Respiratory support system and method

Abstract

A respiratory support system includes a first passageway and a second passageway each connectable to a patient interface. The first passageway is configured to convey a first gas during an accumulation period. The second passageway is configured to accumulate a second gas during at least part of the accumulation period and to convey the first gas during a delivery period such that the accumulated second gas is displaced from the second passageway to the patient interface. A controller is configured to control a commencement of the delivery period based on a breathing cycle of the patient.

Description

RESPIRATORY SUPPORT SYSTEM AND METHODCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from United States Patent Application No. 63 / 519,000, filed August 11, 2023, the entire content of which is incorporated herein by reference.FIELD

[0002] The present disclosure relates to a system and a method for providing respiratory support to a patient. The system and method may be used in any type of breathing therapy. For example, unsealed respiratory therapy, such as high flow therapy, or sealed respiratory therapy, such as continuous positive airway pressure (CPAP) therapy or bilevel positive air pressure (BPAP) therapy.BACKGROUND

[0003] Respiratory support can be provided to a patient for various reasons, including to help with breathing by opening up the patient's airways and / or to supply specific breathing gases for a particular therapeutic purpose.

[0004] In the case of high flow therapy (HFT), the breathing gas may be supplied at a high flow rate (e.g., over 15 L / min) that meets or exceeds the peak inspiratory demand of the patient. The high flow rate may need to be provided across the whole breathing cycle, that is during both inhalation and exhalation phases to achieve the flushing benefits within the patient's anatomical dead space, or dead space within the system such as the patient interface.

[0005] High flow therapy is sometimes also referred to as nasal high flow (NHF), humidified high flow nasal cannula (HHFNC), high flow nasal oxygen (HFNO), high flow therapy (HFT), or tracheal high flow (THF), for example.

[0006] Some respiratory support systems use a mixed breathing gas, such as a blend of air and oxygen that is supplied to a patient via an inspiratory tube. The required oxygen saturation levels in the patient's blood may be achieved by adjusting the ratio of the oxygen in the oxygen / air blend. The mixed breathing gas may be supplied to the patient during both inhalation and exhalation, which may result in wastage of the oxygen.SUMMARY

[0007] In one aspect, a system for providing respiratory support to a patient, includes: a first passageway connectable to a patient interface, the first passageway configured to convey a first gas during an accumulation period, a second passageway connectable to a patient interface, the second passageway configured to accumulate a second gas during at least part of the accumulation period and to convey the first gas during a delivery period such that the accumulated second gas is able to be displaced from the second passageway to the patient interface, and a controller that is configured to control a commencement of the delivery period based on a breathing cycle of the patient.

[0008] Throughout this specification, the term "system" refers to an apparatus that conducts a breathing gas to a patient. The system may be unidirectional in the sense that any of the breathing gas that is not inhaled by the patient need not be returned to its source and may be vented. Exhaled gas may be vented to atmosphere or captured. Similarly, if required breathing gas not inhaled may be vented or captured.

[0009] Throughout this specification, the first and / or second passageways may be described as: i) the first and / or second flow passageway including an element of the system or another element not being part of the system, such as a sensor or the controller, ii) the first and / or second passageways being connected to an element, Hi) an element being completely in, or at least partially in the first and / or second passageway, or iv) an element being on the first and / or second passageway. Depending on the circumstances these elements may or may not form part of the respective passageway. Examples of the elements include a humidification chamber, a valve, an active valve mechanism, a first or second gas inlets, a reservoir for the second gas, a vent, an exhalation port, joiners, and so forth. Moreover, the first and / or second passageway may include multiple lengths, portions or sections that are connected together in series or in parallel, with or without one or more of the elements being arranged therebetween. Depending on the circumstances, one of the elements described in relation to the second passageway may or may not form part of the second passageway. When the element does form part of the second passageway, the element could also provide volume for storing the second gas during the accumulation period, or at least dead space through which the second gas may be conveyed to be delivered to the patient.

[0010] The controller may control a conclusion of the delivery period based on the breathing cycle.

[0011] The controller may control the delivery period and the accumulation period so that at least one is occurring at any time during the breathing cycle.

[0012] The controller may control the delivery period and the accumulation period so that only one occurs at any time during the breathing cycle.

[0013] The controller may control the commencement of the delivery period based on a phase of the breathing cycle, and the delivery period.

[0014] The controller may control the commencement of the delivery period such that the delivery period occurs during a desired phase in the breathing cycle. In this instance, the phase of the breathing cycle may be the same as, or to different to, the desired instance in the breathing cycle.

[0015] The controller may control the commencement of the delivery period based on the onset of patient inhalation.

[0016] The controller may control the commencement of the delivery period based on the conclusion of patient inhalation.

[0017] The controller may control the commencement of the delivery period based on the onset of patient exhalation.

[0018] The controller may control the commencement of the delivery period based on the conclusion of patient exhalation.

[0019] The controller may control the commencement of the delivery period based on a high flow phase of patient inhalation, in which the high flow phase is a predetermined range before and / or after peak flow of patient inhalation. Moreover, the high flow phase may be the peak phase of patient inhalation.

[0020] The controller may control the commencement of the delivery period to occur during patent inhalation.

[0021] The controller may control the commencement of the delivery period to occur during a high flow phase of patient inhalation, in which the high flow phase is apredetermined range before and / or after peak flow of patient inhalation. Moreover, the high flow phase may be the peak phase of patient inhalation.

[0022] The controller may control the conclusion of the delivery period to occur during patent inhalation.

[0023] The controller may control the commencement of the delivery period to occur during patent exhalation.

[0024] The controller may control the conclusion of the delivery period to occur before the end of patient inhalation.

[0025] The delivery period may be in the range of 50 to 90% of the duration of the patient inhalation, or suitably 60 to 80%, or even more suitably 70 to 80% of the duration of the patient inhalation.

[0026] The controller may control the commencement of the accumulation period based on the onset of patient inhalation.

[0027] The controller may control the commencement of the accumulation period based on the conclusion of patient inhalation.

[0028] The controller may control the commencement of the accumulation period based on the onset of patient exhalation.

[0029] The controller may control the commencement of the accumulation period based on the conclusion of patient exhalation.

[0030] The controller may control the commencement of the accumulation period based on a high flow phase of patient inhalation, in which the high flow phase is a predetermined range before and / or after peak flow of patient inhalation.

[0031] The controller may control the commencement of the accumulation period to occur during at least part of the patient exhalation.

[0032] The controller may control the conclusion of the accumulation period to occur during at least part of the patient exhalation.

[0033] The controller may control the accumulation period to occur during at least part of the patient exhalation.

[0034] The controller may control the accumulation period to occur during at least part of the patient inhalation.

[0035] The controller may receive an input relating to the breathing cycle of the patient, and the controller determines the phase of the breathing cycling based on the input including : patient inhalation or the onset, conclusion or high flow phase thereof; or patient exhalation or the onset or conclusion thereof.

[0036] The controller may be configured to determine when the input is outside a threshold range and discard these inputs for determining the phase of the breathing cycle. When the input is determined as being outside the threshold range, the input represents an irregular breath in the breathing cycle.

[0037] The controller may control flow and / or pressure of the first gas supplied to the first passageway during at least part of patient exhalation and patient inhalation.

[0038] The controller may calculate phases of the breathing cycle(s) of the patient, that correspond to a patient exhalation and a patient inhalation.

[0039] The controller may calculate an average of the duration of number of the breathing cycles. The average may re-calculated after a predetermined time.

[0040] The controller may calculate the duration of the breathing cycle based on sensor outputs of at least one sensor that monitors the breathing cycle of the patient. For example, the sensor may measure a parameter of one of the gases within the system, namely the first gas, the second gas, or the exhalation gas of the patient. The parameter may be flow rate in one of the passageways or the exhalation port, gas pressure in at least one of the passageways or in an exhalation port, gas composition such as oxygen or carbon dioxide content of the gas in at least one of the passageways or the exhalation port.

[0041] The controller may control the flow and / or pressure of the first gas in the second passageway so that the conclusion of the delivery period occurs before the end of patient inhalation, and so that flow rate and / or pressure of the first gas supplied to the first passageway increases or starts before the end of patient inhalation to maintain flow and / or pressure at the patient interface.

[0042] The controller may control the flow and / or pressure of the first gas in the second passageway so the conclusion of the delivery period occurs after the second gas that accumulated in the second passageway has been delivered to the patient interface.

[0043] The controller may control the conclusion of the delivery period by stopping or reducing the flow and / or pressure of the first gas supplied to the second passageway when the second gas that accumulated in the second passageway has been supplied to the patient interface, or by a period after the second gas that accumulated in the second passageway has been delivered to the patient interface.

[0044] The controller may control the conclusion of the delivery period at some stage after the second gas that has accumulated in the second passage has been supplied to the patient interface.

[0045] The patient interface receives a breathing gas which may comprise the first gas, the second gas, or a mixture of the first gas and the second gas.

[0046] The system includes a controller that controls flow of the first gas in the first passageway so that the first passageway conveys the first gas during at least part of patient exhalation and patient inhalation.

[0047] The controller may control the flow of the first gas in the second passageway so the first gas is supplied for a period after the second gas that accumulated in the second passageway has been delivered to the patient interface. In this instance a breathing gas supplied to the patient interface toward the end of patient inhalation may comprise a mixture of the first gas and the second gas.

[0048] The controller may receive an input from a clinician, herein the clinician input, which the controller uses to calculate the delivery period, the clinician input includes the clinician's measurement or estimation of either one or a combination of: i) the tidal volume of the patient; ii) an internal volume of the second passageway and / or the system in which the second gas can accumulate; iii) the duration of the breathing cycle of the patient; or iv) the duration of the patient inhalation.

[0049] The controller may calculate the delivery period based on one or both of: i) the onset of patient inhalation; ii) the duration of the patient inhalation from the onset of the patient inhalation, and / or iii) a function of a portion of patient inhalation.

[0050] The controller may determine one or both of: i) the onset of patient inhalation; and ii) the duration of the patient inhalation from the onset of the patient inhalation, based on sensor outputs of at least one sensor that monitors breathing of the patient. The at least one sensor includes an external sensor attached to the abdomen of the patient, or an external sensor that monitors the thoracic and / or abdominal expansion of the patient. Theat least one sensor measures a parameter of one of the gases within the system, namely the first gas, the second gas, or the exhalation gas of the patient, in which the parameter includes flow rate in one of the passageways or the exhalation port, gas pressure in at least one of the passageways or in an exhalation port, gas composition such as oxygen or carbon dioxide content of the gas in at least one of the passageways or the exhalation port.

[0051] The controller may control the commencement of the delivery period based on one or more event in the breathing cycling including : i) an onset of patient inhalation, ii) high flow phase of patient inhalation in which the high flow phase is a predetermined range before and / or after peak flow of patient inhalation, iii) a conclusion of patient inhalation; iv) an onset of patient exhalation, or v) conclusion of patient exhalation.

[0052] The second gas may be delivered to the patient interface at a particular moment in the breathing cycle and the controller can adjust the commencement of the delivery period so that the second gas is delivered to the patent interface at the particular moment. For instance, the second gas may be delivered to the patient interface at any one of the following moments: i) a period before the onset of inhalation, ii) at the commencement of inhalation, or iii) a period after the onset of inhalation.

[0053] The second gas that is delivered to the patient interface may be accumulated during a preceding accumulation period.

[0054] The second gas that is delivered to the patient interface may be accumulated entirely during a preceding breath of the breathing cycle.

[0055] The controller may control the commencement of the delivery period as a function of a delay interval between the first gas being supplied to the second passageway and the second gas being delivered to patient interface. This may assist in flushing residual breathing gas or exhalated gas from the system. This may assist in delivering the second gas to the patient interface at, or close to, the start of patient inhalation.

[0056] The controller may control the commencement of the delivery period earlier in the breathing cycle as a function of the delay interval, herein referred to as the advance period.

[0057] The controller may control the commencement of the delivery period so as to occur before the onset of the inhalation period.

[0058] The controller may estimate the delay interval . For example, the controller may estimate the delay interval based on the flow rate of the first gas being conveyed in thesecond passageway. In another example, the controller may estimate the delay interval based on an internal volume of the system downstream of the second gas accumulated in the second passageway. In yet another example, the controller may estimate the delay interval based on a rate of leakage from the system, such as intentional leakage and unintentional leakage.

[0059] Moreover, the controller may estimate the delay interval based on parameters including any one or a combination of: i) the flow rate of the first gas being conveyed in the second passageway, ii) an internal volume of the system downstream of the second gas accumulated in the second passageway, or iii) rate of leakage from the system, such as intentional leakage and unintentional leakage.

[0060] The controller may control the commencement of the delivery period so that the flow and / or pressure of the first gas supplied to the second passageway prior to the onset of patient inhalation flushes residual breathing gas or exhaled gas from the system.

[0061] The controller may control the commencement of the delivery period as a function of an interval between onset of patient inhalation and a high flow phase of patient inhalation.

[0062] The controller may control the commencement of the delivery period later in the breathing cycle by a function of the interval, herein referred to as the postponement period.

[0063] The controller may control the commencement of the delivery period by the postponement period so that the second gas is delivered to the patient interface during a high flow phase of patient inhalation.

[0064] The controller may determine the postponement period as a function of an output of a sensor that is received by the controller, in which the sensor monitors at least one of the following : i) the period of the breathing cycle of the patient, in other words the respiration rate of the patient, ii) the tidal flow of the patient, and / or iii) the flow rate of the patient inhalation.

[0065] The controller may determine the postponement period as a function of an input from a clinician.

[0066] The controller may control the flow rate and / or pressure of the first gas supplied to the second passageway so that the second gas is delivered to the patient interface during a high flow phase of patient inhalation.

[0067] In one example, the commencement of the delivery period may occur before the onset of patient inhalation. In another example, the commencement of the delivery period may occur after the onset of patient inhalation.

[0068] The controller may control the commencement of the delivery period to occur before the peak flow of patient inhalation and controls the conclusion of the delivery period to occur after the peak flow of patient inhalation.

[0069] The controller may control the commencement of the delivery period to occur at the peak flow of the patient.

[0070] The controller may control the commencement of the delivery period so that the second gas is provided at the peak flow of the patient.

[0071] The controller may control the supply of the second gas to the second passageway so that second gas is supplied for the entire accumulation period.

[0072] The controller may control the supply of the second gas to the second passageway so that the second gas is supplied for only part of the accumulation period.

[0073] The second gas may be held in the second passageway for the duration of the accumulation period.

[0074] The controller may control the flow rate and / or pressure of the second gas supplied to the second passageway during at least part of the accumulation period.

[0075] The accumulation period may occur during patient exhalation and during a later stage of patient inhalation.

[0076] The accumulation period may occur during the patient exhalation, save for the later stages of patient exhalation.

[0077] The accumulation period may occur during the later stage of the patient inhalation and patient exhalation, save for the later stage of patient exhalation.

[0078] The controller may control the flow rate and / or pressure of the second gas supplied to the second passageway throughout patient inhalation and patient exhalation.

[0079] The controller may control the flow rate and / or pressure of the second gas supplied to the second passageway during the accumulation period and the controller controls theflow rate and / or pressure of the first gas supplied to the patient interface by the first passageway.

[0080] The controller may control supply of the second gas to the second passageway and may control supply of the first gas to the first and second passageways, in which control of the supplying the first gas and control of the supplying of the second gas are controlled independent of the other.

[0081] The controller may control supply of the second gas to the second passageway and supply of the first gas to the first and second passageways so the supply of the first and second gases is independent of the other.

[0082] The controller may control the flow rate of the second gas so as not to the supply the second gas to the second passageway when the patient or the patient interface is receiving breathing gas from second passageway.

[0083] The controller may calculate the accumulation period as a function of an output of at least one sensor that detects the breathing cycle of the patient.

[0084] The at least one sensor may monitor at least one or a combination of flow rate of exhaled gas, the flow rate of the inhaled gas, the flow rate of gas vented from the system, gas pressure in the system, gas composition in the system.

[0085] The controller may control the flow rate and / or pressure of the second gas supplied to the second passageway based on a known volume of the second passageway and the accumulation period.

[0086] The controller may control the flow rate and / or pressure of the second gas as a function of the know volume of the second passageway for storing the second gas, and at least one of: i) the accumulation period, ii) respiration rate of the patient, or iii) a duration of the patient inhalation.

[0087] The duration of patient inhalation can be provided by a clinician, the patient, or calculated by the controller as a function of the sensor output of one or more sensor(s).

[0088] The controller may control the flow rate and / or pressure of the second gas so that a treatment volume of the second gas enters the second passageway during the accumulation period. In one example, the treatment volume may be approximately equal to a storage volume of the second passageway. In another example, the treatment volumemay be a product of the accumulation period and the flow rate of the second gas supplied to the second passageway.

[0089] The controller may calculate the treatment volume and controls the accumulation period and / or the supply of the second gas to the second passageway so that the treatment volume fills the alveoli of the patient.

[0090] In one example, the controller may receive in an input value for the treatment volume, and the controller determines the flow rate and / or pressure of the second gas based on the accumulation period and the input value for the treatment volume.

[0091] The controller may calculate the treatment volume as a percentage of an expected or measured tidal volume of the patient.

[0092] The treatment volume may range from 50 to 100% of the tidal volume of the patient, or the volume can range from 50 to 90% of the tidal volume of the patient, or the volume can range from 60 to 80% of the tidal volume of the patient, or the volume can range from the 60 to 70% of the tidal volume of the patient.

[0093] The controller may change the treatment volume or flow rate of the second gas in response to a change in a clinical state of the patient, including a change in an Sp02 level, also known as oxygen saturation level, or in response to a change in respiration rate of patient inhalation.

[0094] The controller may change the flow rate and / or pressure of the second gas to try and obtain a desired clinical outcome, including increasing the flow rate or the treatment volume of the second gas when SpO2 decreases.

[0095] The controller may recommend re-selecting the second passageway, including recommending a second passageway be changed with another having a larger internal volume when the treatment volume is greater than a storage volume of second passageway.

[0096] The controller may recalculate the accumulation period when one or more of the following events occurs: i) the second passageway is changed, ii) the flow rate of the second gas is changed, iii) the inspiration rate of the patient changes, iv) the expiration rate of the patient changes, v) the duration of patient inhalation changes, vi) the duration of patient exhalation changes, vii) the clinical state of the patient changes, iix) an increase in leakage from the patient interface occurs or thought to have occurred.

[0097] The system may include sensors that have sensor outputs and changes in the sensor outputs can trigger the controller to recalculate the accumulation period.

[0098] The controller may have operating controls, including at least one of touch screen buttons, push buttons, switching buttons and so forth to allow a user to trigger the controller to recalculate the accumulation period.

[0099] The controller may control the flow rate of the second gas to the second passageway, for example, during the accumulation period. The flow rate may be a constant rate.

[0100] In one example, the accumulation period may occur during patient exhalation. That is to say, the second gas is not supplied to the second passageway when the patient is receiving breathing gas from second passageway. This may occur during inhalation, such as during initial stages of inhalation, or during peak inspiration flow rate of inhalation.

[0101] In another example, the accumulation period may occur during patient exhalation and during a later stage of patient inhalation. In yet another example, the accumulation period may occur during the patient exhalation save for the later stages of patient exhalation. In yet another example, the accumulation period may occur during the later stage of the patient inhalation and patient exhalation save for the later stage of patient exhalation.

[0102] The controller may also control the flow rate of the second gas to second passageway throughout patient inhalation and patient exhalation. The controller may control the flow rate of the second gas to the second passageway throughout the accumulation period.

[0103] The system may include a first flow generator connected to the first passageway for generating flow and / or pressure of the first gas therein, and a second flow generator connected to the second passageway for generating flow and / or pressure of the first gas therein.

[0104] The second flow generator may be operated to convey the first gas along the second passageway at a known flow rate for the delivery period so as to be able to displace the second gas accumulated in the second passageway to the patient interface.

[0105] The second flow generator may be operated to provide flow of the first gas in the second passageway for the delivery period after the second gas that accumulated in the second passageway has been delivered to the patient interface.

[0106] The second flow generator may be operated to reduce or stop flow of the first gas in the second passageway once the second gas that has accumulated in the second passageway has been delivered to the patient interface.

[0107] When at the commencement of the delivery period the second flow generator may be operated so the first gas is supplied to the second passageway at the onset of patient inhalation or during initial stage of patient inhalation, and at the conclusion of the delivery period the second flow generator can be operated to reduce or stop the first gas being supplied to the second passageway during a later stage of patient inhalation, that is whilst the rate of inspiration during patient inhalation is decreasing, and the first flow generator can be operated so the first gas is supplied to the first passageway during a later stage of patient inhalation and during the at least part of the patient exhalation.

[0108] The second flow generator may be operated so the first gas is supplied to the second passageway prior to the onset of patient inhalation.

[0109] The second flow generator may be operated so that flow of the first gas in the second passageway delivers the second gas accumulated to the patient interface during a period of high patient inhalation.

[0110] The controller may control the flow and / or pressure of the first gas in the second passageway by operating a motor speed driving the second flow generator.

[0111] The controller may control the flow and / or pressure of the first gas in the first passageway by operating the motor speed driving the first flow generator.

