Closed loop oxygen control

Abstract

The present disclosure provides a flow therapy device that can implement one or more closed-loop control systems to control a gas flow of the flow therapy device. The flow therapy device may monitor the blood oxygen saturation (SpO2) of a patient and control the oxygen fraction (FdO2) delivered to the patient. The flow therapy device may automatically adjust FdO2 in order to achieve a target SpO2 value for the patient.

Description

Technical Field

[0001] The present disclosure relates to methods and systems for controlling oxygen delivery in flow therapy devices.

[0002] background

[0003] Respiratory devices are used to deliver a flow of gas to a user or patient in a variety of environments, such as a hospital, medical facility, home care, or home environment. Respiratory devices or flow therapy devices may include an oxygen inlet to allow delivery of supplemental oxygen and gas flow, and / or a humidification device to deliver heated and humidified gas. Flow therapy devices may allow for adjustment and control of characteristics of the gas flow, including flow, temperature, gas concentration (such as oxygen concentration), humidity, pressure, etc. Summary of the invention

[0004] According to certain features, aspects and advantages of the first embodiment disclosed herein, there is provided a respiratory apparatus for providing a flow of gas to a patient, the respiratory apparatus comprising: a gas composition sensor configured to determine at least an oxygen content (FdO2) of the flow of gas during operation of the respiratory apparatus; a controller configured to control gas delivery to the patient using closed-loop control, wherein the controller is configured to: receive patient parameter data indicative of an oxygen saturation (SpO2) of the patient from at least one sensor; receive data indicative of a measured delivered oxygen fraction (FdO2) of the flow of gas from the gas composition sensor; receive flow data indicative of or corresponding to a flow rate of the flow of gas provided by the respiratory apparatus; determine at least one time-related parameter, the or each time-related parameter being based at least in part on the flow data; and generate a patient-specific model, the patient-specific model being based at least in part on the at least one time-related parameter, wherein the patient-specific model is used to predict changes in the patient's oxygen saturation (SpO2) in response to changes in the measured delivered oxygen fraction (FdO2) of the flow of gas.

[0005] In some configurations of the first embodiment, the determination of the at least one time-dependent parameter is based at least in part on whether the flow rate is below a defined threshold.

[0006] In some configurations of the first embodiment, the at least one time-related parameter is a device-specific delay time associated with a delivery delay time of oxygen from the respiratory apparatus to the patient.

[0007] In some configurations of the first embodiment, the at least one time-related parameter is a patient-specific delay time associated with a delivery delay time of oxygen from the upper airway of the patient to the tissue perfusion monitoring site.

[0008] In some configurations of the first embodiment, the at least one time-dependent parameter is a decay value associated with a time taken for the patient's SpO2 level to decay to a stable range of values ​​after a change in FdO2 by the controller.

[0009] In some configurations of the first embodiment, the flow data indicates or corresponds to a specified flow configured by a user.

[0010] In some configurations of the first embodiment, the flow data indicates or corresponds to a measured flow of gas provided by the breathing apparatus.

[0011] In some configurations of the first embodiment, the flow rate is received from a flow sensor disposed in the gas flow.

[0012] In some configurations of the first embodiment, the determination of the at least one time-related parameter is based at least in part on at least one criterion associated with one or more physical characteristics of the patient.

[0013] In some configurations of the first embodiment, the determination of the at least one time-related parameter is based at least in part on at least one criterion associated with the patient's head size.

[0014] In some configurations of the first embodiment, the at least one criterion associated with the one or more physical characteristics of the patient is flow rate.

[0015] In some configurations of the first embodiment, the at least one criterion associated with the one or more physical characteristics of the patient is a detected patient interface type.

[0016] In some configurations of the first embodiment, at least one criterion associated with one or more physical characteristics of the patient is a patient interface type configured by a user.

[0017] In some configurations of the first embodiment, the at least one criterion associated with the one or more physical characteristics of the patient is heart rate.

[0018] In some configurations of the first embodiment, the at least one criterion associated with the one or more physical characteristics of the patient is a breathing rate.

[0019] In some configurations of the first embodiment, the at least one criterion associated with one or more physical characteristics of the patient is a measure of breathing intensity and / or volume.

[0020] In some configurations of the first embodiment, the at least one criterion associated with the one or more physical characteristics of the patient is a previous treatment type or mode.

[0021] In some configurations of the first embodiment, the controller is further configured to select the first algorithm or the second algorithm to determine the at least one time-related parameter based at least in part on whether the flow rate satisfies a defined threshold.

[0022] In some configurations of the first embodiment, selecting the first algorithm or the second algorithm to determine the at least one time-related parameter is further based at least in part on at least one criterion associated with one or more physical characteristics of the patient.

[0023] In some configurations of the first embodiment, the closed-loop control includes using a first closed-loop control model configured to determine a target delivered oxygen fraction (FdO2) of the gas flow.

[0024] In some configurations of the first embodiment, a target FdO2 for the gas flow is determined based at least in part on a target SpO2 and a patient parameter indicative of an oxygen saturation (SpO2) of the patient.

[0025] In some configurations of the first embodiment, the target FdO2 for the gas flow is further based at least in part on received data indicative of a measured delivered oxygen fraction (FdO2) of the gas flow.

[0026] In some configurations of the first embodiment, the target FdO2 is further based at least in part on a previously determined target FdO2.

[0027] In some configurations of the first embodiment, the closed-loop control includes using a second closed-loop control model configured to determine a control signal for the oxygen inlet valve based at least in part on a difference between a target FdO2 for the gas flow and received data indicative of a measured delivered oxygen fraction (FdO2) of the gas flow.

[0028] In some configurations of the first embodiment, a control signal for the oxygen valve is determined based at least in part on a target FdO2 and received data indicative of a measured delivered oxygen fraction (FdO2) of the gas flow.

[0029] In some configurations of the first embodiment, a control signal for the oxygen valve is further determined based at least in part on the received flow data.

[0030] In some configurations of the first embodiment, the received flow data corresponds to or is indicative of a total gas flow provided by the breathing apparatus.

[0031] In some configurations of the first embodiment, the patient-specific model is generated during a current treatment session.

[0032] In some configurations of the first embodiment, the patient-specific model is generated during a current treatment session based at least in part on a default model.

[0033] In some configurations of the first embodiment, the patient-specific model is updated during the current treatment session.

[0034] In some configurations of the first embodiment, the patient-specific model includes the patient's oxygen efficiency.

[0035] In some configurations of the first embodiment, the oxygen efficiency is determined based at least in part on received data indicative of an oxygen saturation (SpO2) of the patient and received data indicative of a measured delivered oxygen fraction (FdO2) of the gas flow.

[0036] In some configurations of the first embodiment, the oxygen efficiency is determined based at least in part on received data indicative of oxygen saturation (SpO2) divided by received data indicative of a measured fraction of delivered oxygen (FdO2).

[0037] In some configurations of the first embodiment, the oxygen efficiency is determined based at least in part on a non-linear relationship between received data indicative of the patient's oxygen saturation (SpO2) and received data indicative of a measured fraction of delivered oxygen (FdO2).

[0038] In some configurations of the first embodiment, the controller is configured to predict the patient's SpO2 based at least in part on received data indicative of a measured fraction of oxygen delivered (FdO2).

