the phase of the breathing cycle.

[0325] The humidity of the first flow of gases may be similarly independent or dependent, constant or variable.

[0326] Approximating the homeostatic conditions of the upper respiratory tract of a healthy and comfortable human may provide therapeutic benefits for the patient. Ambient air breathed in during the inspiratory phase is normally at ambient conditions. Air that is exhaled has normally been warmed and humidified by the upper respiratory tract.

[0327] Accordingly, it may be beneficial to vary one or more of the temperature and humidity of the second flow of gases 170. In some examples, the aeration system 140 may alternate between providing the second flow of gases at one or more of a first temperature and a first humidity for a first interval, and one or more of a second temperature and a second humidity for a second interval. The first temperature may be lower than the second temperature, e.g., about 21 °C and 31 °C, respectively. The first humidity may be lower than the second humidity, e.g., about 50 % and 80 % relative humidity, respectively. The first interval may be controlled to coincide with the inspiratory phase of the first gas source 126. The second interval may be controlled to coincide with the expiratory phase of the first gas source 126.

[0328] In some examples, the temperature and / or humidity of the second flow of gases 170 may be controlled to about 37 °C and 100 % relative humidity at the onset of the expiratory phase. The temperature and / or humidity may decrease in over a remainder of the expiratory phase. This may mimic the normal temperature / humidity profile of an exhaled breath of a healthy human. The temperature and humidity may be substantially constant throughout the inspiratory phase. This may mimic ambient conditions (e.g., 21 °C and 50 % relative humidity) and / or the normal temperature / humidity profile of an inspired breath of a healthy human.

[0329] In other examples, the temperature of the second flow of gases 170 may be varied over longer time periods. For example, the temperature may oscillate between the first temperature and the second temperature with a period of between about 15 minutes and 2 hours.

[0330] The second gas source 146 may be configured to control the composition of the second flow of gases 170 supplied to the patient. In some examples, the second gas source 146 may be configured to maintain a substantially constant composition of the second flow of gases 170. In other examples, the second gas source 146 may be configured to vary the composition of the second flow of gases 170 over time.

[0331] In some examples, the second gas source 146 may be configured to coordinate a variation in the composition of the second flow of gases 170 with the breathing cycle of the first flow of gases 160. In some examples, the second gas source 146 may be configured to vary the composition of the second flow of gases 170 between theinspiratory phase and the expiratory phase of each breathing cycle. In some examples, the second gas source 146 may be configured to vary the composition of the second flow of gases 170 within one or more of the inspiratory phase and the expiratory phase of a single, or each, breathing cycle. For example, the second gas source 146 may be configured to ramp up the proportion of carbon dioxide (CO2) within an expiratory phase, or each expiratory phase, which may mimic homeostasis.

[0332] In some examples, the second gas source 146 may be configured to vary the composition of the second flow of gases 170 over longer time periods (i.e., longer than the breathing cycle period).

[0333] In some examples, the second gas source 146 may be configured to control or vary the proportion of oxygen (O2) in the second flow of gases 170. The second gas source 146 may comprise a supplementary gas inlet to receive supplementary O2, e.g., from a compressed gas cylinder or an oxygen concentrator. In other examples, the second gas source 146 may receive an alternative gas, e.g., CO2 or an inert gas such as nitrogen (N2), to dilute the concentration of O2 (and / or other gases) in the second flow of gases 170.

[0334] In some examples, the proportion of O2 may vary over time, e.g., within each breathing cycle. For example, the proportion of O2 may be higher during the inspiratory phase than during the expiratory phase. Or the proportion of O2 may alternate between two different levels at predetermined intervals, e.g., based on inputs from medical personnel.

[0335] In some examples, the proportion of O2 in the second flow of gases 170 may depend on, e.g., correspond to, the proportion of O2 of the first flow of gases 160. In other examples, the proportion of O2 may be independent of the first flow of gases 160, e.g., alternating between two different levels at predetermined intervals, e.g., based on inputs from medical personnel.

[0336] In some examples, the second gas source 146 may be configured to control or vary the proportion of O2 in the second flow of gases 170 to between about 10% and 21%, or between about 17% and 18%. In some examples, the second gas source 146 may be configured to control the proportion of O2 in the second flow of gases 170, e.g., during an inspiratory phase, to between about 18% and 21%, e.g., about 21%. In some examples, the second gas source 146 may be configured to control the proportion of O2 in the second flow of gases 170 of gases, e.g., during an expiratory phase, to between about 10% and 16%. In other examples, the proportion of O2 in the second flow of gases 170 may be higher than ambient air, e.g., higher than about 21% O2.

[0337] In some examples, the second gas source 146 may be configured to control or vary the proportion of carbon dioxide (CO2) in the second flow of gases 170. The second gas source 146 may comprise a supplementary gas inlet to receive supplementary CO2, e.g., from a compressed gas cylinder. In other examples, the second gas source 146 may receive an alternative gas, e.g., O2 or N2, to dilute the concentration of CO2 in the second flow of gases 170.

[0338] In some examples, the proportion of CO2 may vary over time, e.g., within each breathing cycle. For example, the proportion of CO2 may be higher during the expiratory phase than during the inspiratory phase of the first gas source 126. Or the proportion of CO2 may alternate between two different levels at predetermined intervals, e.g., based on inputs from medical personnel.

[0339] In some examples, the proportion of carbon dioxide (CO2) in the second flow of gases 170 may be higher than ambient air, which may be about 0.04 % CO2. The proportion of CO2 may be similar to, or higher than, that of gases expired by a healthy human, e.g., about 4 % CO2. The second flow of gases 170 may comprise between about 0.04 % and 6 % CO2, or between about 0.1 % and 4 % CO2, e.g., about 0.4% CO2.

[0340] In some examples, the second gas source 146 may be configured to control the proportion of CO2 in the second flow of gases 170, e.g., during the expiratory phase, to between about 0.04% and 6%, or between about 2% and 4%, or between about 2% and 3%. In some examples, the second gas source 146 may be configured to control the proportion of CO2 in the second flow of gases 170, e.g., during the inspiratory phase, to between about 0% and 4%, or between about 0% and 1%, e.g., about 0.4%.

[0341] In some examples, the second gas source 146 may be configured to ramp up the proportion of CO2 within part of each breathing cycle, e.g., during an expiratory phase of the first flow of gases 160, which may mimic homeostasis.

[0342] In some examples, the second gas source 146 may alternatively or additionally be configured to control or vary one or more other supplementary gases, e.g., heliox, nitric oxide, and odorants, in a similar manner. For example, varying the concentration within each breathing cycle, e.g., between the inspiratory phase and the expiratory phase.

[0343] A mixture of gases may be provided which approximates the composition of an exhaled breath, for example comprising about 4 % CO2 and about 16 % O2.

[0344] Controlling or varying the composition of the second flow of gases 170, e.g., within each breathing cycle, may at least in part restore homeostasis or provideother therapeutic benefits to the patient. Relatively lower proportions of O2 (e.g., less than about 21%, less than about 19%, or less than about 17%) and / or relatively higher proportions of CO2 (e.g., greater than about 0.04%, greater than about 0.1%, greater than about 0.5%, greater than about 1%, greater than about 2%, greater than about 3%, or greater than about 4%) in the second flow of gases 170, e.g., with respect to ambient air, may favor one or more of anaerobic and capnophilic bacteria that are commensal to the patient and / or associated with normal respiratory flora.

[0345] In some examples, therapeutic agents may be added to the second flow of gases 170. For example, the aeration system 140 may comprise a nebulizer configured to dispense a nebulized substance into the second flow of gases. It may be beneficial to nebulize an agent, such as menthol, making the patient more sensitive to temperature, for example. In some examples, the nebulizer may be located downstream of the second humidifier and / or the second gas source 146, e.g., between an outlet of the second gas source 146 and an inlet of the delivery conduit 152. In other examples, the nebulizer may be located upstream of the second humidifier, directly into the humidifier chamber of the second humidifier, or proximal the patient. The nebulized substance may be dispensed into the second flow of gases at the start of therapy, periodically, and / or continuously throughout the therapy.

[0346] As a variation on the periodic profiles illustrated in FIGs. 4-15, the aeration system 140, e.g., second gas source 146, may be configured to periodically or intermittently provide an augmented cycle.

[0347] During an augmented cycle, one or more of a peak flow rate, peak inspiratory flow rate, peak expiratory flow rate, breathing cycle period, inspiratory phase duration, expiratory phase duration, and inspiratory: expiratory ratio, may vary from that of a normal cycle (e.g., the time-varying flow rate profile of any one of FIGs. 4-15). For example, varying with respect to the immediately-preceding cycle, or a weighted average of preceding cycles.

[0348] In some examples, the augmented cycle may comprise a peak flow rate of between about 200% and 400%, between about 250% and 350%, or between about 275% and 325%, e.g., about 300%, of the peak flow rate of a normal cycle 1602.

[0349] In some examples, the augmented cycle may comprise a duration of between about 150% and 250%, or between about 175% and 225%, e.g., about 200%, of the period of a normal cycle 1602.

