Respiratory systems and methods

Abstract

The present disclosure relates to a system and method for providing a flow of respiratory gas to a patient, the system including a controller, a flow regulator, and one or more sensors, the controller configured to control the flow regulator to regulate the flow of respiratory gas in response to a determined pressure in the system that exceeds or does not exceed a pressure threshold.

Description

[Technical field]

[0001] The present disclosure relates to systems and methods for controlling the flow of respiratory gas to a patient.

[0002] In particular, but not by way of limitation, the systems and methods control the flow of breathing gas to a patient in response to changes in system pressure downstream of a flow regulator that provides the flow of breathing gas. [Background technology]

[0003] Patients may lose respiratory function during anesthesia or sedation, or more generally during certain medical procedures. Prior to a medical procedure, the patient may be pre-oxygenated by a medical professional to provide a reservoir of oxygen saturation, this pre-oxygenation is generally performed with bag ventilation and a face mask. Once general anesthesia is received, the patient must be intubated to administer oxygen to the patient. In some cases, intubation is completed in 30-60 seconds, but in some cases, especially if the patient's airway is difficult to navigate (e.g., due to cancer, severe injury, obesity, or spasms of the neck muscles), intubation takes much longer. While pre-oxygenation provides a buffer against a drop in oxygen saturation, for long intubation procedures, it is necessary to interrupt the intubation process and reapply the face mask to increase the patient's oxygen saturation to a sufficient level. Interruptions to the intubation process may occur multiple times for difficult intubation procedures, which is time consuming and exposes the patient to serious health risks. After about three intubation attempts, the medical procedure is abandoned.

[0004] In procedures requiring multiple respiratory support systems, there may be concerns that combining support systems may result in overpressure delivery (e.g., when a cannula is placed on the patient and the anesthesiologist wishes to deliver respiratory support through a mask placed over the top of the cannula).

[0005] Moreover, switching between different support systems can be time consuming or difficult. It may therefore be desirable to have a configuration that can facilitate switching between a respiratory support system, for example support via high flow, and respiratory support via a face mask and bag or anesthesia machine. It may also be desirable to be able to quickly and easily stop or reduce gas flow.

[0006] The reference herein to a patent document, or any other matter identified as prior art, is not to be construed as an admission that the document or other matter was known or that the information it contains was part of the common general knowledge at the priority date of any claim. Summary of the Invention [Means for solving the problem]

[0007] In one aspect of the disclosure, a breathing system for providing a flow of respiratory gas to a patient is provided, the system including a flow regulator and a controller configured to receive inputs of a flow rate and a pressure of the respiratory gas flow in the system and configured to control the flow regulator to provide the respiratory gas flow to the patient at a target flow rate, and to control the flow regulator to regulate the respiratory gas flow to the target pressure when the pressure of the respiratory gas flow in the system meets or exceeds a pressure threshold corresponding to the target flow rate.

[0008] In some embodiments, the target pressure comprises a pressure threshold corresponding to the target flow rate or a pressure threshold corresponding to a flow rate less than the target flow rate.

[0009] In some embodiments, the controller is configured to control the flow regulator to regulate the flow of breathing gas to the target pressure when the flow rate of the breathing gas flow is less than the target flow rate.

[0010] In some embodiments, the controller is configured to control the flow regulator to regulate the flow of respiratory gas to the target flow rate when the flow rate of the respiratory gas exceeds the target flow rate.

[0011] In some embodiments, the controller is configured to control the flow regulator to the target pressure when the pressure of the flow of breathing gas exceeds a pressure threshold corresponding to the target flow rate or a pressure threshold corresponding to a flow rate less than the target flow rate.

[0012] In some embodiments, when the system begins operation from an "off" or resting state, the controller is configured to monitor the flow rate of respiratory gas flow in the system and to control the flow regulator to regulate the respiratory gas flow to a target flow rate, which in some embodiments is varied over time to increase from a current value to a flow rate set point.

[0013] In some embodiments, the target flow rate is a flow rate set point. The flow rate set point may be determined by a user of the breathing system. In some embodiments, the flow rate set point may be set by a user providing input to the controller.

[0014] In some embodiments, the controller includes a flow controller providing a flow control output and a pressure controller providing a pressure control output, and the control input to the flow regulator is the minimum of the flow control output and the pressure control output.

[0015] In some embodiments, the flow regulator includes a blower and the flow control output and the pressure control output include an angular velocity of the blower.

[0016] In some embodiments, the flow regulator includes a proportional valve, and the flow control output and the pressure control output include a fixed size flow path restriction through the proportional valve.

[0017] In some embodiments, the controller is configured to receive a flow value indicative of a flow rate of breathing gas provided to the patient.

[0018] In some embodiments, the controller may be operable in a first control mode when the flow rate exceeds the target flow rate to control the flow rate to a target flow rate, and the controller may be operable in a second control mode when the pressure of the respiratory gas flow exceeds a pressure threshold corresponding to the target flow rate or exceeds a certain or a certain pressure threshold corresponding to a flow rate less than the target flow rate to control the pressure to the target pressure.

[0019] In some embodiments, the respiratory system includes one or more flow sensors configured to allow the patient to sense the flow rate of the respiratory gas flow in the system.

[0020] In some embodiments, the respiratory system includes one or more pressure sensors configured to allow the patient to sense the pressure of the respiratory gas flow within the system.

[0021] In some embodiments, the controller is further configured to receive an input indicative of the flow rate of the respiratory gas flow in the system from one or more flow sensors, and an input indicative of the pressure of the respiratory gas flow in the system from one or more pressure sensors.

[0022] In some embodiments, the breathing system includes a delivery conduit for providing a flow of gas from the flow regulator to a patient interface, the patient interface configured to deliver the flow of breathing gas to the patient.

[0023] In some embodiments, the patient interface includes nasal cannulas, optionally non-sealing nasal cannulas.

[0024] In some embodiments, the patient interface includes a gas delivery side arm in fluid communication with the delivery conduit, a manifold provided at an end of the gas delivery side arm, and one or more nasal elements extending from the manifold, the one or more nasal elements configured to provide a flow of respiratory gas to one or more nares of the patient, the gas delivery side member including a foldable portion.

[0025] The foldable portion may be operable in a first configuration in which the foldable portion is substantially open, and in a second configuration in which the foldable portion is substantially closed.

[0026] In some embodiments, when the controller controls the flow regulator to the target pressure, the flow to the patient is reduced to a reduced flow rate of about 15 L / min or less, or about 10 L / min or less, or about 10 L / min, or about 5 L / min to about 10 L / min, or less than about 5 L / min, or 0 L / min.

[0027] In some embodiments, the controller is configured to control the flow regulator to increase the flow of breathing gas towards the target flow rate.

[0028] In some embodiments, the delivery conduit further includes a delivery circuit and a patient breathing circuit arranged between the delivery circuit and the patient interface, the patient breathing circuit being connected to the delivery circuit by an outlet connector.

[0029] In some embodiments, the flow regulator includes one or more of a flow generator configured to be controlled by the controller to regulate the flow of respiratory gas to the patient, and a proportional valve configured to be controlled by the controller to regulate the flow of respiratory gas.

[0030] In some embodiments, the flow generator includes a blower configured to be controlled by the controller to generate the flow of breathing gas.

[0031] In some embodiments, the respiratory system includes an oxygen (O2) pressure sensor configured to sense pressure in an O2 delivery circuit of the respiratory system.

[0032] In some embodiments, the respiratory system includes an oxygen (O2) flow sensor configured to sense a flow rate of O2 flow in an O2 delivery circuit of the respiratory system. In some embodiments, the proportional valve may be arranged between the O2 pressure sensor and the O2 flow sensor in the O2 delivery circuit.

[0033] In some embodiments, the patient breathing circuit may be connected to the O2 delivery circuit and the air delivery circuit, and the patient breathing circuit and / or the patient interface may further include a patient pressure sensor and a patient flow sensor. In some embodiments, the flow regulator may include a blower, and the blower may be arranged in the patient breathing circuit before the patient pressure sensor and the patient flow sensor.

[0034] In some embodiments, the controller is in operative communication with or includes a memory component that stores one or more of a function, curve, look-up table, or algorithm that provides a relationship between a pressure threshold and a corresponding flow rate.

[0035] In some embodiments, the controller is configured to control the flow regulator to reduce the flow of breathing gas by a variable reduction rate.

[0036] In some embodiments, the relationship between the pressure threshold and the corresponding flow rate may be represented by a pressure limit curve or function that defines a curve having a sigmoidal shape.

[0037] In some embodiments, the relationship between the pressure thresholds and the corresponding flow rates includes a first pressure region, a second pressure region, and a transition region arranged between the first pressure region and the second pressure region.

[0038] In some embodiments, the first pressure area may correspond to when the foldable portion is substantially in the first configuration, and the second pressure area may correspond to when the foldable portion is substantially in the second configuration.

[0039] In some embodiments, the first pressure region includes a pressure threshold offset from a reference pressure value by a first pressure margin, and the second pressure region includes a pressure threshold offset from the reference pressure value by a second pressure margin, whereby the first pressure margin is greater than the second pressure margin.

[0040] In some embodiments, the first and second margins provide an offset of the pressure threshold limit value within a first pressure region that is substantially parallel to an offset of the pressure threshold value within a second pressure region of the pressure limit curve, the first pressure region and the second pressure region corresponding to a minimum rate of change of respiratory gas flow.

[0041] In some embodiments, the slope of the transition region of the pressure limit curve corresponds to the maximum rate of change of breathing gas flow.

[0042] In some embodiments, the transition region of the pressure limit curve may be centered around the transition flow rate, hi some embodiments, the controller is configured to control the flow regulator such that the breathing gas flow reaches a maximum rate of change when the pressure and corresponding flow rate are within the transition region of the pressure limit curve.

[0043] In some embodiments, the first and second pressure margins provide a margin for temporarily reducing the system pressure of the respiratory gas flow from below the pressure threshold without the controller controlling the flow regulator to increase the respiratory gas flow.

[0044] Viewed from another aspect, the present invention provides a breathing system for providing a flow of respiratory gas to a patient, the system including a controller and a flow regulator configured to be controlled by the controller to provide the flow of respiratory gas to the patient, the controller configured to control the flow regulator to a flow rate to a determined pressure setpoint, and the controller configured to control the flow regulator to limit a flow rate of the flow of respiratory gas to less than or equal to the flow rate setpoint.

[0045] In some embodiments, the flow rate set point is set by a user of the breathing system. In some embodiments, the flow rate set point may be set by a user providing input to the controller.

[0046] In some embodiments, the system includes a plurality of flow rate determined set points, and the controller is configured to control the flow regulator to the set points.

[0047] In some embodiments, the flow rate determined set point is based on the flow rate of the breathing gas flow.

[0048] In some embodiments, the set point at which the flow rate is determined is predetermined.

[0049] In some embodiments, the pressure set point at which the flow rate is determined when the respiratory gas flow rate is at or near the flow rate set point is a first margin away from the normal system pressure value, and the pressure set point at which the flow rate is determined when the respiratory gas flow rate is at or near 0 L / min is a second margin away from the normal system pressure value, the first margin being greater than the second margin.

[0050] In some embodiments, when the breathing gas flow rate is at or near 0 L / min, the flow-determined pressure set point is 0 cmH2O.

[0051] In some embodiments, the flow regulator includes a blower and / or a proportional valve.

[0052] In some embodiments, the breathing system further comprises one or more of a flow sensor, a pressure sensor, and a user interface.

[0053] In some embodiments, the respiratory system further comprises a non-sealing nasal interface in fluid communication with the flow regulator and configured to provide a flow of respiratory gas to the patient.

[0054] In some embodiments, the non-sealing nasal interface includes a gas delivery side arm, a manifold provided at an end of the gas delivery side arm, and one or more nasal elements extending from the manifold, the one or more nasal elements configured to provide a flow of respiratory gas to one or more nares of the patient, the gas delivery side member including a foldable portion.

[0055] In some embodiments, the foldable portion is operable in a first configuration in which the foldable portion is substantially in an open state, and in a second configuration in which the foldable portion is substantially in a closed state.

[0056] In some embodiments, the flow rate set point is greater than 0 L / min, optionally greater than 0 L / min to about 120 L / min, optionally from about 20 L / min to about 90 L / min, and optionally from about 40 L / min to about 70 L / min.

[0057] In another aspect of the disclosure, a respiratory system for providing a respiratory gas flow to a patient is provided, the system including a controller and a flow regulator configured to be controlled by the controller to provide the respiratory gas flow to the patient, the controller configured to receive one or more pressure inputs indicative of a system pressure corresponding to the respiratory gas flow downstream of the flow regulator, receive an input related to a flow rate set point, receive one or more flow rate inputs indicative of the respiratory gas flow downstream of the flow regulator, compare the received pressure and / or flow rate inputs to predetermined pressure thresholds and flow rate set points corresponding to the flow rates, and control the flow regulator between two control modes, a first control mode including controlling the flow regulator to provide the respiratory gas flow at the flow rate set point when the system pressure is lower than the predetermined pressure threshold for a corresponding flow rate, and a second control mode including controlling the flow regulator to regulate the respiratory gas flow to a target pressure when the flow rate of the respiratory gas flow is lower than the flow rate set point.

[0058] In another aspect of the disclosure, a respiratory system for providing a flow of respiratory gas to a patient is provided, the system including a controller and a flow regulator configured to be controlled by the controller to provide a flow of respiratory gas to the patient, the controller configured to receive an input indicative of a system pressure, compare the system pressure to one or more pressure thresholds for corresponding flow rates, control the flow regulator to reduce the system pressure in response to the system pressure meeting or exceeding the one or more pressure thresholds for the corresponding flow rates, and control the flow regulator to reach a target flow rate in response to a system pressure not meeting or exceeding the pressure thresholds for the corresponding flow rates.

[0059] In another aspect of the present disclosure, a breathing system for providing a flow of respiratory gas to a patient is provided, the system including a controller and a flow regulator configured to be controlled by the controller to provide the flow of respiratory gas to the patient, the controller configured to control the flow regulator to a flow rate set point, and the controller configured to control the flow regulator to limit a pressure of the flow of respiratory gas to below a determined pressure limit.

[0060] In another aspect of the disclosure, a respiratory system for providing a respiratory gas flow to a patient is provided, the system including a controller, a flow regulator configured to be controlled by the controller to provide the respiratory gas flow to the patient, and one or more sensors configured to determine a pressure of the respiratory gas flow in the respiratory system to the patient, the controller is configured to receive input from the one or more sensors indicative of the pressure of the respiratory gas flow in the respiratory system, compare the pressure to a pressure threshold for a corresponding flow rate, control the flow regulator to reduce the respiratory gas flow in response to a pressure that exceeds the pressure threshold for the corresponding flow rate, and control the flow regulator to adjust the respiratory gas flow in response to a pressure that does not exceed the pressure threshold for the corresponding flow rate.

[0061] The controller of the respiratory system may include a microcontroller, a proportional-integral-derivative (PID) controller, or a variation of a PID controller (such as a P, PI or I controller) in which the proportional, derivative and integral elements of the controller can be turned on or off as required, or any other architecture configured to operate according to an algorithm stored in a memory in communication with the controller to direct the operation of the controllable components of the respiratory system. The controller thus enables the respiratory system to control one or more components of the respiratory system in response to changes in pressure and / or flow in the system. The controller may control a flow regulator in response to changes in pressure in the system. The pressure in the system may be the pressure downstream of the flow regulator. This is in contrast to a pressure relief valve, which relieves pressure in the system when the system pressure exceeds a pressure threshold, typically by venting gas to the atmosphere. This venting of the delivered gas may be considered a waste source.

[0062] The controller of the respiratory system receives inputs of pressure in the system and determines whether the value of pressure in the system meets or exceeds a pressure threshold for a corresponding flow rate, indicating an obstruction (some flow across it may still exist) or a blockage (no flow across it). In response, the controller controls components of the respiratory system, which may regulate the flow. The controller also restores the desired flow to the respiratory system after removing the obstruction or blockage. The controller controls the respiratory gas flow to the patient, thus reducing waste of gases such as oxygen. There is also the possibility of reducing undesirable effects on the respiratory gas flow provided to the patient via another respiratory support system, for example, the controller controls the respiratory gas flow to minimize dilution of anesthesia agent provided to the patient via an anesthesia system used with the system of the present disclosure. In situations such as those described below where a mask may be used over a cannula, this can be advantageous by providing better control over the pressure acting on the occluded / blocked (i.e. folded) portion so that the user does not need to apply undue force to the mask over the cannula and control any residual flow across the foldable portion associated with the cannula.