[0039] In some configurations of the first embodiment, one or more previous predictions of SpO2 are compared to currently received data indicative of oxygen saturation SpO2 to calculate a model error.

[0040] In some configurations of the first embodiment, the model error is weighted according to a signal quality of the at least one sensor.

[0041] In some configurations of the first embodiment, the model error is used to correct the current SpO2 prediction.

[0042] In some configurations of the first embodiment, the predicted SpO2 is based at least in part on a Smith predictor.

[0043] In some configurations of the first embodiment, the respiratory apparatus further comprises a patient interface selected from at least one of: a face mask, a nasal mask, a nasal pillow mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

[0044] In some configurations of the first embodiment, the nasal cannula is a non-sealing nasal cannula.

[0045] In some configurations of the first embodiment, the respiratory apparatus is configured to deliver a nasal high flow (NHF) gas flow to the patient.

[0046] In some configurations of the first embodiment, the at least one sensor includes a pulse oximeter configured to determine or provide patient parameter data indicative of at least an oxygen saturation (SpO2) of the patient.

[0047] In some configurations of the first embodiment, the controller is configured to receive device parameter data indicative of an oxygen concentration of the gas flow.

[0048] In some configurations of the first embodiment, the breathing apparatus further includes a supplemental gas inlet valve.

[0049] In some configurations of the first embodiment, the controller is configured to control operation of the supplemental gas inlet valve.

[0050] In some configurations of the first embodiment, the supplemental gas inlet valve is a proportional valve.

[0051] In some configurations of the first embodiment, the supplemental gas inlet valve is an oxygen inlet valve.

[0052] In some configurations of the first embodiment, the supplemental gas inlet valve includes a swivel connector.

[0053] In some configurations of the first embodiment, the breathing apparatus further includes an ambient air inlet.

[0054] In some configurations of the first embodiment, the respiratory device further includes an oxygen inlet valve in fluid communication with the filter module, wherein the respiratory device is configured to entrain oxygen received from the oxygen inlet valve with ambient air from the ambient air inlet into the filter module.

[0055] In some configurations of the first embodiment, the gas composition sensor is positioned downstream of a blower module of the respiratory apparatus.

[0056] In some configurations of the first embodiment, the respiratory device further includes a filter module positioned upstream of the blower module of the respiratory device.

[0057] In some configurations of the first embodiment, the blower module mixes ambient air and oxygen.

[0058] In some configurations of the first embodiment, the respiratory device further includes a humidifier.

[0059] In some configurations of the first embodiment, the respiratory device further includes an integrated blower and humidifier.

[0060] In some configurations of the first embodiment, the breathing apparatus is configured to be portable.

[0061] In some configurations of the first embodiment, the respiratory device is configured to have a controlled variable flow.

[0062] In some configurations of the first embodiment, the breathing apparatus further includes a heated breathing tube.

[0063] In some configurations of the first embodiment, the ultrasonic sensor system includes a first ultrasonic transducer and a second ultrasonic transducer.

[0064] In some configurations of the first embodiment, each of the first ultrasonic transducer and the second ultrasonic transducer is a receiver and a transmitter.

[0065] In some configurations of the first embodiment, the first ultrasonic transducer and the second ultrasonic transducer transmit pulses bidirectionally.

[0066] In some configurations of the first embodiment, the first ultrasonic transducer is a transmitter and the second ultrasonic transducer is a receiver.

[0067] In some configurations of the first embodiment, at least one of the first ultrasonic transducer or the second ultrasonic transducer transmits pulses across the gas flow.

[0068] In some configurations of the first embodiment, the controller is configured to display the first oxygen efficiency characteristic on a display of the breathing apparatus.

[0069] In some configurations of the first embodiment, the controller is configured to display a second indication of oxygen efficiency on a display of the respiratory apparatus, wherein the second indication of oxygen efficiency is based at least in part on the patient's oxygen efficiency and the measured respiratory rate.

[0070] In some configurations of the first embodiment, the second oxygen efficiency characteristic is calculated by dividing received patient parameter data indicative of the patient's oxygen saturation (SpO2) by received data indicative of a delivered oxygen fraction (FdO2) of the gas flow and dividing the resulting value by the measured respiratory rate.

[0071] In some configurations of the first embodiment, the controller is configured to display a graph or a trend line indicating at least one of the first oxygen efficiency characteristic or the second oxygen efficiency characteristic over a defined time period.

[0072] In some configurations of the first embodiment, the respiratory device is changeable between operating in a high flow therapy mode and a bubble CPAP therapy mode.

[0073] In some configurations of the first embodiment, in the high flow therapy mode, the respiratory device is configured to provide high flow therapy.

[0074] In some configurations of the first embodiment, in the bubble CPAP mode, the respiratory device is configured to provide bubble CPAP therapy.

[0075] In some configurations of the first embodiment, one or more of the patient parameter data indicative of oxygen saturation (SpO2) and the flow data are received during provision of therapy to the patient and are related to current operation of the respiratory therapy device.

[0076] In some configurations of the first embodiment, one or more of the patient parameter data indicative of oxygen saturation (SpO2) and the flow data are associated with one or more previous operating states or therapy sessions of the respiratory therapy device.

[0077] In a second embodiment, a respiratory apparatus for providing a flow of gas to a patient, the respiratory apparatus comprising: a gas composition sensor configured to determine at least a delivered oxygen fraction (FdO2) of the flow of gas during operation of the respiratory apparatus; a controller configured to control delivery of the flow of gas to the patient using closed-loop control, wherein the controller is configured to: receive patient parameter data indicative of an oxygen saturation (SpO2) of the patient from at least one sensor; receive data indicative of a measured delivered oxygen fraction (FdO2) of the flow of gas from the gas composition sensor; receive flow data corresponding to or indicative of a flow of the flow of gas provided by the respiratory apparatus; compare the flow data to a defined flow threshold; determine a set of time-dependent parameters using a first model or a second model based at least in part on the comparison of the flow data to the defined flow threshold; generate a patient-specific model based at least in part on the set of time-dependent parameters, wherein the patient-specific model is used to predict changes in the oxygen saturation (SpO2) of the patient in response to changes in the measured delivered oxygen fraction (FdO2) of the flow of gas.

[0078] The respiratory apparatus of the second embodiment may include any one or more of the features of the respiratory apparatus of the first embodiment described above.

[0079] In a third embodiment, a breathing system for providing a flow of gas to a patient, the breathing system comprising: a gas composition sensor configured to determine at least a delivered oxygen fraction (FdO2) of the flow of gas during operation of the breathing system; a patient sensor configured to determine at least an oxygen saturation (SpO2) of the patient; a controller configured to control delivery of the flow of gas to the patient using closed-loop control, wherein the controller is configured to: receive patient parameter data indicative of the patient's oxygen saturation (SpO2) from the patient sensor; receive data indicative of a measured delivered oxygen fraction (FdO2) of the flow of gas from the gas composition sensor; receive flow data corresponding to or indicative of a flow rate of the flow of gas provided by the breathing system; and generate a patient-specific model based at least in part on the flow data, wherein the patient-specific model is used to predict changes in the patient's oxygen saturation (SpO2) in response to changes in the delivered oxygen fraction (FdO2) of the flow of gas.

[0080] The breathing system of the third embodiment may include any one or more of the features of the breathing apparatus of the first embodiment and / or the second embodiment described above.