[0350] In some examples, the second gas source 146 may be configured to provide an augmented cycle between about 1 and 20 times per hour, or between about 1 and 10 times per hour. In some examples, the frequency of the augmented cycles may vary,e.g., dependent on the state of the patient or respiratory support. The frequency may be higher during weaning than during deep sedation. The frequency may be higher during lighter sedation than during deeper sedation. The frequency of the augmented cycle may correspond to typical rates of sighing for a healthy human when awake and asleep, respectively. In one example, the second gas source 146 may be configured to provide an augmented cycle about 10 times per hour during lighter sedation, and / or about 1 time per hour during deeper sedation.

[0351] The aeration system 140, e.g., second gas source 146, may be configured to provide a single augmented cycle before reverting to a normal cycle.

[0352] FIG. 16 illustrates a single augmented cycle 1604 following a normal cycle 1602, e.g., comprising the matched waveform 1500 of FIG. 15. In FIG. 16, the augmented cycle 1604 is shown immediately followed by two further normal cycles 1602.

[0353] In some examples, as shown in FIG. 16, the profile of the augmented cycle 1604 may be scaled from the profile of the normal cycles 1602, e.g., in one or more of magnitude and duration. That is, the general waveform shape and features of the profiles of the normal cycle and the augmented cycle may be the same. In other examples, the profiles of the normal cycles 1602 and the augmented cycle 1604 may differ.

[0354] The augmented cycle may mimic a "sighing breath" of a healthy human. The augmented cycle may provide physiological benefits to the patient and may aid in restoring homeostasis during mechanical ventilation.

[0355] FIG. 17 illustrates an example architecture of the aeration system 140 and second gas source 146 in block diagram form. The aeration system 140 may include the second gas source 146, delivery conduit 152, and nasal cannula 142. Other modules or elements may be present.

[0356] An example second gas source 146 will be described with reference to FIG. 17 to FIG. 24. This is intended as a non-limiting example of an aeration device in accordance with the present technology. For example, the disclosed example of the second gas source 146 utilizes a blower configured to generate the second flow of gases 170 from ambient air. In other examples, the second gas source may comprise an inlet configured to use a hospital wall supply of gases. For example, the second gas source may receive gases from an in-wall ("piped") supply of pressurized gases, and a pressure and / or flow regulator, e.g., a proportional valve, to provide the second flow of gases 170 as described above.

[0357] Referring to FIG. 17, the second gas source 146 may be configured or operable to provide aeration to at least an upper respiratory tract of the patient via the delivery conduit 152 and the nasal cannula 142. The second gas source 146 may be configured to be supported on a support stand.

[0358] The second gas source 146 may be configured to provide nasal high flow (NHF). It will be appreciated that the components, methods, and processes described herein may be applied to other aeration devices and / or to other modes of operation delivered by such a device. When providing such aeration, the patient interface used may be a sealing patient interface, for example.

[0359] The second gas source 146 may be an integrated apparatus including a plurality of components in a single housing, or a discrete component-based arrangement where the components are separate but connected together. For example, the single housing may at least partially enclose both the second gas source 146 and the second humidifier. The humidifier chamber may be external from the housing or removable from the housing for filling, cleaning, or replacement, for example.

[0360] With reference to FIG. 17, the second gas source 146 may include a flow generator 1700 and a humidifier 1702. In some examples, as shown in FIG. 20 to FIG.24, the flow generator 1700 and humidifier 1702 may be part of an integrated second gas source 146, e.g., sharing a common housing 2002. In other examples, the second gas source 146 could be a modular arrangement of discrete components, with the flow generator 1700 and humidifier 1702 being separate modules that can be connected together.

[0361] The second gas source 146 may include an inlet module 1704 for providing gases such as air, oxygen (O2), carbon dioxide (CO2), one or more other supplemental gases, or a mix or two or more of the foregoing gases to the flow generator 1700. The inlet module 1704 may include one or more inlets for receiving flows of (or drawing in) ambient and / or pressurized air, oxygen, carbon dioxide, and / or other gases. For example, with reference to FIG. 18, in some examples the inlet module 1704 may include an ambient air inlet 1802, low-pressure gas inlet 1804, and / or high-pressure gas inlet 1806. A greater or lesser number of inlets may be provided in other examples. Some or all of the inlets may include connectors (such as ports, terminals, couplers, and the like) for establishing pneumatic connections to the sources of the gases. The inlet module 1704 may be considered to form part of the flow generator 1700, the second gas source 146, or it may be a separate, modular component, depending on the context.

[0362] With reference to FIG. 18, a filter or multiple filters may be provided as part of the inlet module 1704, at or immediately downstream of the ambient air inlet 1802, thelow-pressure gas inlet 1804, and / or the high-pressure gas inlet 1806. There may be a single filter 1816 positioned at the inlet or inlets to blower 1708 to filter particulates and pathogens carried with the incoming gases before they reach the blower 1708. Additionally, or alternatively, there may be individual filters positioned at each of the gas inlets 1802, 1804, 1806. In some examples, the filter 1808 may be provided between the high-pressure gas inlet 1806, at or upstream of the proportional valve 1810, in addition to a filter 1816 positioned at the inlet or inlets to the blower 1708, downstream of the proportional valve 1810 and the inlets 1802, 1804.

[0363] The aeration system 140 may include a combination of components or modules selected from the following:• a flow generator 1700, including an inlet module 1704, including one or more gas source inlets and their respective connectors (if applicable), a filter or filter module 1816, and a blower / sensor module 1706,• non-return valve (NRV) 1714,• a humidifier 1702 for humidifying the gases flow,• a delivery conduit 152, and / or• a nasal cannula 142.

[0364] The gas sources connected to the inlet module 1704 or inlets of the inlet module may include an in-wall ('piped') supply of supplementary gas (e.g., oxygen or carbon dioxide) or mixture of gases, a tank of supplementary gases, and / or a gas flow source such as an oxygen concentrator. The gas sources may provide the respective gas or gases at low or high pressures and / or low or high flow rates. In some examples, one or more of the gas sources may include a shut-off valve and / or regulator or other flow or pressure control mechanism which may be manually adjustable by a user. For example, one of the gas sources may be pressurized gas cylinder connected to the high-pressure gas inlet 1806 via a regulator and shut-off valve.

[0365] The flow generator 1700 may include a blower / sensor module 1706. The blower / sensor module 1706 may include a blower 1708 that controls flows delivered to the patient via the delivery conduit 152 and nasal cannula 142. The blower 1708 may be a centrifugal blower, including at least a motor and impeller or fan that is driven by the motor. Other types of blowers may be employed, such as axial blowers. The flow rate and / or pressure of flows of gases being output by the flow generator 1700 can be controlled by varying the output of the blower 1708, for example by varying the rotational speed of the motor driving the impeller or fan. The flow generator 1700 may be configured to provide flows of gases at high flow rates. Examples of high flow rates are described below.

[0366] The blower / sensor module 1706 may include a sensor module 1712. With reference to FIG. 17, in some examples the sensor module 1712 may be positioned downstream of the blower 1708 (i.e., an inlet of the sensor module 1712 may be pneumatically connected to the outlet of the blower 1708). In other examples, the sensor module 1712 may be positioned upstream of the blower 1708. The sensor module 1712 may be located upstream of the humidifier 1702.

[0367] One or more sensors (for example, Hall effect sensors) may be used to measure a motor speed of the blower motor.

[0368] Positioning sensors (e.g., flow rate, pressure, oxygen fraction, and / or other types of sensors in the sensor module 1712) downstream of the blower 1708 may increase accuracy of measurements, such as the measurement of fractional gas concentrations, including oxygen fraction, over systems that position the sensors upstream of the blower 1708 and / or a mixer. Positioning these sensors at a location further along the flow pathway, after the flow of gases has been more mixed (and may therefore be more homogeneous), may yield more consistent and / or repeatable measurements.

[0369] In some examples of the second gas source 146, a non-return valve (NRV) 1714 may be located downstream of the blower 1708 or blower / sensor module 1706. And upstream of the flow generator outlet 1716 and / or the inlet to humidifier chamber 1718. The NRV 1714 may be positioned within the flow generator outlet 1716. The NRV 1714 may inhibit or prevent backflow of gases, aerosols, and / or liquids into the flow generator 1700 via the humidifier 1702. During the provision of aeration, some flows of gases may travel up the delivery conduit 152, back into the humidifier 1702 and potentially reaching the flow generator or displacing other gases that then travel into the humidifier and / or flow generator. These flows of gases may carry pathogens which could contaminate the flow generator. In addition, the flows of gases may transport water vapor (especially if returning via the humidifier 1702) which, over time, may damage the internal hardware of the flow generator if backflow is allowed to occur.

[0370] A humidifier 1702 may be provided between the flow generator 1700 and the device outlet 1720 and / or delivery conduit 152 to humidify the flow of gases being output by the flow generator 1700. Humidification may be particularly useful where high flow rates of otherwise dry gases are delivered to the patient, as it may improve the toleration and comfort. Increasing the humidity of the gases to or closer to the natural levels in a healthy patient (e.g., 370C dew point) may help to maintain the condition of the respiratory tract, mitigating or preventing drying-out or other effects which may cause discomfort and adverse health outcomes. In some examples thehumidifier 1702 may be optional, in which case the second gas source 146 may provide non-humidified gases from the flow generator 1700 to the patient.