[0112] The controller may control operation of the first flow generator using an output signal from a pressure sensor that provides pressure data of one or a combination of : i) pressure of the first gas in the first passageway (to provide back pressure on the nonreturn valve), ii) pressure of the first gas in the second passageway, iii) gas pressure in the third passage, iv) pressure of exhaled gas, or v) gas pressure of patient interface.

[0113] The controller may control operation of the second flow generator using an output signal from a flow sensor that provides flow rate data of one or a combination of: i) flow rate of the first gas in the first flow generator; ii) flow rate of the first gas in the secondflow generator, Hi) flow rate the third passageway, iv) flow rate in the second passageway, and iv) flow rate of the second gas at the second gas inlet.

[0114] The controller operates the first flow generator at a set flow rate during patient exhalation.

[0115] The set flow rate of the first flow generator may be at least the rate of mask leakage, including intentional and unintentional mask leakage during exhalation.

[0116] The controller may operate the second flow generator at a lower flow rate than the first flow generator, during patient exhalation.

[0117] The controller may operate the second flow generator at a zero flow rate or a negative flow rate, during patient exhalation.

[0118] The first flow generator may be operated a set flow rate during patient exhalation, and the second flow generator may be operated a set pressure that is lower than the set pressure at which the first flow generator is operated.

[0119] The controller may operate the first flow generator at a set pressure during patient exhalation.

[0120] The controller may operate the second flow generator at a (set) flow rate and / or pressure during patient inhalation. In one example, the set flow rate may be a percentage of the peak respiration flow rate, such as, from 70 to 150 % of the peak respiration rate. In another example, the set flow rate may be a function of the peak inspiration flow rate and mask leakage rate, such as a sum of the peak inspiration flow rate and mask leakage rate.

[0121] When the second flow generator is operated at a set flow, the first flow generator may be operated at a set pressure, to provide constant pressure or near to constant pressure delivered to the patient.

[0122] When the second flow generator is operated at a set flow, the first flow generator may be operated at a set flow rate that is less than the flow rate being generated by the second flow generator.

[0123] The second flow generator may have a (set) flow rate that is low or zero so as not to dilute the second gas in the second passageway during the accumulation period.

[0124] The system may include a flow generator to provide flow the first gas in the first and second passageways, and an active valve mechanism to adjust flow of the first gas between at least one of the first and / or the second passageways.

[0125] The active valve mechanism may be operated to allow the first gas to be conveyed along the second passageway for period after the second gas that accumulated in the second passageway has been delivered to the patient interface.

[0126] At the commencement of the delivery period, the active valve mechanism may be operated to allow the first gas to be supplied to the second passageway the onset of patient inhalation or initial stage of patient inhalation, that is whilst the rate of inspiration during patient inhalation is increasing, and at the conclusion of the delivery period the active valve mechanism may be operated to reduce or stop the first gas being supplied to the second passageway during a later stage of patient inhalation, that is whilst the rate of inspiration during patient inhalation is decreasing, and at the conclusion of the delivery period the active valve mechanism may be operated to supply the first gas to the first passageway during a later stage of patient inhalation and during at least part of the patient exhalation.

[0127] The controller may control operation of the active valve mechanism.

[0128] The controller may receive at least one input from sources including a clinician, or a sensor, and the controller may determine the delivery period, to control operation of the active valve mechanism to allow flow of the first gas along the second passageway.

[0129] The active valve mechanism can be operated to allow the first gas to be conveyed along the second passageway to flush residual breathing gas or exhalated gas from the system prior to the onset of patient inhalation.

[0130] The controller may control operation of the flow generator.

[0131] The controller may control operation of the flow generator by operating a motor speed driving the flow generator.

[0132] The second gas may enter the second passageway at a second gas inlet located downstream to where the first gas enters the second passageway. Throughout this specification, the downstream direction is toward the patient interface.

[0133] The system may include a flow restriction device such as a non-return valve that inhibits the second gas from passing into the second flow generator.

[0134] The system may include a non-return valve that inhibits the second gas from passing into the flow generator.

[0135] The second gas may enter the second passageway at a second gas inlet that is located distally from the patient interface, and the second gas accumulates in the second passageway by a volume of the second gas increasing in a downstream direction.

[0136] The system may include a flow restriction device, including a non-return valve located in the second passageway upstream of a location where the second gas enters the second passageway, the non-return valve allows flow in the second passageway in a downstream direction only.

[0137] The non-return valve may be fitted to the second passageway between where the second gas enters the second passageway and the second flow generator.

[0138] The second gas accumulating in the second passageway during patient exhalation may flow upstream.

[0139] The system may include a flow restriction device, such as a non-return valve located in the second passageway downstream of a location where the second gas enters the second passageway, and a volume of the second gas accumulates by flowing in an upstream direction during at least part of patient exhalation.

[0140] The flow restriction device may be a non-return valve located in the second passageway downstream of a location where the second gas enters the second passageway.

[0141] The second gas may enter the second passageway proximally to the patient interface and the second gas accumulates by the second gas flowing in an upstream direction.

[0142] The system may include a reservoir provided in or on the second passageway in which the second gas can accumulate. The reservoir may be located upstream of the second flow generator, in which case the second gas can accumulate in the reservoir.

[0143] The first and second passageways may include lengths of tubing for conveying the first gas.

[0144] The tubing for the second passageway may be is selected to allow a required volume of the second gas to be stored in the second passageway.

[0145] The tubing for the second passageway may include one or more lengths being selected based on the storage capacity of the second passageway for storing a preselected volume of the second gas.

[0146] The preselected volume can range from 50 to 100% of the tidal volume of the patient, or the volume range from 50 to 90% of the tidal volume of the patient, or the volume range from 60 to 80% of the tidal volume of the patient, or the volume range from the 60 to 70% of the tidal volume of the patient.

[0147] The controller may generate a signal that can alert a clinician or a patient when an undesirable event occurs.

[0148] The signal may warn that one or more of the following have occurred : i) the second gas is being supplied at a flow rate and over an accumulation period that overfills the second passageway, ii) the second gas is being supplied at a flow rate and over an accumulation period that does not met the treatment volume required, iii) the internal volume of the second passageway for storing the second gas is too small or too large; iv) the respiration rate of the patient is too low, vi) the tidal volume of the patient is too low, vi) an unforeseen leak in the system may have occurred, vii) a blockage in the system has occurred, and viii) inadequate flow of the first gas is present, or iix) concentration of the second gas in the patient interface are too high.

[0149] The system may include the patient interface.

[0150] The patient interface may be unsealed interface.

[0151] The patient interface may be a sealed interface.

[0152] The system may include a third passageway extending from the first passageway and the second passageway that merges the first and the second passageways together, and the third passageway is located downstream of the first and second passageways.

[0153] The third passageway may be connected to the patient interface.

[0154] The system may include an exhalation port for venting the exhaled gas from the system.

[0155] The exhalation port may be located on the first passageway. A benefit this provides is that the second gas entering the second passageway is more likely to be supplied to the patient interface than being vented from the patient interface with exhaledgas. It also limits the dead space of the system between the patient interface and the exhalation port so that exhaled gases are less likely to be re-inhaled.

[0156] The exhalation port may be located on the first passageway proximally to the patient interface.

[0157] The exhalation port may be located on the first passageway distally to the patient interface. This can further reduce the likelihood of the second gas being discharged from the system through the exhalation port without being delivered to the patient interface.

[0158] The exhalation port may be located on the second passageway.

[0159] The exhalation port may be located on the third passageway.

[0160] The exhalation port may be located on the patient interface. For instance, when the patient interface is a sealed patient interface.

[0161] In situations where the second flow generator is a fan or blower, exhaled gases may be vented from the system through the second flow generator. That is to say, negative flow may occur through the second flow generator and an exhalation port may not be required.

[0162] The second gas may be provided by a second gas source.

[0163] The system may include the second gas source that supplies the second gas.

[0164] The second gas may be pressurized oxygen gas.

[0165] The second gas may be a pressurized gas including one or any combination of: oxygen gas, heliox, or an anaesthetic gas.

[0166] In another aspect, a system for providing respiratory support to a patient includes: a first passageway connectable to a patient interface, the first passageway configured to convey a first gas during an accumulation period, a second passageway connectable to a patient interface, the second passageway configured to accumulate a second gas during at least part of the accumulation period and to convey the first gas during a delivery period such that the accumulated second gas is displaced from the second passageway to the patient interface, anda controller that is configured to control a commencement of the delivery period so that the second gas accumulated during the accumulation period is delivered to the patient interface: i) at an onset of patient inhalation, ii) a period before the onset of inhalation, iii) a period after the onset of inhalation, or ii) at high flow phase of patient inhalation, in which the high flow phase is a predetermined range before and / or after peak flow of patient inhalation.

[0167] In another aspect, a system for providing respiratory support to a patient includes: a first passageway that conveys a first gas, the first passageway being connectable to a patient interface; a first flow generator for generating flow of the first gas in the first passageway; a second passageway that conveys the first gas and a second gas, the second passageway being connectable to the patient interface, a second flow generator for generating flow of the first gas in the second passageway, the second passageway is connectable to a second gas source for supplying the second gas into the second passageway.

[0168] In another aspect, a system for providing respiratory support to a patient includes: a first passageway connectable to a patient interface, the first passageway configured to convey a first gas during an accumulation period, a second passageway connectable to a patient interface, the second passageway configured to accumulate a second gas during at least part of the accumulation period and to convey the first gas during a delivery period such that the accumulated second gas is displaced from the second passageway to the patient interface, and a controller that is configured to control the delivery period based on a breathing cycle of the patient.

[0169] In another aspect, a respiratory support system for providing respiratory support to a patient includes: a first passageway including a first gas inlet configured to receive a first gas, the first passageway configured to convey the first gas towards a patient interface;a second passageway including a first gas inlet configured to receive the first gas, and a second gas inlet configured to receive a second gas, the second passageway configured to convey the first gas and the second gas towards the patient interface; a flow control system configured to control one or more of a flow rate or a pressure of the first gas and one or more of a flow rate or a pressure of the second gas, the flow control system including : one or more controllable flow generators, one or more controllable valves, or one or more controllable flow generators and one or more controllable valves; and a controller configured to control operation of the flow control system so that: during an accumulation period, the first gas is conveyed towards the patient interface through the first passageway, and a volume of the second gas accumulates in the second passageway, during a delivery period, the first gas and the volume of the second gas are conveyed towards the patient interface through the second passageway, the accumulation period occurs during a portion of patient inhalation and at least a portion of patient exhalation, and the delivery period occurs during at least a portion of patient inhalation and optionally a portion of patient exhalation.

[0170] In another aspect, a respiratory support apparatus for use in the system of any of the preceding aspects includes the controller.

[0171] In another aspect, a respiratory support apparatus for use in a respiratory support system configured to provide respiratory support to a patient, the respiratory support apparatus including a controller that is configured to control: one or more flow generators of the respiratory support system, one or more valves of the respiratory support system, orone or more flow generators of the respiratory support system, and one or more valves of the respiratory support system, to supply: a first gas to a first passageway of the respiratory support system, the first gas to a second passageway of the respiratory support system, and a second gas to the second passageway, wherein: during an accumulation period the second passageway is configured to accumulate a volume of the second gas and the first passageway is configured to supply the first gas to a patient interface of the respiratory support system, during a delivery period, the second passageway is configured to supply the volume of the second gas to the patient interface, and the controller is configured to control timing of one or more of the accumulation period or the delivery period based on a breathing cycle of the patient.

[0172] In another aspect, a breathing circuit for a respiratory support system includes: a first passageway, the first passageway including an inlet configured to receive a first gas, and an outlet configured to supply first gas to a patient interface; a second passageway, the second passageway including an inlet configured to receive the first gas, a second inlet configured to receive a second gas, an outlet configured to supply the first gas and the second gas to the patient interface, and a non-return valve between the second inlet and the outlet.

[0173] The second passageway may be configured to accumulate a volume of the second gas during part of a breathing cycle of a patient for supply to the patient during another part of the breathing cycle.

[0174] An internal volume of the second passageway may be between about 50 % and 100 %, or between about 50% and 90 %, or between about 60 % and 80 %, or between about 60 % and 70 % of the tidal volume of:a patient, an average adult tidal volume, an average pediatric tidal volume, or an average neonatal tidal volume.

[0175] The second passageway may have an internal volume of: at least about 300 milliliters (mL), at least about 400 mL, at least about 500 mL, between about 300 mL and 700 mL, between about 400 and 650 mL, between about 500 mL and 600 mL, or about 570 mL; between about 50 mL and 300 mL, between about 100 and 300 mL, between about 150 mL and 250 mL, or about 270 mL; or between about 10 mL and 50 mL, between about 20 and 40 mL, or about 118 mL.

[0176] The breathing circuit may be one of two or more different sizes of breathing circuit, the two or more different sizes of breathing circuit each comprising a second passageway with a different internal volume.

[0177] The inlet of the first passageway may be configured to connect with a first flow generator, the inlet of the second passageway may be configured to connect with a second flow generator, and the second inlet of the second passageway may be configured to connect with a second gas source.

[0178] The inlet of the first passageway and the inlet of the second passageway may each be configured to connect with an active valve mechanism, the active valve mechanism configured to receive the first gas from a flow generator, and direct the first gas to one or more of the first passageway or the second passageway.

[0179] The inlet of the first passageway and the inlet of the second passageway may each be configured to connect with a flow generator to receive the first gas, and the outlet of the first passageway and the outlet of the second passageway may be configured to deliver the first gas and the second gas to the patient interface via an active valve mechanism.

[0180] The outlet of the first passageway and the outlet of the second passageway may be configured to supply the first gas and the second gas to the patient interface via one or more of: a Y-piece or a T-piece, or a third passageway.

[0181] The breathing circuit may further include one or more of: an exhalation port, a third passageway, a Y-piece or a T-piece, a patient interface, a filter, a gas supply line, a reservoir, a humidification device, or a sensor.

[0182] In other aspects, a method may include any one or a combination of the features, functions, or steps of the system or controller described herein.

[0183] Another aspect relates to a method of using the system described herein.

[0184] Further aspects will be apparent in view of the following description and the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0185] These and other features, aspects, and characteristics of the present disclosure are described with reference to the drawings of a number of examples, which are intended to illustrate the technology and not to limit the disclosure.

[0186] FIG. 1 is a schematic diagram of a respiratory support system according to a first example, showing gas flows during an accumulation period.

[0187] FIG. 2 is a schematic diagram of the respiratory support system of FIG. 1, showing gas flows during a delivery period.

[0188] FIG. 3 is a schematic diagram of a respiratory support system according to a second example, showing gas flows during an accumulation period.

[0189] FIG. 4 is a schematic diagram of the respiratory support system of FIG. 3, showing gas flows during a delivery period.

[0190] FIG. 5 is a schematic diagram of a respiratory support system according to a third example, showing gas flows during an accumulation period.

[0191] FIG. 6 is a schematic diagram of the respiratory support system of FIG. 5, showing gas flows during a delivery period.

[0192] FIG. 7 is a schematic diagram of a respiratory support system according to a fourth example, showing gas flows during an accumulation period.

[0193] FIG. 8 is a schematic diagram of the respiratory support system of FIG. 7, showing gas flows during a delivery period.

[0194] FIG. 9 is a schematic diagram illustrating sensing and control of the respiratory support systems of any one of FIG. 1 to FIG. 8.

[0195] FIG. 10 is a schematic diagram of a respiratory support system according to a fifth example, showing gas flows during an accumulation period.

[0196] FIG. 11 is a schematic diagram of the respiratory support system of FIG. 10, showing gas flows during a delivery period.

[0197] FIG. 12 is a schematic diagram illustrating sensing and control of the respiratory support system of FIG. 10.

[0198] FIG. 13 is a schematic diagram of a respiratory support system according to a sixth example, showing gas flows during an accumulation period.

[0199] FIG. 14 is a schematic diagram of the respiratory support system of FIG. 13, showing gas flows during a delivery period.

[0200] FIG. 15 is a schematic diagram illustrating sensing and control of the respiratory support system of FIG. 13.

[0201] FIG. 16 is a graph illustrating three breathing cycles of a patient during use of the respiratory support system of any one of FIG. 1 to FIG. 15.

[0202] FIG. 17 is a graph illustrating a breathing cycle of a patient during use of the respiratory support system of any one of FIG. 1 to FIG. 15, in which the delivery period commences before commencement of inhalation.

[0203] FIG. 18 is a graph illustrating a breathing cycle of a patient during use of the respiratory support system of any one of FIG. 1 to FIG. 15, in which the delivery period commences after commencement of inhalation.

[0204] FIG. 19 is a graph illustrating a breathing cycle of a patient during use of the respiratory support system of any one of FIG. 1 to FIG. 15, in which the delivery periodcommences before commencement of inhalation, but delivery of the second gas commences after commencement of inhalation.

[0205] FIG. 20 is a graph illustrating a breathing cycle of a patient during use of the respiratory support system of any one of FIG. 1 to FIG. 15, in which both the delivery period and delivery of the second gas commence after commencement of inhalation.DETAILED DESCRIPTION

[0206] Non-limiting examples of the present technology are described in the following text which includes reference numerals that correspond to features illustrated in the accompanying drawings. To maintain clarity of the drawings, not all reference numerals are included in each drawing. Although certain examples are described in detail, those of skill in the art will appreciate that the disclosure extends beyond the specifically disclosed examples and / or uses.

[0207] FIG. 1 and FIG. 2 are schematic illustrations of an example respiratory support system 100 for delivering a breathing gas to a patient 106.

[0208] The respiratory support system 100 includes a first passageway 102 and a second passageway 104 for conveying breathing gas. The first passageway 102 includes an exhalation port 110 for venting exhaled gas and breathing gas that is not inhaled by the patient.

[0209] A first flow generator 120 is connected to a first inlet 126 at a distal portion of the first passageway 102 to generate a flow of a first gas therein. In some examples, the first gas may be ambient air.

[0210] A second flow generator 122 is connected to a second inlet 128 at a distal portion of the second passageway 104 to generate a flow of the first gas therein.

[0211] A filter 124 may be located at, or upstream of, one or more of the first inlet 126 of the first passageway 102, the first flow generator 120, the second inlet 128 of the second passageway 104, or the second flow generator 122.

[0212] The respiratory support system 100 includes a patient interface 108. The patient interface 108 in FIG. 1 and FIG. 2 is a sealed interface.

[0213] A second gas source 112 is connected to a proximal portion of the second passageway 104, e.g., downstream of a midpoint of the second passageway 104, at asecond gas inlet 116. The second gas source 112 supplies a second gas into the second passageway 104. In some examples, the second gas may be oxygen.

[0214] A non-return valve 114 is located downstream of the second gas inlet 116 to inhibit or prevent the first gas and / or exhaled gas from flowing in the second passageway 104 in an upstream direction. That is, from downstream of the non-return valve 114 through the non-return valve 114 toward the second gas inlet 116.

[0215] The first passageway 102 and second passageway 104 are connected to a third passageway 118 by a joiner, such as a Y- or T-shaped joiner. The third passageway 118 is connected to the patient interface 108. In other examples, one or more of the first passageway 102 or the second passageway 104 may be connected directly to the patient interface 108.

[0216] The arrows in FIG. 1 represent the direction of flow of the first gas, the second gas and the exhaled gas during an accumulation period. The second gas enters the second passageway 104 from the second gas source 112 at the second gas inlet 116. And flows in an upstream direction toward the second flow generator 122 to accumulate a desired volume (bolus) of the second gas in the second passageway 104. In some examples, the second gas may accumulate in the second flow generator 122. Although not shown, a reservoir may be provided in the second passageway 104 and / or upstream of the second flow generator 122. The second gas may accumulate in the reservoir. Providing the reservoir upstream of the second flow generator 122, may mitigate a negative effect on pressure in the second passageway 104.

[0217] The first flow generator 120 may be operated to provide a flow of the first gas in the first passageway 102 toward the patient interface 108. The first gas and exhaled gas may be vented at the exhalation port 110. In some examples, the exhaled gas and the first gas may also leak to ambient from the sealed patient interface 108.

[0218] The arrows in FIG. 2 represent the direction of flow of the first gas and the second gas during the delivery period. During the delivery period, the second gas that has accumulated in the second passageway 104 is displaced to the patient interface 108. The second flow generator 122 may be operated to provide a flow of the first gas which is conveyed along the second passageway 104. The flow of the first gas displaces the desired volume of the second gas that has accumulated in the second passageway 104 to the patient interface 108.

[0219] The first flow generator 120 may be operated to provide a flow of the first gas in the first passageway 102 to inhibit or prevent the second gas from bypassing the patient interface 108 and passing into the first passageway 102 and / or exiting via the exhalation port 110. The first gas conveyed along the first passageway 102 during the delivery period may be vented via the exhalation port 110. In some examples, some of the second gas may leak from the patient interface 108, for example, by the patient interface 108 not being correctly fitted to the patient 106 (i.e., an unintentional leak) or via bias flow holes in the patient interface 108 (i.e., a intentional leak). In some examples, operation of the first flow generator 120 may be controlled so that the pressure in the first passageway 102 does not exceed the pressure in the second passageway 104.