[0081] In a fourth embodiment, a method for controlling gas flow delivery to a patient using closed-loop control comprises: receiving patient parameter data indicative of an oxygen saturation (SpO2) of the patient from at least one sensor; receiving data indicative of a measured delivered oxygen fraction (FdO2) of a gas flow from a gas composition sensor; receiving flow data corresponding to or indicative of a flow rate of the gas flow; determining at least one time-related parameter, the or each time-related parameter being based at least in part on the flow data; and generating a patient-specific model based at least in part on the at least one time-related parameter; wherein the patient-specific model is used to predict changes in the patient's oxygen saturation (SpO2) in response to changes in the measured delivered oxygen fraction (FdO2) of the gas flow.

[0082] The method of the fourth embodiment may include any one or more of the features of the breathing apparatus of the first and / or second embodiments described above, and / or any one or more of the features of the breathing system of the third embodiment described above.

[0083] In a fifth embodiment, a respiratory apparatus for providing a flow of gas to a patient comprises: a supplemental gas inlet valve configured to receive oxygen from an oxygen supply; a flow generator operatively connected to the supplemental gas inlet valve and configured to generate the flow of gas; a user interface comprising a display; and a controller configured to control delivery of the flow of gas to the patient using closed-loop control, wherein the controller is configured to: determine a patient type based on one or more input or estimated or measured parameters of or associated with the patient; determine a patient-specific model based at least in part on the determined patient type; and initiate closed-loop control of the oxygen concentration of the flow of gas using the confirmed patient-specific model.

[0084] The breathing apparatus of the fifth embodiment may include any one or more of the features of the breathing apparatus of the first and / or second embodiments described above, and / or any one or more of the features of the breathing system of the third embodiment described above.

[0085] In some configurations of the fifth embodiment, the controller is further configured to display on the display a request to confirm the determined patient-specific model, and receive user input related to the request.

[0086] In some configurations of the fifth embodiment, the controller is further configured to initiate closed-loop control of the oxygen concentration of the gas flow using the confirmed patient-specific model based on received user input indicating confirmation of the patient-specific model.

[0087] In some configurations of the fifth embodiment, the patient-specific model is used to predict changes in the patient's oxygen saturation (SpO2) in response to changes in a measured delivered oxygen fraction (FdO2) of the gas flow.

[0088] In some configurations of the fifth embodiment, the respiratory apparatus further includes a gas composition sensor configured to determine at least a delivered oxygen fraction (FdO2) of the gas flow during operation of the respiratory apparatus.

[0089] In some configurations of the fifth embodiment, the controller is further configured to receive data indicative of a measured delivered oxygen fraction (FdO2) of the gas flow from the gas composition sensor.

[0090] In some configurations of the fifth embodiment, the controller is further configured to receive patient parameter data indicative of an oxygen saturation (SpO2) of the patient from the at least one sensor.

[0091] In some configurations of the fifth embodiment, closed-loop control of the oxygen concentration of the gas flow using the confirmed patient-specific model includes adjusting the supplemental gas inlet valve based on received patient parameter data indicative of the patient's oxygen saturation (SpO2) and changes in the patient's oxygen saturation (SpO2) as predicted by the patient-specific model.

[0092] In some configurations of the fifth embodiment, the patient type is determined to be one of: an adult patient or a pediatric patient.

[0093] In some configurations of the fifth embodiment, the child patient may be further identified as one of: an infant patient, or a neonatal patient, or a pediatric patient.

[0094] In some configurations of the fifth embodiment, the one or more input or estimated or measured parameters of or associated with the patient include the patient's head size.

[0095] In some configurations of the fifth embodiment, the patient's size is his or her height.

[0096] In some configurations of the fifth embodiment, the respiratory apparatus further includes a flow sensor.

[0097] In some configurations of the fifth embodiment, one or more input or estimated or measured parameters of or associated with the patient are estimated via the flow setting.

[0098] In some configurations of the fifth embodiment, the one or more input or estimated or measured parameters of or associated with the patient are a measured or estimated heart rate of the patient and / or a measured or estimated breathing rate of the patient.

[0099] In a sixth embodiment, a breathing system for providing a gas flow to a patient, the breathing system comprising: an oxygen supply source; a supplemental gas inlet valve, the supplemental gas inlet valve being configured to receive oxygen from the oxygen supply source; a flow generator, the flow generator being operatively connected to the supplemental gas inlet valve and being configured to generate a gas flow; a user interface, the user interface comprising a display; and a controller, the controller being configured to control delivery of the gas flow to the patient using closed-loop control, wherein the controller is configured to: determine a patient type based on one or more input or estimated or measured parameters of or associated with the patient; determine a patient-specific model, the patient-specific model being based at least in part on the determined patient type; and initiate closed-loop control of the oxygen concentration of the gas flow using the confirmed patient-specific model.

[0100] The breathing system of the sixth embodiment may include any one or more of the features of the breathing apparatus of the first and / or second and / or fifth embodiments described above, and / or any one or more of the features of the breathing system of the third embodiment described above.

[0101] In some configurations of the sixth embodiment, the system further includes a patient sensor configured to at least determine an oxygen saturation (SpO2) of the patient.

[0102] In some configurations of the sixth embodiment, the controller is further configured to receive patient parameter data indicative of an oxygen saturation (SpO2) of the patient from the patient sensor.

[0103] Features from one or more embodiments or configurations may be combined with features from one or more other embodiments or configurations. In addition, more than one embodiment may be used together during a patient's respiratory support procedure.

[0104] As used in this specification, the term "comprising" means "consisting at least in part of..." When interpreting each statement in this specification that includes the term "comprising", there may also be features other than the one or those features following the term. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

[0105] Reference to a numerical range disclosed herein (e.g., 1 to 10) is intended to also include reference to all rational numbers within that range (e.g., 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10), as well as any range of rational numbers within that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7), and thus, all subranges of all ranges explicitly disclosed herein are hereby expressly disclosed. These are merely examples of what is specifically intended to be disclosed, and all possible combinations of numerical values ​​between the lowest and highest values ​​enumerated should be considered to be expressly stated in this application in a similar manner.

[0106] It should be understood that alternative embodiments or configurations may include any or all combinations of two or more of the parts, elements or features illustrated, described or mentioned in this specification.

[0107] The present invention may also be broadly said to lie in the parts, elements and features referred to or indicated in the specification of the present application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features.

[0108] For those skilled in the art to which the invention relates, many changes in construction and widely different embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosure and description herein are entirely illustrative and are not intended to be limiting in any sense. Where reference is made herein to specific integers having known equivalents in the art to which the invention relates, such known equivalents are deemed to be incorporated herein as well, as if set forth individually. BRIEF DESCRIPTION OF THE DRAWINGS

[0109] Figure 1A A flow therapy device is shown in diagrammatic form.

[0110] Figure 1B A sensing circuit board is illustrated that includes a flow sensor that may be used in a flow therapy device.

[0111] Figure 1C to Figure 1D Schematic diagrams of various ultrasonic transducer configurations for a sensor system using a cross-flow beam are illustrated.

[0112] Figure 1E to Figure 1F Schematic diagrams of various ultrasonic transducer configurations for a sensor system using a downstream beam are illustrated.

[0113] Figure 1G A respiratory apparatus with a flow generator for providing bubble CPAP is schematically illustrated.