[0371] The humidifier 1702 may be a heated humidifier, wherein the humidifier includes at least one heating element. The humidifier 1702 may be a heated pass-over humidifier. A heated pass-over humidifier typically includes a heater plate 1736, a heating element 1738 arranged and configured to heat the heater plate 1736, and a humidifier chamber 1718 including a heat-conductive base that is in close contact with the heater plate 1736 when in use. The humidifier chamber 1718 may be at least partially filled with water when in use. The heat-conductive base will transfer heat from the heater plate to the water, thereby causing controlled evaporation of the water to increase the humidity of a gases flow travelling through the chamber.

[0372] The nasal cannula 142 may be a non-sealing patient interface such as a nasal cannula. The term 'non-sealing' as used when referring to patient interfaces may be defined as a patient interface having elements that do not completely seal a respiratory passage of the user from the outside environment. For example, a nasal prong of a non-sealing nasal cannula may ideally occlude 80% or less of a user's naris. Non-sealing patient interfaces may help to inhibit or prevent barotrauma (e.g., tissue damage to the respiratory tract and / or lungs due to differences in pressure relative to standard atmospheric pressure).

[0373] Various sensors configured to detect or measure properties or parameters of the aeration system 140 and / or the flow of gases may be disposed at one or more locations throughout the aeration system 140.

[0374] In some examples, the aeration system 140 may include one or more, and optionally all, of:• sensor 1814 at the ambient air inlet 1802 (e.g., a pressure, flow, temperature, and / or humidity (relative and / or absolute) sensor),• sensor 1812 at or optionally downstream of the high-pressure gas inlet 1806 (e.g., a pressure and / or a flow sensor),• sensor 1818 downstream of the proportional valve 1810 (e.g., a pressure and / or a flow sensor),• sensor 1710 at the blower 1708, optionally proximal to the stator windings of the motor driving the blower (e.g., a temperature and / or a motor speed sensor), • sensor 1740 at the heating element 1738, or proximal to the heater plate 1736 (e.g., a temperature sensor),• sensor 1722 downstream of the device outlet 1720 (e.g., a temperature sensor), or• sensor 1724 at a patient end of the delivery conduit 152 (e.g., a temperature sensor).

[0375] One or more of the sensors 1814, 1812, 1818, 1710, 1740, 1722, 1724 may each include multiple sensors. The multiple sensors may be part of a single package or separate, discrete sensors, or a combination of integrated sensor modules and discrete components.

[0376] Additional sensors may be provided as part of or within the sensor module 1712. The sensor module 1712 may be configured to measure properties of the gases flow travelling from the blower 1708 through to flow generator outlet 1716 and beyond. For example, the sensor module 1712 may include a sensor or sensors to detect the flow rate, oxygen concentration, pressure, temperature, and / or humidity of the flow of gases.

[0377] In addition to the sensors described above, various other sensors may be provided in and throughout the aeration system 140. The sensors may be configured to detect, measure, and / or determine flow rate, pressure, temperature, humidity (e.g., relative and / or absolute humidity), oxygen concentration / fraction, and / or motor speed. Other sensors can be placed throughout the system and / or at, on or near the patient — for example, a pulse oximetry sensor 1742 may be attached to the patient and coupled to the controller 1728 via a pulse oximeter. Alternatively, or additionally, sensors from which the above parameters can be derived could be used.

[0378] Some or all of the sensors listed above may be electrically and / or communicatively connected to a controller 1728. The connection may be direct or indirect — e.g., via signal conditioning circuits, driver circuits, another controller, and / or other types of circuit. The connection(s) may be wired or wireless.

[0379] The controller 1728 may be a microprocessor, a microcontroller, a programmable logic device (such as a complex programmable logic device (CPLD) or field-programmable gate array (FPGA)), a digital signal processor (DSP), an applicationspecific integrated circuit (ASIC), or other suitable form of device, and may not necessarily be implemented in a single monolithic integrated circuit (IC) but may include additional discrete electrical and / or electronic components. The controller 1728 may include a single device or multiple devices and components. For example, the controller 1728 may include multiple microprocessors or microcontrollers.

[0380] The controller can include programming instructions for detection of input conditions and control of output conditions. The programming instructions can be stored in a memory of, or associated, with the controller 1728. The programming instructions may correspond to the methods, processes and functions described herein. Theprogramming instructions can be executed by one or more processors of the controller 1728. The programming instructions can be implemented in C, C+ + , Java, or any other suitable programming languages or combinations thereof. Some or all of the portions of the programming instructions can be implemented in application specific circuitry such as ASICs and FPGAs.

[0381] In some examples, the outputs from at least some or all of the sensors described above are sent to the controller 1728 to assist the control of the aeration system 140 and its constituent components or modules (e.g., the blower 1708, heating element 1738, delivery conduit 152, display 8i I / O 1732, and other modules). The controller 1728 may be coupled to one or more of: the proportional valve 1810, blower 1708, humidifier heating element 1738, and / or a heated delivery conduit 152. In some examples, the controller 1728 controls at least these and other parts of the aeration system 140 as described herein. 'Control' as referred to herein may involve direct control of components (i.e., by signals output from the controller 1728) or indirect control via signal conditioning circuits or drivers / driving circuits (such as metal-oxide-semiconductor field-effect transistor (MOSFET) gate drivers or motor drivers), for example.

[0382] In some examples, the controller 1728 can operate the blower 1708 and / or the proportional valve 1810 to provide a flow of gas at a desired flow rate.

[0383] The controller 1728 may receive user input from a user interface of the display 8i I / O 1732. The user interface may include virtual and / or physical button(s) and / or dial(s). The user interface may include a touch-sensitive screen. The user input may include one or more of a target flow rate, pressure, oxygen fraction (e.g., fraction of delivered oxygen, FdO2), mode (high flow, CPAP, etc.), alarm thresholds, and / or other parameters. The user can be a patient, healthcare professional, or others.

[0384] The controller 1728 may output information to a display 8i I / O 1732. The display 8i I / O 1732 may display warnings and / or other alerts. The display 8i I / O 1732 may be configured to display characteristics of sensed gases, or aeration parameters, for example, in real time or otherwise. The aeration parameters may include one or more of aeration time, flow rates, humidity levels, e.g., dew point, or pressures, for example.

[0385] FIG. 19 illustrates a block diagram of an example control system (which can be implemented on, by, or at least partially on or by the controller 1728 (and any other controllers or circuits described herein) that can detect patient and / or system conditions and control operation of the aeration system 140, including any gases source(s). The control system 1900 can determine and generate the output control signals 1924-1932based on one or more received inputs 1902-1922. The inputs 1902-1922 may correspond to sensor measurements and / or user inputs received by the controller 1728. The control system 1900 can receive one or more of pressure sensor inputs 1902, temperature sensor inputs 1904, flow rate sensor inputs 1906, motor speed sensor inputs 1908, gas fraction / concentration sensor inputs 1910, humidity sensor inputs 1912, pulse oximetry sensor inputs 1914 (for example, SpC and / or heart rate), stored or user parameter inputs 1916, duty cycle or pulse width modulation (PWM) duty inputs 1918, voltage inputs 1920, or current inputs 1922.

[0386] The second gas source 146 may include one or more communications modules 1730. The communications modules 1730 may enable data communications with one or more external devices or servers over a data or communication link or data network, whether wired, wireless or a combination thereof. In some examples, the second gas source 146 may include a wireless data transmitter, receiver, and / or transceiver to enable the controller 1728 to send and receive data signals in a wireless manner to / from external devices, including sensors (e.g., sensors affixed to a patient), patient monitoring systems, mobile phones or other devices, and / or remote servers. In one example, the one or more communications modules 1730 may include cellular (e.g., 3G, 4G, 5G, and / or 6G), Bluetooth™, and / or Wi-Fi™ modules. The one or more communications modules 1730 may include a singular module configured to perform communication using cellular, Bluetooth, and Wi-Fi technologies and protocols.

[0387] The one or more communications modules 1730 may deliver data to a remote patient management system (for example, implemented or located on a remote server) and / or enable remote control of the second gas source 146 or aeration system 140. The remote patient management system may include a single server, multiple servers, or multiple computing devices implemented in a cloud computing network. The communication may be two-way (bidirectional) communication between the second gas source 146 and the remote patient management system, and / or another remote system.

[0388] The one or more communications modules 1730 may allow the controller 1728 to wirelessly send information to another local device such as, for example, a user or patient's mobile phone, tablet, smartwatch, etc. The second gas source 146 may additionally, or alternatively, include a Near Field Communication (NFC) module to allow for local data transfer and / or data communication. In some examples, the second gas source 146 may transmit data over a wired or wireless connection to the local user or patient device, for example via universal serial bus (USB), Wi-Fi™, Bluetooth™, or NFC, and the user or patient device may then wirelessly transmit data to a remote server, such as the remote patient management system (for example, via the Internet).