[0220] Any flow of the first gas from the first passageway 102 to the patient interface 108 during the delivery period may have the effect of diluting the second gas received at the patient interface 108. So the first flow generator 120 may be controlled to provide a low flow, or zero flow, during the delivery period. "Low flow" may refer to flow rates of less than about 10 liters per minute (L / min), less than about 5 L / min, or less than about 1 L / min, for example.

[0221] FIG. 3 and FIG. 4 are schematic illustrations of another example respiratory support system 300.

[0222] In this example, the patient interface 108 is an unsealed interface. The unsealed interface may be a nasal cannula. The nasal cannula may include a pair of nasal prongs configured to extend into the patient's nares.

[0223] In this example, the exhalation port 110 is omitted. Exhaled gas and breathing gas that are not inhaled by the patient may be vented at the patient interface 108.

[0224] The arrows in FIG. 3 represent the direction of flow of the first gas and the second gas during an accumulation period. The first gas is conveyed to the unsealed patient interface 108 by the first passageway 102 and the second passageway 104. The first gas and exhaled gas may be vented at the patient interface 108 during patient exhalation.

[0225] The arrows in FIG. 4 represent the direction of flow of the first gas and the second gas during the delivery period.

[0226] Aside from the differences described or shown in the drawings, the respiratory support system 300 may be similar to the respiratory support system 100 of FIG. 1 and FIG. 2, and variants, as described above.

[0227] FIG. 5 and FIG. 6 are schematic illustrations of another respiratory support system 500 for delivering a breathing gas to a patient 106.

[0228] The respiratory support system 500 includes a first passageway 102 and a second passageway 104 for conveying breathing gas. The first passageway 102 includes an exhalation port 110 for venting exhaled gas and breathing gas that is not inhaled by the patient.

[0229] A first flow generator 120 is connected to a first inlet 126 at a distal portion of the first passageway 102 to generate a flow of the first gas therein.

[0230] A second flow generator 122 is connected to a second inlet 128 at a distal portion of the second passageway 104 to generate a flow of the first gas therein.

[0231] A filter 124 may be located at, or upstream of, one or more of the first inlet 126 of the first passageway 102, the first flow generator 120, the second inlet 128 of the second passageway 104, or the second flow generator 122.

[0232] The patient interface 108 in FIG. 5 and FIG. 6 is a sealed interface. The sealed interface may be, for example, a full-face mask, a compact full-face mask, a nasal mask, a compact nasal mask, an oral mask, a total face mask, a nasal pillows interface, or a sealing nasal cannula.

[0233] A second gas source 112 is connected to a distal portion of the second passageway 104 at a second gas inlet 116. The second gas source 112 supplies a second gas into the second passageway 104.

[0234] A non-return valve 114 is located upstream of the second gas inlet 116 to inhibit or prevent the second gas from flowing in the second passageway 104 in an upstream direction. That is, through the second flow generator 122. In other examples, for example when the second flow generator 122 is a positive displacement flow generator and is turned OFF, or the second flow generator 122 is operated to provide back pressure, the non-return valve 114 may be omitted. Regardless, the non-return valve 114 may inhibit or prevent the second gas from entering the second flow generator 122, which may be beneficial to reduce any fire risk if the second gas is flammable.

[0235] The first passageway 102 and the second passageway 104 are connected to a third passageway 118 by a joiner, such as a Y- or T-shaped joiner. The third passageway 118 is connected to the patient interface 108. In other examples, one or more of the firstpassageway 102 or the second passageway 104 may be connected directly to the patient interface 108.

[0236] The arrows in FIG. 5 represent the direction of flow of the first gas, the second gas and exhaled gas during the accumulation period. The second gas enters the second passageway 104 distally from the patient 106, e.g., upstream of a midpoint of the second passageway 104. The second gas flows in a downstream direction toward the patient interface 108 to accumulate a desired volume (bolus) of the second gas in the second passageway 104. Providing the second gas inlet 116 at a distal location may provide one or more of the benefits of simplifying the second passageway 104 close to the patient 106, reducing weight of the second passageway 104 close to the patient 106, reducing drag on the patient interface 108, improving sealing of the patient interface 108, increasing comfort for the patient 106, or improving ease of cleaning.

[0237] The first flow generator 120 may be operated to provide a flow of the first gas in the first passageway 102 toward the patient interface 108. The first gas and exhaled gas may be vented at the exhalation port 110. In some examples, the exhaled gas and the first gas may leak from the sealed patient interface 108.

[0238] The arrows in FIG. 6 represent the direction of flow of the first gas and the second gas during the delivery period. During the delivery period, the second gas that has accumulated in the second passageway 104 is delivered to the patient interface 108. The second flow generator 122 may be operated to provide a flow of the first gas which is conveyed along the second passageway 104. The flow of the first gas displaces the desired volume of the second gas that accumulated in the second passageway 104 to the patient interface 108.

[0239] The first flow generator 120 may be operated to provide flow of the first gas in the first passageway 102 to inhibit or prevent the second gas from bypassing the patient interface 108 and passing onto the first passageway 102 and / or exiting via the exhalation port 110. The first gas conveyed along the first passageway 102 during the delivery period may be vented via the exhalation port 110. In some examples, some of the second gas may leak from the patient interface 108, for example, by the patient interface 108 not being correctly fitted to the patient 106 (i.e., an unintentional leak) or via bias flow holes in the patient interface 108 (i.e., an intentional leak). In some examples, operation of the first flow generator 120 may be controlled so that the pressure in the first passageway 102 does not exceed the pressure in the second passageway 104.

[0240] FIG. 7 and FIG. 8 are schematic illustrations of another example respiratory support system 700.

[0241] In this example, the patient interface 108 is an unsealed interface. The unsealed interface may be a nasal cannula. The nasal cannula may include a pair of nasal prongs configured to extend into the patient's nares.

[0242] In this example, the exhalation port 110 is omitted. Exhaled gas and breathing gas that are not inhaled by the patient may be vented at the patient interface 108.

[0243] The arrows in FIG. 7 represent the direction of flow of the first gas and the second gas during an accumulation period. The first gas is conveyed to the unsealed patient interface 108 by the first passageway 102 and the second passageway 104 during the accumulation period. The first gas is vented from the patient interface with the exhaled gas.

[0244] The arrows in FIG. 8 represent the direction of flow of the first gas and the second gas during the delivery period.

[0245] Aside from the differences described or shown in the drawings, the respiratory support system 700 may be similar to the respiratory support system 500 of FIG. 5 and FIG. 6, and variants, as described above.

[0246] FIG. 9 illustrates sensing and control of any one of the respiratory support systems 100, 300, 500, 700 of FIG. 1 to FIG. 8. The first passageway 102 and the second passageway 104 may be of any length. The second gas source 112 and / or second gas inlet 116 may be located either distally (e.g., upstream of a midpoint of the second passageway 104) or proximally (e.g., downstream of a midpoint of the second passageway) of the patient interface.

[0247] The respiratory support system may include a controller 902. The controller 902 may generate control outputs for controlling operation of one or more of the first flow generator 120 or the second flow generator 122. The controller 902 may be configured to control one or more of the timing or the duration of one or more of the delivery period or the accumulation period. In some examples, as described below, the controller 902 may be configured to control operation of an active control mechanism. The active control mechanism, controlled by the controller, may control the flow rate at which the second gas enters the second passageway 104.

[0248] The respiratory support system may include one or more sensors 904-922, e.g., pressure sensors and / or flow rate sensors. Outputs from the one or more sensors may be received by the controller. The controller may be configured to control the respiratory support system, e.g., one or more of the first flow generator 120 or the second flow generator 122, based at least in part on the output from the sensors.

[0249] In another example, if the first flow generator 120 is a positive displacement flow generator, the first flow generator 120 may be turned OFF to provide back pressure inhibiting flow from the second passageway 104 to the first passageway 102.

[0250] Although not shown in the drawings, a non-return valve may be provided in the first passageway 102, e.g., between the first flow generator 120 and the second gas inlet 116, to inhibit flow toward the first flow generator 120. This non-return valve 114 may be provided irrespective of whether the first flow generator 120 is a positive displacement flow generator or not.

[0251] The first flow generator 120 and the second flow generator 122 may be operated in combination to provide a continuous positive airway pressure (CPAP) or a variable positive airway pressure (VPAP) (e.g., bi-level positive airway pressure, BPAP, or automatic positive airway pressure, APAP) to deliver an inspiratory positive airway pressure (IPAP) and an expiratory positive airway pressure (EPAP) to the patient.

[0252] The pressure that the flow generators 120, 122 are controlled to (i.e., the set pressure) may be the pressure at the patient interface 108 or another location in the circuit. The set pressure may be based on the pressure generated by the flow generator, and an estimation of losses from the flow generator to the patient interface 108 or another location (i.e., because of pressure losses in the flow path between the flow generator and the location).

[0253] In some examples, the controller 902 may be configured to operate the first flow generator 120 to provide a set flow rate, e.g., during the accumulation period. For example, the set flow rate of the first flow generator during the accumulation period may be at least equal to the rate of mask leakage. Including both intentional and unintentional mask leakage. This may ensure that the first flow generator 120 delivers sufficient flow to account for approximately all flow exiting the respiratory support system through mask leak. And that no or minimal flow is provided from the second passageway that would result in the second gas being delivered during the accumulation period.

[0254] The controller 902 may be configured to operate the second flow generator 122 at a lower flow rate than the first flow generator, e.g., during the accumulation period. For example, the controller 902 may operate the second flow generator 122 at a zero flow rate or a negative flow rate. For the respiratory support systems 100, 300 of FIG. 1 to FIG. 4, it may be preferable for the second flow generator 122 to provide zero flow. As the second gas enters the second passageway 104 during the accumulation period, any breathing gases already present in the second passageway are displaced toward the patient. For the respiratory support systems 500, 700 of FIG. 5 to FIG. 8, preferable to provide or allow a negative flow. That is, allow flow to exit the respiratory support system through the inlet of the second flow generator 122. The magnitude of the negative flow rate may be approximately equal to the rate of second gas delivery into the second passageway 104. By operating the second flow generator 122 at a negative flow, breathing gas can escape the system through the second flow generator inlet. Which may ensure that no or minimal second gas is delivered to the patient during the accumulation period.

[0255] The controller 902 may be configured to operate the first flow generator 120 to provide a set flow rate, and the second flow generator 122 to provide a set pressure, e.g., during the accumulation period. The set pressure of the second flow generator 122 may be lower than a set pressure at which the first flow generator 120 is operated. The controller 902 may operate the first flow generator at a set pressure during the accumulation period.

[0256] Alternatively, the first flow generator 120 may be controlled to deliver a set pressure during the accumulation period. In this example, the first flow generator 120 automatically varies the flow to ensure the pressure at the patient interface remains constant. In this way, sufficient flow is always provided to account for any mask leak and maintain the pressure at the desired level.

[0257] The second flow generator 122 may then be operated at a set pressure that is lower than the pressure of the first flow generator 120. This ensures that no flow, minimal flow, or low flow from the second passageway 104 will be delivered to the patient during the accumulation period, as the first flow generator 120 is supplying flow at a higher pressure than the pressure in the second passageway 104.

[0258] During the delivery period, the controller 902 may be configured to operate the second flow generator 122 to provide a set flow rate and / or a set pressure. In one example, the set flow rate may be a percentage of the peak respiration flow rate, e.g., between about 70 % and about 150 % of the peak respiration flow rate. In another example, the set flowrate may be a function of the peak inspiration flow rate and mask leakage rate, such as a sum of the peak inspiration flow rate and the mask leakage rate.

[0259] In some examples, operation of the first flow generator 120 may be controlled so that a pressure in the first passageway 102 does not exceed a pressure in the second passageway 104 during the delivery period. This may be achieved by the first flow generator 120 being operated at a set pressure that is less than a set pressure of the second flow generator 122. The first flow generator 120 may be operated at a set pressure to achieve a desired pressure at an outlet of the first flow generator 120, and / or achieve a desired pressure at one or more points along the first passageway 102 or the patient interface 108.

[0260] When the second flow generator 122 is operated at a set flow rate, the first flow generator 120 may be operated at a set pressure, to provide constant pressure or near to constant pressure delivered to the patient. In this example, the first flow generator 120 supplements flow from the second flow generator 122 to ensure a constant pressure is delivered during the delivery period. Alternatively, the second flow generator 122 is operated at a set flow rate, the first flow generator 120 may be operated at a set flow rate that is less than the set flow rate of the second flow generator 122. The second flow generator 122 may have a set flow rate that is low or zero so as not to dilute the second gas in the second passageway 104 during the accumulation period.

[0261] In examples providing high flow therapy, the first flow generator 120 and second flow generator 122 may be operated at set flow rates as described above, such that a constant flow rate of breathing gases is received by the patient during both the accumulation period and the delivery period.

[0262] Further details of the controller 902 are described below with reference to FIG. 15 to FIG. 20.

[0263] FIG. 10 and FIG. 11 are schematic illustrations of another example respiratory support system 1000 for delivering a breathing gas to a patient 106.

[0264] The respiratory support system 1000 includes a first passageway 102 and a second passageway 104 for conveying breathing gas to a patient interface 108.

[0265] The patient interface 108 may be a sealed interface, in which case the patient interface 108 and / or the first passageway 102 may include an exhalation port 110 for venting exhaled gas and breathing gas that is not inhaled.

[0266] The patient interface 108 may alternatively be an unsealed patient interface 108. In that case, the exhalation port 110 may be omitted. Exhaled gas and breathing gas that is not inhaled may be vented at the patient interface 108.

[0267] The respiratory support system 1000 includes a flow generator 1002 including a flow generator outlet 1004 connected to the distal portions of the first passageway 102 and the second passageway 104. The flow generator outlet 1004 of the flow generator 1002 may be connected to the first passageway 102 and second passageway 104 via a T- or Y- shaped joiner.

[0268] The flow generator 1002 may be operable to supply gas at a controlled pressure. In some examples, the flow generator 1002 may supply the first gas at a first pressure (IPAP) during patient inhalation, and at a second pressure (EPAP) during patient exhalation. In another example, the flow generator 1002 may supply the first gas at a constant pressure across the whole breathing cycle, e.g., CPAP. Alternatively, the flow generator 1002 may supply the first gas at a constant flow rate, e.g., high flow therapy.

[0269] An active valve mechanism 1006 is located in proximal portions of the first passageway 102 and the second passageway 104. The active valve mechanism 1006 is operable to selectively open and close the first passageway 102 and the second passageway 104.

[0270] The active valve mechanism 1006 may include a three-way valve including two valve inlets, connected to the first passageway 102 and the second passageway 104, respectively. A single valve outlet may be connected to the patient interface 108.

[0271] In the case of FIG. 10 and FIG. 11, the active valve mechanism 1006 includes a first valve 1010 and a second valve 1012. The first valve 1010 and the second valve 1012 may be selectively opened and closed independently of each other. The first valve 1010 and the second valve 1012 may be any suitable valves such as globe valves, or gate valves, for example. The active valve mechanism 1006 may have at least one actuator (not shown) that drives the first valve 1010 and the second valve 1012 between opened and closed positions.

[0272] The first passageway 102 and the second passageway 104 are connected to the third passageway 118 via a T- or Y-joiner. The third passageway 118 is connected to the patient interface 108 so as to indirectly connect the first passageway 102 and the second passageway 104 to the patient interface 108. In other examples, one or more of the firstpassageway 102 or the second passageway 104 may be directly connected to the patient interface 108.

[0273] A second gas source 112 is connected to a proximal portion of the second passageway 104 at a second gas inlet 116. The second gas source 112 supplies a second gas into the second passageway 104. The second gas inlet 116 is located upstream of the active valve mechanism 1006. The second gas source 112 may be a pressurized oxygen vessel or an oxygen concentrator, for example. The second gas source 112 may be connected to the second gas inlet 116 by a gas supply line 1008. A gas control valve 924 may be opened and closed to control the rate at which the second gas enters the second passageway 104.

[0274] The arrows in FIG. 10 represent the direction of flow of the first gas and the second gas during an accumulation period. During the accumulation period, the second valve 1012 of the active valve mechanism 1006 is closed and the gas control valve 924 is open to allow the second gas to enter the second passageway 104. The second gas flows in an upstream direction away from the patient interface 108 to accumulate a desired volume (bolus) of the second gas in the second passageway 104. The first valve 1010 of the active valve mechanism 1006 is open and the flow generator 1002 is operated to provide a flow of the first gas in the first passageway 102 toward the patient interface 108.

[0275] If the patient interface 108 is a sealed interface, exhalation gas and the first gas may be vented via the exhalation port 110 and / or via bias flow holes of the sealed patient interface 108. The exhalation port 110 may be provided in the first passageway 102, as shown.

[0276] If the patient interface 108 is an unsealed interface, exhalation gas and the first gas may be vented at the patient interface 108.

[0277] The arrows in FIG. 11 represent the direction of flow in the second passageway 104 during a delivery period.

[0278] During the delivery period, the second gas that has accumulated in the second passageway 104 is delivered to the patient interface 108. The first valve 1010 of the active valve mechanism 1006 is closed and the second valve 1012 is open to allow flow of the first gas to be diverted to the second passageway 104. The flow of the first gas to the second passageway 104 displaces the volume of second gas that has accumulated in the second passageway 104 to the patient interface 108.

[0279] In some examples, the first valve 1010 and the second valve 1012 may be open for an overlapping period, i.e., both open at the same time. For example, one of the first valve 1010 or the second valve 1012 may open for a period of time before the other of the first valve 1010 or the second valve 1012 closes.

[0280] The active valve mechanism 1006 may include an actively-controlled valve. The actively-controlled valve may be, for example, a solenoid valve, a diaphragm valve, a shuttle valve, a spool valve, a ball valve, a gate valve, a butterfly valve, a switch valve, or a three-way valve. The actively-controlled valve may be adjusted by any suitable actuator, such as a solenoid actuator, a pneumatic actuator, or an electric motor, for example. The pneumatic actuator may, in one example, be operated by a dedicated source of pressurized gas. In another example, the pneumatic actuator may be operated by gas flow from the flow generator. In yet another example, the pneumatic actuator may be operated by a second gas supplied by the second gas source. A separate supply line may connect the respective gas source to the pneumatic actuator for operation thereof. This avoids breathing gas in the first passageway 102 and / or second passageway 104 being used to operate the actuator.

[0281] FIG. 12 illustrates sensing and control of the respiratory support system 1000 of FIG. 11 and FIG. 12. The respiratory support system 1000 may include a controller 902 and one or more sensors 1202. Operation of the controller 902 is described in further detail below with reference to FIG. 15. Otherwise, the controller 902 of the respiratory support system 1000 may be similar to the controller described above with respect to FIG. 9.

[0282] FIG. 13 and FIG. 14 are schematic illustrations of another example respiratory support system 1300.

[0283] In this example, the active valve mechanism 1006 is located in distal portions of the first passageway 102 and the second passageway 104. And the second gas source 112 is connected to a distal portion of the second passageway 104 downstream of the active valve mechanism 1006.

[0284] The arrows in FIG. 13 represent the direction of flow of the first gas and the second gas during an accumulation period. The second valve 1012 of the active valve mechanism 1006 is closed and the gas control valve 924 is open to allow the second gas to enter the second passageway 104. The second gas flows downstream from the second gas inlet 116. A volume of the second gas accumulates in the second passageway 104. The first valve1010 of the active valve mechanism 1006 is open, which allows the first gas flowing from the flow generator 1002 to be conveyed along the first passageway 102 to the patient interface 108 via the third passageway 118.

[0285] The arrows in FIG. 14 represent the direction of flow of the first gas and the second gas during a delivery period.

[0286] The respiratory support system 1300 otherwise may be similar to the respiratory support system 1000 of FIG. 10 and FIG. 11, and variants, as described above. For example, the patient interface 108 may be a sealed interface or an unsealed interface. And the first valve 1010 and the second valve 1012 may be open for an overlapping period.

[0287] FIG. 15 illustrates sensing and control of the respiratory support system 1300 of FIG. 13 and FIG. 14.

[0288] With reference to FIG. 12 and FIG. 15, the respiratory support systems 1000, 1300 may include a flow generator 1002 to provide a flow of the first gas in the first passageway 102 and the second passageway 104. The respiratory support systems 1000, 1300 may include an active valve mechanism 1006 to adjust flow of the first gas between the first passageway 102 and the second passageway 104.

[0289] In some examples, the active valve mechanism 1006 may be controlled by the controller 902 to allow the first gas to be conveyed along the second passageway 104 for a period after the second gas that accumulated in the second passageway 104 has been delivered to the patient interface 108.

[0290] The controller 902 in FIG. 9, FIG. 12 and FIG. 15, may control the delivery period, e.g., one or more of a commencement of the delivery period or a conclusion of the delivery period, based on a phase of the breathing cycle of the patient 106. For example, based on a selected event of the breathing cycle. The delivery period may be controlled so that the second gas is delivered to the patient 106 at a desired phase of the breathing cycle. The selected event of the breathing cycle may be the same as, or to different to, the desired phase of the breathing cycle. For example, the delivery period may commence based on detecting commencement of inhalation, such that the second gas is delivered during a high flow phase of patient inhalation. The delivery period may be controlled by the controller 902 to reduce wastage of the second gas whilst achieving the desired therapeutic effect of the second gas.