[0063] In some embodiments, the flow regulator includes a flow generator, for example a blower, configured to be controlled by the controller to generate a flow of breathing gas to the patient.

[0064] In some embodiments, the flow regulator includes a proportional valve configured to be controlled by the controller to regulate the flow of breathing gas.

[0065] In some embodiments, the flow regulator further comprises a proportional valve and a flow generator.

[0066] An algorithm implemented by the controller controls a blower and / or a flow regulator, such as a proportional valve, to provide pressure / flow control to a breathing system that supplies gas to a patient during delivery of respiratory support. Examples of respiratory support are discussed above and include nasal high flow, continuous positive airway pressure, and artificial ventilation. The breathing system may include two or more blowers and / or two or more proportional valves.

[0067] In some embodiments, the controller is further configured to determine a flow rate of the respiratory gas flow from an input indicative of a pressure of the respiratory gas flow.

[0068] In another embodiment, the one or more sensors include one or more flow sensors configured to sense a flow rate of the flow of respiratory gas in the delivery conduit to the patient. The controller is further configured to receive inputs indicative of the flow rate of the flow of respiratory gas in the delivery conduit from the one or more flow sensors. Preferably, the inputs indicative of the flow rate are data indicative of the flow rate.

[0069] In some embodiments, the pressure of the flow of respiratory gas in the breathing system is determined from data indicative of the flow rate of the flow of respiratory gas in the breathing system.

[0070] In some embodiments, the one or more sensors are configured to sense a pressure of the respiratory gas flow in the respiratory system downstream of the flow regulator. Preferably, the one or more sensors are located downstream of the flow regulator.

[0071] In some embodiments, the one or more sensors include one or more pressure sensors configured to sense the pressure of a flow of breathing gas in the system to the patient.

[0072] In some embodiments, the one or more sensors include one or more pressure sensors and one or more flow sensors.

[0073] In some embodiments, the pressure of the respiratory gas flow in the breathing system is the pressure of the respiratory gas flow downstream of the flow regulator.

[0074] In some embodiments, the input comprises data indicative of a pressure of the flow of respiratory gas in the respiratory system.

[0075] In some embodiments, the respiratory system further includes a delivery conduit and a patient interface at one end of the delivery conduit, the patient interface configured to deliver the flow of respiratory gas to the patient.

[0076] In some embodiments, the pressure of the breathing gas flow is the pressure of the breathing gas flow upstream of or at the collapsible portion.

[0077] In one example, the patient interface is in fluid communication with a gas supply, and the gas flow is controlled by a flow regulator of the breathing system. Examples of gas supplies include a pressurized source (such as a gas tank or a hospital wall supply), a blower, a mixer, or combinations thereof. The breathing system may also include a humidifier to humidify the gas before delivery to the patient.

[0078] In some embodiments, the patient interface includes an outlet that is received by the patient's nostril or mouth, and a gas delivery side member extending from a side of the outlet, the gas delivery side member including a lumen for gas flow from the inlet to the outlet of the patient interface, and a collapsible portion. For example, the patient interface is a nasal cannula and optionally a non-sealing nasal cannula.

[0079] In some embodiments, the foldable portion is configured in a first configuration and is foldable from the first configuration into a second configuration. In the second configuration, breathing gas flow through the foldable portion is at a reduced rate compared to when the foldable portion is in the first configuration. For example, the reduced rate is about 15 L / min or less, or about 10 L / min or less, or about 10 L / min, or between about 5 L / min and about 10 L / min, or less than about 5 L / min, or 0 L / min.

[0080] In some embodiments, the controller is further configured to control the flow regulator to reduce the respiratory gas flow to a reduced flow rate in response to the pressure exceeding a pressure threshold for a corresponding flow rate. For example, the respiratory gas flow is reduced to the reduced flow rate in a stepwise manner. In some embodiments, the controller is configured to control the flow regulator to reduce the pressure in the system, which then reduces the respiratory gas flow (as determined by the change in pressure and the resistance to flow in the system). For example, the pressure in the system may be reduced by, for example, reducing the operation of the flow regulator in a stepwise manner.

[0081] In some embodiments, the controller is further configured to control the flow regulator to continuously reduce the breathing gas flow towards the reduced flow rate. Alternatively / additionally, the controller may be configured to control the flow regulator, e.g., by reducing its operation, to continuously reduce the pressure in the system towards a pressure target.

[0082] In some embodiments, the controller is further configured to control the flow regulator to regulate the flow of breathing gas to a target flow rate in response to the pressure not exceeding a pressure threshold for a corresponding flow rate, for example, the target flow rate may be between 40 and 70 L / min.

[0083] In some embodiments, the controller is further configured to control the flow regulator to continuously adjust the flow of breathing gas towards the target flow rate.

[0084] In some embodiments, the controller is further configured to control the flow regulator to increase the flow of breathing gas towards the target flow rate.

[0085] In one example, the flow of breathing gas is increased to the target flow rate in steps. Alternatively, the controller is configured to control the flow regulator to increase the flow of breathing gas continuously towards the target flow rate.

[0086] In some embodiments, the delivery conduit further includes a delivery circuit and a patient breathing circuit arranged between the delivery circuit and the patient interface, the patient breathing circuit being connected to the delivery circuit by an outlet connector.

[0087] In some embodiments, the delivery conduit further includes a delivery circuit and a patient breathing circuit arranged between the delivery circuit and the patient interface, the patient breathing circuit being connected to the delivery circuit by an outlet connector.

[0088] In some embodiments, the controller, flow regulator, one or more sensors, and the delivery circuit are contained within a housing, and the outlet connector is attached to the housing, e.g., the housing is a box.

[0089] In some embodiments, the one or more sensors include an oxygen (O2) pressure sensor configured to sense the pressure of O2 flow from an O2 supply to a patient in an O2 delivery circuit of the respiratory system.

[0090] In some embodiments, the one or more sensors include an oxygen (O2) flow sensor configured to sense a rate of O2 flow from an O2 supply to the patient.

[0091] In some embodiments, the proportional valve is arranged in the O2 delivery circuit between the O2 pressure sensor and the O2 flow sensor.

[0092] In some embodiments, the one or more sensors include an air pressure sensor configured to sense the pressure of the flow of air from ambient air to the patient in an air delivery circuit of the respiratory system.

[0093] In some embodiments, the blower is arranged after the air pressure sensor in the air delivery circuit.

[0094] In some embodiments, the patient breathing circuit is connected to the O2 delivery circuit and the air delivery circuit, and the patient breathing circuit and / or the patient interface further includes a patient pressure sensor and a patient flow sensor.

[0095] In some embodiments, the patient breathing circuit is connected to the O2 delivery circuit and the air delivery circuit, and the patient breathing circuit and / or the patient interface further includes a patient pressure sensor and a patient flow sensor.

[0096] In some embodiments, the blower is arranged in the patient breathing circuit before the patient pressure sensor and the patient flow sensor.

[0097] In some embodiments, the pressure thresholds for corresponding flow rates form a pressure limit curve.

[0098] In some embodiments, the pressure thresholds for corresponding flow rates form a pressure limit curve, in which embodiment the controller is further configured to compare the pressure and flow rate to the pressure limit curve.

[0099] In some embodiments, the pressure limit curve is associated with flow restrictions within the breathing system and / or delivery conduit.

[0100] In some embodiments, the flow regulator is configured to reduce the breathing gas flow with a rate of reduction that corresponds to a pressure limit curve.

[0101] In some embodiments, the pressure limit curve is sigmoidal in shape.

[0102] In some embodiments, the sigmoidal shaped pressure limit curve includes a first pressure region, a second pressure region, and a transition region arranged between the first pressure region and the second pressure region.

[0103] In some embodiments, the first pressure region corresponds to the first configuration and the second pressure region corresponds to the second configuration.

[0104] In some embodiments, in the first configuration, the normal operating pressure of the respiratory gas flow in the delivery conduit is a first pressure margin below the pressure limit curve, and in the second configuration, the normal operating pressure of the respiratory gas flow is a second pressure margin below the pressure limit curve, whereby the first pressure margin is substantially greater than the second pressure margin. The first and second pressure margins can thus provide a margin for temporarily increasing the pressure of the respiratory gas flow from the normal pressure so as not to reduce the respiratory gas flow.

[0105] In another embodiment, the first and second pressure margins provide a margin for temporarily reducing the pressure of the breathing gas flow from normal pressure in order not to increase the breathing gas flow.

[0106] In some embodiments, the first pressure region is substantially parallel to the second pressure region of the pressure limit curve, and the first pressure region and the second pressure region correspond to a minimum rate of reduction in breathing gas flow.

[0107] In some embodiments, the transition region of the pressure limit curve corresponds to a maximum rate of reduction in breathing gas flow.

[0108] In some embodiments, the transition region of the pressure limit curve is centered around a transition flow rate.

[0109] In some embodiments, the flow regulator is configured to reduce the flow of breathing gas at a maximum reduction rate when the pressure and corresponding flow rate are in a transition region of the pressure limit curve.

[0110] In another aspect of the disclosure, a breathing system for providing a flow of breathing gas to a patient is provided, the system including a controller, a flow regulator configured to be controlled by the controller to provide the flow of breathing gas to the patient, one or more sensors configured to determine a pressure of the flow of breathing gas in the breathing system to the patient, and a patient interface in fluid communication with the flow regulator and configured to deliver the flow of breathing gas to the patient, the patient interface having an inlet for receiving the flow of breathing gas from the flow regulator, an outlet for delivering the flow of breathing gas to the airway of the patient, and a patient interface configured to switch between a first configuration and a second configuration. and a gas conduit including a foldable portion configured to adjust the pressure of the respiratory gas flow in the respiratory system when the foldable portion is in the second configuration greater than the pressure of the respiratory gas flow in the respiratory system when the foldable portion is in the first configuration, and the controller is configured to receive an input from the one or more sensors indicative of the pressure of the respiratory gas flow in the respiratory system, compare the pressure to a pressure threshold, and in response to a pressure meeting or exceeding the pressure threshold, control the flow regulator to provide a first adjustment of the respiratory gas flow, and in response to a pressure not meeting or exceeding the pressure threshold, control the flow regulator to provide a second adjustment of the respiratory gas flow.

[0111] In some embodiments, the second adjustment is different from the first adjustment.

[0112] In some embodiments, the first adjustment comprises reducing or maintaining the flow of breathing gas.

[0113] In some embodiments, the first adjustment includes reducing the flow of breathing gas in response to a pressure exceeding a pressure threshold.

[0114] In some embodiments, the first adjustment includes reducing or maintaining the flow of breathing gas in response to the pressure meeting a pressure threshold.

[0115] In some embodiments, the second adjustment comprises increasing the flow of breathing gas.

[0116] In some embodiments, the second adjustment includes adjusting the flow of breathing gas to a target flow rate.

[0117] In some embodiments, the one or more sensors are located downstream of the flow regulator.

[0118] In some embodiments, the breathing system further comprises a delivery conduit configured to deliver the flow of breathing gas from the flow regulator to the patient interface.

[0119] In some embodiments, the delivery conduit further includes a delivery circuit and a patient breathing circuit arranged between the delivery circuit and the patient interface, the patient breathing circuit being connected to the delivery circuit by an outlet connector.

[0120] In some embodiments, the controller, flow regulator, one or more sensors, and the delivery circuit are contained within a housing, and the outlet connector is attached to the housing.

[0121] In some embodiments, the flow regulator includes a flow generator configured to be controlled by the controller to generate a flow of breathing gas to the patient.

[0122] In some embodiments, the flow regulator includes a proportional valve configured to be controlled by the controller to regulate the flow of breathing gas.

[0123] In some embodiments, the flow regulator further comprises a proportional valve and a flow generator.

[0124] In some embodiments, the flow generator includes a blower configured to be controlled by the controller to generate the flow of breathing gas.

[0125] In some embodiments, the one or more sensors include an oxygen (O2) pressure sensor configured to sense the pressure of O2 flow from an O2 supply to a patient in an O2 delivery circuit of the respiratory system.

[0126] In some embodiments, the one or more sensors include an oxygen (O2) flow sensor configured to sense a rate of O2 flow from an O2 supply to the patient.

[0127] In some embodiments, the proportional valve is arranged between the O2 pressure sensor and the O2 flow sensor in the O2 delivery circuit.

[0128] In some embodiments, the one or more sensors include an air pressure sensor configured to sense the pressure of airflow from ambient air to the patient in an air delivery circuit of the respiratory system.

[0129] In some embodiments, the blower is arranged after the air pressure sensor in the air delivery circuit.

[0130] In some embodiments, the patient breathing circuit is connected to the O2 delivery circuit and the air delivery circuit, and the patient breathing circuit and / or the patient interface further includes a patient pressure sensor and a patient flow sensor.

[0131] In some embodiments, the blower is arranged in the patient breathing circuit before the patient pressure sensor and the patient flow sensor.

[0132] In some embodiments, the one or more sensors include one or more pressure sensors configured to sense a pressure of a flow of breathing gas in the system to the patient. The one or more pressure sensors are configured to sense a pressure of a flow of breathing gas in the breathing system downstream of the flow regulator.

[0133] In some embodiments, the input comprises data indicative of a pressure of the flow of respiratory gas in the respiratory system.

[0134] In some embodiments, the pressure of the respiratory gas flow in the breathing system is the pressure of the respiratory gas flow downstream of the flow regulator.

[0135] In some embodiments, the pressure of the breathing gas flow is the pressure of the breathing gas flow upstream of or at the collapsible portion.

[0136] In another aspect of the disclosure, a method of operating a respiratory system to provide a respiratory gas flow to a patient is provided, the method including providing a respiratory gas flow to the patient with the respiratory system, determining a pressure of the respiratory gas flow to the patient in the respiratory system using one or more sensors configured to determine a pressure of the respiratory gas flow in the respiratory system, receiving an input indicative of the pressure of the respiratory gas flow in the system from the one or more sensors, comparing the pressure to a pressure threshold for a corresponding flow rate, controlling a flow regulator to reduce the respiratory gas flow in response to a pressure exceeding the pressure threshold for the corresponding flow rate, and controlling the flow regulator to adjust the respiratory gas flow in response to a pressure not exceeding the pressure threshold for the corresponding flow rate.

[0137] In another aspect of the disclosure, there is provided a method of operating a respiratory system as described above, the method including providing a respiratory gas flow to a patient with the respiratory system, determining a pressure of the respiratory gas flow to the patient in the respiratory system using one or more sensors configured to determine a pressure of the respiratory gas flow in the respiratory system, receiving an input indicative of the pressure of the respiratory gas flow in the system from the one or more sensors, comparing the pressure to a pressure threshold for a corresponding flow rate, controlling a flow regulator to reduce the respiratory gas flow in response to a pressure exceeding the pressure threshold for the corresponding flow rate, and controlling the flow regulator to adjust the respiratory gas flow in response to a pressure not exceeding the pressure threshold for the corresponding flow rate.

[0138] Embodiments of the present disclosure will now be described in more detail with reference to the following figures. [Brief description of the drawings]

[0139] [Figure 1] FIG. 1 is a schematic diagram of an example of a breathing system for providing breathing gas to a patient. [Figure 2a] 1 illustrates a patient wearing a first patient interface for use with a respiratory system for providing respiratory gas to a patient according to an embodiment of the present disclosure. [Figure 2b] 1 illustrates a patient wearing a first patient interface with a second patient interface for use with a respiratory system for providing respiratory gas to a patient according to an embodiment of the present disclosure. [Figure 3a] 1 provides a schematic diagram of a first configuration of a foldable portion of a patient interface. [Figure 3b] 13 provides a schematic diagram of a second configuration of a foldable portion of a patient interface. [Figure 4] FIG. 1 is a schematic diagram of a respiratory system for providing respiratory gas to a patient, according to an embodiment of the present disclosure. [Diagram 5] FIG. 1 is a schematic diagram of a respiratory system for providing respiratory gas to a patient, according to an embodiment of the present disclosure. [Figure 6] FIG. 1 is a schematic diagram of a respiratory system for providing respiratory gas to a patient, according to an embodiment of the present disclosure. [Figure 7] FIG. 1 is a schematic diagram of a respiratory system for providing respiratory gas to a patient, according to an embodiment of the present disclosure. [Figure 8] FIG. 1 is a schematic diagram of a respiratory system for providing respiratory gas to a patient, according to an embodiment of the present disclosure. [Figure 9] 1 is a graph illustrating a curve representing the relationship between flow and pressure used in controlling breathing gas flow according to an embodiment of the present disclosure. [Figure 10] 1 is a graph illustrating a curve representing the relationship between flow and pressure used in controlling breathing gas flow according to an embodiment of the present disclosure. [Figure 11] 11 is a graph illustrating another curve representing the relationship between flow and pressure used in controlling breathing gas flow according to an embodiment of the present disclosure. [Figure 12] 1 is a graph showing that the pressure curve at zero flow can have a nominal pressure limit (curve R) or a zero pressure limit (curve S). [Figure 13] 11 is a graph illustrating a curve representing the relationship between flow and pressure offset used in controlling breathing gas flow, according to an embodiment of the present disclosure. [Figure 14]1 is a graph showing the relationship between changing pressure and flow rate as the resistance to flow experienced by the system increases. [Figure 15] FIG. 1 is a state diagram of operating states of a respiratory system, according to an embodiment of the present disclosure. [Figure 16] 1 is a flow diagram of the operation of a respiratory system, according to an embodiment of the present disclosure. [Figure 17] 1 is a flow diagram of a method of operating a breathing system according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0140] Throughout the figures and the specification, similar reference numerals may be used to indicate the same or similar components, and redundant descriptions thereof may be omitted.