[0389] Estimated, measured, or determined parameters that are generated or received by the second gas source 146 may be logged and / or transmitted via the one or more communications modules 1730 to a remote server. Usage information and selected aeration parameters may be transmitted. Aeration parameters — e.g., aeration time, flow rates, humidity levels, e.g., dew point, pressure, or other aeration parameters — may be transmitted, individually or together. In some examples, the second gas source 146 or the user or patient device may generate an index that includes or is based on aeration parameters and is transmitted by the second gas source 146 or the user or patient device to a remote server.

[0390] The remote patient management system may be implemented on a single server or a network of servers or a cloud computing system or other suitable architecture for operating a remote patient management system. The remote patient management system may include memory for storing received data and various software applications or services that can be executed to perform multiple functions. The remote patient management system may communicate information or instructions to the second gas source 146 at least in part dependent on the data received. For example, the nature of the data received may trigger the remote server (or a software application running on the remote server) to communicate an alert, alarm, or notification to the second gas source 146. The remote patient management system may store the received data for access by an authorized party such as a clinician, or the patient, or another authorized party. The remote patient management system may be configured to generate reports in response to a request from an authorized party. Aeration parameters may be included in the generated reports. The reports may include other data, e.g., respiratory rate, or device parameters such as flow rate(s), pressure(s), temperature(s), and / or humidity level(s).

[0391] With reference to FIG. 20 to FIG. 24, the second gas source 146 may include a housing 2002. The housing 2002 may house the inlet module 1704, blower / sensor module 1706, and the heater plate 1736 and heating element 1738 of the humidifier 1702. The controller 1728, communications modules 1730, display 8i I / O 1732, and peripherals ports 1734 may also be positioned within or on the housing 2002. In other examples, the humidifier 1702 may be a separate module with its own housing and therefore not enclosed by the housing 2002 of the second gas source 146.

[0392] The housing 2002 may include a housing upper chassis 2004 and a housing lower chassis 2006. The housing upper chassis 2004 may include a peripheral side wall 2102. The peripheral side wall 2102 may define a humidification chamber bay 2018 for receipt of the removable humidifier chamber 1718. The removable humidifier chamber 1718 may contain a suitable liquid for humidifying gases, such as water. A floor portion of the humidification chamber dock 2202 (hidden) can have a recess to receive a heaterarrangement such as a heater plate 1736 or other suitable heating arrangements(s) for heating liquid in the humidifier chamber 1718 during a humidification process.

[0393] The second gas source 146 may include an arrangement to enable the blower to deliver air, oxygen (or alternative auxiliary gases), or a suitable mixture thereof to the humidifier chamber 1718 and thereby to the patient. This arrangement can include an ambient air inlet in the peripheral side wall 2102 of the housing lower chassis 2006 of the housing 2002. Additionally, or alternatively, the ambient air inlet may be positioned in an underside / bottom wall 2106 of the housing 2002.

[0394] A filter cartridge can be positioned adjacent the ambient air inlet internally in the main housing and in communication with the blower 1708 to deliver filtered air and / or oxygen to the blower 1708 via an inlet port in the blower / sensor module 1706. The filter cartridge can include a filter 1816 configured to remove particulates (e.g., dust) and / or pathogens (e.g., viruses or bacteria) from the gases flow. The second gas source 146 can include a separate oxygen inlet port positioned adjacent one side of the housing 2002 or at a rear end thereof, the oxygen port 1806 being for receipt of oxygen from an oxygen source such as a tank or source of piped oxygen. The oxygen inlet port 1806 may be in fluid communication with a proportional valve 1810. The proportional valve 1810 can suitably be a solenoid valve that enables electronic control of the amount of oxygen that is added to the gases flow that is delivered to the humidifier chamber 1718.

[0395] With reference to FIG. 20 to FIG. 22, a device outlet 1720 may include an L-shaped removable elbow 2028. The removable elbow 2028 may include a patient outlet port 2108 for coupling to the delivery conduit 152 to deliver a flow of gases to a patient interface. The inlet to the removable elbow 2028 may extend at least substantially along the longitudinal axis 2022 while the outlet of the removable elbow 2028 (i.e., the patient outlet port 2108) may extend at least substantially along a vertical axis 2024. In other words, the patient outlet port 2108 may extend upwardly from the housing upper chassis 2004 of the second gas source 146 main housing 2002.

[0396] The patient outlet port 2108, gases inlet 2016 and gases outlet 2020 of the humidifier 1702 (or the inlet and outlet ports of the gases manifold 2014), device outlet 1720, and patient outlet port 2108 each or all can have soft seals such as O-ring seals or T-seals to provide a sealed gases passageway between the flow generator 1700, the humidifier chamber 1718, and the delivery conduit 152.

[0397] The housing upper chassis 2004 may include an upper surface section 2010. With reference to FIG. 20 and FIG. 21, the upper surface section 2010 may protrudeoutwardly from the housing upper chassis 2004, such that it may extend at least partially over the flow generator outlet 1716 and the inlet to the removable elbow 2028.

[0398] The housing upper chassis 2004 may include the display 8i I / O 1732. The display 8i I / O 1732 can include a user interface which may include a display screen and input devices such as mechanical buttons or dials, a touch screen (e.g., a touch-sensitive liquid crystal display (LCD) or light emitting diode (LED) screen), a combination of a touch screen and mechanical buttons or dials, or the like. In one example, the user interface of the display 8i I / O 1732 may include a separate display and / or touch screen that is not permanently integrated with the housing 2002 but may be communicatively connected to the apparatus in a wired or wireless fashion. The second gas source 146 may include a docking element for securing the separate display screen to the second gas source 146, e.g., the housing 2002.

[0399] With reference to FIG. 20 to FIG. 22, the second gas source 146 may include a display screen 2008 that may be part of the display 8i I / O 1732 (i.e., it may be the aforementioned display screen or touch-sensitive screen). The display screen 2008 can protrude from the housing 2002, for example, in an angled fashion. The angle of the display screen relative to a plane defined by the surface of the housing upper chassis 2004 may help to improve visibility and / or usability of the screen for users. For example, an angled display screen may be more easily viewed from a distance than a completely flat screen provided in the housing upper chassis 2004.

[0400] With reference to FIG. 17 and FIG. 20, a delivery conduit 152 can be coupled to a device outlet 1720 formed in or as part of the housing 2002 of the second gas source 146 at one end, and to a nasal cannula 142, such as a non-sealing interface (for example, a non-sealing nasal cannula) at another end.

[0401] The gases flow generated by the flow generator 1700 may be humidified before being delivered to the patient via the delivery conduit 152 and the nasal cannula 142. The controller 1728 can control the flow generator 1700 to generate a flow of gases at a desired flow rate, and / or one or more valves (such as proportional valve 1810) to control the mixing of air and oxygen, carbon dioxide, and / or other supplemental gases by the blower 1708. The controller 1728 may control a heating element 1738 in or associated with the humidifier 1702, if present, to heat the gases flow to a desired temperature that achieves a desired level of temperature and / or humidity for delivery to the patient. The delivery conduit 152 may be a heated conduit, including one or more conductors (i.e., heating elements) embedded within the walls of the supply conduit, which may be supplied with electrical current to heat the internal passageway(s) of the conduit. Alternatively, the heating element(s) may be attached to the interior surfaceof the delivery conduit 152, or even float within the interior of conduit. The power supplied to the heating elements can be controlled by the controller 1728.

[0402] The humidifier 1702 of the apparatus may be configured to increase the humidity of the gases flow by introducing water vapor to gases passing through the humidifier chamber 1718. Various humidifier configurations may be employed. In one example, the humidifier 1702 may include a removable humidifier chamber 1718 that is configured to contain one or more liquids. For example, the humidifier 1702 may be configured to allow the humidifier chamber 1718 to be partially or entirely removed or disconnected from the flow path and / or second gas source 146. The humidifier chamber may be removed for refilling, cleaning, replacement and / or repair. With reference to at least FIG. 20 to FIG. 22, in one example, the humidifier chamber 1718 may be received and retained by or within the humidification chamber bay 2018 of the second gas source 146, or may otherwise couple onto or within the housing 2002 of the second gas source 146.

[0403] With continued reference to at least FIG. 20 to FIG. 22, the humidifier chamber 1718 of the humidifier 1702 may include at least a gases inlet 2016 and a gases outlet 2020 to enable connection to the gases flow path of the second gas source 146, optionally via a gases manifold 2014 that connects between the flow generator outlet 1716 and humidifier gases inlet 2016, and the humidifier gases outlet 2020 and device outlet 1720. For example, the flow of gases from the device outlet 1720 of the flow generator 1700 is received into the humidifier chamber via its gases inlet and exits the humidifier chamber via its gases outlet 2020, after being heated and / or humidified.

[0404] The humidifier chamber 1718 may be configured to contain a volume of liquid, typically water. In operation, the liquid in the humidification chamber is controllably heated by one or more heaters (e.g., heater plate 1736) or heating elements (e.g., heating element 1738 of the heater plate 1736) associated with the humidifier 1702 to generate water vapor and thereby increase the humidity of the gases flowing through the humidifier chamber 1718.