[0114] Figure 2 Graphs are illustrated which show various stages of operation of a flow therapy device.

[0115] Figure 3 Graphs showing fitted trend lines for the patient models are illustrated.

[0116] Figure 4 A graph showing iterations of a trend line for a patient model is illustrated.

[0117] Figure 5 A graph showing the signal hysteresis between the predicted SpO2 value and the actual SpO2 value is illustrated.

[0118] Figure 6 A Smith Predictor is illustrated utilized with a PID controller.

[0119] Figure 7 A graph of predicted SpO2 values ​​with delay time is illustrated.

[0120] Figure 8 Graphs showing the output of different calculation models for a PID controller are illustrated.

[0121] Fig.9A A flow chart illustrating a process of a method for controlling operation of a flow therapy device during a flow therapy session.

[0122] Fig. 9B A flow chart illustrating the sub-process for the learning phase of a flow therapy session.

[0123] Fig. 9C A flow chart illustrating the sub-processes for the control phase of a flow therapy session.

[0124] Fig.10 It is a schematic diagram of a closed-loop control system.

[0125] Fig.11 The process used to calculate a patient's oxygen efficiency is illustrated.

[0126] Fig.12 Graphs are illustrated which show various stages of operation of a flow therapy device.

[0127] Fig.13A A flow chart illustrating a process of a method for controlling operation of a flow therapy device during a flow therapy session.

[0128] Fig. 13B A flow chart of the sub-processes for the setup phase of a flow therapy session is illustrated.

[0129] Fig. 13C A flow chart illustrating the sub-processes for the control phase of a flow therapy session.

[0130] Fig.14 is a first bottom perspective view of the main housing of the flow therapy device showing the recess for the motor and / or sensor module subassembly located inside the housing.

[0131] Fig.15 is a second bottom perspective view of the main housing of the flow therapy device showing the recess for the motor and / or sensor module subassembly.

[0132] Fig.16 is a perspective view of the motor and / or sensor subassembly, the underside of the main housing, and the fixed elbow of a flow therapy device.

[0133] Fig.17 is an exploded perspective view of components of a motor and / or sensor subassembly schematically illustrating the gas flow path through the subassembly by arrows.

[0134] Fig.18 is a bottom side view of the cover and sensing PCB of the motor and / or sensor subassembly, showing the location of the sensors.

[0135] Fig.19 is a rear perspective view of the flow therapy device cut away adjacent the rear edge of the device illustrating the arrangement of a portion of the main housing providing a recess for receiving a motor and / or sensor subassembly.

[0136] Fig. 20 is a left front perspective view of a flow therapy device.

[0137] Fig.21 is a left front perspective view of a flow therapy device.

[0138] Fig. 22 is a left front perspective partial cross-sectional view showing the valve module and the filter module.

[0139] Fig.23 is a schematic gas flow path diagram of the filter module and the valve module, wherein the solid arrows represent the flow of oxygen (or another gas) and the dashed arrows represent the flow of ambient air.

[0140] Fig.24 is a cross-sectional view showing the gas flow path through the filter module and the valve module.

[0141] Fig.25 is a rear top perspective view of a valve module in a first configuration.

[0142] Fig.26 is a rear top perspective view illustrating the gas flow paths through the valve module in a first configuration, with solid arrows representing oxygen (or another gas) flow and dashed arrows representing ambient air flow.

[0143] Fig. 27 is a cross-sectional view of a valve module of a first configuration.

[0144] Fig.28 is a cross-sectional view showing the coupling of the valves of the valve module and the valve manifold of the first configuration and the gas flow path therethrough.

[0145] Fig.29 is a flow chart illustrating an exemplary tuning method according to a configuration. DETAILED DESCRIPTION

[0146] Patients with various health conditions and diseases can benefit from oxygen therapy. For example, patients with chronic obstructive pulmonary disease (COPD), pneumonia, asthma, bronchopulmonary dysplasia, heart failure, cystic fibrosis, sleep apnea, lung disease, respiratory trauma, acute respiratory distress receive preoperative and postoperative oxygen delivery, and other conditions or diseases can benefit from oxygen therapy. A common way to solve such problems is to prevent their blood oxygen saturation (SpO2) from falling too low (e.g., below about 90%) by supplying supplemental oxygen to the patient. However, supplying too much oxygen to the patient will overoxygenate his blood and is also considered dangerous. In general, the patient's SpO2 is maintained in the range of about 80% to about 99%, preferably about 92% to about 96%, although these ranges may vary due to the patient's condition. Due to various factors, such as respiratory rate, lung tidal volume, heart rate, activity level, height, weight, age, gender and other factors, there is no prescribed level of supplemental oxygen that can consistently achieve SpO2 response in a targeted range for each patient. Individual patients will periodically need to monitor and adjust their fraction of oxygen (FdO2) delivered to the patient to ensure they are receiving the correct FdO2 to achieve a target SpO2. Achieving a correct and consistent SpO2 is an important factor in treating patients with a variety of health conditions or diseases. Additionally, patients with these health issues can benefit from a system that automatically controls oxygen saturation.

[0147] The fraction of oxygen (FdO2) delivered to the patient can be manually controlled. The clinician can manually adjust the oxygen supply valve to change the flow or fraction of oxygen delivered to the patient. The clinician can use a patient monitor (e.g., a pulse oximeter) to determine the patient's SpO2 level. The clinician can continue to manually adjust the amount of oxygen delivered to the patient until the patient's SpO2 level reaches a determined level.

[0148] One problem with current methods is that when a clinician is trying to achieve a specific SpO2 level, they will need to change the FdO2, wait for the SpO2 reading to stabilize, and then apply further changes to the FdO2 until the SpO2 is at the desired level. The repetitive process of changing the FdO2 and waiting for the SpO2 to stabilize can be a very time-consuming process, especially if multiple patients require the same treatment.

[0149] Another problem is that some control algorithms may not properly account for the size of the patient. The control algorithm may be inappropriate because, due to the small size of newborns and children, their SpO2 levels will respond significantly faster than larger patients. This may be due in large part to the physically shorter distance that oxygenated blood has to travel to the patient's extremities (where the pulse oximetry monitoring site is typically located).

[0150] Another issue is the accuracy of SpO2 that can be achieved. The accuracy of SpO2 control can depend on how fine the increments are for the displayed SpO2 and the selectable FdO2. As the clinician may approach the ideal SpO2 and decide not to change the FdO2 further, the increasing amount of time required to obtain increasingly accurate values ​​can hinder accuracy.

[0151] Another problem is that other factors may cause a patient's SpO2 level to change over time without any change in FdO2. The patient will need to be checked regularly and their FdO2 adjusted in order to maintain their SpO2 at the correct value. This process can be quite time-consuming for the clinician. Furthermore, if the time between adjustments is too long, the patient is at risk of their SpO2 straying too far from the target level.

[0152] While there are some systems that attempt to do something similar, many of them suffer from further problems stemming from the difficulty of measuring a patient's oxygen saturation. The signals generated by pulse oximeters and similar devices lag far behind corresponding changes in the fraction of delivered oxygen. Furthermore, oxygen saturation readings can become inaccurate due to a variety of factors.