[0141] As mentioned, the breathing system provides gas for delivery to the patient. The breathing system may take a number of forms, such as continuous positive airway pressure (CPAP) systems and high flow breathing gas systems (e.g., for high flow therapeutic and anesthesia procedures).

[0142] As used herein, "high flow" refers to any gas flow at a higher than normal / normal rate, such as, without limitation, higher than the normal inspiratory flow rate of a healthy patient. Alternatively or additionally, "high flow" may be higher than some other threshold flow rate relevant to the situation, for example, when providing a gas flow to a patient at a rate that meets the inspiratory demand, that flow rate may be considered "high flow" because it is higher than the nominal flow rate that might otherwise be provided. "High flow" is thus situation dependent, and what constitutes "high flow" depends on many factors, such as the patient's health status, the type of procedure / treatment / assistance provided, the characteristics of the patient (large, small, adult, pediatric), and the like. Those skilled in the art will recognize what constitutes "high flow" from the context. "High flow" is a magnitude of flow rate that exceeds the rate that might otherwise be provided.

[0143] However, without limitation, some values ​​indicative of high flow can be as follows:

[0144] In some configurations, delivery of gas to the patient at a flow rate of about five or ten liters per minute (5 or 10 LPM or L / min) or greater.

[0145] In some configurations, gas is delivered to the patient at a flow rate of about 5, or 10 LPM to about 150 LPM, or about 15 LPM to about 95 LPM, or about 20 LPM to about 90 LPM, or about 25 LPM to about 85 LPM, or about 30 LPM to about 80 LPM, or about 35 LPM to about 75 LPM, or about 40 LPM to about 70 LPM, or about 45 LPM to about 65 LPM, or about 50 LPM to about 60 LPM. For example, according to various embodiments and configurations described herein, the flow rate of gas supplied or provided through the system or from a flow source or flow regulator to an interface may include, but is not limited to, flows of at least about 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 LPM or more, and useful ranges may be selected to be any of these values ​​(e.g., about 20 LPM to about 90 LPM, about 40 LPM to about 70 LPM, about 40 LPM to about 80 LPM, about 50 LPM to about 80 LPM, about 60 LPM to about 80 LPM, about 70 LPM to about 100 LPM, about 70 LPM to about 80 LPM).

[0146] At "high flow," the delivered gas is selected depending, for example, on the intended use of the therapy. The delivered gas may include a percentage of oxygen. In some configurations, the percentage of oxygen in the delivered gas may be about 15% to about 100%, 20% to about 100%, or about 30% to about 100%, or about 40% to about 100%, or about 50% to about 100%, or about 60% to about 100%, or about 70% to about 100%, or about 80% to about 100%, or about 90% to about 100%, or about 100%, or 100%.

[0147] In some embodiments, the delivered gas may include a percentage of carbon dioxide. In some configurations, the percentage of carbon dioxide in the delivered gas may be greater than 0%, between about 0.3% and about 100%, between about 1% and about 100%, between about 5% and about 100%, between about 10% and about 100%, between about 20% and about 100%, between about 30% and about 100%, between about 40% and about 100%, between about 50% and about 100%, between about 60% and about 100%, between about 70% and about 100%, between about 80% and about 100%, between about 90% and about 100%, or about 100%.

[0148] The flow rate for "high flow" for premature babies / infants / children (within the range of body weight of about 1 to about 30 kg) may vary. The flow rate can be set at 0.4 to 8 L / min / kg, with a minimum of about 0.5 L / min and a maximum of about 70 L / min. For patients under 2 kg, the maximum flow may be set at 8 L / min.

[0149] High flows have been found to be effective in meeting or exceeding a patient's normal inspiratory flow to increase a patient's oxygenation and / or reduce the work of breathing. Additionally, high flow therapy may have a flushing effect on the nasopharynx such that the anatomical dead space of the upper airway is washed away by the high inlet gas flow. This creates a reserve of fresh gas available with every breath while minimizing rebreathing of carbon dioxide, nitrogen, etc.

[0150] By way of example, a high flow breathing system 10 will be described with reference to Figure 1. High flow may be used as a means to improve gas exchange and / or respiratory support through the delivery of oxygen and / or other gases, as well as through the removal of CO2 from the patient's airways. High flow may be particularly effective before, during or after medical and / or anesthesia procedures.

[0151] When used prior to a medical procedure, the high gas flow can preload the patient with oxygen so that the patient's blood oxygen saturation and capacity of oxygen in the lungs are higher to provide an oxygen buffer while the patient is in the apneic phase during the medical procedure.

[0152] A continuous supply of oxygen is important to maintain healthy respiratory function during medical procedures (such as during anesthesia) when respiratory function may be compromised (e.g., decline or cease). When this supply is compromised, hypoxia, hypoxemia, and / or hypercapnia may occur. During medical procedures such as anesthesia and / or sedation, where the patient is unconscious or may become unconscious, the patient is monitored to detect when this occurs. When oxygen delivery and / or CO2 removal is compromised, the clinician stops the medical procedure and expedites oxygen delivery and / or CO2 removal. This can be accomplished, for example, by manually ventilating the patient, for example by bag mask ventilation, or by using a high flow breathing system to provide a high flow of gas to the patient's airway. It will further be appreciated that the mask used for sedation / ventilation (not necessarily limited to bag mask) may also be used for pre-oxygenation and to monitor patient parameters such as end-tidal carbon dioxide, etc.

[0153] Further benefits of high gas flow include that it increases pressure within the patient's airways, thereby providing a pressure supply that opens the airways, trachea, lungs / alveoli, and bronchioles. Opening these structures enhances oxygenation and aids in some degree in the removal of CO2.

[0154] When humidified, high gas flow can also prevent airway drying, mitigate mucociliary damage, and reduce the risk of laryngospasm and the risks associated with dry airways, such as nosebleeds, aspiration (as a result of nosebleeds), and airway obstruction, swelling, and bleeding. Another advantage of high gas flow is that the flow can clear smoke generated in the airways during surgery. For example, smoke can be generated by lasers and / or cauterizing devices.

[0155] With reference to FIG. 1, system 10 may include an arrangement based on integrated or separate components, generally shown within dashed box 11 in FIG. 1. In some configurations, system 10 may include a modular arrangement of components. System 10 may include a flow source 12, such as a wall-mounted oxygen source, an oxygen tank, a blower, a flow therapy device, or any other source of oxygen or other gas, or a combination thereof. In some embodiments, flow source 12 includes a flow regulator, and in some embodiments, the flow regulator includes a flow generator, such as a blower, a bellows, and / or a piston. In some embodiments, the flow regulator includes a flow generator and a proportional valve, and the proportional valve may function to control the oxygen concentration in a mixed gas flow, such as air (preferably filtered air) and oxygen delivered to the patient. In some embodiments, the flow regulator includes a proportional valve, and in such embodiments, the flow regulator may not include a flow generator. Examples of systems including flow generators and proportional valves in this context are described in connection with FIGS. 7 and 8. In other embodiments, the flow source 12 need not include a flow generator, and in such embodiments, the flow source 12 may include a wall-mounted gas source and / or a mixed gas or other gas supply. In some embodiments, the flow source 12 may include a compressed gas source (e.g., a wall-mounted gas source, an oxygen tank supply, etc.) and a blower.

[0156] In some embodiments, the flow source 12 includes or is part of an anesthesia machine. The system 10 may also include an additive gas source 12A that includes one or more other gases that may be combined with the gas from the flow source 12. The flow source 12 may provide a gas flow 13 that may be delivered to a patient 16 via a delivery conduit 14 and a patient interface 15 (such as a nasal cannula). The gas flow 13 may deliver a high flow to the patient in the context previously described. A controller 19 controls the flow source 12 and the additive gas source 12A through valves or the like to control the flow and other characteristics, such as any one or more of the flow rate, pressure, composition, concentration, volume, etc., of the gas flow 13. A humidifier 17 is also optionally provided, which may humidify the gas and / or control the temperature of the gas, for example under the control of the controller 19. One or more sensors 18a, 18b, 18c, 18d, such as flow, oxygen, pressure, humidity, temperature or other sensors, may be placed throughout the system and / or on, on, or near the patient 16. The sensors may include a pulse oximeter 18d on the patient to determine the oxygen level in the blood.

[0157] Controller 19 may be operatively coupled to one or more components of system 10 by various means, including wired or wireless connections. For example, controller 19 may be operatively coupled to one or more of flow source 12, additive gas source 12A, humidifier 17, and sensors 18a-18d, as well as input / output (I / O) interface 20. By way of example, controller 19 may be provided on or in a high flow device, a separate component, and / or may be incorporated into or utilized with another device, such as an anesthesia machine or a ventilator, or may be in communication with one or more separate controllers that comprise part of system 10 and control the operation of separate components used with system 10 to provide respiratory assistance to a patient. The controller may include a microcontroller, a proportional-integral-derivative (PID) controller, or a variation of a PID controller (such as a P, PI, or I controller) in which the proportional, derivative, and integral components of the controller can be turned on or off as needed, or any other architecture configured to operate with algorithms stored in a memory that communicates with the controller to direct the operation of the controllable components of the respiratory system. The controller 19 may thus control the flow source 12 and other components of the system 10, or other components used with the system 10, to provide a delivered gas flow to the patient with specific characteristics, such as a desired flow rate, pressure, composition (if more than one gas is provided), volume, and / or other parameters based on feedback from one or more sensors 18a-18d. The controller 19 may also control any other suitable parameters of the flow source to meet the oxygenation, airway pressure, and / or flow requirements of the patient, and / or system pressure and / or flow requirements of the system (e.g., predetermined or set by a user through the interface 20). The controller 19 may also control the humidifier 17, which control may be based on feedback from one or more sensors 18a-18d.Using input from the sensors, the controller may determine operational changes required to meet the oxygen administration requirements and, as necessary, alter control parameters of the flow source 12 and / or the humidifier 17 and / or other added gas sources 12A and / or other components of the system.

[0158] An input / output (I / O) interface 20 (such as a display and / or input devices) may be provided. The interface 20 may receive information and input (such as required patient respiratory assistance parameters) from a user (e.g., a clinician or patient) that may be used to determine oxygen administration, pressure, flow requirements, and / or other system settings used to control one or more of the flow source 12, the additive gas source 12A, and other components of the system 10 to achieve a gas flow 13 with the necessary characteristics to provide the required respiratory assistance. In some embodiments, the system may be devoid of a controller and / or I / O interface. A medical professional, such as a nurse or technician, may provide the necessary control functions.

[0159] As mentioned above, the high gas flow (optionally humidified) may be delivered to the patient 16 via the delivery conduit 14 and the patient interface 15 or "interface" such as a cannula, mask, nasal interface, oral device or combinations thereof. In some embodiments, the high gas flow (optionally humidified) may be delivered to the patient 16 for surgical use, such as surgical insufflation. In these embodiments, the "interface" may be a surgical cannula, trocar, or other suitable interface. The patient interface may seal, substantially seal, partially seal, not seal, substantially not seal, or not partially seal with the patient's airway. As used herein, a nasal interface is a device such as a cannula, nasal mask, nasal pillows, or other type of nasal device, or combinations thereof configured to direct the gas flow to one or both of the patient's nostrils.

[0160] The nasal interface may also be used in combination with a facial mask 300 as shown in FIG. 2b or an oral device (such as a tube inserted into the mouth), and / or a mask or oral device (such as a tube inserted into the mouth) that can be detached from and / or attached to the nasal interface.

[0161] A nasal cannula is a nasal interface that may include one or more prongs configured for insertion into a patient's nasal passages. A mask refers to an interface that covers a patient's nasal passages and / or mouth, and may also include devices in which the portion of the mask that covers the patient's mouth may be removed. A mask also refers to a nasal interface that includes nasal pillows that create a substantial seal with the patient's nostrils.

[0162] Figures 2a and 2b show an example of a patient 16 wearing a patient interface 200 with a collapsible respiratory conduit portion, such as the nasal cannula 15 of the respiratory system 10 of Figure 1. The patient depicted is an adult. However, the patient may also be an infant, a child or an adolescent.

[0163] The patient interface 200 includes a first gas (delivery) conduit 202. The first gas conduit 202 is adapted to receive gas from the respiratory system 10 of FIG. 1 (e.g., via conduit 14 shown in FIG. 1) and direct the gas to the patient 16. The first gas conduit 202 may include a reinforcing element 203 adapted to strengthen and / or add rigidity to the first gas conduit to prevent deformation or folding of the first gas conduit 202 due to application of force against the first gas conduit 202. The reinforcing element 203 may include a number of structures including, but not limited to, plastic or metal reinforcing beads in or on the wall of the first conduit lumen 202.

[0164] The patient interface 200 may include a gas delivery side arm in fluid communication with a first gas conduit 202. The first gas conduit 202 is in pneumatic communication with a flow manifold 206 provided at the end of the gas delivery side arm. The flow manifold 206 receives gas from the first gas conduit 202 and passes it to one or more nasal delivery elements 208 (e.g., nasal prongs) extending from the manifold. The one or more nasal delivery elements 208 extend outwardly from the flow manifold 206. The one or more nasal delivery elements 208 are adapted to be positioned without sealing in one or more nares of the patient 16. The first patient interface 200 is thus a non-sealing patient interface. As shown, the patient interface 200 includes two nasal prongs 208 adapted to be positioned one in each of the patient's nostrils. Each nasal prong 208 may be shaped or angled such that the nasal prongs 208 extend inwardly toward the patient's nasal septum. Alternatively, the first patient interface 200 may be a sealing nasal interface.

[0165] In the embodiment shown in FIGS. 2a and 2b, the flow manifold 206 receives flow from one side of the flow manifold 206 (e.g., relative to an imaginary vertical plane that bisects the face of the patient P) and provides a passageway for flow through the manifold to each of the nasal prongs 208. In some embodiments, the conduits may extend from a single side of the manifold, such as from the left side or from the right side of the manifold. In some situations, providing a conduit on the left side of the patient interface may be preferred for clinician access, such as for intubation. Alternatively, a conduit extending from the right side may be preferred, for example, for procedures such as endoscopy, where the patient typically lies on their left side. In other configurations, the patient interface 200 may include more (e.g., three or four) or fewer (e.g., one) nasal delivery elements 208. In other configurations, each of the nasal delivery elements 208 may have different characteristics. For example, one of a pair of nasal delivery elements 208 may be relatively long and the other nasal delivery element 208 may be relatively short.

[0166] In some configurations, the flow manifold 206 may be configured to receive flow from two sides of the flow manifold 206 (e.g., from the "left" and "right" of the flow manifold 206, instead of only the patient's right side of the flow manifold 206 as seen in Figs. 2a and 2b). In some such configurations, multiple gas conduits may be used to provide pneumatic communication between the flow manifold 206 and the respiratory system 10. For example, the patient interface may include a dual conduit, with a first gas conduit 202 extending from a first side of the interface (the patient's right side in the example shown) and a second gas conduit (not shown) extending from a second, opposite side of the interface. In some configurations, the flow manifold 206 may be configured to receive flow from a non-side of the flow manifold 206 (e.g., from the "bottom" or "top" of the flow manifold 206, or both), or from a front side of the flow manifold 206 opposite the patient 16.