[0405] In some examples, the humidifier 1702 may be a heated pass-over humidifier. In other examples, the humidifier may be a non-heated (i.e., cold) pass-over humidifier. In yet other examples, the humidifier may be a non-pass-over humidifier.

[0406] The second gas source 146 may be a nasal high flow (NHF) device.GLOSSARY

[0407] "Aerate" and "aeration" refer to providing a flow of gases within at least part of the upper respiratory tract of the patient. The flow of gases may include any gas orgases mixture. For example, any one or more of air, oxygen, carbon dioxide, heliox, or water vapor. The flow of gases may flow through, or circulate within, at least part of the upper respiratory tract, e.g., one or more of the nasal cavity, oral cavity, nasopharynx, oropharynx, or laryngopharynx. Aeration may advantageously mitigate or avoid stagnancy within the upper respiratory tract, and one or more of the associated adverse health outcomes.

[0408] "Gas" or "gases," unless the context clearly requires otherwise, are each intended to encompass both a single gas, e.g., pure oxygen, or a gas mixture, e.g., air (i.e., nitrogen, oxygen, argon, carbon dioxide, and trace amounts of other gases).

[0409] "Homeostasis" refers to the maintenance of a metabolic equilibrium within a patient by compensating for the disruption from invasive ventilation, e.g., by aerating the upper respiratory tract of the patient.

[0410] "Invasive patient interface" refers to a patient interface which is inserted into a patient's respiratory tract, e.g., the trachea or pharynx, and bypasses the upper respiratory tract, e.g., at least the nasal cavity and the oral cavity. The invasive patient interface may be fitted to a patient by intubation or a surgical procedure such as a tracheotomy. The invasive patient interface may include a cuff. The cuff may be configured to isolate at least part of the lower respiratory tract from at least part of the upper respiratory tract. Examples of invasive patient interfaces include, without limitation, an oral endotracheal tube, a nasal endotracheal tube, a tracheostomy tube, or a laryngeal mask.

[0411] "Isolate," "seal," "functionally separate" and similar terms refer to inhibiting, or some cases preventing, the unintended passage of fluids, e.g., a gas or a liquid. Such terms are not intended to imply that there is necessarily perfect isolation or perfect sealing, e.g., completely isolating the lower respiratory tract 112 from the upper respiratory tract 114. It is anticipated that there may be some unintended leakage. Moreover, in some contexts there may be an intentional "leak," as in the example of bias flow holes in a nasal face mask or full face mask for venting gases to ambient air. The term "sealing patient interface," for example, is not intended to exclude such patient interfaces.

[0412] "Lower respiratory tract" refers to the portion of the respiratory tract of an invasively ventilated patient below the cuff of the invasive patient interface. The lower respiratory tract may include a lower part of the trachea, bronchi, and lungs. If the invasive patient interface does not have a cuff, or is otherwise not configured to form a seal within the patient's respiratory tract, the "lower respiratory tract" refers to theportion of the respiratory tract that lies within the chest of the patient, including the trachea, bronchi, and lungs.

[0413] "Mechanical ventilator" refers to a medical device designed to provide ventilatory support to a patient by delivering a controlled flow of gases and pressure to a patient's respiratory tract via a patient interface. When the flow of gases is delivered to the lower respiratory tract of the patient, i.e., the lungs, the mechanical ventilator may provide respiratory support, assisting or replacing spontaneous breathing. When the flow of gases is delivered only to the upper respiratory tract, there may be other physiological benefits to the patient. The mechanical ventilator may be equipped with sensors, control systems, and safety mechanisms to regulate parameters such as tidal volume, respiratory rate, inspiratory and expiratory pressures, and oxygen concentration, ensuring precise and safe ventilation tailored to the patient's needs.

[0414] "Nasal high flow" (NHF) refers to a flow of humidified gases via an intentionally unsealed or non-sealing patient interface. Typical flow rates for adults often range from, but are not limited to, about 15 l / min to about 60 l / min or greater. Typical flow rates for pediatric users (such as neonates, infants, or children) often range from, but are not limited to, about 1 l / min per kilogram of user weight to about 3 l / min per kilogram of user weight or greater. For example, for an adult patient 'nasal high flow' may refer to the delivery of gases to a patient at a flow rate of greater than or equal to about 10 l / min, such as between about 10 l / min and about 100 l / min, or between about 15 l / min and about 95 l / min, or between about 20 l / min and about 90 l / min, or between about 25 l / min and about 85 l / min, or between about 30 l / min and about 80 l / min, or between about 35 l / min and about 75 l / min, or between about 40 l / min and about 70 l / min, or between about 45 l / min and about 65 l / min, or between about 50 l / min and about 60 l / min. For a neonatal, infant, or child patient 'nasal high flow' may refer to the delivery of gases to a patient at a flow rate of greater than 1 l / min, such as between about 1 l / min and about 25 l / min, or between about 2 l / min and about 25 l / min, or between about 2 l / min and about 5 l / min, or between about 5 l / min and about 25 l / min, or between about 5 l / min and about 10 l / min, or between about 10 l / min and about 25 l / min, or between about 10 l / min and about 20 l / min, or between about 10 l / min and 15 l / min, or between about 20 l / min and 25 l / min. A nasal high flow device with an adult patient, a neonatal, infant, or child patient, may deliver gases to the patient at a flow rate of between about 1 l / min and about 100 l / min, or at a flow rate in any of the sub-ranges outlined above. Nasal high flow can also optionally involve delivery of gas mixture compositions, e.g., including supplemental oxygen, carbon dioxide, or heliox, and / or administration of therapeutic medicaments.

[0415] "Non-invasive patient interface" refers to a patient interface which is external to the patient, or in some cases extends into the patient's nasal cavity or oral cavity,and supplies gases to the upper respiratory tract of the patient. The non-invasive patient interface may be fitted to a patient without the need for intubation or a surgical procedure such as a tracheotomy. Examples of non-invasive patient interfaces include, without limitation, a total face mask (sealing around the patient's eyes, nose, and mouth), a full face mask (sealing around the patient's nose and mouth), a nasal face mask (sealing around the patient's nose or nares), an oral face mask (sealing around the patient's mouth), an intraoral mask (extending and / or sealing within a patient's mouth), a nasal pillows interface, (sealing around and / or in each of the patient's nares), or a nasal cannula (extending into either or both of the patient's nares, in a sealing or non-sealing manner).

[0416] "Upper respiratory tract" refers to the portion of the respiratory tract of an invasively ventilated patient above the cuff of the invasive patient interface. The upper respiratory tract may include the nasal cavity, oral cavity, nasopharynx, oropharynx, and laryngopharynx. If the cuff is located within the trachea of the patient, the upper respiratory tract may also include an upper part of the trachea above the cuff. If the invasive patient interface does not have a cuff, or is otherwise not configured to form a seal within the patient's respiratory tract, the "upper respiratory tract" refers to the portion of the respiratory tract that is superior to the thorax of the patient, including the nasal cavity, oral cavity, pharynx, and larynx.

[0417] "Ventilate" or "ventilation," at least in the context of ventilating the lower respiratory tract of a patent, refers to the provision of a flow of gases to support respiration.

[0418] Anatomical terms such as "nasopharynx," "oropharynx," "laryngopharynx," "bronchi," and "nares" are referenced in accordance with the structures illustrated in Netter, F. H. (2022). Netter Atlas of Human Anatomy: A Systems Approach (8th ed., Enhanced Digital Version). Elsevier.

[0419] The terms "first," "second," and similar descriptors are employed for clarity to distinguish between comparable elements unless the context explicitly dictates otherwise. These terms do not imply a specific sequence or the necessity of another element. For instance, the term "second humidifier configured to heat and humidify the second flow of gases" does not inherently suggest the existence of a first humidifier, regardless of whether it is configured to heat the first flow of gases, the second flow of gases, or otherwise.