[0153] The present disclosure is applicable to a wide variety of patients requiring fast and accurate oxygen saturation control. The present disclosure addresses the issue of patient size by selectively using different functions to determine time-related parameters based on the patient's size, wherein the output of the time-related parameters will allow the controller to quickly respond to the patient's needs when they are input into the controller tuning process. The controller can be configured to apply a closed-loop SpO2 control algorithm that can dynamically determine appropriate time-related parameters based at least in part on the operating characteristics of the flow therapy device to determine FdO2 adjustments for larger patients (e.g., adults) and smaller patients (e.g., neonates and pediatrics).

[0154] The present disclosure provides a closed-loop control of a flow therapy device that allows a patient or clinician to set a target SpO2 instead of a target FdO2. The flow therapy device can automatically change the FdO2 of the flow therapy device to achieve the target SpO2 based on the values ​​of the target SpO2, the current SpO2, and the current FdO2. Automatically controlling FdO2 can help quickly and accurately adjust FdO2 until the target SpO2 is achieved. In some configurations, the system can generate a patient-specific model for each patient at the start of a treatment period. By adjusting FdO2 as needed to remain within the target SpO2 range rather than being constantly monitored by the clinician, the flow therapy device can have greater accuracy in achieving the target SpO2.

[0155] The present disclosure provides a flow therapy device that can implement one or more closed-loop control systems. The features of the closed-loop control system can be combined with the features of one or more configurations disclosed herein.

[0156] The flow therapy device can be operated in an automatic mode or a manual mode. In the automatic mode, the controller can automatically control the FdO2 based on the target FdO2 determined according to the target SpO2 and / or the measured SpO2. A valve at the oxygen inlet can be connected to the controller, which can control the oxygen concentration in the gas flow based on the target FdO2. The controller can execute a control algorithm that can measure the FdO2 output by the flow therapy device. The FdO2 measurement can be performed periodically at a defined frequency (for example, the maximum sampling rate of the gas concentration sensor or at a lower frequency), or it can be measured non-periodically. The controller can continue to adjust the valve at the oxygen inlet until the measured FdO2 reaches the target FdO2. The measured FdO2 can be determined by a gas composition sensor.

[0157] In manual mode, the controller may receive a target FdO2 from a clinician or patient, such as via a user interface. The controller may automatically control FdO2 based on the received target FdO2. The controller may control the oxygen concentration in the gas stream by controlling the oxygen inlet valve based on the target FdO2. The controller may execute a control algorithm that may use a measured FdO2 output by a flow therapy device (e.g., by a gas composition sensor of the flow therapy device) as an input to the controller. FdO2 measurements may be performed periodically at a defined frequency (e.g., the maximum sampling rate of the gas concentration sensor or at a lower frequency), or may be performed non-periodically. The controller may continue to adjust the valve at the oxygen inlet to drive the measured FdO2 toward the target FdO2. The measured FdO2 may be determined by the gas composition sensor.

[0158] The flow therapy device may be configured to change from automatic mode to manual mode when the patient's SpO2 is not within an acceptable patient range. In some cases, the flow therapy device reverts to manual mode when the patient's SpO2 is outside the patient limits (above or below the patient limits), or if the patient's SpO2 does not move within the limits within a defined time period after the treatment period begins. The flow therapy device may revert to manual mode when the signal quality of the patient sensor is below a threshold level within a defined time period. In some configurations, the flow therapy device may trigger an alarm when it switches from automatic mode to manual mode. In some configurations, the flow therapy device may trigger an alarm when the signal quality of the patient sensor is below a threshold level within a defined time period. After the alarm is triggered, the flow therapy device may continue to function in automatic mode. The flow therapy device may provide the user with the option of disabling the alarm or exiting automatic mode through a graphical user interface.

[0159] In automatic mode, the controller may utilize two control loops. The first control loop may determine the target FdO2 based on the target SpO2. The second control loop may use the target FdO2 output by the first control loop and the measured FdO2 to output the oxygen inlet valve control signal. In manual mode, the controller may use only the second control loop, which may receive the target FdO2 output from a user input or a default value.

[0160] During a high flow therapy period, when the flow rate of delivered gas meets or exceeds the patient's peak inspiratory demand, the oxygen concentration measured in the device (the delivered oxygen fraction (FdO2)) can be substantially the same as the oxygen concentration breathed by the user (the inspired oxygen fraction (FiO2)). This means that the volume of gas delivered to the patient by the device during inspiration meets or exceeds the volume of gas inhaled by the patient during inspiration. High flow therapy helps prevent the entrainment of ambient air as the patient exhales and washes out exhaled gases in the patient's airway. As long as the flow rate of delivered gas meets or exceeds the patient's peak inspiratory demand, entrainment of ambient air is prevented and the FdO2 of the gas delivered by the device is substantially the same as the FiO2 of the gas exhaled by the patient.

[0161] Flow therapy equipment

[0162] Figure 1A Flow therapy device 10 is shown in FIG. Device 10 may include a main housing 100 containing a flow generator 11 (e.g., a blower) in the form of a motor / impeller arrangement, an optional humidifier 12, a controller 13, and a user interface 14 (including, for example, a display and input devices, such as buttons, a touch screen, etc.). Controller 13 may be configured or programmed to control the operation of the device. For example, the controller may control components of the device, including, but not limited to: operating flow generator 11 to generate a gas flow (a flow of each gas) for delivery to a patient, operating humidifier 12 (if present) to humidify and / or heat the generated gas flow, controlling the flow of oxygen into the flow generator blower, receiving user input from user interface 14 to reconfigure and / or user-defined operations of device 10, and outputting information to the user (e.g., on a display). The user may be a patient, a healthcare professional, or any other person interested in using the device. As used herein, "gas flow" may refer to any gas flow that may be used in a respiratory assistance or breathing apparatus, such as an ambient air flow, a flow comprising substantially 100% oxygen, a flow comprising some combination of ambient air and oxygen, and / or the like.

[0163] The patient's breathing conduit 16 is connected to the gas flow outlet 21 in the housing 100 of the flow therapy device 10 at one end. The patient's breathing conduit 16 is connected to the patient interface 17 at the other end, such as an unsealed nasal cannula with a manifold 19 and a nasal plug 18. In addition or alternatively, the patient's breathing conduit 16 can be connected to an interface, a nasal mask, a nasal pillow mask, an endotracheal tube, a tracheostomy interface and / or the like. The gas flow generated by the flow therapy device 10 can be humidified and delivered to the patient through the cannula 17 via the patient's conduit 16. The patient's conduit 16 can have a heating wire 16a to heat the gas flow passing through the patient. The heating wire 16a can be controlled by the controller 13. The patient's conduit 16 and / or the patient's interface 17 can be considered as part of the flow therapy device 10, or alternatively on the periphery of the flow therapy device. The flow therapy device 10, the breathing conduit 16 and the patient's interface 17 can form a flow therapy system together.

[0164] The controller 13 can control the flow generator 11 to generate a gas flow of a desired flow rate. The controller 13 can also control the supplemental oxygen inlet to allow the delivery of supplemental oxygen, the humidifier 12 (if present) can humidify the gas flow and / or heat the gas flow to an appropriate level and / or the like. The gas flow is led out to the patient through the patient conduit 16 and the cannula 17. The controller 13 can also control the heating element in the humidifier 12 and / or the heating element 16a in the patient conduit 16 to heat the gas to a desired temperature to achieve the patient's desired treatment level and / or comfort level. The controller 13 can be programmed with a suitable target temperature for the gas flow or can determine a suitable target temperature for the gas flow.