[0167] The patient interface 200 may further include a mounting and / or support portion, such as a cheek support 210, for mounting and / or supporting the gas conduit 202 or multiple conduits on the patient's face. Alternatively or additionally, the patient interface 200 may be held in place via one or more head straps or headgear (not shown).

[0168] The first gas conduit 202 of the patient interface 200 includes a first portion 204 configured to transition from a first configuration in which a first level of gas can pass through the first portion 204, to a second configuration in which a second level of gas can pass through the first portion 204.

[0169] FIG. 2b shows a patient 16 wearing a patient interface 200 including two nasal prongs 208 simultaneously under a facial mask assembly 300 (second patient interface). In this arrangement, the facial mask assembly 300 is placed over the patient interface 200 worn by the patient 16. FIG. 2b shows the facial mask assembly 300 diagrammatically as a transparent structure to show the patient interface 200 under the facial mask assembly 300. The first patient interface 200 may be used with a first respiratory support system 10 and the facial mask assembly (second patient interface) 300 may be used with a second respiratory support system (not shown). In some configurations, the first and second respiratory support systems are the same system and / or the first and second respiratory support systems include a common flow source despite the different modes of respiratory support provided by the first and second respiratory support systems. In other configurations, the first and second respiratory support systems are separate systems.

[0170] The configuration shown in Figure 2b may be advantageous in providing selective delivery of distinct modes of therapy or support to a patient using different patient interfaces, and / or in stopping or pausing delivery of therapy from an interface, and / or in being able to sample gases provided by the interface. For example, the configuration may find particular application in emergency resuscitation, surrounding intubation of a patient undergoing high flow therapy, in ear, nose and throat (ENT) surgery, assisting in conditioning a patient in a pre-operative state prior to administration of anaesthetic agents, and post-extubation and during recovery.

[0171] The facial mask assembly 300 may be used as or with a second respiratory assistance system and / or to deliver one or more substances other than the substance delivered by the cannula 200, such as to deliver anaesthetic and / or oxygen to the patient, or to deliver the same substance as the first patient interface 200, but at a different flow and / or pressure level. Alternatively, the facial mask assembly 300 may be used to reduce or stop delivery of therapy from the first respiratory assistance system through the first patient interface 200. In some embodiments, the facial mask assembly 300 may be adapted to measure respiratory gases, such as carbon dioxide exhaled from the patient, whose measurements may otherwise be affected by flow from the patient interface 200 of the first respiratory assistance system.

[0172] The configuration shown in Figure 2b is capable of switching between two different respiratory assistance systems. Additionally, this configuration may allow the first patient interface 200 to remain on the patient throughout a medical procedure and / or during recovery (whether or not the patient continues to receive treatment through the patient interface 200 throughout the procedure) without interfering with other clinical care.

[0173] In the embodiment shown, the facial mask assembly 300 includes a full face mask 302 configured to cover both the patient's nose and mouth. In other configurations, the facial mask assembly 300 may include a nasal mask placed over the patient interface 200 to cover only the patient's nasal region.

[0174] As shown, the facial mask 302 includes a sealing region 304 adapted to seal against the patient's face. The facial mask assembly 300 is connected to a second gas source, such as via a filter element 350, that supplies one or more other gases to the patient through the facial mask. In some configurations, the second gas source is different from the source (e.g., an auxiliary gas source or flow generator) that supplies gas to the patient interface 200. In some configurations, the second gas source is the same as the source that supplies gas to the patient interface 200.

[0175] In some embodiments, the face mask assembly 300 is connected to a second flow source that is or includes a separate gas source or separate breathing support system configured to provide a breathing supply separate from any flow source, or a breathing support system that delivers a gas flow to the first patient interface 200. For example, the separate breathing support system can be a ventilator or a CPAP or a high flow therapy device or a manual resuscitator (e.g. a portable face mask with a bag). Alternatively or additionally, the face mask assembly 300 may be connected to a device for measuring the characteristics of the breathing gas.

[0176] Alternatively, the separate respiratory assistance system may be or may include an anesthesia device and / or the second gas source may include anesthesia gas, or air, or oxygen, or a combination of gases, for delivery via the face mask 302.

[0177] The configuration shown in FIG. 2b is capable of delivering gases from multiple sources through at least two different respiratory support modes, and further allows a physician, clinician or medical professional to quickly and easily change between types of respiratory support modes.

[0178] In one specific application, a patient undergoing an anesthesia procedure may be preoxygenated by delivering a high flow of oxygen or humidified gas or a mixture of both, for example, via a nasal cannula, while the patient is still breathing spontaneously and before administration of an anesthetic agent. Preoxygenation increases the patient's oxygen reserves before an anesthesia procedure. The term "anesthesia procedure" may refer to, without limitation, general anesthesia, procedural sedation, and regional / local anesthesia. In some circumstances, an anesthesiologist administering an anesthesia procedure to a patient may wish to switch between delivery of gas flow from one patient interface (e.g., nasal cannula 200) and another patient interface, such as via a face mask 300.

[0179] Anesthesiologists also use a mask with a bag to administer oxygen to the patient, and in some cases find it more beneficial to use a bag mask if the patient's vital signs begin to drop, for example to deliver more pressure to support the patient's airway or to have greater manual control over the variation in the delivered pressure. In some situations, medical professionals may wish to switch between different breathing systems or support modes. In a first mode, breathing support may be provided by a first breathing support system (e.g., via the patient interface 200), and in a second mode, breathing support may be provided by a second breathing support system (e.g., via the facial mask assembly 300) with support from the first system reduced or stopped. For example, it may be desirable to stop the high flow from the first patient interface 200 when delivering anesthesia through the facial mask assembly 300, since the high flow from the interface 200 may modify the expected behavior of the anesthesia circuit provided by the facial mask 300 (the facial mask 300 is typically a sealed circuit) and may dilute the anesthesia agent delivered by the facial mask assembly 300. In this way it may be advantageous to be able to stop or substantially reduce the additional flow from the first breathing system.

[0180] In some configurations, switching between two respiratory support modes or subsystems may be facilitated by the structure of the first gas conduit 202 having a first portion 204 configured to transition between a first configuration in which a first level of gas can pass through the first portion 204 and a second configuration in which a second level of gas can pass through the first portion 204.

[0181] In some configurations, the first portion 204 is configured to be more foldable or otherwise better adapted to alter the gas flow through the first portion 204 (reducing gas flow through the conduit to the patient) than other portions of the conduit 202 and / or to allow the mask seal to seal the top of the conduit. In other configurations, the entire conduit 202 may be configured to be foldable or otherwise better adapted to alter the gas flow through the conduit 202. In some configurations, a vent arrangement may be provided upstream of the foldable portion to vent gases from the conduit upstream of the foldable portion to atmosphere.

[0182] In some embodiments, the first configuration is a fully or substantially open state and the second configuration is a fully or substantially closed state, i.e., the conduit 202 is configured to be more collapsible, deformable, or otherwise adapted to fully or substantially close flow in the first portion 204 when in the second configuration, than other portions of the conduit 202. It will be appreciated that one or more intermediate states may exist between the first and second configurations, where these one or more intermediate states may be less open (or more closed) than the fully or substantially open state (first configuration), but more open (or less closed) than the fully or substantially closed condition (second configuration).

[0183] 3a and 3b provide schematic diagrams of the first and second configurations, where FIG. 3a shows the first configuration (substantially open) and FIG. 3b shows the first portion 204 in the second configuration (substantially closed) by adding the seal 304 of the facial mask 302 over the first portion 204. In some embodiments, the first portion 204 of the first gas conduit 202 (i.e. the more foldable or deformable portion) should be of a length greater than the width of the portion of the seal 304 of the facial mask 302 that fits over the first portion 204 of the first gas conduit 202. This ensures that the seal of the facial mask 302 does not fit over the non-foldable portion of the first gas conduit 202. For example, the first portion 204 may extend from a distance of 35 mm or less from the center of the user's nose to at least 50 mm from the center of the user's nose. The first portion 204 may have a length of at least about 5 mm, a length of about 1 mm to about 30 mm, or a length of about 5 mm to about 15 mm, or a length of about 10 mm. In some embodiments, the length of the first portion may be at least 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm or more.

[0184] The first portion 204 may advance between the first configuration and the second configuration based on a relative level of force applied to the walls of the first portion 204. For example, as shown in Figures 2 and 3, the force may be applied by a seal 304 of the facial mask 302. In this example, the first portion 204 is configured to be positioned below the seal 304 of the facial mask 302.

[0185] Alternatively, force may be applied to first portion 204 by other means, such as a clamp (not shown), or alternatively, a medical professional may compress the conduit by pressing against the conduit wall with a thumb or finger.

[0186] In some embodiments, a face mask seal acting on the first portion 204 of the gas conduit 202 causes the first portion 204 to form a seal or at least a partial seal between the nasal outlet of the first patient interface 200 and the flow source 12. Additionally, the face mask seal forms a seal or at least a partial seal over the first portion 204 of the gas conduit 202.

[0187] Switching between respiratory assistance therapies can therefore be accomplished simply by placing the mask on the patient's face such that the seal of the mask folds (partially or completely) the first portion 204 of the gas conduit 202 supplying the first interface 200, to reduce or stop the therapy delivered by the first interface 200. This also provides a seal between the facial mask 300 and the exterior of the first portion 204 of the conduit 202, such that respiratory assistance or therapy can be provided by the facial mask 300 when the respiratory assistance or therapy provided by the first patient interface 200 can be reduced or stopped. The patient interface 200 with the foldable conduit portion 204 allows a user, such as an anesthesiologist or nurse or clinician, to select and control the delivery of gas from multiple respiratory assistance systems to provide different therapy or assistance modes using the facial mask assembly 300 on the patient interface 200. The first patient interface 200 may be constructed to function in a manner that prevents high flow and delivery of other respiratory therapies or anesthetic agents through the patient interface 200 when the first portion 204 is in the second configuration. In some embodiments, removal of the facial mask assembly 300 from the patient's face may return the first portion 204 to its first configuration such that the respiratory assistance or therapy delivered by the first patient interface 200 may resume or return to operation in the state prior to the change in configuration.

[0188] The embodiments of the present disclosure improve the control of the respiratory gas flow provided to the patient. In some embodiments, the respiratory support system includes a pressure relief valve or device. The system 10 may include such a pressure relief or regulation device, or a pressure limiting device 100 (e.g., a pressure relief valve or PRV). The pressure limiting device 100 may be a valve having the characteristics described in WO2018 / 033863, the entirety of which is incorporated by reference herein. In some embodiments, the breathing system does not include or exclude a pressure relief valve or device. In some embodiments, the breathing system does not include or exclude a flow-compensated pressure relief valve or device, such as a flow-compensated pressure relief valve having the characteristics as described in WO2018 / 033863.

[0189] Pressure relief and pressure control may be desirable for use in respiratory assistance systems such as the high flow system 10 that includes a non-sealing patient interface (such as a nasal cannula in the first patient interface 200) to provide an upper limit on pressure that may be generated downstream from the flow source 12 and then impact the patient airway pressure (also referred to as patient pressure). Importantly, the upper pressure limit may be configured to provide a safety threshold to ensure patient pressure safety and / or prevent damage to tubing, fluid connections, or other components in the system 10 due to overpressure. Similarly, the pressure relief or restriction device 100 may be used in sealed systems such as CPAP (continuous positive airway pressure), BiPAP (bilevel positive airway pressure), and / or bubble CPAP systems to regulate the pressure provided to the patient.

[0190] A respiratory system 22 for providing a flow of respiratory gas to a patient is shown in Figures 4-8 according to different embodiments of the present disclosure.

[0191] 4 illustrates a respiratory system 22 including a controller 24 and a flow source 12 that may include a flow regulator configured to be controlled by the controller 24 to regulate the flow of respiratory gas to a patient 16. The controller may be configured to receive inputs of a flow rate and a pressure of the respiratory gas flow in the system, and configured to provide the respiratory gas flow to the patient at a target flow rate and control the flow regulator to regulate the respiratory gas flow to the target pressure when the pressure of the respiratory gas flow in the system meets or exceeds a pressure threshold corresponding to the target flow rate. In some embodiments, the target pressure includes a pressure threshold corresponding to the target flow rate or a pressure threshold corresponding to a flow rate less than the target flow rate. The pressure threshold corresponding to the target flow rate may be determined by the controller using functions stored in a memory component of the controller or a memory component operatively coupled to the controller, for example, as described anywhere herein. The target pressure or pressure threshold may be defined as an absolute pressure value or a gauge pressure value.

[0192] As noted, flow source 12 may include a flow generator, such as a blower, configured to be controlled by controller 24 to generate a flow of breathing gas. Alternatively or additionally, flow source 12 may include a proportional valve configured to be controlled by controller 24 to regulate the flow of breathing gas from the gas source, or flow source 12 may include a combination of a flow generator and a proportional valve.

[0193] Typically, the system 22 further includes one or more sensors 28 configured to determine characteristics of the respiratory system, such as characteristics of the respiratory gas flow within the respiratory system and / or provided to the patient. The system 10 may use ultrasonic transducers, flow sensors such as thermistor flow sensors, pressure sensors, temperature sensors, humidity sensors, or other sensors in communication with the controller 24 to monitor characteristics of the system and / or operate the system 22 in a manner to provide appropriate respiratory assistance. Such characteristics may include gas concentration, flow rate, pressure, temperature, humidity, or other characteristics. The sensors 28, such as pressure, temperature, humidity, and / or flow sensors, may be located at various locations in the system 22, such as, for example, in the main housing containing components of the system 22, the patient conduit 12, and / or the patient interface 200. The controller 24 may receive signals from the sensors 28 that provide controller inputs used to determine control of one or more components of the respiratory assistance system 22 in a manner to provide appropriate respiratory assistance. For example, controller 24 may use signals from one or more sensors 28 to determine an appropriate target temperature, humidity, flow rate, and / or oxygen concentration of the gas stream, or an appropriate pressure that may be generated downstream from source 12 in the system. Providing adequate respiratory support may include meeting the patient's inspiratory acceptance. Appropriate respiratory support flow rates, such as high flow rates and / or flow rates that meet or exceed the patient's inspiratory acceptance, are described elsewhere herein.

[0194] In some embodiments, the sensor includes a flow sensor (e.g., ultrasonic, temperature-based, or other suitable flow sensor, etc.) configured to sense the flow rate of the gas stream provided to the patient 16, and the sensed flow rate is used by the controller 24 to determine a safe upper pressure limit for operation of the system 22 at the sensed flow rate. The controller 24 can then control operation of one or more components (e.g., actuators) of the system 22, such as the flow source 12 (or transfer control signals to one or more components of the system), for example, to modify a blower speed to achieve a target flow rate stored in the controller or a memory in operative communication with the controller or any other components of the system. The target flow rate may be a flow rate set point entered by a user of the system through the I / O interface 20, or the target flow rate may be determined or preprogrammed into the controller or associated memory / components. Modifying the flow rate may involve an increase or decrease in the blower speed (and / or an increase or decrease in the size of the proportional valve hole) to achieve an increase or decrease in the flow rate, respectively.

[0195] In some embodiments, when the system begins operation from an "off" or resting state, the controller is configured to monitor the rate of respiratory gas flow in the system and is configured to control the flow regulator to adjust the respiratory gas flow to achieve a target flow rate. Ideally, the target flow rate changes over time to increase from a current value to a flow rate set point. The controller may also be configured to monitor the rate of respiratory gas flow to a new target flow rate in other circumstances, such as when a user changes the flow rate set point at which the system operates.

[0196] The controller 24 may receive input from one or more pressure sensors. The controller can measure or infer the pressure delivered to the patient from the pressure sensor input. The pressure sensor is located downstream of the flow source 12. For example, the pressure sensor can be located at or near the patient interface 200. The pressure sensor can also be located immediately after the flow source. The pressure delivered to the patient's airway (patient pressure) can be determined by the controller calculating the difference between the ambient pressure and the absolute pressure downstream of the flow source. The patient pressure can be estimated by measuring the pressure in the main device housing downstream of the flow generator and calculating the pressure drop along the delivery conduit 202. The pressure sensor can also be located elsewhere in the pneumatic circuit downstream of the gas flow of the flow source 12. The pressure sensor can include one or more gauge pressure sensors, or alternatively one or more absolute pressure sensors. The gauge pressure sensor can directly measure the difference between the absolute pressure downstream of the flow generator and the ambient pressure. In a system with two absolute pressure sensors, one sensor can be placed downstream of the flow source to measure the absolute pressure downstream of the flow source and the other sensor can be placed in a different location to measure the ambient pressure. The controller can determine the pressure delivered to the patient by determining the difference between the pressure measurements made by the two absolute pressure sensors.