[0420] The expressions "one or more of," "at least one," and "and / or" are intended to denote any possible combination of the listed elements. For example, "one or more ofX, Y, or Z," is meant to cover scenarios such as a single X alone, two instances of X alone, the combination of X and Y, the combination of Y and X, and so forth.LISTING OF DRAWING ELEMENTS100 respiratory support system110 patient112 lower respiratory tract114 upper respiratory tract116 nares118 mouth120 ventilation system122 oral endotracheal tube124 cuff126 first gas source130 first breathing circuit132 inspiratory limb134 expiratory limb136 first interface conduit140 aeration system142 nasal cannula144 nasal prong146 second gas source150 second breathing circuit152 delivery conduit160 first flow of gases170 second flow of gases302 nasal cavity304 oral cavity306 nasopharynx308 oropharynx310 laryngopharynx312 trachea400 rectangular waveform402 first flow rate404 second flow rate406 first interval408 second interval410 period412 flow delta500 trapezoidal waveform02 first flow rate04 second flow rate06 first interval08 second interval10 period12 flow delta14 ramp period00 triangular waveform02 first interval04 second interval06 period08 first flow rate10 second flow rate12 flow delta00 curved waveform02 first flow rate704 second flow rate706 first interval708 second interval710 period712 flow delta800 piecewise sinusoidal waveform 802 first interval804 second interval806 period808 first amplitude810 second amplitude902 inspiratory phase904 expiratory phase906 breathing cycle908 peak inspiratory flow rate 910 initial portion912 end portion914 initial portion916 end portion918 peak expiratory flow rate 1000 bi-level waveform1002 first flow rate1004 second flow rate1100 bi-level waveform1200 matched waveform1300 partially-matched waveform 1400 matched waveform1402 first flow rate1404 variable flow rate1500 matched waveform1502 first variable flow rate 1504 second variable flow rate 1602 normal cycle1604 augmented cycle1700 flow generator1702 humidifier1704 inlet module1706 blower / sensor module 1708 blower1710 sensor1712 sensor module1714 NRV1716 flow generator outlet 1718 humidifier chamber 1720 device outlet1722 sensor1724 sensor1726 battery pack1728 controller1730 communications modules 1732 display & I / O1734 peripherals ports1736 heater plate1738 heating element1740 sensor1742 pulse oximetry sensor 1802 ambient air inlet1804 low-pressure gas inlet 1806 high-pressure gas inlet 1808 filter1810 proportional valve1812 sensor1814 sensor1816 filter1818 sensor1900 control system1902 pressure sensor inputs1904 temperature sensor inputs1906 flow rate sensor inputs1908 motor speed sensor inputs1910 gas fraction / concentration sensor inputs1912 humidity sensor inputs1914 pulse oximetry sensor inputs1916 user parameter inputs1918 PWM duty inputs1920 voltage inputs1922 current inputs1924 blower motor control outputs1926 proportional valve control outputs1928 heater plate control outputs1930 heated breathing tube control outputs1932 display & audio control outputs2002 housing2004 housing upper chassis2006 housing lower chassis2008 display screen2010 upper surface section2012 flow generator outlet2014 gases manifold2016 gases inlet2018 humidification chamber bay2020 gases outlet2022 longitudinal axis2024 vertical axis2026 lateral axis2028 removable elbow2102 peripheral side wall2104 feet2106 underside / bottom wall2108 patient outlet port2202 floor portion of the humidification chamber dock

Claims

CLAIMSWhat we claim is:

1. A respiratory support system for providing respiratory support to a patient, the respiratory support system comprising:a first gas source configured to provide a first flow of gases;a first patient interface configured to receive the first flow of gases from the first gas source for supply to at least part of a lower respiratory tract of the patient;a second gas source configured to provide a second flow of gases, the second gas source configured to control the second flow of gases to have a time-varying flow rate profile with a predetermined frequency; anda second patient interface configured to receive the second flow of gases from the second gas source for supply to at least part of an upper respiratory tract of the patient.

2. The respiratory support system of claim 1, wherein the time-varying flow rate profile is independent of the first flow of gases and the first gas source.

3. A respiratory support system for providing respiratory support to a patient, the respiratory support system comprising:a first gas source configured to provide a first flow of gases;a first patient interface configured to receive the first flow of gases from the first gas source for supply to at least part of a lower respiratory tract of the patient;a second gas source configured to provide a second flow of gases, the second gas source configured to control the second flow of gases to have a time-varying flow rate profile independent of the first flow of gases and the first gas source; anda second patient interface configured to receive the second flow of gases from the second gas source for supply to at least part of an upper respiratory tract of the patient.

4. The respiratory support system of claim 3, the time-varying flow rate profile comprising a predetermined frequency.

5. The respiratory support system of claim 1 or 4, wherein the predetermined frequency of the second gas source is different to a frequency of the first gas source.

6. The respiratory support system of any one of claims 1 to 5, the first gas source and the second gas source configured to operate asynchronously.

7. The respiratory support system of any one of claims 1 to 6, wherein the second gas source is configured to operate without communicating with the first gas source.

8. The respiratory support system of any one of claims 1 to 7, the time-varying flow rate profile comprising:a bi-level waveform,a rectangular waveform,a trapezoidal waveform,a square waveform,a triangular waveform,a sawtooth waveform,a curved waveform,a linear curved waveform,a sinusoidal waveform,a piecewise sinusoidal waveform,a non-linear curved waveform,a skewed waveform,an asymmetric waveform, ora normal breathing waveform.

9. A respiratory support system for providing respiratory support to a patient, the respiratory support system comprising:a first gas source configured to provide a first flow of gases;a first patient interface configured to receive the first flow of gases from the first gas source for supply to at least part of a lower respiratory tract of the patient;a second gas source configured to provide a second flow of gases, the second gas source configured to control the second flow of gases to have a time-varying flow rate profile based, at least in part, on the first flow of gases provided by the first gas source; anda second patient interface configured to receive the second flow of gases from the second gas source for supply to at least part of an upper respiratory tract of the patient.

10. The respiratory support system of claim 9, the time-varying flow rate profile comprising:a bi-level waveform,a matched waveform,a normal breathing waveform,a volume controlled ventilation waveform,a pressure controlled ventilation waveform, ora partially-matched waveform.

11. The respiratory support system of claim 9 or 10, the second gas source configured to operate at the same frequency as the first gas source.

12. The respiratory support system of any one of claims 9 to 11, the second gas source configured to operate synchronously with the first gas source.

13. The respiratory support system of any one of claims 9 to 12, the second gas source configured to alternate between providing the second flow of gases at a first flow rate and a second flow rate, wherein the first flow rate is different to the second flow rate.

14. The respiratory support system of claim 13, wherein the first flow rate is greater than the second flow rate.

15. The respiratory support system of claim 13 or 14, the second gas source configured to provide the second flow of gases at:the first flow rate for a portion of an inspiratory phase of the first gas source, andthe second flow rate for:another portion of the inspiratory phase of the first gas source, and at least a portion of an expiratory phase of the first gas source.

16. The respiratory support system of claim 15, the second gas source configured to provide the second flow of gases at the first flow rate for another portion of the expiratory phase of the first gas source.

17. The respiratory support system of any one of claims 13 to 16, the second gas source configured to provide the second flow of gases at the first flow rate to coincide with one or more of:a peak inspiratory flow rate of the first flow of gases, ora peak expiratory flow rate of the first flow of gases.

18. The respiratory support system of claim 17, the second gas source configured to begin providing the second flow of gases at the first flow rate in advance of one or more of:the peak inspiratory flow rate of the first flow of gases, orthe peak expiratory flow rate of the first flow of gases.

19. The respiratory support system of claim 17 or 18, the second gas source configured to continue providing the second flow of gases at the first flow rate beyond one or more of:the peak inspiratory flow rate of the first flow of gases, orthe peak expiratory flow rate of the first flow of gases.

20. The respiratory support system of any one of claims 9 to 19, the second gas source configured to provide the second flow of gases with a time-varying flow rate profile matching or approximating the first flow of gases for at least part of one or more of an inspiratory phase and an expiratory phase of the first gas source.

21. The respiratory support system of any one of claims 9 to 20, the first gas source configured to provide the first flow of gases as a bi-directional gas flow, and the second gas source configured to provide the second flow of gases as a uni-directional approximation of the first flow of gases.

22. The respiratory support system of any one of claims 9 to 21, the second gas source configured to communicate with the first gas source.

23. The respiratory support system of any one of claims 9 to 22, comprising a humidifier configured to heat and / or humidify the first flow of gases.

24. The respiratory support system of claim 23, the second gas source configured to communicate with the humidifier.

25. A respiratory support system for providing respiratory support to a patient, the respiratory support system comprising:a first gas source configured to provide a first flow of gases;a first patient interface configured to receive the first flow of gases from the first gas source for supply to at least part of a lower respiratory tract of the patient;a pressure sensor configured to sense a pressure of the first flow of gases; a second gas source configured to:receive a pressure signal from the pressure sensor;determine a baseline pressure of the first flow of gases based on the pressure signal;determine a phase of the first gas source based on the pressure signal and the baseline pressure; andprovide a second flow of gases comprising a time-varying flow rate profile synchronized with the first flow of gases; anda second patient interface configured to receive the second flow of gases from the second gas source for supply to at least part of an upper respiratory tract of the patient.

26. The respiratory support system of claim 25, the second gas source configured to smooth the pressure signal by applying a moving average.

27. The respiratory support system of claim 25 or 26, the second gas source configured to determine the baseline pressure based on an exponentially-weighted moving average of the pressure signal.

28. The respiratory support system of any one of claims 25 to 27, the second gas source configured to determine whether the first gas source is in:an inspiratory phase if the pressure signal is greater than the baseline pressure of the first flow of gases; and / oran expiratory phase if the pressure signal is less than the baseline pressure of the first flow of gases.

29. The respiratory support system of any one of claims 25 to 27, the second gas source configured to determine:a first threshold based on the baseline pressure;a second threshold based on the baseline pressure;whether the first gas source is in:an inspiratory phase if the pressure signal is greater than the first threshold; and / oran expiratory phase if the pressure signal is less than the baseline pressure.

30. The respiratory support system of any one of claims 1 to 29, comprising one or more of:a humidifier configured to heat and / or humidify the second flow of gases; and a heated conduit configured to heat the second flow of gases.