[0291] The controller 902 may control the conclusion of the delivery period to occur during patient inhalation. This may be carried out by stopping or reducing the flow and / or pressure of the first gas supplied to the second passageway 104. In one example, this may occur when the second gas that accumulated in the second passageway 104 has been supplied to the patient interface 108.

[0292] The controller 902 may control the conclusion of the delivery period to occur before the end of patient inhalation. The controller 902 may control the flow and / or pressure of the first gas in the second passageway 104 so that the conclusion of the delivery period occurs before the end of patient inhalation. The flow rate and / or pressure of the first gas supplied to the first passageway 102 may increase or starts before the end of patient inhalation to maintain flow and / or pressure at the patient interface 108.

[0293] The controller 902 may control flow of the first gas in the first passageway 102 so that the first passageway 102 conveys the first gas during at least part of patient exhalation and patient inhalation. The controller 902 may control the flow of the first gas in the second passageway 104 so that the first gas is supplied for a period after the second gas that accumulated in the second passageway 104 has been delivered to the patient interface 108. A breathing gas supplied to the patient interface 108 toward the end of patient inhalation may include a mixture of the first gas and the second gas, or only the first gas.

[0294] The controller 902 may control the commencement of the delivery period to occur during patient exhalation. For example, so that the second gas is delivered to the patient interface during the subsequent patient inhalation.

[0295] The controller 902 may control the conclusion of the delivery period to occur before the end of patient inhalation.

[0296] The controller 902 may control operation of the active valve mechanism 1006 based on the breathing cycle of the patient.

[0297] In some examples, the active valve mechanism 1006 may be operated so that at the commencement of the delivery period, the first gas is supplied to the second passageway at the onset of patient inhalation or initial stage of patient inhalation. That is, whilst the inspiratory flow rate is increasing. At the conclusion of the delivery period, the active valve mechanism 1006 may be operated to reduce or stop the first gas being supplied to the second passageway 104 during a later stage of patient inhalation. That is, whilst the inspiratory flow rate is decreasing. At the conclusion of the delivery period, the controller 902 may control the active valve mechanism 1006 to supply the first gas to thefirst passageway 102 during a later stage of patient inhalation and during at least part of the patient exhalation.

[0298] The delivery period may be between about 50 % and 90 %, or between about 60 % and 80 %, or between about 70 % and 80 % of the duration of the patient inhalation.

[0299] In some examples, the conclusion of the delivery period may occur a period after the second gas that accumulated in the second passageway 104 has been delivered to the patient interface 108. That is, the first gas may continue to be supplied to the second passageway 104 for a period after the second gas that accumulated in the second passageway 104 has been delivered to the patient interface 108.

[0300] Similarly, the controller 902 in FIG. 9, FIG. 12 and FIG. 15 may control the accumulation period, e.g., one or more of a commencement of the accumulation period or the conclusion of the accumulation period, based on a phase of the breathing cycle of the patient 106.

[0301] The controller 902 may control the volume of the second gas accumulated during the accumulation period so that a desired volume of the second gas is ready in the second passageway 104 for delivery to the patient 106 during the delivery period.

[0302] FIG. 16 to FIG. 20 illustrate various examples of how the controller 902 may control one or more of the delivery period or the accumulation period based on a phase of the breathing cycle of the patient 106.

[0303] As shown in FIG. 16 to FIG. 20, the controller 902 may control the delivery period and the accumulation period so that at least one is occurring at any time during the breathing cycle. The delivery period and the accumulation period may occur sequentially, one after the other, so that only one occurs at any one time during the breathing cycle. However, as indicated above, the first gas may be supplied to both the first passageway 102 and the second passageway 104 at the same time, optionally at different flow rates, depending on the arrangement of the first passageway 102 or second passageway 104. For example, in the case of the respiratory support systems of FIG. 1 to FIG. 8, adequate flow and / or pressure of the first gas may be provided to the first passageway 102 during the delivery period to prevent the second gas from bypassing the patient interface 108. And the controller 902 may control the respiratory support system so that the second gas accumulated during the accumulation period of each breathing cycle is delivered to the patient interface 108 during a subsequent delivery period to avoid amounts of the second gas being stored in the respiratory support system over multiple breathing cycles.

[0304] To reduce wastage of the second gas, controlling the moment at which the second gas reaches the patient interface 108 during the breathing cycle is advantageous. And may depend on factors such as one or more of the disease being treated, the medical condition of the patient 106, or the age of the patient 106, for example. The delivery period may be controlled to occur at a desired phase of patient inhalation, e.g., during a high flow phase of patient inhalation, so that the second gas is delivered to the patient interface at a desired moment. During a high flow phase of patient inhalation, any venting and leakage from the respiratory support system, including intentional or unintentional leakage, will be at its lowest. And in this situation, the second gas that is supplied to the patient interface 108 is mostly likely to enter into the patient's lungs, in particular the alveoli.

[0305] The term high flow phase of patient inhalation will be understood to include a peak in the inspiratory flow rate of the breathing cycle, as represented by the peaks in the breathing cycles shown in FIG. 16 to FIG. 20. And optionally a percentage of tidal volume or flow rate occurring before and / or after the peak flow. The highest inspiratory flow rate is often referred to as the peak inspiratory flow. The high flow phase of patient inhalation may be a time interval that includes the peak inspiratory flow and a duration before and after the peak inspiratory flow. But the high flow phase of patient inhalation does not extend to the commencement of inhalation or the conclusion of patient inhalation.

[0306] The second gas may be delivered to the patient interface 108 at a particular moment in the breathing cycle. And the controller 902 may adjust the commencement of the delivery period so that the second gas is delivered to the patient interface 108 at the particular moment. For example, the second gas may be delivered to the patient interface 108 at any one of the following moments:• a period before the onset of inhalation,• at the commencement of inhalation, or• a period after the onset of inhalation.

[0307] The second gas that is delivered to the patient interface 108 may be accumulated during a preceding accumulation period. In some examples, the entirety of the second gas accumulated during the accumulation period is delivered to the patient interface 108 in the subsequent delivery period. In other examples, the second gas accumulated during the accumulation period may not necessarily all be delivered to the patient interface 108. For example, some of the second gas accumulated during the accumulation period may be conveyed along the second passageway 104 during the initial stages of a subsequent patient exhalation, and vented or leaked, for example at the exhalation port 110. Or some of theaccumulated second gas may not necessarily be delivered to the patient interface 108 during the delivery period immediately following the accumulation period. For example, some of the accumulated second gas could be delivered to the patient interface 108 during one or more subsequent delivery periods. This may occur as a result of the volume of patient inhalation varying over multiple breathing cycles. The second gas accumulated in the second passageway 104 that is not delivered in the patient interface 108 may be vented from the respiratory support system.

[0308] The conclusion of the second gas being delivered to the patient interface 108 may or may not necessarily coincide with the conclusion of the delivery period. In one example, the conclusion of the delivery period occurs when the supply of the first gas to the second passageway 104 has stopped or reduces. In this example, no or insufficient supply of the first gas will result in displacement of the second gas to the patient interface 108 also stopping or reducing. This may occur when the flow rate and / or pressure of the first gas in the first passageway 102 is lower than the pressure and / or flow rate of the first gas supplied to the second passageway 104, for example. In another example, the conclusion of the second gas being delivered to the patient interface 108 may result in all of the second gas accumulated in the second passageway 104 being displaced. The delivery period and the flow rate of the first gas supplied to the second passageway 104 during the delivery period may be such that all of the second gas is displaced to the patient interface 108. In this example, the delivery period may be longer than the period over which the second gas is delivered to the patient interface 108. And the conclusion of the delivery period may be after the conclusion of the second gas being delivered to the patient interface 108. Such an example is illustrated in FIG. 20, in which the delivery of the second gas to the patient interface 108 is completed before the end of the delivery period.

[0309] In some examples, as shown in FIG. 19, the conclusion of the delivery period and the conclusion of the second gas being delivered to the patient interface 108 occurs at the same time. That is, the delivery period and the delivery of the second gas conclude at approximately the same time.

[0310] In some examples, again as shown in FIG. 19, the commencement of delivery of the second gas to the patient interface 108 may be delayed from one or more of the onset of patient inhalation 1602 or the conclusion of patient exhalation 1608 by a postponement period. That is, the commencement of delivery of the second gas to the patient interface 108 may align with the end of the postponement period. In other examples, the second gas could be delivered to the patient interface 108 before or after the end of the postponement period.

[0311] The controller 902 may determine the postponement period based, at least in part, on the output of one or more sensors. For example, one or more of the pressure sensors 904-910, external sensor 912, flow rate sensors 914-922, or sensor 1202. The sensors may monitor one or more of:• the period of the breathing cycle or respiration rate of the patient 106,• the tidal flow of the patient 106, or• the flow rate of the patient inhalation.

[0312] The controller 902 may determine the postponement period based, at least in part, as a function of an input from a clinician.

[0313] In one example, a clinician may manually determine the postponement period that delays the flow of the first gas along the second passageway 104 based on the breathing cycle of the patient 106. This may be done by observing the breathing cycle of the patient 106. Or by measuring the period of the breathing cycle, measuring or estimating the tidal volume of the patient's breathing cycle, or measuring the flow rate of the patient's breathing cycle.

[0314] The controller 902 may control the commencement of the delivery period so that the second gas is received by the patient interface 108 at or during a desired phase of the breathing cycle. For example, by controlling second flow generator 122 or the active valve mechanism 1006 to control the flow rate and / or pressure of the first gas supplied to the second passageway 104.

[0315] The controller 902 may control the commencement of the delivery period with reference to the breathing cycle. For example, with reference to one or more events of the breathing cycle. The controller 902 may use one or more events of the breathing cycle to control, at least in part, the delivery period. For example, the commencement of the delivery period. The events of the breathing cycle may include any one or more of:• the onset of patient inhalation 1602,• the conclusion of patient inhalation 1604,• the onset of patient exhalation 1606,• the conclusion of patient exhalation 1608,• events between the conclusion of patient inhalation 1604 and the onset of patient exhalation 1606,• events between the onset of patient inhalation 1602 and the conclusion of patient exhalation 1608• the peak flow in patient inhalation, or• a high flow phase of patient inhalation, for example a predetermined range including peak flow and optionally a range before and / or after peak flow of patient inhalation.

[0316] The controller 902 may use historical breathing cycle data of the patient to predict one or more events in the breathing cycle. For example, for commencing the delivery period in subsequent breathes. Or so that the second gas may be delivered to the patient interface 108 relative to the event predicted. For example, delivering the second gas to the patient interface 108 before the predicted event, at the predicted event, or after the predicted event. The historical data may be used by the controller 902 when the patient's breathing cycle has been interrupted, e.g., due to abnormal breathing.

[0317] FIG. 16 shows, by way of example, three complete breathing cycles, each including an inhalation and a subsequent exhalation (or vice versa). The flow profile during a patient's respiration is cyclic and usually has a peak inspiratory flow at some point after the commencement of patient inhalation and before the end of patient inhalation. The peak inspiratory flow is represented by the peaks in the flow rate in FIG. 16 to FIG. 20.

[0318] The onset of patient inhalation occurs when the breathing cycle transitions from exhalation to inhalation. The onset of patient inhalation does not require the flow to be exactly zero because it will depend, for example on where the measurement is taken. However, in the case of FIG. 16 to FIG. 20, the onset of patient inhalation 1602 occurs when the inspiratory flow rate rises from zero. And the conclusion of patient inhalation 1604 occurs when the inspiratory flow rate falls to zero.

[0319] The breathing cycle may be monitored by flow rate sensors or other types of sensors, such as a pressure sensor that measure gas pressure in the respiratory support system (e.g., at the patient interface 108), motion sensors, or other patient sensors. When using other sensors, the profile of the breathing cycle, including the transition between patient inhalation and patient exhalation may be based on different parameters other than zero flow as shown in FIG. 16 to FIG. 20.

[0320] The breathing cycle of a patient may have abnormal events, including pauses or no active breathing for short periods (e.g., an apnea event). Or anomalies caused by coughing, movement of the patient, or the patient holding their breath when swallowing, for example, which may result in the patient not breathing cyclically as shown in FIG. 16 to FIG. 20.

[0321] The historical breathing cycle data may be based on a number of the previous breaths. For example, 5-10 breathing cycles, or 5-10 breathing cycles that have been determined as being regular and fall within threshold values. The historical breathing cycle data may include data points at different moments of the breathing cycle, including one or more of the onset of the patient inhalation, the onset of patient exhalation, a high flow phase of patient inhalation, or peak flow.

[0322] The historical breathing cycle data may include input data based on outputs of one or more of the pressure sensors 904-910, external sensor 912, flow rate sensors 914-922, or sensor 1202. The controller 902 may be configured to determine when the input data is outside a threshold range and discard that input data for determining the phase of the breathing cycle. When the input data is determined as being outside the threshold range, the input data may represent an irregular breath in the breathing cycle. To take into account changes in a patient's breathing cycle, for example as the patient's medical conditional changes, the historical breathing data may be updated at any desired interval. For example, the interval may be based on a number of previous breathing cycles, such as after 5 breathing cycles, or multiples thereof including after, such as 10 breathing cycles, or 20 breathing cycles. In another example, the interval at which the historical data may be updated may be a time period, for example every minute, or a multiple thereof. In another example, the historical breathing cycle data may be updated continuously, or every breathing cycle, e.g., as a moving average.

[0323] If input data representing a breathing cycle is outside the threshold value, the input data may be excluded from the historical breathing cycle data. The threshold for excluding input data representing the breathing cycle may be based on the historical breathing cycle data. The historical breathing cycle data, and therefore the threshold for excluding data from the historical breathing cycle data may change over time. For example, as the condition of the patient changes. The rate at which the threshold changes may be controlled by the controller 902.

[0324] The controller 902 may receive inputs relating to events in the breathing cycle, and use the inputs as factors in controlling the respiratory support system, e.g., commencement of the delivery period. The inputs received by the controller 902 may be include outputs from one or more sensors. For example, one or more of the pressure sensors 904-910, external sensor 912, flow rate sensors 914-922, or sensor 1202. Although not shown in the drawings, the sensors may include one or more gas composition sensors, such as sensors for measuring the oxygen or carbon dioxide content of the gas inat least one of the first passageway 102, the second passageway 104, the exhalation port 110, or the patient interface 108.

[0325] The respiratory support system, e.g., controller 902, may include a user interface that a clinician may use to provide inputs in relation to the breathing cycle or other factors. The user interface may include one or more buttons, dials, sliders, touch-sensitive interfaces, or input fields, for example. The controller 902 may receive a clinician input, which the controller 902 may use, at least in part, to determine one or more parameters. For example, the delivery period. The clinician input may include, for example, the clinician's measurement or estimation of one or more of:• the tidal volume of the patient,• an internal volume of the second passageway,• an internal volume of the respiratory support system in which the second gas may accumulate,• the duration of the breathing cycle of the patient,• the respiration rate of the patient, or• the duration of the patient inhalation.

[0326] The controller 902 may be configured to determine when an input, e.g., sensor input or clinician input, is outside a threshold range and discard these inputs for determining the phase or an event of the breathing cycle. When the input is determined as being outside the threshold range, the input represents an irregular breath in the breathing cycle. In this situation, the controller 902 may revert to any number of the previous inputs, such as an average of the inputs of the previous breathes that were determined as being inside the threshold range, and therefore regarded as regular breathes.

[0327] The controller 902 may take into account other factors, unrelated to the breathing cycle of the patient 106, for controlling the respiratory support system, e.g., commencement of the delivery period. For example, dead space in the patient interface 108, anatomical dead space of the patient, and the medical condition being treated.

[0328] The controller 902 may control one or more of the flow rate or pressure of the first gas in the first passageway 102 and the second passageway 104, and supply of the second gas into the second passageway 104. For example, in order to control the commencement of the delivery period and when the second gas is received by the patient interface 108. The controller 902 may control operation of the first flow generator 120 so that the first gas is conveyed along and / or to the first passageway 102 for at least part of the period of patient exhalation. For example, during essentially the entire period of patient exhalationand / or during the accumulation period. The controller 902 may control operation of the second flow generator 122 so that the first gas is conveyed along and / or to the second passageway 104 during the delivery period. And during at least part of the period of patient inhalation. In some examples, the controller 902 may control operation of the first flow generator 120, second flow generator 122, or flow generator 1002, such as the speed of a motor driving of a fan blower. In some examples, the controller may control the active valve mechanism 1006 to adjust flow of the first gas.

[0329] To reduce the possible wastage of the second gas, the controller 902 may be operated so that the second gas displaced from the second passageway 104 is received by the patient's alveoli. For example, the controller 902 may operate the first flow generator 120, or the flow generator 1002 and active valve mechanism 1006, so that the first gas is conveyed along the second passageway 104 during the initial stages of patient inhalation. And reduce or stop flow of the first gas before the end of patient inhalation, e.g., before the conclusion of patient inhalation. Preferably at some time during the later stages of patient inhalation. That is to say, the controller 902 in FIG. 9 may control the second flow generator 122 for the delivery period, and the controller 902 in FIG. 12 and 15 may control the flow generator 1002 and the active valve mechanism 1006 to convey the first gas along the second passageway 104 for the delivery period. The delivery period may approximately equate to the time needed to deliver the full desired volume of the second gas (bolus). The volume of the second gas may be a therapeutically effective volume. This delivery period may be automatically set by the controller 902 or manually set by a clinician, e.g., based on the size of the first passageway 102 and / or patient information (e.g., tidal volume). Alternatively, the delivery period may be set to a portion of the total duration of patient inhalation. The controller 902 may be configured to detect when patient inhalation and patient exhalation commence and conclude based on inputs from one or more sensors. The controller 902 may determine a respiration rate or inspiratory duration, e.g., averaged over a number of successive breaths. This may be used to set the length of time that gas is delivered from the second passageway 104, i.e., the delivery period. For example, the controller 902 may deliver gas from the second passageway 104 for the first 60 % to 70% of the period of patient inhalation.

[0330] The controller 902 may account for the impact dead space may have on the supply of the second gas to the patient. The dead space may be in one or more of the patient interface 108 or in the tubing. For example, in the third passageway 118 connecting the second passageway 104 to the patient interface 108 that may be flushed prior to the commencement of patient inhalation. The second gas (bolus) may be delivered such that it reaches the patient interface 108 before the onset of patient inhalation, at the onset ofpatient inhalation, or after the onset of patient inhalation. The controller 902 may control operation of the second flow generator 122 in the case in FIG. 9, or the flow generator 1002 and the active valve mechanism 1006 in the case of FIG. 12 and FIG. 15, so that the flow of the first gas in the second passageway 104 may commence before the onset of patient inhalation. The controller 902 may determine a delay interval based, for example, one or more factors including :• the duration between commencement of the first gas being conveyed in the second passageway 104 and the second gas being received by the patient interface 108, or• the delay between the controller 902 sending an output signal to control the operation of the equipment item and the equipment item achieving the desired operation.

[0331] For example, there may be a lag between the controller 902 changing the desired speed / flow output of a flow generator and the flow generator achieving the desired speed / flow output. Or the lag between the controller 902 changing the operating position of the active valve mechanism 1006 and the valve of the active valve mechanism 1006 achieving the desired operating position.

[0332] The controller 902 may estimate the delay interval based on factors including one or more of flow rate of the first gas being conveyed in the second passageway 104, an internal volume of the respiratory support system downstream of the second gas accumulated in the second passageway 104, or leakage from the respiratory support system including intentional leakage and / or unintentional leakage. The controller 902 may then move the delivery period earlier in the breathing cycle by a function of the delay interval, denoted as the advance period in FIG. 17, FIG. 19 and FIG. 20, to negate the effect of dead space and flush exhaled air or the first gas.

[0333] The controller 902 may calculate the respiration rate and thereby determine an estimated onset of patient inhalation for each breathing cycle. If the delay interval is known, such as the time it takes for the second gas (bolus) to reach the patient, then the controller 902 may control the second flow generator 122 to convey the second gas before estimated onset of patient inhalation by the advance period. The advance period may be advantageous in respiratory support systems with a relatively large volume between the patient interface 108, and the first passageway 102 and second passageway 104. For example, in respiratory support systems with a third passageway 118, or a relatively long third passageway 118, between the patient interface 108 and the first passageway 102 and second passageway 104. The delay interval may be proportional to this volume.

[0334] In some examples, it may be desired for the second gas to be delivered to the patient interface 108 during the high flow phase of patient inhalation, and in one example at the point of peak inspiratory flow.

[0335] The controller 902 may control operation of the second flow generator 122, or the active valve mechanism 1006, so that the flow of the first gas to the second passageway 104 is delayed from the onset of patient inhalation, by a postponement period as shown in FIG. 18. So that the second gas is delivered to the patient interface 108 during a high flow phase of patient inhalation. The postponement period moves the commencement of delivery period later in the breathing cycle. By delivering the second gas during a high flow phase of patient inhalation, and preferably at the point of peak inspiratory flow, the quantity and / or volume of the second gas that may need to be delivered to the patient interface 108 may be reduced or minimized. As leakage (both intentional and unintentional) is roughly constant at constant pressures, the amount of oxygen lost through leakage during patient inhalation is proportional to the length of time it is delivered. Thus, the amount of the second gas lost due to leakage may be reduced when the delivery period is reduced. And by shortening the delivery period, less time is allowed for the second gas to mix with the first gas and become diluted.