[0197] The controller 24 in various embodiments is configured to receive one or more signals directly from one or more pressure sensors or through a manual input provided to a user interface in operative communication with the controller, or to receive output values ​​indicative of the system pressure in the pneumatic circuit downstream of the flow source 12 through which the flow of respiratory gas in the respiratory system 22 is delivered to the patient 16. The controller 24 may convert the received signals to pressure values, which the controller may compare to pressure thresholds for corresponding flow rates, as stored by the controller or a memory device or module in operative communication with the controller. Because the controller needs to know the flow rate of gas in the pneumatic circuit to determine whether the system pressure meets or exceeds the pressure threshold for the corresponding flow rate, the controller may also receive one or more signals directly from one or more flow sensors, or the controller may obtain the flow rate value through a manual input provided to a user interface in operative communication with the controller, or the controller may derive the flow rate value, for example, by knowing the resistance to flow in the pneumatic components of the system 22 and calculating the flow from, for example, a blower speed in the flow source 12.

[0198] The controller 24 may determine the system pressure continuously or intermittently, and there may be benefits associated with each other. For example, a continuous determination of the system pressure provides the highest response as to how quickly the controller can detect a change in the system pressure meeting or exceeding (or falling below) a pressure threshold for a corresponding flow rate, and how quickly the controller can respond, for example, by controlling the flow source 12 to reduce the blower speed (which may then reduce the breathing gas flow) in response to a pressure meeting or exceeding the pressure threshold for the corresponding flow rate, and to control the flow source 12 to adjust the breathing gas flow in response to a pressure not meeting or exceeding the pressure threshold for the corresponding flow rate. Alternatively, the controller 24 may sense or receive a pressure input intermittently, which provides more economical operation, but may experience a delayed response since the system may change shortly before the controller receives the pressure input, causing the regulation and / or control of the flow source 12 to become unresponsive.

[0199] The pressure thresholds corresponding to the flow rates may be stored in a memory component of the controller 24, or by a memory device or component external to the controller 24 and in operative communication with the controller 24. The relationship between the pressure thresholds and the corresponding flow rates may be stored as one or more of a function, curve, look-up table, or mathematical model, or algorithm used by the controller 24 to determine a particular pressure threshold for a corresponding flow rate. In some embodiments, the relationship between the pressure thresholds and the corresponding flow rates as utilized by the controller 24 may be represented graphically, examples of which are shown in FIGS. 9-14.

[0200] 5 illustrates another embodiment of a respiratory system 22 including a controller 24 and a flow source 12 configured to be controlled by the controller 24 to regulate the flow of respiratory gas to the patient 16 via a patient interface 200 in fluid communication with the flow source 12 and configured to deliver the flow of respiratory gas to the patient 16. The respiratory system 22 also includes one or more sensors 28 configured to determine a system pressure downstream of the flow source 12 and / or a flow rate of the respiratory gas flow in a respiratory assistance system that provides gas to the patient.

[0201] The patient interface 200 receives a flow of breathing gas from the flow source 12 via a conduit 202. The conduit 202 includes a first portion 204 configured to operate in at least a first configuration and a second configuration.

[0202] The controller 24 in the embodiment shown in FIG. 5 may be configured to receive input from the sensor 28 indicative of the pressure and / or flow rate of the respiratory gas flow within the respiratory assistance system 22, compare the sensed pressure to a pressure threshold, and control the flow source 12 to provide a first adjustment of the respiratory gas flow in response to a pressure that meets or exceeds the pressure threshold, and to control the flow regulator 26 to provide a second adjustment of the respiratory gas flow in response to a pressure that does not meet or exceed the pressure threshold.

[0203] As noted, in some embodiments, the second adjustment is different from the first adjustment, where the first adjustment includes maintaining the system pressure downstream of the flow source at a target pressure, e.g., at a pressure threshold, and / or reducing the system pressure downstream of the flow source to a target pressure below the pressure threshold. The second adjustment may include increasing or decreasing the flow rate of breathing gas to a target flow rate in response to the system pressure downstream of the flow source not meeting or exceeding the pressure threshold.

[0204] The corresponding flow rate may be a flow rate of respiratory gas flow provided by a flow source at or along a portion of the pneumatic circuit of the respiratory system 22 that provides gas flow to the patient interface 200 and / or at the patient's airway. As previously described, the corresponding flow rate may be a flow rate obtained by one or more flow sensors that directly provide input to the controller 24, the corresponding flow rate may be entered by a user actuating a user interface in operative communication with the controller, or, if the resistance of the pneumatic components of the system 22 is known, the corresponding flow rate may be inferred from other factors, such as the blower speed of the flow source.

[0205] FIG. 6 illustrates a respiratory system 22 according to another embodiment of the present disclosure. In this embodiment, the system 22 includes a controller 24 and a flow source in the form of a flow regulator or blower 27 configured to be controlled by the controller 24 to generate a flow of respiratory gas to the patient 16 via a delivery conduit 202. Typically, the controller 24 and the blower 27 are contained within a common housing 33, although it is contemplated that the controller can be located apart from or in a separate housing to the blower 27 and other components of the respiratory assistance system. In some embodiments, the housing 33 also contains a humidifier (shown in the embodiment of FIG. 1) that includes a humidification chamber through which the gas flow from the blower passes to humidify the gas provided to the patient by increasing the moisture content and possibly the temperature. The humidified gas is then delivered to the patient interface 200 by the delivery conduit 202 (which may include the humidifier and a portion of the delivery circuit 38 downstream of the patient breathing circuit 40). The respiratory assistance system 22 further includes a patient interface 200 configured to receive the flow of gases through a delivery conduit 202 for delivery to the patient 16. The patient interface 200 may include one or more nasal elements or a face mask assembly configured to provide gases to each or both of the patient's nares or mouth. The patient interface 200 receives the flow of respiratory gases from the blower 27 via a conduit 202. The conduit 202 includes a foldable first portion 204 configured to operate in at least a first configuration and a second configuration as described anywhere herein.

[0206] The foldable portion 204 is configured to operate in a first configuration (e.g., unfolded or fully or substantially open) and be foldable from the first configuration to a second configuration (e.g., folded or fully or substantially closed). It will be appreciated that there may be one or more intermediate states between the first and second configurations, where these one or more intermediate states may be less open (or more closed) than the fully or substantially open state (first configuration), but more open (or less closed) than the fully or substantially closed state (second configuration). As noted, the controller 24 alters the operation of the flow source when the foldable portion 204 is in the second configuration compared to when the foldable portion 204 is in the first configuration. In some embodiments, this is accomplished by adjusting (e.g., reducing) the speed of the blower 27, which may then adjust (e.g., reduce) the respiratory gas flow to a reduced flow rate in the system in response to a sensed system pressure meeting or exceeding a pressure threshold for a corresponding flow rate of the respiratory gas flow provided to the patient. In some embodiments, the controller 24 changes the state (e.g., degree of opening) of one or more proportional valves, which may then adjust (e.g., reduce) the respiratory gas flow to a reduced flow rate in the system in response to a sensed system pressure meeting or exceeding a pressure threshold for a corresponding flow rate of the respiratory gas flow provided to the patient. In some embodiments, the controller 24 changes the operation and / or state of both the blower and the proportional valves.

[0207] The breathing system 22 shown in FIG. 6 includes two types of sensors: a flow sensor 32 configured to sense the flow rate of the breathing gas flow within the breathing system 22, and a pressure sensor 29 configured to sense the pressure within the breathing system 22 downstream of the blower 27, including downstream of the outlet of the housing 33.

[0208] The flow sensor 32 and pressure sensor 29 are positioned downstream of the flow regulator, i.e., blower 27. The flow sensor 32 and pressure sensor 29 are configured to sense the flow rate and pressure, respectively, downstream of the flow regulator and in the delivery conduit 202. The controller 24, in this embodiment, is configured to receive data from the pressure sensor 29 and the flow sensor 32 indicative of the pressure and flow rate of the respiratory gas flow in the delivery conduit 202, and to compare the sensed pressure to a pressure threshold for the corresponding flow rate, as stored by the controller 24 and a memory component operatively associated with the controller.

[0209] In some embodiments, one or more pressure sensors may be placed downstream of the blower 27 near the system outlet to which the delivery conduit 202 is connected to determine the system outlet pressure. The outlet pressure can be used to infer patient pressure as discussed below. In some embodiments, a second pressure sensor 29 may be provided redundantly to provide a backup pressure input if the primary pressure sensor fails. In some embodiments, the controller 24 may receive input from an absolute (ambient) pressure sensor 29a to detect the operating air pressure, which may vary due to altitude, for example, and may affect the performance of its components, such as the flow source and the blower. However, gauge sensors may have superior resolution and may be the preferred pressure sensor for many applications.

[0210] In some embodiments, there is a pressure sensor configured to sense the pressure delivered to the patient in addition to the pressure sensor 29 configured to sense the pressure in the delivery conduit. The controller 24 can then determine the flow rate of gas flow to the patient from the difference in sensed pressure between these two sensors.

[0211] The patient interface 200 has the features described above. Thus, in some embodiments, the patient interface 200 is a nasal cannula, such as a non-sealing nasal cannula, that receives a flow of respiratory gas from a conduit 202 having a collapsible portion 204 that can transition between a first configuration and a second configuration (FIG. 3b).

[0212] The patient interface 200 is hereinafter referred to as the nasal cannula 200 to provide a more specific description of the components involved in the delivery of respiratory gas according to an embodiment of the present disclosure. In some embodiments, the foldable portion 204 is folded into a second configuration when the facial mask assembly 300 is applied to the patient 16 over the nasal cannula 200. The facial mask assembly 300 may be referred to as the mask 300 for short. The delivery conduit 202 is thus configured to deliver a flow of respiratory gas through the foldable portion 204 to the patient 16 when the foldable portion 204 is in the second configuration at a reduced flow rate compared to when the foldable portion 204 is in the first configuration. For example, the reduced flow rate may be less than about 15 L / min, about 0-15 L / min, or about 5-15 L / min, or 0 L / min. The flow rate when the foldable portion 204 is in the first configuration is a high flow rate that may be in the range of more than about 20 L / min, about 20-90 L / min, or about 40-70 L / min.

[0213] The delivery conduit 202 may be considered to provide a delivery circuit 38 and a patient breathing circuit 40 arranged between the delivery circuit 38 and the patient interface 200. The patient breathing circuit 40 is connected to the delivery circuit 38 via an outlet connector 34. In the embodiment of FIG. 6, the controller 24, the blower 27, the pressure sensor 29, the flow sensor 32, and the delivery circuit 38 are housed within the housing 33. The outlet connector 34 may be attached to or pass through the housing 33 to provide a physical connection between the delivery circuit 38 inside the housing and the patient breathing circuit 40 outside the housing. It will be appreciated that the patient interface 200 may be connected to the patient breathing circuit 40 via a connector not shown in this figure. It will also be appreciated that the system 22 may further include one or more proportional valves of the type described above, which may also be housed within the housing 33. As will be appreciated, intentionally folding a portion of the patient interface 200, or a foldable portion 204 from which the patient interface receives gas flow, introduces a restriction to the flow within the breathing system. When this occurs, in the example breathing system 22 in use, the controller 24 may detect the flow restriction by determining that there is an increase in the system pressure and control the flow regulator 26 (e.g. by varying the speed of the blower 27 and / or the size of the flow passage through the proportional valve 25, see FIG. 7) to adjust the system pressure. When the foldable portion 204 returns to the first configuration, the controller 24 may detect the change by determining that there is a reduction in the system pressure and control the blower 27 and / or the proportional valve 25 to increase the flow of breathing gas, which may then increase the system pressure whilst the pressure threshold corresponding to the rate at which gas will flow remains low.

[0214] The respiratory assistance system may be susceptible to accidental restrictions to flow, for example caused by the delivery conduit 202 tearing, bending, or collapsing. Another way in which flow may be restricted in such systems is when the anatomical and / or airway characteristics of a particular patient have a higher resistance. These restrictions may create substantial back pressure in the flow path upstream of the restriction. In some embodiments of the respiratory system 22, when these restrictions occur, the respiratory system may determine, by operation of the controller 24, that the pressure in the delivery conduit 202 exceeds a pressure threshold for the corresponding flow rate, and the controller 24 may control the blower 27 to reduce the flow of respiratory gas, thereby reducing the pressure in the system 22. When the accidental restriction is removed, the controller 24 may further control the blower 27 to increase the flow of respiratory gas, thereby increasing the pressure in the system 22. Alternatively or additionally, the controller 24 may control the proportional valve 25 to open further, thereby increasing the flow of respiratory gas and increasing the pressure in the system 22.

[0215] 7 and 8 are example schematic diagrams of components of the respiratory system 22 that provide a flow of respiratory gas to a patient, according to an embodiment of the present disclosure. More specifically, Figures 7 and 8 show components associated with the respiratory system 22 that deliver respiratory gas from an oxygen (O2) source 42 (e.g., a wall source or an O2 tank) and an ambient air source 44 to a nasal cannula 200 and to the patient.

[0216] The respiratory system 22 shown in Figures 7 and 8 includes a pressure sensor 46 (e.g., an O2 pressure sensor) configured to sense a pressure in an O2 delivery circuit 47 of the respiratory system 22. The pressure sensor may be used to determine that the O2 delivery circuit 47 is connected to an O2 source 42. Control of the O2 flow may be provided by a proportional valve 25 controllable by the controller 24 (not shown). The O2 delivery circuit 47 further includes a flow sensor 48 (e.g., an O2 flow sensor) configured to sense a flow rate of the O2 flow from the O2 supply after the O2 flow has been regulated by the proportional valve 25.

[0217] The breathing system 22 shown in Figures 7 and 8 further includes a flow sensor 50 (e.g., airflow sensor) configured to sense the airflow from the ambient air source 44 in the air delivery circuit 49 of the breathing system 22. In some embodiments, the patient breathing circuit 40 is connected to the O2 delivery circuit 47 and the air delivery circuit 49, and the patient breathing circuit and / or the patient interface further includes a patient pressure sensor and a patient flow sensor. Control of the airflow is provided by a blower 27 of the type described above, controllable by the controller 24. In Figure 7, the blower 27 is provided in the air delivery circuit 49, whereas in Figure 8, the blower 27 is provided in the patient breathing circuit 40. In both embodiments, the breathing system 22 provides closed loop control of pressure and / or flow by the controller 24 controlling operation of the blower 27, e.g. by varying the angular velocity / motor speed of the blower 27 and / or the current or voltage supplied to the blower 27, and / or by controlling the opening of the proportional valve 25, e.g. by varying the current supplied to the valve, to limit or vary the O2 entering the patient breathing circuit 40.

[0218] In some embodiments, the blower 27 regulates the breathing gas flow and the proportional valve 25 controls the oxygen concentration in the breathing gas. Both are controlled by the controller 24. Thus, if the user manipulates the I / O interface 20 to increase the flow from a given flow rate set point, the control to the blower 27 may increase its speed, diluting the O2 concentration. The controller 24 compensates for this by actuating the proportional valve 25 to open further (e.g., by increasing the current to the proportional valve) so that more O2 can flow to the patient to meet the user's required O2 concentration set point. If the user changes the O2 concentration set point to a higher concentration, the controller 24 controls the proportional valve 25 to allow more oxygen to flow into the breathing gas delivered to the patient.

[0219] The patient breathing circuit 40, in the embodiments shown in Figures 7 and 8, is in fluid communication with an O2 delivery circuit 47 and an air delivery circuit 49. As noted, in Figure 8, the patient breathing circuit 40 includes a blower 27 controlled by the controller 24 to deliver a gas flow, typically including air and O2, to the nasal cannula 200. In both embodiments, the patient delivery circuit 40 may include a patient pressure sensor 54 and / or a patient flow sensor 52 configured to monitor the pressure and / or flow rate of the combined O2 and air breathing gas delivered to the patient via the nasal cannula 200.