31. The respiratory support system of claim 30, the humidifier and / or the heated conduit configured to periodically vary one or more of a temperature and / or a humidity of the second flow of gases.

32. The respiratory support system of claim 30 or 31, the humidifier and / or the heated conduit configured to:alternate between heating the second flow of gases to a first temperature and a second temperature, wherein the second temperature is greater than the first temperature; and / oralternate between humidifying the second flow of gases to a first humidity and a second humidity, wherein the second humidity is greater than the first humidity.

33. The respiratory support system of claim 32, the humidifier and / or the heated conduit configured to:heat the second flow of gases to the first temperature during at least part of an inspiratory phase of the first gas source;heat the second flow of gases to the second temperature during at least part of an expiratory phase of the first gas source;humidify the second flow of gases to the first humidity during at least part of the inspiratory phase of the first gas source; and / orhumidify the second flow of gases to the second humidity during at least part of the expiratory phase of the first gas source.

34. The respiratory support system of any one of claims 1 to 33, the second gas source configured to vary, e.g., periodically vary, a composition of the second flow of gases.

35. The respiratory support system of claim 34, the second gas source configured to vary, e.g., periodically vary, a proportion of oxygen in the second flow of gases.

36. The respiratory support system of claim 34 or 35, the second gas source configured to vary, e.g., periodically vary, a proportion of carbon dioxide in the second flow of gases.

37. The respiratory support system of any one of claims 34 to 36, the second gas source configured to:alternate between providing the second flow of gases with a first proportion of oxygen and a second proportion of oxygen, wherein the first proportion of oxygen is greater than the second proportion of oxygen; and / oralternate between providing the second flow of gases with a first proportion of carbon dioxide and a second proportion of carbon dioxide, wherein the second proportion of carbon dioxide is greater than the first proportion of carbon dioxide.

38. The respiratory support system of claim 37, the second gas source configured to:provide the second flow of gases with the first proportion of oxygen during at least part of an inspiratory phase of the first gas source;provide the second flow of gases with the second proportion of oxygen during at least part of an expiratory phase of the first gas source;provide the second flow of gases with the first proportion of carbon dioxide during at least part of the inspiratory phase of the first gas source; and / orprovide the second flow of gases with the second proportion of carbon dioxide during at least part of the expiratory phase of the first gas source.

39. The respiratory support system of any one of claims 1 to 38, comprising a nebulizer configured to dispense a nebulized substance into the second flow of gases.

40. The respiratory support system of any one of claims 1 to 39, the first gas source comprising a mechanical ventilator.

41. The respiratory support system of any one of claims 1 to 40, the first patient interface comprising an invasive patient interface.

42. The respiratory support system of claim 41, the invasive patient interface comprising:an oral endotracheal tube,a nasal endotracheal tube,a tracheostomy tube, ora laryngeal mask.

43. The respiratory support system of any one of claims 1-24 or 30-42, the second gas source comprising a nasal high flow device.

44. The respiratory support system of any one of claims 1 to 43, the second patient interface comprising a nasal cannula.

45. The respiratory support system of claim 44, the nasal cannula comprising:a symmetric dual-prong nasal cannula,an asymmetric dual-prong nasal cannula, ora single-prong nasal cannula.

46. The respiratory support system of claim 44, the nasal cannula comprising a dualprong nasal cannula and the second gas source comprising:a first blower configured to provide a first portion of the second flow of gases to the patient via a left nasal prong of the dual-prong nasal cannula; anda second blower configured to provide a second portion of the second flow of gases to the patient via a right nasal prong of the dual-prong nasal cannula.

47. The respiratory support system of claim 46, the first blower and the second blower configured to provide the first portion of the second flow of gases and the second portion of the second flow of gases to the patient simultaneously.

48. The respiratory support system of claim 46, the first blower and the second blower configured to provide the first portion of the second flow of gases and the second portion of the second flow of gases to the patient alternately.

49. The respiratory support system of any one of claims 44 to 48, the second gas source and / or the nasal cannula configured, or configurable, to alternate between:providing a majority or an entirety of the second flow of gases to the patient via a left naris of the patient, andproviding the majority or the entirety of the second flow of gases to the patient via a right naris of the patient.

50. The respiratory support system of any one of claims 44 to 49, the nasal cannula comprising a dual-prong nasal cannula and the second gas source comprising:a first blower configured to provide a positive gas flow via a first nasal prong of the dual-prong nasal cannula; anda second blower configured to provide a negative gas flow via a second nasal prong of the dual-prong nasal cannula.

51. The respiratory support system of any one of claims 1 to 50, wherein the second gas source is pneumatically isolated from the first gas source.

52. The respiratory support system of any one of claims 1 to 51, the second gas source configured to intermittently provide an augmented cycle to the second flow of gases, the augmented cycle comprising one or more of a peak flow rate, a peak inspiratory flow rate, a peak expiratory flow rate, and a duration which is greater than that of one or more adjacent cycles of the second flow of gases.

53. An aeration device configured to provide a secondary flow of gases for aerating at least part of an upper respiratory tract of a patient simultaneously receiving mechanical ventilation from a primary flow of gases provided by a ventilator, the aeration device comprising:a flow generator configured to generate the secondary flow of gases, and a controller configured to control operation of the flow generator to generate the secondary flow of gases with a time-varying flow rate profile at a predetermined frequency.

54. The aeration device of claim 53, wherein the time-varying flow rate profile is independent of the primary flow of gases and the ventilator.

55. The aeration device of claim 53 or 54, wherein the predetermined frequency of the aeration device is different to a frequency of the ventilator.

56. The aeration device of any one of claims 53 to 55, the aeration device configured to operate asynchronously with the ventilator.

57. The aeration device of any one of claims 53 to 56, wherein the aeration device is configured to operate without communicating with the ventilator.

58. The aeration device of any one of claims 53 to 57, the time-varying flow rate profile comprising:a bi-level waveform,a rectangular waveform,a trapezoidal waveform,a square waveform,a triangular waveform,a sawtooth waveform,a curved waveform,a linear curved waveform,a sinusoidal waveform,a piecewise sinusoidal waveform,a non-linear curved waveform,a skewed waveform,an asymmetric waveform, ora normal breathing waveform.

59. An aeration device configured to provide a secondary flow of gases for aerating at least part of an upper respiratory tract of a patient simultaneously receiving mechanical ventilation from a primary flow of gases provided by a ventilator, the aeration device comprising:a flow generator configured to generate the secondary flow of gases, and a controller configured to control operation of the flow generator to generate the secondary flow of gases with a time-varying flow rate profile based, at least in part, on the primary flow of gases provided by the ventilator.

60. The aeration device of claim 59, the time-varying flow rate profile comprising: a bi-level waveform,a matched waveform,a normal breathing waveform,a volume controlled ventilation waveform,a pressure controlled ventilation waveform, ora partially-matched waveform.

61. The aeration device of claim 59 or 60, the aeration device configured to operate at the same frequency as the ventilator.

62. The aeration device of any one of claims 59 to 61, the aeration device configured to operate synchronously with the ventilator.

63. The aeration device of any one of claims 59 to 62, the aeration device configured to alternate between providing the secondary flow of gases at a first flow rate and a second flow rate, wherein the first flow rate is different to the second flow rate.

64. The aeration device of claim 63, wherein the first flow rate is greater than the second flow rate.

65. The aeration device of claim 63 or 64, the aeration device configured to provide the secondary flow of gases at:the first flow rate for a portion of an inspiratory phase of the ventilator, and the second flow rate for:another portion of the inspiratory phase of the ventilator, and at least a portion of an expiratory phase of the ventilator.

66. The aeration device of claim 65, the aeration device configured to provide the secondary flow of gases at the first flow rate for another portion of the expiratory phase of the ventilator.

67. The aeration device of any one of claims 63 to 65, the aeration device configured to provide the secondary flow of gases at the first flow rate to coincide with one or more of:a peak inspiratory flow rate of the primary flow of gases, ora peak expiratory flow rate of the primary flow of gases.

68. The aeration device of claim 67, the aeration device configured to begin providing the secondary flow of gases at the first flow rate in advance of one or more of:the peak inspiratory flow rate of the primary flow of gases, orthe peak expiratory flow rate of the primary flow of gases.

69. The aeration device of claim 67 or 68, the aeration device configured to continue providing the secondary flow of gases at the first flow rate beyond one or more of: the peak inspiratory flow rate of the primary flow of gases, orthe peak expiratory flow rate of the primary flow of gases.

70. The aeration device of any one of claims 59 to 69, the aeration device configured to provide the secondary flow of gases with a time-varying flow rate profile matching or approximating the primary flow of gases for at least part of one or more of an inspiratory phase and an expiratory phase of the ventilator.

71. The aeration device of any one of claims 59 to 70, the primary flow of gases comprising a bi-directional gas flow, and the aeration device configured to provide the secondary flow of gases as a uni-directional approximation of the bi-directional gas flow.

72. The aeration device of any one of claims 59 to 71, the aeration device configured to communicate with the ventilator.

73. The aeration device of any one of claims 59 to 72, the aeration device configured to communicate with a humidifier configured to heat and / or humidify the primary flow of gases.