[0336] The postponement period may be estimated based on a recorded or estimated breathing cycle for the patient. The postponement period may be a function of the time interval between the onset of patient inhalation and a high flow phase of patient inhalation. In one example, the second gas may be delivered to the patient interface 108 during a high flow phase of patient inhalation. For example, the second gas may be delivered at the point of peak inspiratory flow. The postponement period may be automatically determined by the controller 902 by receiving one or more inputs based on outputs from sensors representing pressure and / or flow rate characteristic of the breathing cycle. The controller 902 may determine the high flow phase of patient inhalation, or the point of peak inspiratory flow. The controller 902 may determine the postponement period based, at least in part, on inputs from a clinician. For example, the clinician may set the postponement period. In some examples, the postponement period may be estimated or set such that the midpoint of the bolus delivery occurs approximately at the point of peak inspiratory flow.

[0337] The postponement period may also be based on historical breathing cycle data as described above, e.g., based on the previous 5-10 breathing cycles that have been determined as being regular and fall within threshold values.

[0338] FIG. 19 represents the situation in which the postponement period moves the commencement of delivery of the second gas to the patient interface later in the breathing cycle. That is, delayed from onset of patient inhalation 1602 by the postponement period. As shown, the postponement period may be less than the advance period. The advance period moves the commencement of the delivery period earlier in the breathing cycle to account for the delay interval as described above, such that the second gas is delivered to the patient interface at the desired time or phase. That is, before the onset of patient inhalation 1602. Although the commencement of the delivery period occurs before the onset of patient inhalation 1602, the second gas is delivered during a period of patient inhalation.

[0339] FIG. 20 represents the situation in which the postponement period moves the commencement of delivery of the second gas later in the breathing cycle. That is, delayed from the onset of patient inhalation 1602. As shown, the postponement period may be greater than the advance period in this example. The combination of the postponement period and the advance period moves the commencement later in the breathing cycle, after the onset of patient inhalation 1602, as the postponement period is greater than the advance period. The delivery period may be between about 50 % and to 90 % of the duration of the patient inhalation, or between about 60 % and 80 %, or between about 70 % and 80 %.

[0340] FIG. 19 and FIG. 20 also show the commencement and conclusion of the accumulation period. In some examples, the controller 902 may control the commencement of the accumulation period, or the conclusion of the delivery period, based at least in part on one or more of:• the onset of patient inhalation 1602,• the conclusion of patient inhalation 1604,• the onset of patient exhalation 1606, or• the conclusion of patient exhalation 1608.

[0341] The controller 902 may control the commencement of the accumulation period based at least in part on a high flow phase of patient inhalation. The high flow phase may be a predetermined range before and / or after the point of peak inspiratory flow, including the point of peak inspiratory flow.

[0342] The controller 902 may control the commencement of the accumulation period to occur during one or more of at least part of the patient exhalation or at least part of the patient inhalation. In some examples, the accumulation period is not coterminous withpatient exhalation, and / or the delivery period is not coterminous with patient inhalation. The accumulation period may be longer than the patient exhalation. The delivery period may be shorter than the patient inhalation. The accumulation period may occur during a majority or vast majority of the patient exhalation (e.g., excluding only a final stage of patient exhalation if there is an advance period), and a part of the patient inhalation. The delivery period may be for only part of the patient inhalation.

[0343] Although the postponement period and the advance periods are not indicated in FIG. 16, FIG. 16 represents the situation in which the postponement period and the advance period are equal or essentially equal, in which case the commencement of the delivery period is at, or close to, the onset of patient inhalation 1602. Alternatively, FIG. 16 may also represent the situation in which the controller does not use the postponement period and the advance period to control the commencement of the delivery period.

[0344] The controller 902 may also control that rate at which the second gas enters the second passageway 104. For example, so that a desired volume of the second gas may accumulate in the second passageway 104, when the first gas is not being conveyed along the second passageway 104. For example, this may include filling the second passageway 104 with the second gas. A potential benefit of this is that the patient 106 may receive a high concentration of the second gas at the start of patient inhalation, or near the start of patient inhalation, so that the second gas reaches the alveoli of the patient's lungs. A lower concentration to the second gas may be provided in the breathing gas in the upper portion of the patient's airways. This may conserve the second gas. And the second gas may be supplied at a rate such that the volume delivered during the accumulation period does not exceed, or does not significantly exceed, the storage volume of the second passageway 104. This too may conserve the second gas.

[0345] In some examples, such as the respiratory support systems 100, 300 of FIG. 1 to FIG. 4, the controller 902 may control the rate at which the second gas is supplied to the second passageway 104 based on the known internal volume of the second passageway 104 (and, optionally, one or more of the reservoir or the humidification device), and the accumulation period. The internal volume may be selected based on the required treatment. The respiratory support system may limit the second gas from flowing in a downstream direction by a restriction device such as the non-return valve 114. The nonreturn valve 114 may allow a flow in a downstream direction during the delivery period. But during patient exhalation, back pressure of the first gas and exhaled gas may cause the non-return valve 114 to close, inhibiting flow of the second gas downstream of the nonreturn valve 114 during patient exhalation. The controller 902 may control operation ofthe first flow generator 120 during patient exhalation to provide adequate back pressure to the non-return valve 114. The first flow generator 120 may be operated to provide high flow therapy or positive airway pressure (PAP) therapy as described herein.

[0346] If the second gas inlet 116 is located in a distal portion of the second passageway 104, e.g., as shown in FIG. 5 to FIG. 8, a flow restriction device such as non-return valve 114 may be located between the second gas inlet 116 and the second flow generator 122. The controller 902 may operate the second flow generator 122 to provide no flow or minimal flow of the first gas to second passageway 104 when the second gas is supplied into the second passageway 104, i.e., during the accumulation period.

[0347] In one example, the controller 902 may control the second gas source 112 so as to control the second gas being supplied to the second passageway 104 over the accumulation period, or over the entire breathing cycle of the patient 106. For example, to accumulate the desired volume of the second gas in the second passageway 104 for supply to the patient interface 108. This may be achieved by delivering a high concentration of the second gas at the start of patient inhalation or near the start of patient inhalation, so that the second gas reaches the alveoli of the patient's lungs, and lower concentrations of the second gas may be provided in the breathing gas in the upper portion of the patient's airways.

[0348] In some examples, the accumulation period does not occur during one or more of the initial stages of patient inhalation, peak inspiratory flow, or the final stage of patient inhalation. For example, as shown in FIG. 17 and FIG. 19, the accumulation period occurs only during patient exhalation and the final stage of patient inhalation. In other examples, the accumulation period may occur only during patient exhalation, or during the initial stage of patient inhalation and middle stage of patient exhalation (i.e., not during the final stage of patient exhalation). In yet other examples, the accumulation period may occur during the later stage of patient inhalation and the initial and middle stages of patient exhalation (i.e., not during the final stages of patient exhalation). In yet other examples, as shown in FIG. 18 and FIG. 20, the accumulation period may occur during patient exhalation and during final and initial stages of patient inhalation.

[0349] The accumulation period may be a function of the treatment regime, taking into account factors such as the disease being treated.

[0350] The treatment volume, being the bolus of the second gas delivered to the patient, may be between about 50 % and 100 %, or between about 50 % and 90%, or betweenabout 60 % and 70% of the tidal volume of the patient, or of an average adult tidal volume, an average pediatric tidal volume, or an average neonatal tidal volume.

[0351] Examples of suitable tidal volumes / treatment volumes / storage capacity and / or dimensions for the second passageway are provided in the following table.Diameter xVolume length (volume)> 300 mL, > 400 mL, > 500 mL, 300-700 mL, 400- 22 mm x 1.5 m Adult650 mL, 500-600 mL, or 570 mL (570 mL)15 mm x 1.5 mPediatric 50-300 mL, 100-300 mL, 150-250 mL, or 270 mL (265 mL)10 mm x 1.5 mNeonatal 10-50 mL, 20-40 mL( 118 mL)

[0352] The controller 902 may control supply of the second gas to the second passageway 104 and may control supply of the first gas to the first passageway 102 and the second passageway 104. Control of the supply of the first gas and the second gas may be independent of each other. For example, the controller 902 may control the supply of the second gas to the second passageway 104 so that the second gas is supplied for only part of the accumulation period. The controller 902 may control one or more of the flow rate or the pressure of the second gas supplied to the second passageway 104 during the accumulation period while also controlling one or more of the flow rate or pressure of the first gas supplied to the patient interface 108 by the first passageway 102. In some examples, the controller 902 may control the flow rate of the second gas so as not to the supply the second gas to the second passageway 104 when the patient 106 or the patient interface 108 is receiving breathing gas from second passageway 104.

[0353] The controller 902 may control the supply of the second gas to the second passageway 104 so that the second gas is supplied for only part of the accumulation period.The second gas may be held in the second passageway 104 for the duration of the accumulation period.

[0354] The accumulation period may be determined manually, for example, by a clinician observing the breathing cycle of a patient. Or automatically, e.g., by the controller 902. The controller 902 may determine the accumulation period as a function of an output of at least one sensor that detects the breathing cycle of the patient. For example, pressure sensors 904-910, external sensor 912, or flow rate sensors 914-922. The sensor may be positioned in the respiratory support system to monitor the flow rate or pressure of one or more of the exhaled gases, inhaled gases, or gases vented from the respiratory support system to ascertain the breathing cycle of patient 106. The breathing cycle may be determined based on an output of one or more external sensors 912 that monitors abdominal movement of the patient caused by breathing, or muscular impulses of the patient. The external sensors external sensor 912 and some other sensors are optional.

[0355] The controller 902 may control the flow of the second gas, including switching provision of the second gas ON and OFF. When the second gas is flowing, the controller 902 may also control one or more of the flow rate or pressure of the second gas supplied to the second passageway 104. This may be achieved using an active gas control valve 924 in the gas supply line 1008. Or using in-built functionality of the second gas supply, such as an oxygen concentrator. In some examples, the second gas is not supplied to the second passageway 104 at times when the patient 106 is receiving gas from the second passageway 104, i.e., during the delivery period. In some examples, the second gas is only supplied to the second passageway 104 during the accumulation period. The controller 902 may control one or more of the flow rate or pressure of the second gas as a function of the volume of the second passageway 104 (and the optional reservoir or humidification device) for storing the second gas, and at least one of:• the accumulation period,• respiration rate of the patient 106, or• a duration of the patient inhalation.

[0356] The duration of patient inhalation may be provided by a clinician, the patient, or calculated by the controller as a function of the sensor output of one or more sensors.

[0357] The second passageway 104 may be loaded with the second gas so that the second gas delivered to the patient 106 has an optimal therapeutic effect. Supply of the second gas to the second passageway 104 may be delivered at a rate such that the volume delivered during an accumulation period does not exceed, or significantly exceed, thevolume that may be held by the second passageway 104. This may conserve the second gas.

[0358] The controller 902 may control one or more of the flow rate or pressure of the second gas so that a treatment volume of the second gas enters the second passageway 104 during the accumulation period. In some examples, the treatment volume may be approximately equal to a storage volume of the second passageway 104 (and, optionally, the reservoir and humidification device). In some examples, the treatment volume may be a product of the accumulation period and the flow rate of the second gas supplied to the second passageway 104. The controller 902 may be able to automatically determine a flow rate of the second gas, e.g., oxygen, to accurately fill the second passageway 104 with minimal wastage during the accumulation period. The controller 902 may receive data relating to the volume of the second passageway 104 to determine the volume of the second gas requiring delivery. This data may be entered by a clinician, or may be determined automatically using any suitable automatic component identification method. For example, an external sensor 912 such as a pulse oximeter.

[0359] The controller 902 may receive output signals from one or more of the pressure sensors 904-910, external sensor 912, flow rate sensors 914-922, or sensor 1202, to determine the breathing cycle. And, in turn, determine the accumulation period. The controller 902 may also take into account other factors such as fluid dynamic properties of the respiratory support system including the distance and time required for the volume of the second gas accumulated in the second passageway 104 to flow in order to reach the patient interface 108, details of the treatment regime, or changes in condition of the patient 106. For example, the controller 902 may receive inputs such as an estimate of the tidal volume of the patient 106, a percentage of the tidal volume to receive the second gas for effective therapeutic purposes, and the respiration rate of the patient 106. These inputs may be received from a clinician or by other means. Possible changes in the medical condition of the patient 106 include changes in oxygen saturation levels of the patient's blood, also known as SpO2 level, or changes in respiration rate.

[0360] The controller 902 may calculate a treatment volume of the second gas for treating of the patient 106. The treatment volume may be a product of the accumulation period and the flow rate of the second gas supplied to the second passageway 104.

[0361] In one example, the treatment volume may be a percentage of an expected or measured tidal volume of the patient 106. For example, the expected or measured treatment volume may be between about 50 % and 100 %, between about 50 % and 90%,between about 60 % and 80 %, or between about 60 % and 70 % of the tidal volume of the patient 106.

[0362] The controller 902 may determine a flow rate at which the second gas enters the second passageway 104 to fill a percentage of the internal volume of the second passageway 104 (or the respiratory support system) during the accumulation period. For example, the controller 902 may determine a maximum flow rate in which the internal volume of the second passageway 104 is filled to 100 % of capacity by the second gas. The controller 902 may determine an intermediate flow rate in which the internal volume of the second passageway 104 is filled to between about 20 % and 99 %, between about 30 % and 90 %, between about 40 % and 80 %, or to about 50 % to 70 % by the second gas. The controller 902 may determine a minimum flow rate in which the internal volume of the second passageway 104 is filled to between about 0 % and 20 %, or between about 0 % and 10 % by the second gas. In some examples, the controller 902 may monitor the volume of the second gas supplied to the second passageway 104 and turn OFF the supply of the second gas to the second passageway 104 when the capacity of the second passageway 104 has been reached. This may occur irrespective of whether the accumulation period has expired or not.

[0363] The controller 902 may automatically change settings during therapy in order to find optimal parameters for a patient 106. For example, the controller 902 might receive feedback about a patient 106 condition (such as SpO2) and alter the flow rate of the second gas. The controller 902 may determine a maximum second gas flow rate setting wherein the second passageway 104 is filled during the accumulation period. And optionally a minimum flow rate setting wherein no supplemental second gas is provided. Alternatively, the maximum and minimum flow rates for the second gas may be set by a clinician. The controller 902 may titrate flow rate of the second gas within the range set by the minimum and maximum such that a patient condition is kept within desired levels. For example, when the second gas is oxygen, if SpO2 decreases, the flow rate and / or treatment volume of the oxygen may be increased. The controller 902 may also recommend setting changes to a clinician, such as recommending a larger second passageway 104 if sufficient oxygen cannot be delivered. The accumulation period over which the second gas is delivered to the second passageway 104 may be automatically changed when the size of the second passageway 104 and / or the flow rate of the second gas is changed.

[0364] Although not shown, the respiratory support systems described herein may include one or more humidification devices located in the first passageway 102, the second passageway 104, or the third passageway 118. The humidification devices may form partof the first passageway 102 and / or the second passageway 104. And depending on the position of the humidification devices and the second gas inlet 116, the desired volume of the second gas may (at least in part) or may not accumulate in the humidification device.

[0365] The first flow generator 120, the second flow generator 122, and the flow generator 1002 of the respiratory support systems described herein may be any suitable device. For example, a fan or blower driven by a variable speed motor.

[0366] In some examples, one or more of the first flow generator 120, second flow generator 122, or the flow generator 1002 may be a positive displacement flow device, e.g., a piston / cylinder mechanism, a plugger / syringe mechanism, or another linear mechanism.

[0367] An advantage in using a positive displacement flow device for the second flow generator 122 is that the second flow generator 122 may be used to provide a flow of the second gas to the patient 106, and the first flow generator 120, which may not necessarily be a positive displacement flow device, may be operated to control pressure of the breathing gas delivered to the patient 106. The positive displacement flow device may inherently inhibit or prevent a reverse flow (negative flow rate). Whereas a centrifugal blower, for example, requires active control at a set pressure or set flow rate to inhibit or prevent negative flow.

[0368] In yet another example, the controller 902 may control the flow of the first gas in the second passageway 104 by deflating a bag of the first gas to convey the first gas along the second passageway 104. When the second gas is in the second passageway 104, deflating the bag may displace the second gas along the second passageway 104 toward the patient 106. The bag may be deflated by squeezing the bag, e.g., by applying mechanical or pneumatic pressure to an exterior of the bag. In this example, the first flow generator 120 may be operated to control pressure of the breathing gas delivered to the patient 106, e.g., during both the accumulation period and the delivery period. And the second flow generator 122, including the bag, may provide a flow of the second gas to the patient 106, e.g., during the delivery period.

[0369] As described above, in various examples the patient interface 108 may be an unsealed interface or a sealed interface. The unsealed interface may be a nasal cannula, an unsealed face mask, or a tracheostomy interface that is inserted into the respiratory tract of a patient through an incision in the patient's neck. Unsealed patient interfaces, particularly nasal cannulas, are well suited for delivering high flow therapy. The sealed interface may be a full-face mask, a sealed nasal cannula, a sealed oral mask, a sealednasal mask, or a nasal pillows interface, for example. The sealed patient interface 108 may or may not have bias flow holes for venting.

[0370] The first gas may be pressurized air or pressurized air enriched with oxygen. The air may be filtered, for example by the filters 124. The second gas may be any therapeutic gas. The gas should be accurately administered to the patient 106 to provide the required medical benefits. And to reduce wastage of the second gas, which may be valuable and / or scarce. For example, the second gas may be pressurized oxygen gas supplied from a liquified oxygen source, a bottled oxygen source, an oxygen concentrator, or a source providing air enriched with oxygen. In some examples, the second gas may include one or more of oxygen, heliox, or an anaesthetic gas. The anaesthetic gas may be nitrous oxide. In one example, the second gas may be a 50: 50 mixture of nitrous oxide and oxygen.

[0371] The respiratory support system may include sensors that provide sensor outputs. Changes in the sensor outputs may trigger the controller to recalculate the accumulation period. The controller 902 may predetermine the accumulation period when one or more of the following occurs:• the second passageway 104 is changed, for example when the second passageway 104 is swapped with a replacement passageway of the same size or with a different size;• the inspiration rate of the patient 106 changes;• the respiration rate of the patient 106 changes;• the expiration rate of the patient 106 changes;• the clinical state of the patient 106 changes, for example the SpO2 level of the patient 106 changes; or• leakage from the respiratory support system changes, for example the level of leakage of a sealed mask increases or decreases.

[0372] The controller 902 may have operating controls to allow a user to trigger the controller 902 to recalculate the accumulation period. For example, one or more of touch screen buttons, push buttons, or switching buttons.

[0373] With reference to FIG. 9, the respiratory support system may have one or more of pressure sensors 904-910, external sensor 912, or flow rate sensors 914-922. Each of the sensors may provide output signals that may be used as an input received by the controller 902 to control operation of one or more of the first flow generator 120 or the second flow generator 122 based on the breathing cycle of the patient 106. That is, the controller 902 may use the output signals from the sensors as inputs for determining the delivery period,including the commencement of the delivery period. The output signals may include output signals from one or more of:• pressure sensor 904 for sensing pressure of the first gas in the first passageway 102, that is preferably at or close to the outlet of the first flow generator 120,• pressure sensor 906 for sensing pressure of the first gas in the second passageway 104, that is preferably at or close to the outlet of the second flow generator 122,• pressure sensor 908 for sensing gas pressure in the third passageway 118,• a pressure sensor configured to sense a gas pressure of exhaled gas,• pressure sensor 910 for sensing gas pressure of patient interface 108,• flow rate sensor 914 of the first passageway 102,• flow rate sensor 916 of the second passageway 104, or• flow rate sensor 918 of the third passageway 118.

[0374] Other sensors may be used, at least in part, to determine the patient's respiratory phases. For example, dedicated contact or non-contact respiratory sensors or an external sensor 912, that may determine when a patient 106 is breathing in and breathing out and may communicate directly or indirectly with the controller 902. For example, an external sensor 912 may be attached to the abdomen of a patient 106 or an external sensor 912 that monitors the thoracic and / or abdominal expansion of the patient 106 to indicate if the patient 106 is inhaling and / or exhaling. Or a pulse oximeter, accelerometer, piezoelectric sensor, capnography sensor, or bioimpedance sensor, for example.

[0375] Similarly, output signals from the external sensors 912 may be used to determine if the patient 106 is inhaling or exhaling. And, in turn, the first gas supplied to the first passageway 102 during exhalation and the first gas supplied the second passageway 104 during patient inhalation.

[0376] The controller 902 may control operation of the first flow generator 120 based, at least in part, on pressure within the respiratory support system. For example, the controller 902 may receive an output signal from one or more of pressure sensors 904-910.

[0377] The output signals from the pressure sensors 904, 906 may be used for closed loop control of the first flow generator 120 and second flow generator 122, respectively.