[0165] The oxygen inlet port 28 may include a valve through which pressurized gas may enter the flow generator or blower. The valve may control the flow of oxygen into the flow generator blower. The valve may be any type of valve, including a proportional valve or a two-position valve. The oxygen source may be an oxygen tank or a hospital oxygen supply. Medical grade oxygen is typically between 95% and 100% pure. Lower purity oxygen sources may also be used. Examples of valve modules and filters are disclosed in U.S. Provisional Application No. 62 / 409,543, filed on October 18, 2016, entitled “Valve Modules and Filter,” and U.S. Provisional Application No. 62 / 488,841, filed on April 23, 2017, entitled “Valve Modules and Filter,” which are incorporated herein by reference in their entirety. The following description of valve modules and filters is provided herein. Figures 17 to 25 Let's discuss the valve modules and filters in further detail.

[0166] The flow therapy device 10 can measure and control the oxygen content of the gas delivered to the patient, and therefore measure and control the oxygen content of the gas inhaled by the patient. During high flow therapy, the high flow of the delivered gas meets or exceeds the patient's peak inspiratory demand. This means that the volume of gas delivered to the patient by the device during inspiration meets or exceeds the volume of gas inhaled by the patient during inspiration. Therefore, high flow therapy helps prevent the entrainment of ambient air and washes out the exhaled gas in the patient's airway when the patient exhales. As long as the flow rate of the delivered gas meets or exceeds the patient's peak inspiratory demand, the entrainment of ambient air is prevented, and the gas delivered by the device is substantially the same as the gas exhaled by the patient. Therefore, the oxygen concentration measured in the device (delivered oxygen fraction (FdO2)) will be substantially the same as the oxygen concentration breathed by the user (inspired oxygen fraction (FiO2)), and thus such terms can be considered equivalent.

[0167] Operational sensors 30, 31, 32 (such as flow sensors, temperature sensors, humidity sensors and / or pressure sensors) can be placed in various locations in the flow therapy device 10. Additional sensors (e.g., sensors 20, 25) can be placed in various locations on the patient conduit 16 and / or cannula 17 (e.g., a temperature sensor 29 can be present at or near the end of the inspiratory tube). The output from the sensors can be received by the controller 13 to assist the controller in operating the flow therapy device 10 in a manner that provides appropriate therapy. In some configurations, providing appropriate therapy includes meeting the patient's peak inspiratory needs. The device 10 can have a transmitter and / or receiver 15 to enable the controller 13 to receive signals 8 from the sensors and / or control various components of the flow therapy device 10, including but not limited to the flow generator 11, the humidifier 12 and the heating wire 16 or accessories or peripherals associated with the flow therapy device 10. In addition or alternatively, the transmitter and / or receiver 15 can transmit data to a remote server or enable remote control of the device 10.

[0168] After the oxygen and ambient air have been mixed, the oxygen can be measured by placing one or more gas composition sensors (e.g., ultrasonic transducer systems, also referred to as ultrasonic sensor systems). The measurement can be made within the device, delivery conduit, patient interface, or at any other suitable location.

[0169] The oxygen concentration may also be measured by using flow sensors on at least two of the ambient air inlet conduit, the oxygen inlet conduit, and the final delivery conduit to determine the flow of at least two gases. By determining the flow of two inlet gases or one inlet gas and a total flow along with an assumed or measured oxygen concentration of the inlet gas (about 20.9% for ambient air and about 100% for oxygen), the oxygen concentration of the final gas composition may be calculated. Alternatively, flow sensors may be placed at all three of the ambient air inlet conduit, the oxygen inlet conduit, and the final delivery conduit to allow for redundancy and to test that each sensor is operating correctly by checking the consistency of the readings. Other methods of measuring the oxygen concentration delivered by the flow therapy device 10 may also be used.

[0170] The flow therapy device 10 may include a patient sensor 26 (e.g., a pulse oximeter or patient monitoring system) to measure one or more physiological parameters of the patient (e.g., the patient's blood oxygen saturation (SpO2), heart rate, respiratory rate, perfusion index) and provide a measure of signal quality. The sensor 26 may communicate with the controller 13 via a wired connection or via communication via a wireless transmitter on the sensor 26. The sensor 26 may be a disposable adhesive sensor designed to be attached to the patient's finger. The sensor 26 may be a non-disposable sensor. Sensors designed for different age groups and to be attached to different locations on the patient are available and can be used with the flow therapy device. The pulse oximeter will be attached to the user (usually at their finger), although other locations (e.g., earlobe) are also an option. The pulse oximeter will be connected to a processor in the device and will continuously provide a signal indicating the patient's blood oxygen saturation. The patient sensor 26 may be a hot-swappable device that can be attached or interchanged during operation of the flow therapy device 10. For example, the patient sensor 26 may be attached using a USB interface or using a wireless communication protocol (such as, for example, near field communication, WiFi, or ) is connected to the flow therapy device 10. When the patient sensor 26 is disconnected during operation, the flow therapy device 10 can continue to operate in its previous operating state for a defined period of time. After the defined period of time, the flow therapy device 10 can trigger an alarm, transition from automatic mode to manual mode, and / or completely exit a control mode (e.g., automatic mode or manual mode). The patient sensor 26 can be a bedside monitoring system or other patient monitoring system that communicates with the flow therapy device 10 through a physical or wireless interface.

[0171] Flow treatment device 10 may include high flow treatment device. As used herein, "high flow" treatment refers to the application of gas to the patient's airway with a relatively high flow that meets or exceeds the patient's peak inspiratory demand. The flow rate for achieving "high flow" can be any one of the flows listed below. For example, in some configurations, for adult patients, "high flow treatment" may refer to gas being delivered to the patient with the following flow rate: greater than or equal to about 10 liters / minute (10 LPM), such as between about 10 LPM and about 100 LPM, or between about 15 LPM and about 95 LPM, or between about 20 LPM and about 90 LPM, or between about 25 LPM and 75 LPM, or between about 25 LPM and about 85 LPM, or between about 30 LPM and about 80 LPM, or between about 35 LPM and about 75 LPM, or between about 40 LPM and about 70 LPM, or between about 45 LPM and about 65 LPM, or between about 50 LPM and about 60 LPM. In some configurations, for a neonatal, infant, or pediatric patient, "high flow therapy" may refer to delivering gas to the patient at a flow rate greater than 1 LPM, such as between about 1 LPM and about 25 LPM, or between about 2 LPM and about 25 LPM, or between about 2 LPM and about 5 LPM, or between about 5 LPM and about 25 LPM, or between about 5 LPM and about 10 LPM, or between about 10 LPM and about 25 LPM, or between about 10 LPM and about 20 LPM, or between about 10 LPM and 15 LPM, or between about 20 LPM and 25 LPM. A high flow therapy device for an adult patient, a neonatal, an infant, or a pediatric patient may deliver gas to the patient at a flow rate between about 1 LPM and about 100 LPM, or at a flow rate in any of the sub-ranges outlined above. The flow therapy device 10 may deliver any concentration of oxygen (e.g., FdO2) up to 100% at any flow rate between about 1 LPM and about 100 LPM. In some configurations, any of these flow rates can be combined with oxygen concentrations (FdO2) of about 20%-30%, 21%-30%, 21%-40%, 30%-40%, 40%-50%, 50%-60%, 60%-70%, 70%-80%, 80%-90%, and 90%-100%. In some combinations, the flow rate can be between about 25 LPM and 75 LPM and combined with oxygen concentrations (FdO2) of about 20%-30%, 21%-30%, 21%-40%, 30%-40%, 40%-50%, 50%-60%, 60%-70%, 70%-80%, 80%-90%, and 90%-100%. In some configurations, the flow therapy device 10 may include safety thresholds when operating in manual mode that prevent the user from delivering too much oxygen to the patient.