74. An aeration device configured to provide a secondary flow of gases for aerating at least part of an upper respiratory tract of a patient simultaneously receiving mechanical ventilation from a primary flow of gases provided by a ventilator, the aeration device comprising:a flow generator configured to generate the secondary flow of gases;a pressure sensor configured to sense a pressure of the primary flow of gases; anda controller configured to:receive a pressure signal from the pressure sensor;determine a baseline pressure of the primary flow of gases based on the pressure signal;determine a phase of the ventilator based on the pressure signal and the baseline pressure; andcontrol the flow generator to generate the secondary flow of gases with a time-varying flow rate profile synchronized with the primary flow of gases.

75. The aeration device of claim 74, the controller configured to smooth the pressure signal by applying a moving average.

76. The aeration device of claim 74 or 75, the controller configured to determine the baseline pressure based on an exponentially-weighted moving average of the pressure signal.

77. The aeration device of any one of claims 74 to 76, the controller configured to determine whether the ventilator is in:an inspiratory phase if the pressure signal is greater than the baseline pressure of the primary flow of gases; and / oran expiratory phase if the pressure signal is less than the baseline pressure of the primary flow of gases.

78. The aeration device of any one of claims 74 to 76, the controller configured to determine:a first threshold based on the baseline pressure;a second threshold based on the baseline pressure;whether the ventilator is in:an inspiratory phase if the pressure signal is greater than the first threshold; and / oran expiratory phase if the pressure signal is less than the baseline pressure.

79. The aeration device of any one of claims 53 to 78, comprising one or more of: a humidifier configured to heat and / or humidify the secondary flow of gases; and a heated conduit configured to heat the secondary flow of gases.

80. The aeration device of claim 79, the humidifier and / or the heated conduit configured to periodically vary one or more of a temperature and / or a humidity of the secondary flow of gases.

81. The aeration device of claim 79 or 80, the humidifier and / or the heated conduit configured to:alternate between heating the secondary flow of gases to a first temperature and a second temperature, wherein the second temperature is greater than the first temperature; and / oralternate between humidifying the secondary flow of gases to a first humidity and a second humidity, wherein the second humidity is greater than the first humidity.

82. The aeration device of claim 81, the humidifier and / or the heated conduit configured to:heat the secondary flow of gases to the first temperature during at least part of an inspiratory phase of the ventilator;heat the secondary flow of gases to the second temperature during at least part of an expiratory phase of the ventilator;humidify the secondary flow of gases to the first humidity during at least part of the inspiratory phase of the ventilator; and / orhumidify the secondary flow of gases to the second humidity during at least part of the expiratory phase of the ventilator.

83. The aeration device of any one of claims 53 to 82, the controller configured to control operation of the flow generator to vary, e.g., periodically vary, a composition of the secondary flow of gases.

84. The aeration device of claim 83, the controller configured to control operation of the flow generator to vary, e.g., periodically vary, a proportion of oxygen in the secondary flow of gases.

85. The aeration device of claim 83 or 84, the controller configured to control operation of the flow generator to vary, e.g., periodically vary, a proportion of carbon dioxide in the secondary flow of gases.

86. The aeration device of any one of claims 83 to 85, the controller configured to control operation of the flow generator to:alternate between providing the secondary flow of gases with a first proportion of oxygen and a second proportion of oxygen, wherein the first proportion of oxygen is greater than the second proportion of oxygen; and / oralternate between providing the secondary flow of gases with a first proportion of carbon dioxide and a second proportion of carbon dioxide, wherein the second proportion of carbon dioxide is greater than the first proportion of carbon dioxide.

87. The aeration device of claim 86, the controller configured to control the flow generator to:provide the secondary flow of gases with the first proportion of oxygen during at least part of an inspiratory phase of the ventilator;provide the secondary flow of gases with the second proportion of oxygen during at least part of an expiratory phase of the ventilator;provide the secondary flow of gases with the first proportion of carbon dioxide during at least part of the inspiratory phase of the ventilator; and / orprovide the secondary flow of gases with the second proportion of carbon dioxide during at least part of the expiratory phase of the ventilator.

88. The aeration device of any one of claims 53 to 87, comprising a nebulizer configured to dispense a nebulized substance into the secondary flow of gases.

89. The aeration device of any one of claims 53 to 88, the aeration device configured to supply the secondary flow of gases to the patient via a nasal cannula, the nasal cannula comprising:a symmetric dual-prong nasal cannula,an asymmetric dual-prong nasal cannula, ora single-prong nasal cannula.

90. The aeration device of any one of claims 53 to 89, the aeration device comprising:a first blower configured to generate a first portion of the secondary flow of gases, anda second blower configured to generate a second portion of the secondary flow of gases.

91. The aeration device of claim 90, the first blower and the second blower configured to generate the first portion of the secondary flow of gases and the second portion of the secondary flow of gases to the patient simultaneously.

92. The aeration device of claim 90, the first blower and the second blower configured to generate the first portion of the secondary flow of gases and the second portion of the secondary flow of gases to the patient alternately.

93. The aeration device of any one of claims 90 to 92, the aeration device configured, or configurable, to alternate between:providing a majority or an entirety of the secondary flow of gases to the patient via a left naris of the patient, andproviding the majority or the entirety of the secondary flow of gases to the patient via a right naris of the patient.

94. The aeration device of any one of claims 90 to 93:the first blower configured to generate a positive gas flow; andthe second blower configured to generate a negative gas flow.

95. The aeration device of any one of claims 53 to 93, wherein the aeration device is pneumatically isolated from the ventilator.

96. The aeration device of any one of claims 53 to 95, the controller configured to control operation of the flow generator to intermittently provide an augmented cycle to the secondary flow of gases, the augmented cycle comprising one or more of a peak flow rate, a peak inspiratory flow rate, a peak expiratory flow rate, and a duration which is greater than that of one or more adjacent cycles of the secondary flow of gases.

97. A method for aerating an upper respiratory tract of a patient receiving mechanical ventilation from a primary flow of gases provided by a ventilator, the method comprising simultaneously providing a secondary flow of gases to an upper respiratory tract of the patient, the secondary flow of gases comprising a time-varying flow rate profile with a predetermined frequency.

98. A method for aerating an upper respiratory tract of a patient receiving mechanical ventilation from a primary flow of gases provided by a ventilator, the method comprising simultaneously providing a secondary flow of gases to an upper respiratory tract of the patient, the secondary flow of gases comprising a time-varying flow rate profile independent of the primary flow of gases.

99. A method for aerating an upper respiratory tract of a patient receiving mechanical ventilation from a primary flow of gases provided by a ventilator, the method comprising simultaneously providing a secondary flow of gases to an upper respiratory tract of the patient, the secondary flow of gases comprising a time-varying flow rate profile based, at least in part, on the primary flow of gases provided by the ventilator.

100. A method for aerating an upper respiratory tract of a patient receiving mechanical ventilation from a primary flow of gases provided by a ventilator, the method comprising:sensing a pressure of the primary flow of gases;determining a phase of the ventilator based on the pressure of the primary flow of gases; andproviding a secondary flow of gases to an upper respiratory tract of the patient with a time-varying flow rate profile synchronized with the primary flow of gases.

101. The method of any one of claims 97 to 100, comprising fitting the patient with a nasal cannula configured to receive the secondary flow of gases for delivery to the upper respiratory tract of the patient.

102. The method of any one of claims 97 to 101, comprising isolating the lower respiratory tract and the upper respiratory tract of the patient.

103. The method of any one of claims 97 to 102, comprising alternating between providing the secondary flow of gases at a first flow rate and a second flow rate, wherein the first flow rate is different to the second flow rate.

104. The method of any one of claims 97 to 103, comprising continuously varying a flow rate of the secondary flow of gases.

105. The method of any one of claims 97 to 104, comprising varying, e.g., periodically varying, one or more of:a temperature of the secondary flow of gases,a humidity of the secondary flow of gases, and / ora composition of the secondary flow of gases.

106. The method of any one of claims 97 to 105, comprising periodically alternating between providing the secondary flow of gases at:a first temperature and a second temperature, wherein the second temperature is greater than the first temperature;a first humidity and a second humidity, wherein the second humidity is greater than the first humidity;a first proportion of oxygen and second proportion of oxygen, wherein the first proportion of oxygen is greater than the second proportion of oxygen; and / ora first proportion of carbon dioxide and a second proportion of carbon dioxide, wherein the second proportion of carbon dioxide is greater than the first proportion of carbon dioxide.

107. The method of any one of claims 97 to 106, comprising dispensing a nebulized substance into the secondary flow of gases.

108. The method of any one of claims 97 to 107, comprising periodically alternating between :providing a majority or an entirety of the secondary flow of gases to a left naris of the patient, andproviding a majority or an entirety of the secondary flow of gases to a right naris of the patient.

109. The method of any one of claims 97 to 108, comprising intermittently providing an augmented cycle to the secondary flow of gases, the augmented cycle comprising one or more of a peak flow rate, a peak inspiratory flow rate, a peak expiratory flow rate, and a duration which is greater than that of one or more adjacent cycles of the secondary flow of gases.

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