[0378] The controller 902 may control operation of the second flow generator 122 based on a flow rate within the respiratory support system. For example, the controller 902 may receive output signals from one or more of:• flow rate sensor 914 for sensing flow rate of the first gas in the first flow generator 120, preferably located between an inlet and a fan or blower of the first flow generator 120;• flow rate sensor 916 for sensing the flow rate of the first gas in the second flow generator 122,• flow rate sensor 918 for sensing the flow rate the third passageway 118,• flow rate sensor 920 for sensing the flow rate in the second passageway 104, or• flow rate sensor 922 for sensing the flow rate of the second gas at the second gas inlet 116.

[0379] The output signals from the flow rate sensor 914 may be used for closed loop control of the first flow generator 120. The output signal of the flow rate sensor 916 may be used for closed loop control operation of the second flow generator 122.

[0380] Although not shown in the drawings, the flow rate sensors 914, 916 may be located downstream of the outlets of the first flow generator 120 and second flow generator 122, respectively.

[0381] If there is a pressure loss between the first flow generator 120 or second flow generator 122 and the patient interface 108, the controller 902 may estimate the pressure at the patient interface 108 based on the output signals of one or more of the pressure sensors 904, 906 or flow rate sensors 914, 916.

[0382] Alternatively, or additionally, sensors may be used downstream of the Y- or T- piece, e.g., proximal to or in the patient interface 108. For example, the pressure sensor 910 on the patient interface 108 may allow for direct control of the pressure delivered to the patient 106 using closed loop feedback, without the need to estimate pressure losses within the respiratory support system. The flow rate sensor 918 enables more direct measurement of patient breathing patterns and flows which may provide a good indication of changes in the breathing phase.

[0383] In some examples, the respiratory support system may include the pressure sensor 904 and flow rate sensor 914 at the first flow generator 120, and the pressure sensor 906 and flow rate sensor 916 at the second flow generator 122. Optionally, the respiratory support system may include a pressure or flow rate sensor at or near the patient interface 108, such as pressure sensor 910. The respiratory support system may be operated without the external sensor 912, and without sensors 920, 908, and 918. The controller 902 may still control operation of the first flow generator 120 and second flow generator 122. Forexample, controlling one or more of the commencement of the delivery period, or conclusion of the delivery period.

[0384] For the controller 902 to determine the advance period as a function of the delay interval between the first gas being supplied to the second passageway 104 and the second gas being delivered to the patient interface 108, the controller 902 may use, for example, outputs from the flow rate sensor 916 or the pressure sensor 906 of the second flow generator 122 as an indication that the first gas has been supplied to the second passageway 104.

[0385] In some examples, the controller 902 may use outputs from the pressure sensor 908 and pressure sensor 910, or flow rate sensor 918, for example, as an indication that the second gas has reached patient interface 108.

[0386] The controller 902 may determine the advance period as a function of the leakage from the respiratory support system. The output from flow rate sensor 918, for example, may be used by the controller 902 to estimate mask leakage. This may be found by determining a flow offset between the flow that is expected and the flow actually being delivered, at a certain pressure. The intended leaks from the respiratory support system, such as the bias flows of the mask and the exhalation port 110, may have a known response to a certain pressure. Thus, if the first flow generator 120 is operated at a set pressure, the difference between the expected and actual flow required to meet this pressure may be used to determine the unintended mask leak.

[0387] The output signals from pressure sensor 906 and pressure sensor 908, and flow rate sensor 916 and flow rate sensor 918, may be received as inputs by the controller 902 to calculate or evaluate leakage from the system. Leakage from the system may be a factor in the delay interval for the advance period between the first gas being supplied to the second passageway 104 and the second gas being delivered to the patient interface 108. That is, the output signals from one or more of the pressure sensor 908 or flow rate sensor 918, and one or more of the pressure sensor 906 or flow rate sensor 916 may be used to calculate the advance period and in turn operate the second flow generator 122 based on this determination.

[0388] The controller 902 may estimate the delay interval for the advance period as a function of the internal volume of the respiratory support system downstream of the second gas accumulated in the second passageway 104.

[0389] The commencement of the delivery period may be moved earlier in the breathing cycle, e.g., before the onset of patient inhalation 1602, by the advance period. The controller 902 may determine the advance period as a function of one or more of:• The delay interval between the first gas being supplied to the second passageway 104 and the second gas being delivered to patient interface 108. For example, the controller 902 may use outputs from sensor 1202 at the flow generator outlet 1004 to indicate that the first gas is being supplied to the second passageway 104, and outputs from the sensors at or near the patient interface 108 to indicate that the second gas is being delivered to the patient interface 108. In another example, an oxygen sensor, not shown, may also be located in one or more of the second passageway 104 or the third passageway 118;• The internal volume downstream of the second gas accumulated in the second passageway 104, and the flow rate of the first gas supplied to the second passageway 104. For example, the controller 902 may determine the volume downstream of the second gas accumulated in the second passageway 104 from an input representing the total volume of the second passageway 104, and an estimation of the volume of the second gas supplied during the accumulation period based on the control signal used to control the gas control valve 924. The flow rate of the first gas supplied to the second passageway 104 may be based on an output signal of the sensor at or near the outlet of the flow generator 1002;• The controller 902 may determine the delay interval based on the time elapsed to displace the second gas past a certain point in the respiratory support system. For example, the respiratory support system may include a sensor that detects the second gas. Once the sensor detects that the second gas is no longer present, the controller 902 may determine or predict the delay interval for the second gas to be delivered to the patient interface 108; or• Leakage from the respiratory support system. For example, the controller 902 may determine the leakage from the output of sensors located at or near the outlet of the flow generator 1002, output of the sensors located in the second passageway 104, output of the sensor located in the patient interface 108, and the expected flow at the patient interface 108.

[0390] As described above, the commencement of the delivery period may also be moved later in the breathing cycle by the postponement period, e.g., after the onset of patient inhalation 1602. For example, so that the second gas is delivered to the patient interface108 during a high flow phase of patient inhalation, or another part of the breathing cycle. The controller 902 may determine the postponement period based on outputs from one or more of the sensors 1202 at or near the flow generator 1002, outputs from the sensor in the second passageway 104, outputs from the sensor at the patient interface 108, or the output of the external sensor 912. These outputs may be used to determine the onset of the patient inhalation and peak flow or a high flow phase of patient inhalation.

[0391] During the accumulation period the controller 902 in FIG. 12 may control operation of the flow generator 1002 and the active valve mechanism 1006 to allow the first gas to flow in the first passageway 102 as shown in FIG. 10. The controller 902 in FIG. 15 may control operation of the flow generator 1002 and the active valve mechanism 1006 to allow the first gas to flow in the first passageway 102 as shown in FIG. 13.

[0392] In FIG. 12 and FIG. 15, assuming the flow generator 1002 is operating at a desired output, the controller 902 may operate the second valve 1012 of active valve mechanism 1006 to maintain a set pressure in the second passageway 104. And operate the first valve 1010 of the active valve mechanism 1006.

[0393] During the delivery period, the controller 902 of FIG. 12 and FIG. 15 may control the flow generator 1002 and the active valve mechanism 1006 to convey the first gas which is then able to displace the second gas into the patient interface 108 at a set flow rate, e.g., a percentage of the peak inspiratory flow, or at a set pressure.

[0394] By way of example, the set flow rate may be between about 70 % and 150 % of the peak inspiration flow rate during patient inhalation. For example, the flow rate may be equal to a sum of the peak inspiration flow rate and the mask leakage rate. In this situation, the first flow generator 120 may be operated at a low set flow, which may be zero or minimal flow, such that it does not dilute the oxygen being provided through the second passageway 104.

[0395] The controller 902 may estimate the postponement period and in turn control the commencement of the delivery period. And taking into account the advance period estimated. The controller 902 may estimate the postponement period using one or more of:• the delay interval between the first gas being supplied to the second passageway 104 and the second gas being delivered to patient interface 108;• the internal volume downstream of the second gas accumulated in the second passageway 104, and the flow rate of the first gas supplied to the second passageway 104; and• leakage from the respiratory support system.

[0396] The controller 902 may control the commencement of the delivery period by a postponement period. The postponement period may be a function of the interval between the onset of patient inhalation and a high flow phase of patient inhalation. To determine the postponement period, the controller 902 may use, for example, outputs from one or more of the flow rate sensor 916, pressure sensor 906, pressure sensor 910, or an external sensor 912, e.g., a contact or non-contact sensor. Outputs from the high flow phase of the patient inhalation may be assessed. The controller 902 may use, for example, outputs from one or more of the flow rate sensor 916, flow rate sensor 920, pressure sensor 906, pressure sensor 908, or pressure sensor 910.

[0397] If the respiratory support system includes pressure sensor 904 and flow rate sensor 914 at the first flow generator 120, pressure sensor 906 and flow rate sensor 916 at the second flow generator 122, and, optionally, a pressure or flow rate sensor at or near the patient interface such as pressure sensor 910, the controller 902 may use output signals from these sensors for determining the advance period and postponement period, respectively.

[0398] With reference to FIG. 1 to FIG. 9, the controller 902 may control the second flow generator 122 to operate at a set flow rate during the delivery period. And control the first flow generator 120 at a set pressure. The set flow rate for the second flow generator 122 may be approximately equal to the peak inspiration flow rate of the patient 106, such that substantially all of the inspiratory demand of the patient 106 is met by gas from the second passageway 104. Alternatively, the flow rate may be equal to the sum of the patient's peak inspiration flow rate and the mask leak rate. When the second flow generator 122 is operated at a set flow rate during inhalation (assuming flow of the second gas into the second passageway 104 is stopped), the controller 902 may control the pressure delivered to the patient interface 108. This may be done by the controller 902 adjusting the flow of the first gas of the first flow generator 120 during the delivery period.

[0399] When the second flow generator 122 is operated at a set flow rate or at a set pressure, the first flow generator 120 may be operated at a set flow rate that is less than the flow rate being generated by the second flow generator 122. For example, the secondflow generator 122 may have a set flow rate of, for example, zero or a low flow so as not to dilute the second gas in the second passageway 104.

[0400] Alternatively, the second flow generator 122 may be controlled to deliver a set pressure during patient inhalation. The second flow generator 122 may automatically vary the flow to ensure the pressure at the patient interface 108 remains constant, and thus meets the inspiratory demand of the patient 106.

[0401] During the accumulation period, the controller 902 may control the flow rates so that the flow rate in the second passageway 104 is less than the flow rate in the first passageway 102. For example, in the case of the respiratory support systems of FIG. 1 to FIG. 8, the second flow generator 122 may have a zero, minimal, or low flow rate. The controller 902 may control the second flow generator 122 so that there will be no flow passing through the non-return valve 114, and the second gas will accumulate along the second passageway 104 over the accumulation period, pushing any residual gas in the second passageway 104 toward the patient interface 108. In the case of the respiratory support systems of FIG. 1 to FIG. 4, the second gas accumulating in the second passageway 104 over the accumulation period flows in an upstream direction which will displace any of the first gas through the second flow generator 122.

[0402] With reference to the respiratory support systems of FIG. 1 to FIG. 8, the controller 902 may operate the second flow generator 122 at a negative flow rate such that the first gas is exhausted from the second flow generator 122 during exhalation. The magnitude of the negative flow rate may be approximately equal to the rate of second gas that enters the second passageway 104. In the case of the respiratory support systems of FIG. 1 to FIG. 4, the second gas entering the second passageway 104 may displace any residual breathing gas upstream backwards towards the second flow generator 122. By operating the second flow generator 122 at a negative flow, this gas may escape the system through the second flow generator 122, ensuring that no second gas goes through the non-return valve 114 and is delivered to the patient interface 108 during patient exhalation.

[0403] In the respiratory support systems of FIG. 10 and FIG. 13, the controller 902 may operate the active valve mechanism 1006 to close the second valve 1012 in the second passageway 104.

[0404] In some examples, the respiratory support system may be operated at a set pressure. The controller 902 may operate the second flow generator 122 at a set pressure in the second passageway 104 during the accumulation period. In this situation, the controller 902 may control the first flow generator 120 to vary the flow and ensure thepressure at the patient interface 108 remains constant. In this way, sufficient flow of the breathing gas is always provided to account for any mask leakage and retain the pressure at the desired level.

[0405] In the situation where the first flow generator 120 is operated (for example at a set flow rate or a set pressure) during patient exhalation, the second flow generator 122 may be operated at a set pressure that is lower than the set pressure at which the first flow generator 120 is operated. This ensures that no flow from the second passageway 104 will be delivered to the patient 106, as the first flow generator 120 is supplying flow at a higher pressure than the pressure in the second passageway 104. In the case of the respiratory support systems of FIG. 1 to FIG. 4, when the second gas enters the second passageway 104 at a higher pressure than the set pressure for the second flow generator 122, the second flow generator 122 will allow residual gas to escape the respiratory support system through of the second flow generator 122. In the case of the respiratory support systems of FIG. 5 to FIG. 8, the lower pressure in the second flow generator 122 compared to at the patient interface 108 means the non-return valve 114 (NRV) will not open and flow will not be delivered.

[0406] With reference to the respiratory support systems of FIG. 12 and FIG. 15, the respiratory support systems may include at one or more sensors 1202. The sensors provide outputs that are received as inputs by the controller 902 to control operation of the flow generator 1002 and the active valve mechanism 1006. For example, to control the commencement of the delivery period. The controller 902 may receive inputs from other sources, including a clinician or an external sensor that may or may not contact the patient 106, as presented by the dashed line extending from patient 106 to the sensor 1202. In FIG. 12 and FIG. 15, the sensors are represented by a single representative sensor 1202. Dashed lines extend from parts of the respiratory support system to the representative sensor 1202 to indicate potential sensor locations. Outputs from the sensors 1202 are received as an input by the controller 902 and are represented by the dashed lines from the sensor 1202 to the controller 902. The controller 902 may then control the flow generator 1002, the active valve mechanism 1006, and the flow of the second gas into the second passageway 104 via gas control valve 924.

[0407] As shown in FIG. 12 and FIG. 15, the sensors 1202 may be located one or more of the following locations:• at or near the patient interface 108,• at or near the flow generator outlet 1004,in the first passageway 102, in the second passageway 104, or externally, e.g., an external sensor that may or may not contact the patient 106.

[0408] In one example, the sensor 1202 may include a pressure sensor located at or near the flow generator outlet 1004, or located on the patient interface 108. In an example, the sensor 1202 may include a pressure sensor at the second gas inlet 116, or at a vent in the first passageway 102, or at an exhalation port 110. In an example, the sensor 1202 may include a flow rate sensor located at one or more of the following : i) at or near the flow generator outlet 1004, ii) at or near the patient interface 108; iii) at the second gas inlet 116.

[0409] Additionally, or alternatively, a flow rate sensor, a pressure sensor, or a temperature sensor may also be located at other locations of the respiratory support system, such as at or near the patient interface 108.

[0410] In one example, the respiratory support systems shown in FIG. 12 and FIG. 15 may include flow and / or pressure sensors at the flow generator 1002. That is, the respiratory support system may be without sensors in the first passageway 102 and second passageway 104. And may have no external sensors. But the respiratory support systems according to this example may, optionally, include a pressure sensor or flow rate sensor at or near the patient interface 108. Regardless, the controller 902 may control operation of the flow generator 1002. For example, the commencement of the delivery period and the conclusion of the delivery period.

[0411] The controller 902 in FIG. 12 and FIG. 15 may control the flow generator 1002 at a (set) flow rate or at a (set) pressure for the accumulation period. Specifically, the controller 902 in Figures 12 and 15 may control operation of the flow generator 1002 and the active valve mechanism 1006 to control the first gas conveyed in the first passageway 102 at a (set) flow rate or at a (set) pressure for the accumulation period, and control the flow rate of the second gas via gas control valve 924 and the total volume of the second gas that enters the second passageway 104 during the accumulation period. In the case of the set flow rate, the flow rate of the first gas in the first passageway 102 is at least equal to the rate of mask leakage, including intentional and unintentional mask leakage during patient exhalation. In the event that exhaled gas is discharged from the respiratory support system through mask leakage, the first gas may be vented via the exhalation port 110 with the remainder of the exhaled gas.

[0412] In some examples, approximately all flow leaving the respiratory support system as mask leakage or throug the exhalation port 110 during patient exhalation may be either exhaled gas or gas from the flow generator 1002. Thereby reducing the possible wastage of the second gas. The first flow generator 120, or the flow generator 1002, may provide sufficient flow to account for approximately all gas flow exiting the respiratory support system through mask leakage, regardless of whether exhaled breath is contributing to this or not.

[0413] The controller 902 may be any suitable controller 902 including a processor for carrying out calculations, and is configured to receive inputs and generate control outputs. The controller 902 may have a transmitter for transmitting control outputs to the flow generators 120, 122, 1002, the active valve mechanism 1006, and the gas control valve 924. The transmitter may, for example be a wireless transmitter, or transmit outputs via conductors. The controller 902 may have a receiver for the receiving the inputs based on outputs from the sensors. The receiver may, for example be a wireless receiver, or receive inputs via conductors. The controller 902 may also include a memory with a data storage capacity for storing, for example, the historical breathing cycle data.

[0414] The controller 902 may include programming instructions for detection of input conditions and control of output conditions. The programming instructions may be stored in the memory of the controller 902. The programming instructions may correspond to the methods, processes and functions described herein. The programming instructions may be executed by one or more hardware processors of the controller 902. The programming instructions may be implemented in C, C+ + , JAVA, or any other programming languages. Some or all of the portions of the programming instructions may be implemented in application specific integrated circuit (ASIC), programmable logic device (PLD), or field programmable gate array (FPGA).

[0415] The controller 902 may include circuits for receiving sensor signals. The controller 902 may include a display, e.g., for indicating a status of the respiratory support system or the patient 106. The display may show warnings and / or other alerts. The display may be configured to display sensed characteristics of the gases, in real-time or otherwise. The controller 902 may receive user inputs via the user interface. The user interface may include one or more buttons, dials, or switches. The user interface may include a touch screen.

[0416] In some examples, the controller may be provided (e.g., manufactured, packaged, sold, or offered for sale) separately from other components of the disclosed respiratory support systems. The controller may be enclosed in a controller housing. The controllerhousing may be separate to the first flow generator 120 and the second flow generator 122, or to the flow generator 1002. The controller housing may be configured to be removably attached to the first flow generator 120, second flow generator 122, or flow generator 1002. Alternatively, the controller may be integrated with one or more of the first flow generator 120, second flow generator 122, or flow generator 1002, e.g., within a common housing.

[0417] The controllable flow generators and / or valves of the disclosed respiratory support systems may be collectively referred to as a flow control system. The flow control system may be configured to control one or more of the flow rate or pressure of the first gas and one or more of the flow rate or pressure of the second gas under electronic control of the controller 902.

[0418] Aspects of the systems and methods described above may be operable on any type of general-purpose computer system or computing device, including, but not limited to, a desktop, laptop, notebook, tablet, smart television, gaming console, or mobile device. The term "mobile device" includes, but is not limited to, a wireless device, a mobile phone, a smart phone, a mobile communication device, a user communication device, a personal digital assistant, a mobile hand-held computer, a laptop computer, a wearable electronic device such as a smart watch or head-mounted device, an electronic book reader and reading devices capable of reading electronic contents, and / or other types of mobile devices typically carried by individuals and / or including some form of communication capabilities (e.g., wireless, infrared, short-range radio, cellular, etc.).

[0419] Aspects of the systems and methods described above may be operable or implemented on any type of specific-purpose or special computer, or any machine or computer or server or electronic device with a microprocessor, processor, microcontroller, programmable controller, or the like, or a cloud-based platform or other network of processors and / or servers, whether local or remote, or any combination of such devices.

[0420] Furthermore, the present technology may be implemented, at least in part, by one or more of hardware, software, firmware, middleware, microcode, or machine code. When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine-readable medium such as a storage medium or other storage. A processor may perform the necessary tasks. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and / or receiving information, data,arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc.

[0421] In the above description, a storage medium may represent one or more devices for storing data, including read-only memory (ROM), random access memory (RAM), magnetic disk storage mediums, optical storage mediums, flash memory devices and / or other machine or computer readable mediums for storing information.

[0422] The various illustrative logical blocks, modules, circuits, elements, and / or components described in connection with the examples disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic component, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, conventional processor, controller, microcontroller, circuit, and / or state machine. A processor may also be implemented as a combination of computing components, e.g., a combination of a DSP and a microprocessor, a number of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0423] The methods described in connection with the examples disclosed herein may be embodied directly in hardware, in a software module executable by a processor, or in a combination of both, in the form of processing unit, programming instructions, or other directions, and may be contained in a single device or distributed across multiple devices. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD- ROM, or any other form of storage medium. A storage medium may be coupled to the processor such that the processor may read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor.

[0424] One or more of the components and functions illustrated in the drawings may be rearranged and / or combined into a single component or embodied in several components without departing from the scope of the disclosure. For example, the first flow generator 120 and second flow generator 122 may be enclosed by a single housing. Or the flow generator 1002 and active valve mechanism 1006 may be enclosed by a single housing. One or more sensors or other components of the respiratory support systems may beenclosed by the single housing. Additional elements or components may also be added without departing from the scope of the disclosure.