[0172] High flow therapy can be applied to the user's nostrils and / or orally, or via a tracheostomy interface. High flow therapy can deliver gas to the user at a flow rate that is at or exceeds the peak inspiratory flow requirement of the expected user. High flow therapy can generate a flushing effect in the nasopharynx so that the anatomical dead space of the upper airway is flushed by the incoming high gas flow. This can produce a reserve of fresh gas available for each breath while minimizing the rebreathing of nitrogen and carbon dioxide. In addition, when trying to control the patient's FdO2, it is important to meet the inspiratory demand and flush the airway. High flow therapy can be delivered using an unsealed patient interface (such as, for example, a nasal cannula). The nasal cannula can be configured to deliver breathing gas to the user's nostrils at a flow rate that exceeds the peak inspiratory flow requirement of the expected user.

[0173] The term "unsealed patient interface" as used herein may refer to an interface that provides a pneumatic link between a patient's airway and a source of gas flow (e.g., from flow generator 11) that does not completely block the patient's airway. An unsealed pneumatic link may include less than about 95% blockage of the patient's airway. An unsealed pneumatic link may include less than about 90% blockage of the patient's airway. An unsealed pneumatic link may include between about 40% and about 80% blockage of the patient's airway. The airway may include one or more of the patient's nostrils or mouth. For a nasal cannula, the airway passes through the nostrils.

[0174] The flow generator or blower 11 may include an ambient air inlet port 27 to entrain ambient room air into the blower. The flow therapy device 10 may also include an oxygen inlet port 28 leading to a valve through which pressurized gas may enter the flow generator or blower 11. The valve may control the flow of oxygen into the flow generator blower 11. The valve may be any type of valve, including a proportional valve or a two-position valve.

[0175] The blower can be operated at a motor speed greater than about 1,000 RPM and less than about 30,000 RPM, greater than about 2,000 RPM and less than about 21,000 RPM, or any of the foregoing values. The operation of the blower can mix the gas entering the blower through the inlet port. Using a blower as a mixer can reduce the pressure drop that would otherwise occur in a system with a separate mixer (e.g., a static mixer including baffles) because mixing requires energy.

[0176] Additional references Figure 1B, shows a sensing circuit board 2200 that can be implemented in the flow therapy device 10. The sensing circuit board 2200 can be positioned in the sensor chamber so that the sensing circuit board 2200 is at least partially immersed in the gas flow. The gas flow can exit the blower 11 through a conduit and enter the flow path in the sensor chamber. At least some of the sensors on the sensing circuit board 2200 can be positioned in the gas flow to measure gas properties in the flow. After passing through the flow path in the sensor chamber, the gas can exit to the humidifier 12 described above.

[0177] The sensing circuit board 2200 may be a printed sensing circuit board (PCB). Alternatively, the circuit on the board 2200 may be constructed using wires connecting electronic components, rather than printing the circuit on the circuit board. At least a portion of the sensing circuit board 2200 may be mounted outside the gas flow. The gas flow may be generated by the flow generator 11 described above. The sensing circuit board 2200 may include an ultrasonic transducer 2204. The sensing circuit board 2200 may include one or more of thermistors 2205. Thermistors 2205 may be configured to measure the temperature of the gas flow. The sensing circuit board 2200 may include a thermistor flow sensor 2206. The sensing circuit board 2200 may include other types of sensors, such as a humidity sensor (including a humidity sensor only to be used with a separate temperature sensor, and a combined humidity sensor and temperature sensor), a sensor for measuring atmospheric pressure, a sensor for measuring differential pressure, and / or a sensor for measuring gauge pressure. The thermistor flow sensor 2206 may include a hot wire flow meter, such as a platinum wire and / or a thermistor (e.g., a negative temperature coefficient (NTC) thermistor, or a positive temperature coefficient (PTC) thermistor). Other non-limiting examples of heated temperature sensing elements include glass or epoxy encapsulated thermistors, or non-encapsulated thermistors. The thermistor flow sensor 2206 may be configured to measure the flow of a gas by supplying it with constant power, or maintaining it at a constant sensor temperature, or maintaining a constant temperature difference between the sensor and the gas flow.

[0178] The sensing circuit board 2200 may include a first portion 2201 and a second portion 2202. The first portion 2201 may be positioned within the flow path of the gas, and the second portion 2202 may be positioned outside the flow path of the gas. Figure 1B The direction of the gas flow can be straight or as shown in FIG. Figure 1B The one shown is curved.

[0179] Positioning one or more of thermistors 2205 and / or thermistor flow sensors 2206 downstream of the combined blower and mixer can take into account the heat supplied to the gas flow from the blower. Also, immersing the temperature-based flow sensor in the flow path can improve the accuracy of the measurement because the sensor immersed in the flow is more likely to be subject to the same conditions (e.g., temperature) as the gas flow and therefore provide a better representation of the gas properties.

[0180] The sensing circuit board 2200 may include an ultrasonic transducer, transceiver, or sensor of the sensing circuit board to measure gas properties of the gas flow, such as the gas composition or concentration of one or more gases within the gas flow. As will be appreciated, any suitable transducer, transceiver, or sensor may be mounted to the sensing circuit board 2200. In this configuration, the sensing circuit board includes an ultrasonic transducer system (also referred to as an ultrasonic sensor system) that uses ultrasonic or sound waves to determine gas concentration. Figure 1C to Figure 1F to describe various sensor configurations.

[0181] The ultrasonic transducer system can determine the relative gas concentrations of two or more gases in a gas stream. The ultrasonic transducer system can be configured to measure the oxygen fraction in a bulk gas stream consisting of atmospheric air enhanced with supplemental oxygen, the atmospheric air being essentially a binary gas mixture of nitrogen (N2) and oxygen (O2). It will also be appreciated that the ultrasonic transducer system can be configured to measure the gas concentrations of other enhanced gases (including nitrogen (N2) and carbon dioxide (CO2)) that have been blended with the atmospheric air in the gas stream. The ultrasonic transducer can determine the gas concentrations of gases in the gas stream at relatively high frequencies. For example, the ultrasonic transducer can output the measured FdO2 value at the maximum sampling rate of the sensor or at a frequency lower than the maximum sampling rate, such as between about 1 Hz and 200 Hz, between about 1 Hz and 100 Hz, between about 1 Hz and 50 Hz, and between about 1 Hz and 25 Hz.

[0182] In some configurations, the sensing circuit board 2200 includes a pair of ultrasonic transducers provided on opposite sides of the sensing circuit board. Various alternative configurations of ultrasonic transducers may be used to sense characteristics of airflow by transmitting and receiving ultrasonic beams or pulses.