[0220] Relatedly, in the embodiment of Figures 7 and 8, there may be an open flow path in the air delivery circuit 49 (e.g., between the inlet of the blower 27, which receives ambient air from source 44 in Figure 7, and a location in the flow path downstream of the blower 27), which allows for bidirectional flow. An open flow path includes a flow path that is free of one-way valves or components that only allow for one-way flow of gas. This may be beneficial in scenarios where there is a blockage at the outlet of the system that interfaces with the patient breathing circuit 40, for example, so that excess gas that has built up in the system can safely "leak" out of the air delivery circuit 49 through the blower 27, avoiding high system pressures that could damage some components. Many prior art respiratory assistance systems rely on one-way valves to deliver flow to the patient, which in the described circumstances would prevent backflow and could cause component damage and / or system failure.

[0221] In the embodiment of Figure 7, O2 is mixed with ambient air downstream of the blower 27. This may be beneficial for embodiments that humidify the gas provided to the patient, since the gas mixed downstream of the blower 27 may have a lower temperature than the gas mixed upstream of the blower (as in Figure 8), and operation of the blower should heat the gas passing through it. This may improve the accuracy of humidification when control of the humidifier is based on the temperature of the gas entering the humidification chamber. In some embodiments, one or more pressure sensors may monitor ambient air pressure to be able to adapt to different operating conditions, such as changes in altitude.

[0222] 9-14 are graphs illustrating curves representing relationships between flow and pressure that are used in embodiments of the present disclosure in controlling components of a respiratory system to deliver a flow of respiratory gas to a patient. As noted, the controller 24 is configured to control the flow regulator 26 to increase, maintain, or reduce the flow of respiratory gas. For example, the controller 24 is configured to control the blower 27 to increase, maintain, or reduce the angular velocity (i.e., speed) of the blower 27 by providing an electrical control signal or by directly controlling the voltage or current supply to the blower, which in turn increases, maintains, or reduces the flow of respiratory gas. The controller 24 determines appropriate control for the flow regulator 26 in response to pressures that do not meet or exceed, or meet or exceed one or more pressure thresholds at a corresponding flow rate, such as the flow rates represented in the curves of FIGS. 9-14 (which may hereinafter be referred to as pressure limit curves C). In some embodiments, the controller 24 determines appropriate control for the flow regulator 26 in response to system pressures that are below or meet or exceed a pressure threshold at a corresponding flow rate. The pressure threshold or thresholds may be predetermined pressure thresholds. As mentioned, the pressure thresholds and corresponding flow rates may be stored in a memory component of the controller 24 or a memory component operatively coupled to the controller 24.

[0223] In some embodiments, the controller 24 is configured to control the flow regulator to regulate the respiratory gas flow to the target pressure when the flow rate of the respiratory gas flow is less than the target flow rate. This avoids a situation where the controller attempts to increase the flow to approach the target flow rate where the system pressure may cause the pressure threshold to exceed the current flow rate. Alternatively / additionally, the controller may be configured to control the flow regulator to regulate the respiratory gas flow to the target flow rate when the flow rate of the respiratory gas flow exceeds the target flow rate, i.e., to regulate the flow down to the target flow rate when the respiratory gas flow rate is exceeded, avoiding risk of harm to the patient. In some embodiments, the controller is configured to control the flow regulator to the target pressure when the pressure of the respiratory gas flow exceeds a pressure threshold corresponding to the target flow rate or a pressure threshold corresponding to a flow rate less than the target flow rate.

[0224] The pressure limit curve C has been determined by considering the known resistance to flow of the system components and the known range of flow rates delivered to the patient. It will be appreciated that the pressure limit curve C may be stored in memory accessible to the controller 24 as previously discussed, which may include a computer readable medium (e.g., a disk, hard drive, USB, optical drive, or other data storage device) containing program instructions for the controller 24 to perform the necessary control, as described herein.

[0225] In some embodiments, the pressure limit curve C provides a safety threshold corresponding to a safe patient pressure for a corresponding flow rate of gas to the patient when the foldable portion 204 is in a collapsed configuration and flow to the nasal cannula 200 is restricted, such as when the mask is worn. This pressure threshold is applied to reduce the risk of overpressurization to the patient, which may cause barometric obstruction of the patient's airway. Thus, in some embodiments, the controller 24 automatically reduces flow to the patient through the nasal cannula 200 when there is an obstruction in the delivery conduit 202, such as an accidental obstruction, or when the mask 300 is used to ventilate the patient and is placed over the nasal cannula with pressure, for example, in the second configuration, to sufficiently collapse the foldable portion 204. When this occurs, the controller 24 may implement pressure control of the system 22 by controlling the operation of other components, such as the blower 27 and / or the proportional valve 25, to reach the target pressure induced by the pressure limit curve C. Additionally, the controller 24 may automatically increase the breathing gas flow when the mask is removed, and the collapsible portion 204 can return to the first configuration.

[0226] In some embodiments, the controller 24 may control only the blower 27 (e.g., angular velocity), the blower 27 and one or more proportional valves 25, or only one or more proportional valves 25 to control the flow rate and / or pressure of the respiratory gas stream. In embodiments where the proportional valves and blowers are in parallel flow paths (e.g., FIG. 7), check valves (not shown) may be provided in the air delivery circuit 49 before and after the blower to prevent backflow of flow out of the air delivery circuit 49 via the ambient air source 44 such that the flow and / or pressure of the respiratory gas stream is controlled by the proportional valve. In some embodiments, a pressure relief valve (not shown) may be provided in systems where a pressure relief valve (e.g., a valve venting to atmosphere) is operable by the controller 24 to control the flow and / or pressure of the respiratory gas stream.

[0227] In some embodiments, the controller 24 may be programmed to apply a further safety threshold, a pressure limit, which when reached triggers the controller 24 to substantially reduce or stop operation of the flow regulator 26, for example by turning off the blower 27 and / or stopping the proportional valve 25. This safety threshold may be a value above about 20 cmH2O, such as about 30 cmH2O, about 40 cmH2O, about 50 cmH2O, or about 60 cmH2O, or about 70 cmH2O, etc. In some embodiments, a safety threshold of about 60 cmH2O may be preferred, or a safety threshold calculated as a safety margin above a predefined pressure threshold for a corresponding flow rate may be used or calculated as a safety margin above a normal expected region or range of system pressure.

[0228] The resistance to flow of the system components may be measured, calculated, and / or estimated, including the resistance of all components of the respiratory assistance system 22, optionally downstream of the outlet of the flow regulator 26. This requires that the consumables of the system 22 be carefully designed to have tight tolerances on resistance to flow, or that conservative assumptions be used to allow for less tight manufacturing tolerances. Knowing the resistance of the system 22 allows the patient pressure to be inferred from the system pressure by estimating the pressure difference across the respiratory assistance system 22. The respiratory system 22 may also determine in real time the characteristics of the resistance in the delivery conduit 30 from the pressure sensor 29 and flow sensor 32, and compare this to the known resistance to reduce expected variations in patient pressure. Knowing the current patient pressure to ensure the pressure can be controlled according to the pressure limit curve C, which allows the respiratory system 22 to better control the pressure / flow to the nasal cannula 31. In effect, controller 24 operates blower 27 and other components of system 22 to avoid or minimize operation of the system in an "overpressure" region corresponding to region 64, as discussed below.

[0229] During operation of the respiratory assistance system 22, the "normal" operating pressure values ​​for the corresponding flow rates are shown to lie below the pressure limit curve C. More specifically, Figures 9 and 10 show the region 58 corresponding to the normal operating system pressure at the corresponding flow rate. Advantageously, the normal operating band provides a range of safe system pressures for the corresponding flow rate, and thus in effect a "safety" band that provides a range for the clinician to safely manipulate components of the system, such as the delivery conduit 202, collapsible section 204, manifold 206, cannula 200, and other components necessary to deliver gas to the patient, without risking delivering overpressure to the patient's airway and risking barotrauma or other injury.

[0230] FIG. 10 illustrates a restricted operating region 60 in which a pressure limit curve C may be defined for use in controlling the operation of the system to deliver respiratory gas to a patient. In some embodiments, the controller calculates the shape of curve C using a function stored in a memory component of the controller or a memory component operatively coupled to the controller. Thus, upon receiving a "set point flow rate" entered by the user into the I / O interface 20, the controller uses the function to fit the curve within the restricted operating region 60 by defining an upper flow rate of curve C required and knowing a lower pressure limit (which may be defined by the manufacturer or user as an operating limit of the system). When the controller 24 determines that the system pressure is within the restricted operating region 60 and below curve C, the controller 24 may not immediately change the control of the system components to reduce the flow, but rather allow the flow to continue to be delivered at the current control. The restrictive operating region 60 may be desirable to prevent the controller 24 from immediately reducing the flow rate every time there is a bend in the tubing, which may be unintentional or may occur when a clinician interacts with the patient and / or positions various components of the respiratory assistance system, including the patient interface, on the patient, resulting in a temporary or momentary blockage or restriction to the flow. This region is not present in the embodiment shown in Figures 9 and 11 because the pressure limit curve C is defined immediately adjacent to the normal operating region and provides a pressure threshold that the controller may use. The control parameters conveyed by the embodiment of Figures 9 and 11 may be utilized in scenarios where it may be desirable to limit the degree of unintentional (or intentional) temporary blockage in the delivery conduit 202 before the flow rate is reduced.

[0231] The area below the pressure limit curve C and below the normal operating area is the mismatch area 62. Operation in this area may occur if the delivery conduit leaks or becomes disconnected from the flow generating components of the system, for example, if the delivery conduit becomes separated from the housing 33. Flow rates and pressures within this mismatch area 62 may also occur if mismatched or unintended system components are used. This area may also include pressures for corresponding flow rates that may be undesirable and such pressures may not achieve sufficient or intended respiratory support. In some embodiments, when the controller 24 detects a pressure within the mismatch / disconnect zone 62, the controller 24 may sound an alarm or warning, which may be visible and / or audible, communicating to the system user that the system has detected a mismatch condition, such as a condition that may signify a leak or disconnect in the system 22.

[0232] The area above the pressure limit curve C and above the limit operating area 60 shown in FIG. 10 is referred to as the overpressure area 64. In embodiments that apply a safety threshold (FIG. 11), this limit may be placed within the overpressure area 64. When the controller 24 determines that the system pressure exceeds the threshold defined by the pressure limit curve C, the controller 24 may vary the control of the blower 27 to reduce the blower speed in order to reduce the system pressure to a target pressure, e.g., a pressure value at or below the curve C at the corresponding flow rate. Alternatively / additionally, the controller 24 may control the operation of a valve, such as the proportional valve 25, to reduce the pressure in the system. In some embodiments, the controller 24 may be configured to track the time spent within the limit operating area 60 and / or above the pressure limit curve C, and if the pressure in the breathing system 22 remains in this area after a certain period of time, the controller 24 may trigger an audible and / or visual alarm to alert the user to a possible blockage in the gas delivery conduit or other components of the system.

[0233] FIG. 10 also shows that the sigmoid pressure limit curve C allows the pressure to be temporarily increased without the controller reducing the pressure and / or flow. That is, in a first configuration of the foldable portion 204 in use, the nominal (reference) system pressure in the normal operating pressure region 58 is lower than the pressure limit curve C by more than a first pressure margin M1. In a second configuration of the foldable portion 204, the nominal (reference) system pressure in the normal operating pressure region 58 is lower than the pressure limit curve C by more than a second pressure margin M2. The nominal (reference) system pressure may be the upper limit pressure of the normal operating pressure region 58. It can be seen from FIG. 10 that the first pressure margin M1 is greater than the second pressure margin M2. That is, the system 22 provides an acceptable variation of pressure changes in the system 22. When the system 22 is in the normal operating region 58, there is a greater margin of acceptable variation from the normal system pressure at higher flows than when the flows are low. A tight pressure margin at low flow, which may correspond to a collapsed state, and a larger margin at high flow, which may correspond to an uncollapsed state, ensures that in the absence of significant pressure and / or flow changes, control of system 22 remains in the "collapsed" or "uncollapsed" state, respectively, in those regions. Accordingly, controller 24 ensures that before initiating a change in control (e.g., from pressure control to flow control or vice versa), as may be necessary when collapsible portion 204 transitions from the second (collapsed) configuration to the first (uncollapsed) configuration, the pressure in the system must change significantly, and control is not changed until the blockage is substantially released (triggering a transition to flow control) or the blockage becomes more than transient (triggering a transition to pressure control).

[0234] 11, during operation of the respiratory assistance system 22 within the normal operating pressure region 58, the controller 24 is configured to control the flow regulator 26 to provide a flow of respiratory gas at a target flow rate, e.g., a set point flow rate prescribed by a user, such as a clinician, using the I / O interface 20. As long as the system pressure remains below the pressure value defined by the pressure limit curve C at the target flow rate within the normal operating pressure region 58, the controller 24 controls the flow regulator to provide a flow of gas at the target flow rate. In such a situation, the controller may be considered to be in a first control mode, which is a flow control mode. According to the control shown in FIG. 11, when the controller 24 determines that the system pressure meets or exceeds the pressure value defined by the pressure limit curve C at the target flow rate (e.g., when an obstruction begins to occur), the controller 24 is configured to control the flow regulator 26 to regulate the flow of respiratory gas to a target pressure that is equal to or less than the pressure value defined by the pressure limit curve C. In such a situation, the controller may be considered to be in a second control mode, which is a pressure control mode. 11 embodiment, the target pressure comprises a pressure value along pressure limit curve C. As obstruction increases (e.g., as collapsible portion 204 collapses more), the flow rate of breathing gas flow through the system decreases and the target pressure corresponding to the reduced flow rate also decreases. In response, controller 24 controls flow regulator 26 to adjust the flow of breathing gas downward along pressure limit curve C as the amount of obstruction increases.

[0235] It should be appreciated that while the controller 24 may be configured to identify the system pressure as "meeting" the pressure limit curve C when the sensed pressure input value is equal to the value of the curve for the corresponding flow rate, it may also be programmed to initiate a control change when the sensed system pressure is "approximating" or very close to the value of the pressure limit curve C, for example, within about 10% of the curve value, or within about 5% of the curve value, or within about 3% of the curve value, or within about 2% of the curve value, or within about 1% of the curve value. In some embodiments, the flow rate of the respiratory gas flow may be gradually reduced, eventually reaching a very low flow rate approaching (or even reaching) 0 L / min. This may reduce the pressure in the respiratory system 22 and prevent the pressure in the system 22 from meeting or exceeding the pressure limit curve C.

[0236] In some embodiments, the controller 24 controls the flow regulator 26 to control the flow of breathing gas to maintain the system pressure at or along the pressure limit curve C. If the system pressure falls below a pressure limit along the pressure limit curve C at the corresponding flow rate, the controller 24 may control the flow regulator 26 to increase the flow of breathing gas to achieve a target pressure. This target pressure may be a pressure value along the pressure limit curve C. This target pressure may be a higher target pressure along the pressure limit curve C. In other words, as the obstruction decreases or as the blower increases speed for a given system pressure, the flow rate of breathing gas increases and the corresponding target pressure along the pressure limit curve C increases, so that the controller controls the flow regulator 26 to adjust the flow rate of breathing gas upward along the pressure limit curve C toward the flow rate set point as the obstruction decreases. Control to the target pressure may optionally be switched to flow control when the target flow rate is met and the system pressure is lower than a pressure value along the pressure limit curve C at that target flow rate. The increase and / or decrease in breathing gas flow may be a continuous increase and / or decrease, or may be a stepwise increase and / or decrease.

[0237] The pressure limit curve C is designed to provide instructions to the controller 24 to avoid or reduce the likelihood of restricted flow within the system 22 resulting in an overpressure event or condition that may deliver an unsafe patient or system pressure that may damage system components. As noted, the restriction may be intentionally introduced by folding the foldable portion 204 that provides or forms part of the nasal cannula 200 with the mask 300, or the restriction may be accidentally introduced, for example, by a tear, kink, or bend in a portion of the delivery conduit. The shape of the pressure limit curve C in Figures 10 and 13 has a sigmoid or "S" shape. In embodiments utilizing a sigmoid pressure limit curve, the controller 24 may operate the flow regulator 26 to regulate the flow rate of gas by a variable increase or decrease rate. The sigmoid pressure limit curve C allows the controller 24 to control the flow regulator to provide or maintain a low system pressure at a low flow. While this can be beneficial in the sense that the foldable portion 204 can remain folded, it also minimizes the chance of there being a pressure differential or significant pressure differential across the foldable portion when in the second configuration, which may otherwise result in residual flow being carried through the foldable portion 204 to the patient, or making it difficult to fit the mask over a cannula for delivery of the required respiratory assistance. In some embodiments, the pressure limit curve C may be defined such that a known amount or range of amounts of residual flow across the foldable portion 204 in the second configuration is achieved, for example by applying a particular amount of pressure differential across the foldable portion 204 in the second configuration to reach a particular amount of residual flow. The smoothness of the pressure threshold curve C provides a smooth tactile feedback to the user that can be felt through the foldable portion 204 and the mask 300, and through the mask 300 if there is a force exerted by the system pressure.