[0425] In its various aspects, the present technology may be embodied in a computer implemented process, a machine (such as an electronic device, or a general-purpose computer or other device that provides a platform on which computer programs may be executed), processes performed by these machines, or an article of manufacture. Such articles may include a computer program product or digital information product in which a computer readable storage medium contains computer program instructions or computer readable data stored thereon, and processes and machines that create and use these articles of manufacture.

[0426] The first passageway 102 and the second passageway 104 may be any suitable tubing, conduit, or ducting including a single lumen or multiple lumens, for example. As previously described, the volume of the second passageway 104 (and optional reservoir and humidification device) in which the second gas accumulates may be selected or selectable based on the required volume of the second gas to be stored in the second passageway 104. For example, the tidal volume of the patient. The tubing for the second passageway 104 may be provided in one or more lengths. The appropriate length may be selected based on the desired storage capacity of the second passageway 104 for storing a preselected volume, such as the treatment volume of the second gas. The preselected volume may be between about 50 % and 100 %, between about 50 % and 90%, between about 60 % and 80 %, or between about 60 % and 70 % of the tidal volume of the patient.

[0427] The internal volume of the tubing may be selected by selecting tubing from among a range of various diameters and / or lengths. For example, a longer and smaller internal diameter tubing may have the same volume as a shorter and larger internal diameter tubing. A longer and smaller internal diameter tubing may be used when the flow generator 120, 122, 1002 and / or second gas inlet 116 is located a relatively large distance from the patient 106. This may minimize clutter and complexity of the respiratory support system near the patient 106. A shorter and relatively large internal diameter tubing may be used when the respiratory support system is closer to the patient 106. This may minimize resistance to flow in the second passageway 104.

[0428] Although not shown in the Figures, the first passageway 102 and second passageway 104 may include tubing of any suitable structure. For example, the first passageway 102 and the second passageway 104 may be separate tubes. The tubes may be unconnected along their length. Or they may be connected side-by-side by usingconnector clips or a permanent adhesive, or be integrally formed. An integrally formed structure may be extruded. The tubes may be corrugated or helically-wound, for example.

[0429] The first passageway 102, second passageway 104, and / or tubing may be between about 1 meter (m) and 2 m, between about 1.2 m and 1.8 m, or about 1.5 m in length. The first passageway 102, second passageway 104, and / or tubing may have an internal diameter of about 22 mm, e.g., for an adult patient, about 15 mm, e.g., for a pediatric patient, or about 10 mm, e.g., for a neonatal patient.

[0430] In some examples, the first passageway 102 and second passageway 104 may be provided at least in part by a multi-lumen tube. Separate lumens provide the first passageway 102 and second passageway 104. For example, the multi-lumen tube may include side-by-side passageways, in which a partition along the tube defines in part the first passageway 102 and second passageway 104 along the tube. The multi-lumen tube including side-by-side passageways may be extruded. In another example, the multi-lumen tube may include a concentric lumens, in which one passageway is arranged centrally and the other passageway is arranged about the periphery of the central passageway.

[0431] In yet another example, the first passageway 102 and second passageway 104 may be arranged as a single conduit formed from a spirally wound hollow body. The conduit may include a first elongate member including a hollow body spirally wound to form at least in part an elongate tube including a hollow wall surrounding the conduit lumen. The conduit may also include a second elongate member spirally wound and joined between adjacent turns of the first elongate member. The spirally wound hollow body may provide either one of the first passageway 102 or second passageway 104, and the conduit lumen formed by the spirally wound hollow body may provide the passageway.

[0432] The spirally wound hollow body may provide a smaller internal volume than the conduit lumen. In some situations, it is desirable that the flow rate provided during exhalation be smaller than the flow rate provided during inhalation. In this example, the spirally wound hollow body may provide the first passageway 102, and the conduit lumen may provide the second passageway 104. In another example, the spirally wound hollow body may provide the second passageway 104, and the conduit lumen may provide the first passageway 102.

[0433] Alternatively, the conduit lumen may be the second passageway 104 and the second gas inlet 116 may be provided into the spirally wound hollow body. The second gas may enter a distal portion of the spirally wound hollow body, flow along the spirally wound hollow body towards the patient, and then flow into a proximal portion of the conduit lumen.This effectively allows a proximal second gas inlet 116 without needing an additional conduit near the patient interface 108.

[0434] Examples of conduits including spiral wound hollow bodies are disclosed in International (PCT) Patent Publication No. WO 2012 / 164407 Al (Application No. PCT / IB2012 / 001786) entitled MEDICAL TUBES AND METHODS OF MANUFACTURE, filed 30 May 2012, the content of which is hereby incorporated by reference.

[0435] A breathing circuit for use in the respiratory may be provided as a kit, e.g., in sealed packaging, for use in the respiratory support systems of the present disclosure. The breathing circuit kit may be provided disassembled, partially pre-assembled, or completely pre-assembled.

[0436] The breathing circuit may be configured to pneumatically connect the flow generator(s), second gas source, and patient interface. Either directly or indirectly, e.g., via a Y-piece. The breathing circuit may be configured to connect with the first flow generator 120, the second flow generator 122, and the second gas source 112. Or with the flow generator 1002, e.g., via a Y-piece, and the second gas source 112. Or with the active valve mechanism 1006, e.g., first valve 1010 and second valve 1012, and the second gas source 112.

[0437] The breathing circuit kit may include any one or more of the following components of the respiratory support systems described above:• first passageway 102,• second passageway 104,• exhalation port 110,• non-return valve 114,• third passageway 118,• Y-piece,• patient interface 108• filter 124,• gas supply line 1008,• reservoir,• humidification device, or• sensors.

[0438] In some examples, a breathing circuit kit may include at least the first passageway 102, the second passageway 104, and the non-return valve 114.

[0439] The breathing circuit may be disposable. A disposable breathing circuit may minimize the risk of infection between patients. Or the breathing circuit may be re-usable. A re-usable breathing circuit may be configured to withstand reprocessing, e.g., at least 5, at least 10, or at least 20 reprocessing cycles. A reprocessing cycle may include one or more of chemical disinfection or autoclaving.

[0440] The controller 902 may generate a warning signal that may alert a clinician or a patient 106 when an undesirable event occurs. For example, the signal may be a warning of one or more of:• the second gas is being supplied at a flow rate and over an accumulation period that overfills the second passageway 104,• the internal volume of the second passageway 104 for storing the second gas is too small;• the respiration rate of the patient 106 is too low,• the tidal volume of the patient 106 is too low,• an unforeseen leak in the respiratory support system may have occurred,• a blockage in the respiratory support system has occurred, or inadequate flow of the first gas is present,• concentration of the second gas in the patient interface 108 is too high, or• there is an unexpected pressure loss in the respiratory support system.

[0441] The controller 902 may automatically take action, for example one or more of:• transmitting that warning signal to raise an alarm,• change a flow rate within the respiratory support system, or• suggest an action to be taken to a clinician, such as to use a larger second passageway 104.

[0442] In another example, the controller 902 may provide a warning when the concentrations of the second gas, e.g., oxygen, received by the patient 106 is too high. This may be determined by oxygen sensors, such as an oxygen sensor in the flow path and / or near the patient 106, or by estimation based on the oxygen flow rate provided and / or patient information.

[0443] "High flow therapy" is intended to be given its typical ordinary meaning, as understood by a person of skill in the art, which generally refers to a respiratory system delivering a targeted flow of respiratory gases via an intentionally unsealed or non-sealing patient interface with flow rates generally intended to meet or exceed the inspiratorydemand of a user. High flow therapy is typically provided at desired flow rates high enough to meet or exceed a patient's inspiratory demand. The flow rate provided is ideally sufficient such that ambient gases are not entrained as the patient inspires. Typical patient interfaces used for high flow therapy include, but are not limited to, a non-sealing nasal cannula or a tracheal 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 or neonatal users often range from, but are not limited to, about 1 L / min per kilogram of user weight (L / min / kg) to about 3 L / min / kg or greater.

[0444] High flow therapy is often referred to as nasal high flow (NHF), humidified high flow nasal cannula (HHFNC), high flow nasal oxygen (HFNO), high flow therapy (HFT), or tracheal high flow (THF), among other common names. For example, in some configurations, for an adult patient "high flow therapy" may refer to the delivery of gases to a patient at a flow rate of greater than or equal to about 10 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.

[0445] In some configurations, for a neonatal, infant, or child patient "high flow therapy" may refer to the delivery of gases to a patient at a flow rate of greater than 1 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.

[0446] High flow therapy can be effective in meeting or exceeding the patient's inspiratory demand, increasing oxygenation of the patient and / or reducing their work of breathing. Additionally, high flow therapy may generate a flushing effect in the nasopharynx such that the anatomical dead space of the upper airways is flushed by the high incoming gases flow. The flushing effect can create a reservoir of fresh gas available of each and every breath, while minimizing re-breathing of carbon dioxide, nitrogen, etc. High flow therapy can also increase expiratory time of the patient due to pressure provided during expiration. This in turn reduces the respiratory rate of the patient.

[0447] Conditional language used herein, such as, among others, "can," "might," "may," "for example," and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and / or states. Thus, such conditional language is not generally intended to imply that features, elements and / or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without input or prompting, whether these features, elements and / or states are included or are to be performed in any particular embodiment. The terms "comprising," "including," "having," and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term "or" is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term "or" means one, some, or all of the elements in the list. Further, the term "each," as used herein, in addition to its ordinary meaning, may mean any subset of a set of elements to which the term "each" is applied.

[0448] Disjunctive language such as the phrase "at least one of X, Y and Z," unless specifically stated otherwise, is to be understood with the context as used in general to convey that an item, term, etc., may be either X, Y, or Z, or any combination thereof. Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y and at least one of Z to each be present.

[0449] Unless otherwise explicitly stated, articles such as "a" or "an" should generally be interpreted to include one or more described items. Accordingly, phrases such as "a device configured to" are intended to include one or more recited devices. Such one or more recited devices may also be collectively configured to carry out the stated recitations. For example, "a processor configured to carry out recitations A, B and C" may include a first processor configured to carry out recitation A working in conjunction with a second processor configured to carry out recitations B and C.

[0450] While the above detailed description has shown, described, and pointed out novel features as applied to various examples, it will be understood that various omissions, substitutions, and changes in the form and details of the devices or methods illustrated may be made without departing from the spirit of the disclosure. As will be recognized, certain examples of the technology described herein may be embodied within a form that does not provide all of the features and benefits set forth herein, as some features may be used or practiced separately from others.LISTING OF DRAWING ELEMENTS100 respiratory support system102 first passageway104 second passageway106 patient108 patient interface110 exhalation port112 second gas source114 non-return valve116 second gas inlet118 third passageway120 first flow generator122 second flow generator124 filter126 first inlet128 second inlet300 respiratory support system500 respiratory support system700 respiratory support system902 controller904 pressure sensor906 pressure sensor908 pressure sensor910 pressure sensor912 external sensor914 flow rate sensor916 flow rate sensor918 flow rate sensor920 flow rate sensor922 flow rate sensor924 gas control valve1000 respiratory support system1002 flow generator1004 flow generator outlet1006 active valve mechanism1008 gas supply line1010 first valve1012 second valve1202 sensor1300 respiratory support system1602 onset of patient inhalation1604 conclusion of patient inhalation1606 onset of patient exhalation1608 conclusion of patient exhalation

Claims

CLAIMSWhat is claimed is:

1. A system for providing respiratory support to a patient, the system comprising : a first passageway connectable to a patient interface, the first passageway configured to convey a first gas during an accumulation period, a second passageway connectable to a patient interface, the second passageway configured to accumulate a second gas during at least part of the accumulation period and to convey the first gas during a delivery period such that the accumulated second gas is able to be displaced from the second passageway to the patient interface, and a controller that is configured to control a commencement of the delivery period based on a breathing cycle of the patient.

2. The system of claim 1, wherein the controller is configured to control a conclusion of the delivery period based on the breathing cycle.

3. The system of claim 1 or 2, wherein the controller is configured to control the delivery period and the accumulation period so that at least one is occurring at any time during the breathing cycle.

4. The system of any one of claims 1 to 3, wherein the controller is configured to control the delivery period and the accumulation period so that only one occurs at any time during the breathing cycle.

5. The system of any one of claims 1 to 4, wherein the controller is configured to control the commencement of the delivery period based on: a selected event of the breathing cycle, and the delivery period.

6. The system of any one of claims 1 to 5, wherein the controller is configured to control the commencement of the delivery period so that the delivery period occurs during a desired phase in the breathing cycle.

7. The system of claim 6 when appended to claim 5, wherein the desired phase of the breathing cycle is different to the selected event in the breathing cycle.

8. The system of any one of claims 1 to 7, wherein the controller is configured to control the commencement of the delivery period based on an onset of patient inhalation.

9. The system of any one of claims 1 to 8, wherein the controller is configured to control the commencement of the delivery period based on a conclusion of patient inhalation.

10. The system of any one of claims 1 to 9, wherein the controller is configured to control the commencement of the delivery period based on an onset of patient exhalation.

11. The system of any one of claims 1 to 10, wherein the controller is configured to control the commencement of the delivery period based on a conclusion of patient exhalation.

12. The system of any one of claims 1 to 11, wherein the controller is configured to control the commencement of the delivery period based on a high flow phase of patient inhalation, the high flow phase of patient inhalation comprising a predetermined period before and / or after a peak inspiratory flow.

13. The system of any one of claims 1 to 12, wherein the controller is configured to control the commencement of the delivery period to occur during patient inhalation.

14. The system of any one of claims 1 to 13, wherein the controller is configured to control the commencement of the delivery period to occur during a high flow phase of patient inhalation, the high flow phase of patient inhalation comprising a predetermined period before and / or after a peak inspiratory flow.

15. The system of any one of claims 1 to 12, wherein the controller is configured to control the commencement of the delivery period to occur during patient exhalation.

16. The system of any one of claims 1 to 15, wherein the controller is configured to control a conclusion of the delivery period to occur during patient inhalation.

17. The system of any one of claims 1 to 16, wherein the controller is configured to control a conclusion of the delivery period to occur before the end of patient inhalation.

18. The system of any one of claims 1 to 17, wherein the delivery period is between about 50 % and 90 %, between about 60 % and 80 %, or between about 70 % and 80 % of a duration of the patient inhalation.

19. The system of any one of claims 1 to 18, wherein the controller is configured to control a commencement of the accumulation period based on the onset of patient inhalation.

20. The system of any one of claims 1 to 19, wherein the controller is configured to control a commencement of the accumulation period based on a conclusion of patient inhalation.

21. The system of any one of claims 1 to 20, wherein the controller is configured to control a commencement of the accumulation period based on an onset of patient exhalation.

22. The system of any one of claims 1 to 21, wherein the controller is configured to control a commencement of the accumulation period based on a conclusion of patient exhalation.

23. The system of any one of claims 1 to 22, wherein the controller is configured to control a commencement of the accumulation period based on a high flow phase of patient inhalation, the high flow phase of patient inhalation comprising a predetermined period before and / or after a peak inspiratory flow.

24. The system of any one of claims 1 to 23, wherein the controller is configured to control a commencement of the accumulation period to occur during patient exhalation.

25. The system of any one of claims 1 to 24, wherein the controller is configured to control a conclusion of the accumulation period to occur during patient exhalation.

26. The system of any one of claims 1 to 25, wherein the controller is configured to control the accumulation period to occur during at least part of the patient exhalation.

27. The system of any one of claims 1 to 26, wherein the controller is configured to control the accumulation period to occur during at least part of the patient inhalation.

28. The system of any one of claims 1 to 27, wherein the controller is configured to receive an input relating to the breathing cycle of the patient, and to determine a phase of the breathing cycle based on the input, the phase of the breathing cycle comprising one or more of: a patient inhalation, an onset of patient inhalation, a conclusion of patient inhalation, a high flow phase of patient inhalation, patient exhalation,an onset of patient exhalation, or a conclusion of patient exhalation.

29. The system of claim 28, wherein the controller is configured to determine when the input is outside a threshold range and discard the input.

30. The system of claim 29, wherein the input determined to be outside the threshold range represents an irregular breath in the breathing cycle.

31. The system of any one of claims 1 to 30, wherein the controller is configured to control one or more of a flow rate or a pressure of the first gas supplied to the first passageway during at least part of patient exhalation and at least part of patient inhalation.

32. The system of any one of claims 1 to 31, wherein the controller is configured to control one or more of a flow rate or a pressure of the first gas in the second passageway so that: a conclusion of the delivery period occurs before the end of patient inhalation, and the flow rate and / or the pressure of the first gas supplied to the first passageway increases or starts before an end of patient inhalation to maintain the flow rate and / or pressure at the patient interface.

33. The system of any one of claims 1 to 32, wherein the controller is configured to control one or more of a flow rate or a pressure of the first gas in the second passageway so that a conclusion of the delivery period occurs after the second gas that accumulated in the second passageway has been delivered to the patient interface.

34. The system of any one of claims 1 to 33, wherein the controller is configured to control a conclusion of the delivery period by stopping or reducing one or more of a flow rate or a pressure of the first gas supplied to the second passageway when the second gas that accumulated in the second passageway has been supplied to the patient interface, or by a period after the second gas that accumulated in the second passageway has been delivered to the patient interface.

35. The system of any one of claims 1 to 34, wherein the controller is configured to control a conclusion of the delivery period to occur after the second gas that has accumulated in the second passageway has been supplied to the patient interface.

36. The system of any one of claims 1 to 35, wherein the controller is configured to receive a clinician input from a clinician, and to use the clinician input to determine the delivery period, the clinician input comprising a measurement or estimation of one or more of: a tidal volume of the patient; an internal volume of the second passageway or the system in which the second gas can accumulate; a duration of the breathing cycle of the patient; or a duration of the patient inhalation.

37. The system of any one of claims 1 to 36, wherein the controller is configured to determine the delivery period based on one or more of: an onset of patient inhalation, a duration of the patient inhalation, or a function of a portion of patient inhalation.

38. The system of claim 37, wherein the controller is configured to determine one or more of the onset of patient inhalation or the duration of the patient inhalation based on sensor outputs from at least one sensor that is configured to monitor breathing of the patient.

39. The system of claim 38, wherein the at least one sensor comprises: an external sensor attached to the abdomen of the patient, or an external sensor that monitors the thoracic and / or abdominal expansion of the patient.

40. The system of claim 39, wherein the at least one sensor is configured to measure a gas parameter within the system, the gas parameter comprising one or more of a flow rate, a gas pressure, or a gas composition in one or more of the first passageway, the second passageway, or an exhalation port.

41. The system of any one of claims 1 to 40, wherein the controller is configured to control a commencement of the delivery period based on one or more events in the breathing cycle, the one or more events comprising one or more of:an onset of patient inhalation, a high flow phase of patient inhalation, the high flow phase of patient inhalation comprising a predetermined period before and / or after a peak inspiratory flow, a conclusion of patient inhalation; an onset of patient exhalation, a conclusion of patient exhalation.

42. The system of any one of claims 1 to 41, wherein the second gas is delivered to the patient interface: a period before the onset of inhalation, at the commencement of inhalation, or a period after the onset of inhalation.

43. The system of any one of claims 1 to 42, wherein the second gas that is delivered to the patient interface during the delivery period is accumulated during a preceding accumulation period.

44. The system of any one of claims 1 to 43, wherein an entirety of the second gas that is accumulated during the accumulation period is delivered to the patient interface during the delivery period.

45. The system of any one of claims 1 to 44, wherein the controller is configured to control a commencement of the delivery period as a function of a delay interval between the first gas being supplied to the second passageway and the second gas being delivered to patient interface.

46. The system of claim 45, wherein the controller is configured to control a commencement of the delivery period as a function of the delay interval.

47. The system of claim 45 or 46, wherein the controller is configured to control the commencement of the delivery period to occur before an onset of the inhalation period.

48. The system of any one of claims 45 to 47, wherein the controller is configured to estimate the delay interval.

49. The system of any one of claims 45 to 48, wherein the controller is configured to estimate the delay interval based on a flow rate of the first gas being conveyed in the second passageway.

50. The system of any one of claims 45 to 49, wherein the controller is configured to estimate the delay interval based on an internal volume of the system downstream of the second gas accumulated in the second passageway.

51. The system of any one of claims 45 to 50, wherein the controller is configured to estimate the delay interval based on a rate of leakage from the system, such as intentional leakage and an unintentional leakage.

52. The system of any one of claims 45 to 48, wherein the controller is configured to estimate the delay interval based on one or more parameters, the one or more parameters comprising one or more of: a flow rate of the first gas being conveyed in the second passageway, an internal volume of the system downstream of the second gas accumulated in the second passageway, or a rate of leakage from the system, such as intentional leakage and unintentional leakage.

53. The system of any one of claims 45 to 52, wherein the controller is configured to control a commencement of the delivery period so that one or more of a flow rate or a pressure of the first gas supplied to the second passageway prior to the onset of patient inhalation flushes residual breathing gas or exhaled gas from the system.

54. The system of any one of claims 1 to 53, wherein the controller is configured to control a commencement of the delivery period as a function of a time interval between an onset of patient inhalation and a high flow phase of patient inhalation.

55. The system of claim 54, wherein the controller is configured to control a commencement of the delivery period based on a postponement period, the postponement period comprising a function of the interval.

56. The system of claim 55, wherein the controller is configured to control the commencement of the delivery period by the postponement period so that the second gas is delivered to the patient interface during a high flow phase of patient inhalation.

57. The system of claim 55 or 56, wherein the controller is configured to determine the postponement period as a function of an output of a sensor that is received by the controller, wherein the sensor monitors one or more of: a period of the breathing cycle of the patient, a respiration rate of the patient, a tidal flow of the patient, or a flow rate of the patient inhalation.

58. The system of any one of claims 55 to 57, wherein the controller is configured to determine the postponement period as a function of a clinician input received from a clinician.

59. The system of any one of claims 1 to 58, wherein the controller is configured to control one or more of a flow rate or a pressure of the first gas supplied to the second passageway so that the second gas is delivered to the patient interface during a high flow phase of patient inhalation.

60. The system of any one of claims 1 to 59, wherein a commencement of the delivery period is configured to occur before an onset of patient inhalation.

61. The system of any one of claims 1 to 59, wherein a commencement of the delivery period is configured to occur after an onset of patient inhalation.

62. The system of any one of claims 1 to 61, wherein the controller is configured to control a commencement of the delivery period to occur before a peak inspiratory flow and controls a conclusion of the delivery period to occur after the peak inspiratory flow.

63. The system of any one of claims 1 to 62, wherein the controller is configured to control a supply of the second gas to the second passageway so that the second gas is supplied for an entirety of the accumulation period.

64. The system of any one of claims 1 to 62, wherein the controller is configured to control a supply of the second gas to the second passageway so that the second gas is supplied for only part of the accumulation period.

65. The system of any one of claims 1 to 64, wherein the second gas is held in the second passageway for the duration of the accumulation period.

66. The system of any one of claims 1 to 65, wherein the controller is configured to control one or more of a flow rate or a pressure of the second gas supplied to the second passageway during at least part of the accumulation period.

67. The system of any one of claims 1 to 66, wherein the accumulation period occurs during patient exhalation and during a final stage of patient inhalation.

68. The system of any one of claims 1 to 66, wherein the accumulation period occurs during patient exhalation, but does not occur during a final stage of patient exhalation.

69. The system of any one of claims 1 to 68, wherein the accumulation period occurs during a final stage of patient inhalation and during patient exhalation, but does not occur during a final stage of patient exhalation.

70. The system of any one of claims 1 to 69, wherein the controller is configured to control one or more of a flow rate or a pressure of the second gas supplied to the second passageway throughout patient inhalation and patient exhalation.

71. The system of any one of claims 1 to 70, wherein the controller is configured to control : one or more of a flow rate or a pressure of the second gas supplied to the second passageway during the accumulation period, and one or more of a flow rate or a pressure of the first gas supplied to the patient interface by the first passageway.

72. The system of any one of claims 1 to 71, wherein the controller is configured to control : a supply of the second gas to the second passageway, and a supply of the first gas to the first passageway and the second passageway, wherein the supply of the first gas and the supply of the second gas are controlled independently of each other.

73. The system of any one of claims 1 to 72, wherein the controller is configured to control a flow rate of the second gas so as not to the supply the second gas to the secondpassageway when the patient or the patient interface is receiving breathing gas from the second passageway.

74. The system of any one of claims 1 to 73, wherein the controller is configured to determine the accumulation period as a function of an output of at least one sensor that detects the breathing cycle of the patient.

75. The system of claim 74, wherein the at least one sensor is configured to monitor one or more of: a flow rate of exhaled gas, a flow rate of inhaled gas, a flow rate of gas vented from the system, a gas pressure in the system, or a gas composition in the system.

76. The system of any one of claims 1 to 75, wherein the controller is configured to control one or more of a flow rate or a pressure of the second gas supplied to the second passageway based on a volume of the second passageway and the accumulation period.

77. The system of any one of claims 1 to 76, wherein the controller is configured to control one or more of a flow rate or a pressure of the second gas as a function of a volume of the second passageway for storing the second gas, and at least one of: the accumulation period, a respiration rate of the patient, or a duration of the patient inhalation.

78. The system of claim 77, wherein the duration of patient inhalation is: received as an input from a clinician or the patient, or determined by the controller as a function of one or more sensor outputs from one or more sensors.

79. The system of any one of claims 1 to 78, wherein the controller is configured to control one or more of a flow rate or a pressure of the second gas so that a treatment volume of the second gas enters the second passageway during the accumulation period.

80. The system of claim 79, wherein the treatment volume is approximately equal to a storage volume of the second passageway.

81. The system of claim 79 or 80, wherein the controller is configured to determine the treatment volume and controls one or more of the accumulation period or the supply of the second gas to the second passageway so that the treatment volume fills a storage volume of the second passageway or alveoli of the patient.

82. The system of any one of claims 79 to 81, wherein the treatment volume is a product of the accumulation period and the flow rate of the second gas supplied to the second passageway.

83. The system of claim 82, wherein the controller is configured to receive an input for the treatment volume, and the controller determines one or more of the flow rate or the pressure of the second gas based on the accumulation period and the input for the treatment volume.

84. The system of claim 82 or 83, wherein the controller is configured to determine the treatment volume as a percentage of an expected or measured tidal volume of the patient.

85. The system of any one of claims 82 to 84, wherein the treatment volume is between about 50 % and 100 %, between about 50 % and 90%, between about 60 % and 80 %, or between about 60 % and 70 % of the tidal volume of the patient.

86. The system of any one of claims 82 to 85, the treatment volume comprising: at least about 300 milliliters (mL), at least about 400 mL, at least about 500 mL, between about 300 mL and 700 mL, between about 400 and 650 mL, between about 500 mL and 600 mL, or about 570 mL; between about 50 mL and 300 mL, between about 100 and 300 mL, between about 150 mL and 250 mL, or about 270 mL; or between about 10 mL and 50 mL, between about 20 and 40 mL, or about 118 mL.

87. The system of any one of claims 82 to 86, wherein the controller is configured to change the treatment volume or the flow rate of the second gas in response to a change in a clinical state of the patient, the change in the clinical stage of the patient comprising a change in one or more of: an oxygen saturation level, or a respiration rate.

88. The system of any one of claims 82 to 87, wherein the controller is configured to increase one or more of the flow rate, the pressure, or the treatment volume of the second gas in response to a decrease in an oxygen saturation level of the patient.

89. The system of any one of claims 1 to 88, wherein the controller is configured to recommend changing the second passageway.

90. The system of claim 89, wherein the controller is configured to recommend changing the second passageway for another including a larger internal volume when the treatment volume is greater than a storage volume of the second passageway.

91. The system of any one of claims 1 to 89, wherein the controller is configured to redetermine the accumulation period upon a change in one or more of: the second passageway, a flow rate of the second gas, an inspiration rate of the patient, an expiration rate of the patient, a duration of patient inhalation, a duration of patient exhalation, a clinical state of the patient changes, or a leakage from the patient interface.

92. The system of claim 91, wherein the system comprises one or more sensors configured to provide a sensor output, and a change in the sensor output triggers the controller to redetermine the accumulation period.

93. The system of any one of claims 1 to 92, wherein the system comprises a user interface configured to allow a user to trigger the controller to recalculate the accumulation period.

94. The system of any one of claims 1 to 93, wherein the system comprises: a first flow generator connected to the first passageway for generating a flow of the first gas in the first passageway, and a second flow generator connected to the second passageway for generating a flow the first gas in the second passageway.

95. The system of claim 94, wherein the second flow generator is operable to convey the first gas along the second passageway to displace the second gas accumulated in the second passageway to the patient interface.

96. The system of claim 94 or 95, wherein the second flow generator, during the delivery period, is operable to continue to supply the first gas to the second passageway after the second gas that accumulated in the second passageway has been delivered to the patient interface.

97. The system of claim 94 or 95, wherein the second flow generator is operable to reduce or stop the flow of the first gas in the second passageway once the second gas that has accumulated in the second passageway has been delivered to the patient interface.

98. The system of any one of claims 94 to 97, wherein: at a commencement of the delivery period the second flow generator is operated so that the first gas is supplied to the second passageway at an onset of patient inhalation or during an initial stage of patient inhalation, at a conclusion of the delivery period the second flow generator is operated to reduce or stop the flow of the first gas to the second passageway during a final stage of patient inhalation, while the inspiratory flow rate during patient inhalation is decreasing, andthe first flow generator is operated so that the first gas is supplied to the first passageway during a final stage of patient inhalation and during at least part of the patient exhalation.

99. The system of any one of claims 94 to 98, wherein the second flow generator is operable so that the first gas is supplied to the second passageway prior to an onset of patient inhalation.

100. The system of any one of claims 94 to 99, wherein the second flow generator is operable so that the flow of the first gas in the second passageway delivers the second gas accumulated to the patient interface during a high flow phase of patient inhalation.

101. The system of any one of claims 94 to 100, wherein the controller is configured to control one or more of a flow rate or a pressure of the first gas in the second passageway by controlling a motor speed of a motor driving the second flow generator.

102. The system of any one of claims 94 to 101, wherein the controller is configured to control one or more of a flow rate or a pressure of the first gas in the first passageway by controlling a motor speed of a motor driving the first flow generator.

103. The system of claim 102, wherein the controller is configured to control operation of the first flow generator using output signals from one or more pressure sensors that provide pressure data on one or more of: a pressure of the first gas in the first passageway, a pressure of the first gas in the second passageway, a gas pressure in a third passageway, a pressure of exhaled gas, or a gas pressure in the patient interface.

104. The system of any one of claims 94 to 103, wherein the controller is configured to control operation of the second flow generator using output signals from one or more flow rate sensors that provide flow rate data on one or more of: a flow rate of the first gas in the first flow generator, a flow rate of the first gas in the second flow generator,a flow rate in a third passageway, a flow rate in the second passageway, or a flow rate of the second gas at the second gas inlet.

105. The system of any one of claims 94 to 104, wherein the controller is configured to operate the first flow generator at a set flow rate during patient exhalation.

106. The system of any one of claims 94 to 105, wherein a set flow rate of the first flow generator is at least equal to a rate of mask leakage.

107. The system of claim 106, wherein the controller is configured to operate the second flow generator at a lower flow rate than the first flow generator during patient exhalation.

108. The system of claim 107, wherein the controller is configured to operate the second flow generator at a zero flow rate or a negative flow rate during patient exhalation.

109. The system of any one of claims 94 to 104, wherein the controller is configured to operate the first flow generator at a set pressure during patient exhalation.

110. The system of any one of claims 94 to 104, wherein the first flow generator is operated at the set pressure during patient exhalation.

111. The system of any one of claims 94 to 110, wherein the controller is configured to operate the second flow generator at one or more of a set flow rate or a set pressure during patient inhalation.

112. The system of claim 111, wherein the set flow rate of the second flow generator during patient inhalation is a percentage of a peak inspiratory flow, for example between about 70 % and 150 % of the peak inspiratory flow.

113. The system of claim 111, wherein the set flow rate is a function of a peak inspiratory flow and a mask leakage rate, such as a sum of the peak inspiratory flow and mask leakage rate.

114. The system of claim 111, wherein when the second flow generator is operated at a set flow rate, the first flow generator is operated at a set pressure to provide constant pressure or near-constant pressure delivered to the patient.

115. The system of claim 111, wherein when the second flow generator is operated at a set flow rate, the first flow generator is operated at a set flow rate that is less than the set flow rate of the second flow generator.

116. The system of claim 111, wherein the second flow generator is operated at a set flow rate that is low or zero to mitigate dilution of the second gas in the second passageway during the accumulation period.

117. The system of any one of claims 1 to 116, wherein the system comprises: a flow generator to provide a flow the first gas to the first passageway and the second passageway, and an active valve mechanism to adjust the flow of the first gas in at least one of the first passageway and the second passageway.

118. The system of claim 117, wherein the active valve mechanism is operable to allow the first gas to be conveyed along the second passageway for a period after the second gas that accumulated in the second passageway has been delivered to the patient interface.

119. The system of claim 117 or 118, wherein: at a commencement of the delivery period the active valve mechanism is operated to allow the first gas to be supplied to the second passageway during an onset of patient inhalation or an initial stage of patient inhalation, while the inspiratory flow rate during patient inhalation is increasing, at a conclusion of the delivery period the active valve mechanism is operated to reduce or stop the first gas being supplied to the second passageway during a final stage of patient inhalation, while the inspiratory flow rate during patient inhalation is decreasing, and at the conclusion of the delivery period the active valve mechanism is operated to supply the first gas to the first passageway during a final stage of patient inhalation and during at least part of a patient exhalation.

120. The system of any one of claims 117 to 119, wherein the controller is configured to control operation of the active valve mechanism.

121. The system of any one of claims 117 to 120, wherein the controller is configured to determine the delivery period to control operation of the active valve mechanism and allow flow of the first gas along the second passageway.

122. The system of any one of claims 117 to 121, wherein the active valve mechanism is operable to allow the first gas to be conveyed along the second passageway to flush residual breathing gas or exhaled gas from the system prior to the onset of patient inhalation.

123. The system of any one of claims 117 to 122, wherein the controller is configured to control operation of the flow generator.

124. The system of claim 123, wherein the controller is configured to control operation of the flow generator by controlling a motor speed of a motor driving the flow generator.

125. The system of any one of claims 1 to 124, wherein the second gas is configured to enter the second passageway at a second gas inlet located downstream to where the first gas enters the second passageway.

126. The system of claim 125, when directly or indirectly appended to any one of claims 82 to 100, wherein the system comprises a flow restriction device, such as a non-return valve, that is configured to inhibit the second gas from passing into the second flow generator.

127. The system of claim 125, when directly or indirectly appended to any one of claims 117 to 122, wherein the system comprises a non-return valve that is configured to inhibit the second gas from passing into the flow generator.

128. The system of any one of claims 1 to 127, wherein the second gas is configured to enter the second passageway at a second gas inlet that is located distally from the patient interface, and the second gas accumulates in the second passageway in a downstream direction.

129. The system of claim 128, wherein the system comprises a non-return valve located in the second passageway upstream of a second gas inlet of the second passageway, the nonreturn valve allows flow in the second passageway in a downstream direction only.

130. The system of claim 129, when directly or indirectly appended to any one of claims 93 to 109, wherein the non-return valve is fitted to the second passageway between a second gas inlet and the second flow generator.

131. The system of claim 130, wherein the second gas accumulating in the second passageway during patient exhalation flows upstream.

132. The system of claim 125, wherein the system comprises a flow restriction device and a volume of the second gas accumulates by flowing in an upstream direction during at least part of patient exhalation.

133. The system of claim 132, wherein the flow restriction device is a non-return valve located in the second passageway downstream of where the second gas enters the second passageway.

134. The system of claim 133, wherein the second gas enters the second passageway proximally to the patient interface and the second gas accumulates by flowing in an upstream direction.

135. The system of any one of claims 1 to 134, wherein a reservoir is provided in or on the second passageway, in which the second gas can accumulate.

136. The system of claim 135, wherein the reservoir is located upstream of the second flow generator.

137. The system of any one of claims 1 to 136, wherein the first passageway and the second passageway comprise lengths of tubing for conveying the first gas.

138. The system of claim 137, wherein the tubing for the second passageway is selected to allow a required volume of the second gas to be stored in the second passageway.

139. The system of claim 137, wherein the tubing for the second passageway comprises one or more lengths being selected based on a storage capacity of the second passageway for storing a volume of the second gas.

140. The system of claim 139, wherein the storage capacity is between about 50 % and 100 %, or between about 50% and 90 %, or between about 60 % and 80 %, or between about 60 % and 70 % of the tidal volume of the patient.

141. The system of any one of claims 1 to 140, wherein the controller is configured to generate a signal to alert a clinician or a patient when an undesirable event occurs.

142. The system of claim 141, wherein the signal comprises a warning regarding one or more of:the second gas overfilling the second passageway, the second gas not meeting a required treatment volume, the internal volume of the second passageway for storing the second gas is too small or too large, the respiration rate of the patient is too low, the tidal volume of the patient is too low, an unforeseen leak in the system, a blockage in the system, inadequate flow of the first gas, or concentration of the second gas in the patient interface is too high.

143. The system of any one of claims 1 to 142, wherein the system comprises the patient interface.

144. The system of claim 143, wherein the patient interface is an unsealed interface.

145. The system of claim 143, wherein the patient interface is a sealed interface.

146. The system of any one of claims 1 to 145, wherein the system comprises a third passageway located downstream of the first passageway and the second passageway.

147. The system of claim 146, wherein the third passageway is connected to the patient interface.

148. The system of any one of claims 1 to 147, wherein the system comprises an exhalation port for venting the exhaled gas from the system.

149. The system of claim 148, wherein the exhalation port is located on the first passageway.

150. The system of claim 148 or 149, wherein the exhalation port is located on the first passageway proximally to the patient interface.

151. The system of claim 148 or 149, wherein the exhalation port is located on the first passageway distally to the patient interface.

152. The system of claim 148, wherein the exhalation port is on the second passageway.

153. The system of claim 148 when appended directly or indirectly to any one of claim 146 or 147, wherein the exhalation port is located on the third passageway.

154. The system of claim 148 when appended to claim 151, the exhalation port is located on the patient interface.

155. The system of any one of claims 1 to 154, wherein the second gas is provided by a second gas source.

156. The system of claim 155, wherein the system comprises the second gas source.

157. The system of any one of claims 1 to 156, wherein the second gas is a pressurized gas comprising one or more of: oxygen, heliox, an anaesthetic gas, or air enriched with oxygen.

158. The system of claim 157, wherein the second gas is pressurized oxygen gas.

159. The system of any one of claims 1 to 158, wherein the controller is configured to control the commencement of the delivery period by controlling : one or more flow generators, one or more valves, or one or more flow generators and one or more valves.

160. The system of claim 159, comprising the: one or more flow generators,one or more valves, or one or more flow generators and one or more valves.

161. A system for providing respiratory support to a patient, the system comprising: a first passageway connectable to a patient interface, the first passageway configured to convey a first gas during an accumulation period, a second passageway connectable to a patient interface, the second passageway configured to accumulate a second gas during at least part of the accumulation period and to convey the first gas during a delivery period such that the accumulated second gas is displaced from the second passageway to the patient interface, and a controller that is configured to control a commencement of the delivery period so that the second gas accumulated during the accumulation period is delivered to the patient interface: from an onset of patient inhalation, from a period before the onset of inhalation, from a period after the onset of inhalation, or during a high flow phase of patient inhalation, the high flow phase of patient inhalation comprising a predetermined period before and / or after a peak inspiratory flow.

162. A respiratory support system for providing respiratory support to a patient, the respiratory support system comprising: a first passageway comprising a first gas inlet configured to receive a first gas, the first passageway configured to convey the first gas towards a patient interface; a second passageway comprising a first gas inlet configured to receive the first gas, and a second gas inlet configured to receive a second gas, the second passageway configured to convey the first gas and the second gas towards the patient interface; a flow control system configured to control one or more of a flow rate or a pressure of the first gas and one or more of a flow rate or a pressure of the second gas, the flow control system comprising:one or more controllable flow generators, one or more controllable valves, or one or more controllable flow generators and one or more controllable valves; and a controller configured to control operation of the flow control system so that: during an accumulation period, the first gas is conveyed towards the patient interface through the first passageway, and a volume of the second gas accumulates in the second passageway, during a delivery period, the first gas and the volume of the second gas are conveyed towards the patient interface through the second passageway, the accumulation period occurs during a portion of patient inhalation and at least a portion of patient exhalation, and the delivery period occurs during at least a portion of patient inhalation and optionally a portion of patient exhalation.

163. A respiratory support apparatus for use in the respiratory support system of any one of claims 1 to 162, the respiratory support apparatus comprising the controller.

164. A respiratory support apparatus for use in a respiratory support system configured to provide respiratory support to a patient, the respiratory support apparatus comprising a controller that is configured to control : one or more flow generators of the respiratory support system, one or more valves of the respiratory support system, or one or more flow generators of the respiratory support system, and one or more valves of the respiratory support system, to supply: a first gas to a first passageway of the respiratory support system, the first gas to a second passageway of the respiratory support system, anda second gas to the second passageway, wherein: during an accumulation period the second passageway is configured to accumulate a volume of the second gas and the first passageway is configured to supply the first gas to a patient interface of the respiratory support system, during a delivery period, the second passageway is configured to supply the volume of the second gas to the patient interface, and the controller is configured to control timing of one or more of the accumulation period or the delivery period based on a breathing cycle of the patient.

165. The respiratory support apparatus of claim 164, comprising: the one or more flow generators, the one or more valves, or the one or more flow generators and the one or more valves.

166. The respiratory support apparatus of claim 164 or 165, the controller configured to control timing of the accumulation period and the delivery period so that neither are coterminous with patient exhalation or patient inhalation.

167. The respiratory support apparatus of any one of claims 164 to 166, the controller configured to control the timing of the accumulation period to occur during : at least a portion of patient exhalation, and a portion of patient inhalation.

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