[0238] However, it should be understood that the pressure threshold curve C may have various shapes in every situation, and is shaped to directly control to achieve gas delivery below the pressure limit for the corresponding flow rate, and is ideally relatively smooth to achieve smooth control (although stepped controls resulting from stepped curve C may also be accommodated in some embodiments, although these may cause control instabilities between steps). The normal operating region 58 under curve C may be determined by the resistance to flow of the components in the system 22, allowing for different manufacturing tolerances as discussed above. The parameters of curve C may vary depending on operating preferences. In some embodiments, a higher pressure limit (y-intercept) at zero flow may cause a larger residual flow across the foldable portion 204 when in the second configuration. In other embodiments, the target pressure at zero flow may be closer to or equal to 0 cmH2O. Alternatively / additionally, a higher pressure limit at high flow rates (i.e., a larger difference between pressure limit curve C and the normal operating pressure in region 58) may accommodate more deformation in the system state (e.g., a collapsed or blocked cannula state) before controller 24 adjusts control of the flow regulator to reduce pressure. This allows for a larger tolerance for system pressure to rise before the pressure limit of pressure limit curve C at the target flow rate is met or exceeded. In some embodiments, curve C may be or include a linear portion between the control endpoints defined by the minimum and maximum operating pressures. However, controlling the linear curve C may result in an undesirable amount of residual flow across the collapsible portion 204 when in the second configuration at low flow rates. Alternatively / additionally, curve C may be or include a quadratic curve portion, which may in some cases be prone to inadvertent triggering of pressure threshold detection if there is an inadvertent or momentary bend or twist, or other condition that causes high system pressure. Thus, it has been determined that a sigmoid or other S-shaped curve, in conjunction with a "limited" operating region 60, may be preferable to guide control in some embodiments.

[0239] FIG. 12 is a graph showing that the pressure curves can have a nominal pressure limit (curve R) or a zero pressure limit (curve S) at zero flow. The zero pressure limit at zero flow theoretically provides zero residual flow when a blocked or collapsed condition exists in the system. The higher the nominal zero flow pressure limit (curve R), the more residual flow may occur when collapsed. In some embodiments, it may be desirable to operate the system 22 with a low or zero flow and a small amount of residual pressure (e.g., when the foldable portion 204 is in the second state). In such an embodiment, the controller 24 controls and maintains the operation of the flow regulator 26 such that a small amount of system pressure is maintained at zero (or low) flow, e.g., the blower 27 is maintained at a very low angular velocity. This has the advantage of helping to restore flow in the system and to the patient as the foldable portion 204 changes toward the first configuration. Specifically, when the collapsible portion 204 changes from the second configuration to the first configuration (i.e., the obstruction is reduced), the flow rate of the respiratory gas flow increases and the system pressure drops. For a given increased flow rate, the controller 24 controls the flow regulator 26 to regulate the respiratory gas flow to a new target pressure. In attempting to reach that new target pressure, the flow rate of the respiratory gas flow is again increased to provide the new target pressure.

[0240] In response, the controller 24 controls the flow regulator 26 to regulate the flow of breathing gas to the target pressure along the pressure limit curve C until the flow set point is met, at which point the controller 24 switches to the flow control mode. However, a small amount of system pressure at zero (or low flow) may cause a pressure difference across the collapsible portion 204, which may result in residual flow. In some applications, residual flow is desirable. In other applications, residual flow is undesirable, and such residual flow may be stopped or substantially reduced by configuring the pressure limit curve such that the y-axis of the pressure-flow graph intersects at the origin (0,0), which would correspond to a complete stop of the flow regulator 26. In such an embodiment, the absence of any flow in the system may make it impossible for the controller 24 to determine whether there has been a change in the pressure and / or flow in the system in order to fully operate the controller 24 in the pressure control (pressure-induced control) and / or flow control (flow-induced control) mode. In response, the controller 24 may be configured to control the flow regulator 26 to deliver a short burst or pulse of flow corresponding to a "test pulse" to determine if there has been a change in system pressure indicating that an occlusion or blockage (e.g., caused by the collapsible portion 204 being in the second configuration) has been removed. If the test pulse results in only an increase in system pressure (with only a slight increase in flow rate), the controller determines that the occlusion or blockage remains and pressure-induced control (or deactivation of the flow regulator except for the test pulse) should continue. Recognizing that more regular (or longer) pulses may increase residual flow if the blockage has not been removed, the duration between test pulses may be preprogrammed and / or varied on demand. Conversely, if the duration between pulses is long, the residual flow may be significantly reduced, but the controller may not respond adequately because it cannot detect the reduction in system pressure until the test pulse occurs. If the controller detects an increase in flow in response to the test pulse, it may determine that the blockage has been removed and adjust the control of the flow regulator to increase speed, thereby increasing system flow and / or pressure.

[0241] In one example, the controller 24 continuously or periodically receives sample data indicative of the pressure and / or flow rate of the respiratory gas flow of the system 22 and compares the received data to values ​​obtained from the pressure limit curve C. Ideally, the controller 24 seeks to achieve a target flow rate corresponding to a flow set point, provided that the pressure in the system does not exceed the target pressure corresponding to a value along the curve C. The controller 24 may control the flow regulator 26 in response to the received pressure value. For example, if the received pressure value indicates that the system pressure meets or exceeds the value of the curve C for the corresponding flow rate, the controller 24 controls the system to achieve a system pressure that is equal to or less than the value of the curve C for the corresponding flow rate (i.e., pressure-driven control). Alternatively, if the received pressure value indicates that the system pressure does not meet or exceed the value of the curve C, the controller controls the system to achieve the target flow rate (i.e., flow-driven control). As an example, the controller 24 may adjust the operation of the system 22 to reduce the respiratory gas flow in response to a received pressure that exceeds the value of the pressure limit curve C for the corresponding flow rate by controlling the flow regulator 26 to reduce or stop the respiratory gas flow provided to the patient. Alternatively or additionally, the controller may operate the proportional valve 25 to reduce the system pressure. Conversely, the controller may adjust operation of the system 22 to increase the breathing gas flow in response to a received pressure that does not exceed the value of the pressure limit curve C for the corresponding flow rate by controlling the flow regulator 26 (and optionally the proportional valve 25) to increase the breathing gas flow in response to a pressure that does not exceed the value of the pressure limit curve C for the corresponding flow rate.

[0242] If the controller 24 determines that the received pressure does not exceed the pressure limit curve C, and the controller 24 determines a difference between the target flow rate and the measured flow rate, the controller 24 can then output commands, such as by way of a digital communication interface or by adjusting the supply voltage or current, to increase or decrease the motor speed of the blower 27 and / or open or close the proportional valve 25. The control can be binary (e.g., switching the blower on / off) or continuous, such as by controlling the supply voltage or current to the blower and / or proportional valve to modify the blower angular speed and valve opening based on the difference. If the sensed pressure value meets or exceeds the pressure limit curve C, the controller 24 may reduce the supply voltage or current to the blower by using a set amount of reduction, a set rate, a variable rate of reduction, or a pressure-based PID control or such as those described above. The blower angular speed may be reduced with each iteration of the feedback control until the sensed pressure value is below the pressure limit curve C or until the flow threshold is reached. This may indicate a blockage condition. The angular velocity of the blower may be reduced at a constant rate or at a variable rate.

[0243] FIG. 13 shows an example of a sigmoid pressure limit curve C in characterizing offset pressure for clarity. FIG. 13 shows normalized system pressure and how the pressure threshold for low flow (e.g., 1 cmH2O) differs from the pressure threshold for high flow (e.g., 20 cmH2O). The sigmoid-shaped pressure limit curve C has a first pressure region 66 corresponding to the nasal cannula 31 in a normal state, a second pressure region 68 corresponding to the nasal cannula 31 in a collapsed state, or some other restriction of flow in the system 22 or delivery conduit 30. The sigmoid-shaped pressure limit curve C has a transition region indicated by a dashed line 69 arranged between the first pressure region 66 and the second pressure region 68. The first pressure region 66 is substantially parallel to the second pressure region 68 of the pressure limit curve C. The first pressure region 66 and the second pressure region 68 correspond to pressure thresholds for corresponding flow rates within the respective regions. The transition region may be determined according to the required operating parameters, typically a trade-off between whether it is desirable to enjoy the benefits of a lower pressure threshold at a wider range of low flow, or the benefits of a higher pressure threshold at a wider range of high flow. Linked by a smooth "S" shaped transition, it provides smoother control and avoids oscillations and / or instability that may occur in the system if the pressure transition were a momentary step. It will be appreciated that although two pressure regions have been described in relation to pressure limit curve C, additional pressure regions may be provided.

[0244] The transition region 69 of the pressure limit curve represents the maximum increase / decrease rate of control of the respiratory gas flow and is centered around a transition flow rate less the flow set point (i.e., target flow rate) during normal operation. That is, the controller 24 is configured to control the flow regulator 26 to decrease the respiratory gas flow at the maximum decrease rate when the sensed pressure and flow rate are within the transition region 69 of the pressure limit curve and the sensed pressure exceeds the pressure limit curve C for the corresponding flow rate. In one example, the system 22 prevents the patient airway pressure from exceeding safety limits when in this transition region 69, for example, by decreasing the flow (ideally down to near zero) when the nasal cannula 200 is collapsed for bag-mask ventilation.

[0245] As mentioned, the difference between the transition region flow rate and the target flow rate allows for a temporary increase in system pressure, and the controller 24 can reduce the breathing gas flow at an initial minimum reduction rate until the transition flow rate is approached, in case the cause of the pressure increase is a temporary restriction and the temporary pressure increase is quickly removed.

[0246] FIG. 14 is a graph provided to illustrate the changing relationship between pressure and flow rate as the resistance to flow experienced by the system increases, for example as the clinician applies increasing pressure to a mask placed over the cannula (or when there is another type of increased blockage in the system). As the clinician presses down on the mask, the cannula begins to collapse and the resistance to flow in the system increases, which is detected as an increase in system pressure. The increase in resistance to flow is represented in FIG. 14 as dashed lines with increasing slopes R1-R4, where R1 represents the lowest resistance on the graph and R4 represents the highest resistance. These demonstrate that for a given flow rate, the increase in resistance to flow by collapsing the cannula increases the system pressure, and when the resistance to flow is high enough (e.g., the cannula is fully collapsed), the system pressure intersects the pressure limit curve C. Higher resistance intersects the curve further below the pressure limit curve C, as indicated by intersection points P1, P2, and P3. P3 corresponds to a completely or nearly completely collapsed cannula (or another type of complete or nearly complete blockage) with high resistance to flow (R4 curve) that easily crosses the pressure limit curve C at low pressures and flows.

[0247] In some embodiments, when the controller 24 determines that the system 22 is encountering an obstruction or the collapsible portion is in the second state, the folded state 68 (FIG. 13) has been reached, the controller 24 controls the flow regulator 26 to reduce the flow. The controller 24 may be further configured to provide an output, such as a visual or audible alarm, by the I / O device 20 or any other system component to indicate that the collapsible portion is in the folded state and / or that delivery of the anesthetic agent may begin. This output may, in some embodiments, include a control signal provided to the anesthesia machine. This may be advantageous when the anesthetic agent is delivered via inhalation through a mask 300 over the nasal cannula 200, since if the flows provided to the patient are not substantially reduced, these flows may dilute the anesthetic agent.

[0248] 10, a sigmoidal pressure limit curve C may be defined, showing a restricted region 60 where a momentary increase in pressure may occur before the controller 24 changes control of the flow regulator 26. This momentary increase in pressure may occur, for example, due to an unintentional kinking of the tubing of the breathing system 22. In some embodiments, the pressure limit curve C may be set as close as possible to the expected normal pressure in order to minimize flow at lower pressures and to be able to move the mask 300 over the nasal cannula 200 without rapidly increasing flow to the flow rate set point.

[0249] It will be appreciated that the pressure limit curve C is not limited to a sigmoidal shape. However, the sigmoidal shape allows for a quick transition in pressure between two pressure regions without an instantaneous jump between the two regions. An instantaneous jump may not be ideal as this discontinuity may cause instability in the control of the breathing system 22. For example, the output from the controller 24 (e.g., the blower speed control parameter) should change significantly corresponding to the instantaneous rate of change of pressure and flow within the transition region, and this instantaneous rate of change of the controller output will cause instability.

[0250] 13, while the breathing system 22 can operate within the normal operating region 66, when operating closer to the transition region 69 of the sigmoidal pressure limit curve C, the breathing system 22 may transition more quickly between pressure states (i.e., lower pressure offsets to higher pressure offsets to normal operating pressures). As mentioned above, different overall shapes of curves are envisioned, such as a "Z" shaped curve, which still allows for quick transitions in pressure. A "Z" shaped curve allows the pressure limit curve to be "flat" (stable at the pressure limit) in both the unfolded and folded states.

[0251] Figure 15 is a state diagram of the operating states of the breathing system 22 with reference to the pressure limit curves of Figures 9-14. From the normal state of operation of the breathing system 22, the normal state may transition to a mismatch / disconnect state. In the mismatch / disconnect state, the controller may increase the flow of breathing gas to approach the target flow rate / set point, but the sensed pressure never meets the expected value, so the controller 24 may trigger an alarm to the user of the breathing system 22 and / or the controller may operate the flow regulator 26 or the proportional valve 25 to reduce or stop the flow.

[0252] The normal state may transition to a restricted state where the system pressure meets (but does not exceed), for example, the pressure limit curve C for the corresponding flow rate. That is, in some embodiments, when the sensed pressure is at the pressure limit curve C for a given flow rate, the controller begins pressure-induced control to stay at or return below the pressure limit. In other embodiments, the controller may reduce the blower speed or decrease the opening of the proportional valve of the flow regulator when the sensed pressure meets or exceeds the pressure limit curve C. Alternatively, the controller 24 may remain in pressure-induced control but change the target flow rate to a lower set point. For example, when the pressure meets or exceeds the pressure limit curve, the controller may override the operator-defined target flow rate of, for example, 70 L / min and set a new target flow rate at a lower set point, for example, 20 L / min. When the controller 24 determines that the system pressure has dropped below the pressure limit, the controller may then switch to flow-induced control and increase the blower speed or increase the opening of the proportional valve of the flow regulator to (gradually) meet the flow rate set point. The controller 24 may periodically or continuously check the system pressure and, if the system pressure has not been reduced below the pressure limit, maintain or further reduce the flow regulator parameters discussed above. A reduced blower speed may be achieved by reducing the control signal or supply current (or voltage) to the flow regulator, for example to reduce the blower angular velocity. Alternatively / additionally, the controller may control the operation of the proportional valve to reduce the flow. In other embodiments, rather than periodically or continuously determining the system pressure, the controller 24 may be configured to determine the current system pressure only once it has been established by the flow input that the system is operating at the lower flow set point.

[0253] Under normal conditions, the controller may control the flow regulator 26 to deliver a target flow rate (also referred to as a set point flow rate) to the patient through the nasal cannula 200. The controller 24 may control the respiratory system 22 to allow operation in a restricted state without switching between flow-induced and pressure-induced control to minimize accidental or unwanted pressure and / or flow-restricting events that occur in response to momentary or temporary changes in system pressure. This allows the user of the respiratory system 22 more freedom to perform normal tasks of working with the respiratory system 22 by being able to move / fold the circuit, check if the patient is breathing, move the head, possibly awaken the patient, perform nasal fiber optic intubation, etc., without transitioning to any of the overpressure states described. The pressure limit curve C is set in some embodiments to be as high as possible while still ensuring patient safety.

[0254] The restrictive state transitions to an overpressure state when the sensed pressure increases its intersection with the pressure limit curve C at the corresponding flow rate. In the overpressure state, the controller 24 is configured to control the flow regulator 26 or proportional valve 25 to reduce or stop the flow of breathing gas as described above and / or trigger an audible and / or visual alarm if this state occurs for an extended period of time. Ideally, a transition to an overpressure state transitions the controller to pressure induced control, and in some embodiments the controller may be configured to sound an alarm while the controller is in the pressure induced control mode or if the pressure induced control persists for more than a preprogrammed duration or a preprogrammed percentage of the period during which respiratory support was provided to the patient. One or more warnings or triggering of an alarm during an overpressure state may also occur for other parameters, such as whether there is flow delivered to the patient and / or what percentage (e.g., 90%) of the target flow rate is achieved.

[0255] In some embodiments, the controller is configured to provide an alarm system to convey prioritized information or attention to the user. For example, a first visual and / or audible alarm may be a continuous tone with a red color and a higher volume and / or a highest priority, a second visual and / or audible alarm may be an orange color and a lower volume and / or a pulsing tone with a second priority, a third visual and / or audible alarm may be a green color (or yellow or white, etc.) and / or a pulsing tone with a lower pulse frequency indicating a third priority, and so on. The visual alarm may be provided by the I / O interface 20, or by an LED or the like provided on the housing 33 or on a component that may be located away from the housing, e.g., on an IV pole, bed rail, or other component that may be attached to the user for the convenience of the user. The different priorities may correspond to different system conditions with different priorities of alarms (based on the patient's care requirements). The warning may be generated by the controller 24 or by any combination of system controllers / microcontrollers, such as a secure microcontroller that may be configured to provide or enable multiple levels of brightness for LEDs (e.g., dim and brightest) to ensure that there is always at least one LED illuminated when the device receives power. This ensures that any failure of the system (e.g., a crash of the microcontroller driving the LEDs) does not falsely indicate that the entire system is off. In this arrangement, the warning LEDs are only completely turned off when power to the device is completely disconnected.

[0256] In still further embodiments, the controller may be configured to provide different warnings according to where the system is operating on the pressure limit curve C. By way of example, the controller 24 may be configured to issue a first audible warning, e.g., five beeps per second, from the I / O interface 20 when a shutoff is introduced into the system causing the system pressure to meet or exceed the pressure limit curve at or near the target flow rate, triggering the controller 24 to switch to pressure induced control (see X in FIG. 9). Alternatively / additionally, the controller 24 may be configured to issue a second audible warning, e.g., three beeps per second, from the I / O interface 20 when the system pressure progresses along the pressure limit curve C (towards and through Y in FIG. 9), and a third audible warning, e.g., one beep per second, may be issued when the system pressure and / or flow is reduced even further (see Z in FIG. 9). The beep rates provided in this example are suggested only to illustrate the utility of different audible warnings (or visual cues) representative of different operating states of the system that provide useful feedback to the clinician, such as whether the foldable portion 204 is fully folded. It should be understood that these and other warnings may be provided audibly or visually by a controller that operates the I / O interface 20 and / or other components that may be located remotely from the system housing 33 as described above.

[0257] A further state of the respiratory system 22 that may be transitioned from the normal or restricted state is blocked. The blocked state is transitioned from the restricted or normal state when the sensed flow rate reaches a threshold, for example 2 L / min, or reaches 0 L / min, and the system pressure is equal to or greater than the pressure limit curve C for the corresponding flow rate. In some embodiments, when in the blocked state, the controller 24 controls the flow regulator 26 to regulate the respiratory gas flow (which may be 0 L / min) to a target pressure above 0 cmH2O (which is where the pressure limit curve C intersects the y-intercept). Thus, in such an embodiment, there is a system pressure at zero or a substantially low flow rate. When an obstruction or blockage in the system is removed, the system pressure decreases and the flow rate of the respiratory gas flow increases. The controller 24 therefore controls the flow regulator 26 to regulate the respiratory gas flow to a new higher target pressure corresponding to the higher flow rate. As the flow regulator 26 increases the pressure of the respiratory gas flow, the flow rate increases accordingly, resulting in a new higher flow rate that establishes a new target pressure corresponding to the new higher flow rate. In response, the flow regulator 26 is configured to adjust the flow of breathing gas to an increasing target pressure until the flow set point is met, after which the controller 24 switches to flow-directed control. Additionally or alternatively, the controller 24 determines whether the sensed pressure and flow correspond to a pressure waveform that coincides with when the nasal cannula 31 is collapsed indicating bag-mask ventilation has occurred. If this is not determined, the controller 24 may continue to increase the flow and return to the first configuration.

[0258] 16 is a high level schematic diagram of the operational control of the breathing system 22 according to an example of the present disclosure. In the example shown, the controller 24 may be considered to provide a flow controller providing a flow control output, and a pressure controller providing a pressure control output, operating as separate modules of the controller 24. The flow controller uses as input a flow set point (which may be a target flow rate) and a sensed flow rate (flow measurement), and the pressure controller uses as input a pressure set point calculated from a pressure limit curve C for a corresponding measured flow rate and a sensed pressure (pressure measurement). The controller 24 implementing these pressure and flow controllers simultaneously can thus provide pressure-induced and flow-induced control to the breathing system 22. Changes in control of either the pressure-induced or flow-induced control mode may be achieved by changing the control of the proportional valve, for example by changing the control of the flow regulator to achieve a change in the angular velocity of the blower, and / or by changing the supply current or voltage to achieve the required increase or decrease in flow rate. As noted, the predetermined pressure thresholds and corresponding flow rates represented by curve C are stored in a memory component of the controller 24 or a memory component operatively coupled to the controller 24 and may be represented in one or more suitable forms, such as a function, curve, look-up table or algorithm or the like. To implement control, the controller 24 selects minimum control values, as determined by the flow control system and the pressure control system, for controlling a flow regulator / blower or proportional valve.

[0259] 17, there is shown schematic steps in a method 70 of operating a respiratory assistance system 22 according to an embodiment of the present disclosure to provide a respiratory gas flow to a patient. In step 71, a respiratory gas flow is provided to the patient with the respiratory assistance system 22, which may be a target flow rate. This typically involves applying a patient interface to the patient, who receives a respiratory gas flow from a flow source of the respiratory assistance system under the control of a controller of the respiratory assistance system. In step 72, the controller determines a system pressure corresponding to the gas pressure downstream of the flow regulator. The system pressure is typically determined using one or more sensors, such as one or more pressure sensors configured to determine the pressure of the respiratory gas flow in the respiratory system, although in other embodiments the system pressure may be measured and provided to the controller by manual means, such as by an operator entering a value, using an input / output interface in operative communication with the controller. In step 73, the controller receives an input indicative of the flow rate of the respiratory gas flow in the system. Typically the flow rate is measured by one or more sensors, such as one or more flow sensors. In step 74, the controller compares the system pressure determined in step 72 to a predetermined pressure threshold for a corresponding flow rate at which the respiratory assistance system may be operated. Specifically, the controller compares the system pressure determined in step 72 to a pressure threshold for a corresponding target flow rate. The pressure threshold may be stored in a memory component of the controller or a memory component operatively coupled to the controller and may be represented in one or more suitable forms, such as a function, curve, look-up table or algorithm, or the like. In some embodiments, the memory component may include a computer readable medium (e.g., a disk, hard drive, USB, optical drive, or other data storage device) containing program instructions for causing the controller to perform the necessary controls as described herein.In step 75, the controller controls components of the respiratory assistance system, such as a flow regulator, to maintain, increase, or reduce the respiratory gas flow in response to the system pressure meeting or exceeding or not meeting or exceeding the pressure threshold at the target flow rate, as determined by the controller in step 74. In embodiments where the comparison in step 74 determines that the pressure threshold meets or exceeds the target flow rate, the controller may switch to a pressure-driven control mode (FIG. 15) in which the controller controls operation of system components to reduce the system flow and / or pressure. Alternatively, the controller may remain in the flow-driven control mode but change the target flow rate to a lower set point. In embodiments where the comparison in step 74 determines that the pressure has dropped below the pressure threshold and the target flow rate has been achieved, the controller switches to the flow-driven control mode (FIG. 15). In embodiments where the comparison in step 74 determines that the pressure has dropped below the pressure threshold but the target flow rate has not been achieved, the controller may remain in the pressure-driven mode in which the controller controls the flow regulator to the target pressure.

[0260] It will be appreciated that various modifications, additions and / or substitutions may be made to the parts described above without departing from the scope of the present invention as defined in the claims appended hereto.

[0261] The present invention may be said to broadly consist of the parts, elements, and features mentioned or illustrated in the details of this application, either individually or collectively, in any or all combinations of a plurality of said parts, elements or features. Where reference has been made in the foregoing description to integers or components having their known equivalents, those integers are incorporated herein as if set forth individually.

[0262] When any or all of the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims), they are to be interpreted as specifying the presence of stated features, integers, steps or components, but not to exclude the presence of one or more other features, integers, steps or components or groups thereof.

[0263] It is understood that the following claims are provided by way of example only and are not intended to limit the scope of what may be future claimed. Features may be added or subtracted from the claims at a later date to further define or redefine one or more inventions.

Claims

1. 1. A breathing system for providing a flow of breathing gas to a patient, comprising: A flow regulator; configured to receive an input of a flow rate and a pressure of the flow of breathing gas in the system; controlling the flow regulator to provide the flow of breathing gas to a patient at a target flow rate; a controller configured to control the flow regulator to regulate the flow of breathing gas to a target pressure when the pressure of the flow of breathing gas in the system meets or exceeds a pressure threshold corresponding to the target flow rate; Respiratory system, including:

2. The target pressure includes the pressure threshold corresponding to the target flow rate or a pressure threshold corresponding to a flow rate less than the target flow rate; and / or the controller is configured to control the flow regulator to regulate the flow of breathing gas to the target pressure when the flow rate of the flow of breathing gas is less than the target flow rate; and / or the controller is configured to control the flow regulator to regulate the flow of breathing gas to the target flow rate when the flow rate of the breathing gas flow exceeds the target flow rate; and / or 2. The respiratory system of claim 1, wherein the controller is configured to control the flow regulator to the target pressure when the pressure of the flow of breathing gas exceeds the pressure threshold corresponding to the target flow rate or a pressure threshold corresponding to a flow rate less than the target flow rate.

3. 3. A respiratory system as described in claim 1 or 2, wherein when the system starts operation from an "off" or resting state, the controller is configured to monitor the flow rate of the respiratory gas flow in the system and to control the flow regulator to regulate the respiratory gas flow to the target flow rate, and optionally the target flow rate is changed over time to increase from a current value to a flow rate set point.

4. the target flow rate is a flow rate set point; and / or A breathing system according to any one of claims 1 to 3, wherein the flow set point is determined by a user of the breathing system.

5. 5. A respiratory system according to any one of claims 1 to 4, wherein the controller comprises a flow controller providing a flow control output and a pressure controller providing a pressure control output, and the control input to the flow regulator is the minimum of the flow control output and the pressure control output.

6. the flow regulator comprises a blower, and the flow control output and the pressure control output comprise an angular velocity of the blower; and / or the flow regulator comprises a proportional valve, and the flow control output and the pressure control output comprise a fixed size flow restriction through the proportional valve; and / or the flow regulator includes a flow generator configured to be controlled by the controller to regulate the flow of breathing gas to the patient; and / or the flow regulator includes a proportional valve configured to be controlled by the controller to regulate the flow of breathing gas; Optionally, the flow generator includes a blower configured to be controlled by the controller to generate the flow of breathing gas.

6. A breathing system as claimed in claim 5.

7. the controller is configured to receive a flow value indicative of a flow rate of breathing gas provided to the patient; and / or the respiratory system includes one or more flow sensors configured to sense a flow rate of the respiratory gas flow to the patient in the system; and / or the respiratory system includes one or more pressure sensors configured to sense the pressure of the flow of respiratory gas to the patient in the system; and / or the controller is further configured to receive an input indicative of the flow rate of the flow of breathing gas in the system from the one or more flow sensors, and an input indicative of the pressure of the flow of breathing gas in the system from the one or more pressure sensors. A breathing system according to any one of the preceding claims.

8. 8. The respiratory system of claim 7, wherein the controller is operable in a first control mode to control the flow rate to the target flow rate when the flow rate exceeds the target flow rate, and the controller is operable in a second control mode to control the pressure to the target pressure when the pressure of the flow of breathing gas exceeds the pressure threshold corresponding to the target flow rate or exceeds a constant or pressure threshold corresponding to a flow rate less than the target flow rate.

9. a delivery conduit for providing a flow of gas from the flow regulator to a patient interface, the patient interface configured to deliver the flow of breathing gas to the patient; Optionally, the patient interface comprises a gas delivery side arm in fluid communication with the delivery conduit, a manifold provided at an end of the gas delivery side arm, and one or more nasal elements extending from the manifold, the one or more nasal elements configured to provide the flow of respiratory gas to one or more nares of the patient, the gas delivery side member comprising a foldable portion; Further optionally, the foldable portion is operable in a first configuration in which the foldable portion is substantially open and in a second configuration in which the foldable portion is substantially closed; and / or The patient interface includes nasal cannulas, optionally non-sealing nasal cannulas; and / or the delivery conduit further includes a delivery circuit and a patient breathing circuit arranged between the delivery circuit and the patient interface, the patient breathing circuit being connected to the delivery circuit by an outlet connector. A breathing system according to any one of claims 1 to 8.

10. and / or, when the controller controls the flow regulator to the target pressure, flow to the patient is reduced to a reduced flow rate of about 15 L / min or less, or about 10 L / min or less, or about 10 L / min, or about 5 L / min to about 10 L / min, or less than about 5 L / min, or 0 L / min; and / or A respiratory system according to any one of claims 1 to 9, wherein the controller is configured to control the flow regulator to increase the flow of breathing gas towards the target flow rate.

11. The respiratory system is configured to supply oxygen (O 2 ) configured to sense pressure within the delivery circuit. 2 and / or a pressure sensor The respiratory system is configured to supply oxygen (O 2 ) O in the delivery circuit 2 configured to sense the flow rate of the stream. 2 or The respiratory system includes an O2 pressure sensor configured to sense a pressure in an oxygen (O2) delivery circuit of the respiratory system, and an O2 flow sensor configured to sense a flow rate of O2 flow in the oxygen (O2) delivery circuit of the respiratory system, the respiratory system further comprising: an O2 pressure sensor configured to sense a pressure in an oxygen (O2) delivery circuit of the respiratory system; 2 In the delivery circuit 2 Pressure sensor and the O 2 A breathing system as claimed in any preceding claim, including a proportional valve arranged between the flow sensor and the proportional valve.

12. The patient breathing circuit includes 2 a patient interface connected to the patient breathing circuit and the air delivery circuit, the patient interface further comprising a patient pressure sensor and a patient flow sensor; 12. A breathing system according to claim 11 when dependent on claim 9, optionally wherein the flow regulator includes a blower, the blower being arranged in the patient breathing circuit before the patient pressure sensor and the patient flow sensor.

13. A respiratory system according to any one of claims 1 to 12, wherein the controller is in operative communication with or includes a memory component storing one or more of a function, curve, look-up table or algorithm providing a relationship between the pressure threshold and a corresponding flow rate.

14. the controller is configured to control the flow regulator to reduce the flow of breathing gas by a variable reduction rate; and / or The relationship between the pressure threshold and the corresponding flow rate may be represented by a pressure limit curve or function that defines a curve having a sigmoid shape; and / or 14. The respiratory system of claim 13, wherein the relationship between the pressure thresholds and corresponding flow rates includes a first pressure region, a second pressure region, and a transition region arranged between the first pressure region and the second pressure region.

15. the first pressure area corresponds to when the foldable portion is substantially in the first configuration, the second pressure area corresponds to when the foldable portion is substantially in the second configuration, and Optionally, the first pressure region includes pressure thresholds offset from a reference pressure value by a first pressure margin, and the second pressure region includes pressure thresholds offset from a reference pressure value by a second pressure margin, whereby the first pressure margin is greater than the second pressure margin; and Optionally, the first and second margins provide an offset of the pressure threshold within the first pressure region of the pressure limit curve that is substantially parallel to an offset of the pressure threshold within the second pressure region, the first pressure region and the second pressure region corresponding to a minimum rate of change of the respiratory gas flow.

16. the slope of the transition region of the pressure limit curve corresponds to a maximum rate of change of the respiratory gas flow; and / or the transition region of the pressure limit curve is centered at a transition flow rate; and Optionally, the controller is configured to control the flow regulator such that the breathing gas flow reaches the maximum rate of change when the pressure and the corresponding flow rate are within the transition region of the pressure limit curve.

17. A breathing system as described in any one of claims 14 to 16, wherein the first and second pressure margins provide a margin for temporarily reducing the system pressure of the breathing gas flow from below the pressure threshold without the controller controlling the flow regulator to increase the breathing gas flow.

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