[0183] The distance between the ultrasonic transducers 2204 on opposite ends of the sensing circuit board 2200 can affect the measurement resolution. The increased distance between each of the ultrasonic transducers 2204 can reduce proportional or fractional errors because the measured length will have a certain amount of error overall, and if the length is increased, the error ratio generated during the measurement is less than the error ratio for a shorter length. Therefore, the overall uncertainty of the measurement is reduced. The increase in distance can also improve the measurement resolution and accuracy because it allows a longer period of time for the acoustic signal between the ultrasonic transducers 2204. However, the increase in distance will result in a weaker signal.

[0184] The ultrasonic transducers 2204 can be positioned so that the space between the ultrasonic transducers 2204 at least partially coincides with the flow path. In some configurations, the ultrasonic transducers are positioned on opposite ends of the sensing circuit board. Because the entire face of the flow path is exposed to the acoustic path, the sound waves propagate through all the gas in the flow path. Averaging of the waves can occur over the entire flow path rather than a segment of the flow path. Averaging over a longer distance reduces errors and reduces dependence on air-oxygen mixing. The ultrasonic transducers can be configured to measure gas properties from any angle relative to the flow path.

[0185] Instead of being positioned outside of the flow path or module, positioning the sensors in the flow path or module allows the transducers 2204 to both operate within a smaller temperature range relative to each other or both operate at substantially one temperature (i.e., the temperature of the gas flow). Since the transducers are sensitive to temperature, having them at a substantially uniform temperature improves accuracy. Further, positioning the sensors along the flow path allows for measurements and calculations that take into account the effects of gas velocity, such that the effects of gas velocity can be removed from the sensor measurements.

[0186] The ultrasonic transducer system is configured as an ultrasonic binary gas sensing system. Binary gas analysis using ultrasound is based on sensing the speed of acoustic pulses passing through a gas sample, in this case, the gas sample is a bulk or main stream of a gas stream flowing through a sensing channel of a sensor housing. The speed of sound is a function of the average molecular weight of the gas and the temperature. The system can receive a sensor signal indicating the temperature of the gas flowing between the beam paths between the ultrasonic transducers. Knowing the sensed speed of sound and the sensed temperature, the gas composition in the gas stream can be determined or calculated. In particular, the measurement of the speed of sound across the sensing channel can be used to derive the ratio of two known gases by reference to empirical relationships, standard algorithms, or data stored in the form of a lookup table, as known in the field of binary gas analysis using ultrasound. It will be appreciated that, alternatively, if a temperature sensor is not employed, an estimate of the temperature of the gas stream in the beam path of the ultrasonic transducer can be used in the calculation of the binary gas analysis. In such alternative embodiments, the temperature of the gas stream can be regulated or controlled to be placed within a narrow temperature band so that an estimate of the temperature of the gas stream in the beam path can be used.

[0187] In some configurations, the flow therapy device may also be provided with a humidity sensor located in the flow path and configured to generate a humidity signal indicative of the humidity of the gas flow passing through the sensor assembly. In such embodiments, the gas composition may be determined by the sensed velocity of sound and the sensed temperature and / or the sensed humidity. The humidity sensor may be a relative humidity sensor or an absolute humidity sensor. In some embodiments, the gas composition may be determined based on the sensed velocity of sound and the sensed humidity without a temperature sensor.

[0188] Ultrasonic transducer systems can be used to measure the relative ratio of any two known gases in a gas composition. Ultrasonic transducer systems can determine the relative gas concentrations in a mixture of air blended with supplemental oxygen, which is essentially equivalent to a nitrogen / oxygen mixture. In such a binary gas mixture, by monitoring the speed of sound and taking the temperature into account, the average molecular weight of the gas can be determined, and therefore the relative concentrations of the two gases can be determined. From this ratio, the oxygen fraction or nitrogen fraction of the gas stream can be inferred.

[0189] refer to Figure 1C to Figure 1F , various configurations of ultrasonic transducers for sensing the speed of sound through a gas flow by transmitting and receiving ultrasonic beams or pulses will be described with respect to a gas composition sensing system. Like reference numerals represent like components.

[0190] refer to Figure 1C, transducer configuration 2300 provides an arrangement in which there is a pair of transducers 2302, 2304, which are opposite to each other and positioned on opposite sides of a sensing channel 2306, wherein the gas flow path direction is generally indicated by 2308. In this configuration, each of the transducers 2302, 2304 is driven as a dedicated transmitter or receiver, so that ultrasonic pulses 2310 are transmitted unidirectionally across the gas flow path from the transmitter to the receiver transducer. As shown, the transducer pair is aligned relative to the air flow path direction 2308 (i.e., not shifted upstream or downstream of each other), and is configured to transmit cross-flow pulses substantially perpendicular to the gas flow path direction.

[0191] refer to Figure 1D , illustrates an alternative transducer configuration 2320 in which a pair of transducers 2322, 2324 are provided on opposite sides of a sensing channel relative to one another, but in which each transducer is operable as both a transmitter and a receiver (i.e., the transducers are ultrasonic transmitter-receivers or transceivers). In this configuration, bidirectional ultrasonic pulses 2326 may be sent between the transducer pair 2322, 2324. For example, the pulses may be sent alternating back and forth between the transducers or in any other sequence or pattern. Again, the transducer pair is aligned relative to the gas flow path direction and is configured to transmit cross-flow pulses substantially perpendicular to the gas flow path direction.

[0192] refer to Figure 1E , an alternative transducer configuration 2360 is illustrated in which there is a pair of transducers 2362, 2364 from opposite ends of a sensing channel 2306 and facing each other, with the gas flow path direction or axis generally indicated by 2308. In this configuration 2360, each of the transducers 2362, 2364 is driven as either a dedicated transmitter or receiver so that downstream ultrasonic pulses 2366 are transmitted unidirectionally in a beam path between the transmitter and the receiver that is substantially aligned with or parallel to the gas flow path axis 2308 in the sensing channel 2306. In the illustrated embodiment, the transmitter is upstream of the receiver, but it will be appreciated that the reverse arrangement may be employed. With this configuration, a flow sensor is provided in the sensing channel to provide a flow signal that is indicative of the flow rate of the gas flow in the sensing channel. It will be appreciated that the velocity of sound in the sensing channel may be derived or determined in a manner similar to that previously described, and the flow signal utilized in signal processing to remove or compensate for the gas flow in the calculated velocity of the acoustic signal.

[0193] refer to Figure 1F , illustrates an alternative transducer configuration 2370, wherein and Figure 1EAs in the embodiment of the present invention, a pair of transducers 2372, 2374 are provided from opposite ends of the sensing channel and opposite to each other, but wherein each transducer is operable as both a transmitter and a receiver (i.e., the transducers are ultrasonic transmitter-receivers or transceivers). In this configuration, bidirectional downstream ultrasonic pulses 2376 may be transmitted between the transducer pair 2372, 2374. For example, the pulses may be transmitted alternately back and forth between the transducers or in any other sequence or pattern. Again, the transducers are aligned with the gas flow path axis 2308 and are configured to transmit downstream pulses in one or more beam paths that are substantially aligned with or parallel to the gas flow path axis 2308 in the sensing channel 2306. With this configuration, it is not necessary to provide a separate flow sensor because the flow component of the velocity of the acoustic signal can be directly derived or determined from processing of the transmitted and received acoustic pulses.

[0194] Some examples of flow therapy devices are disclosed in International Application No. PCT / NZ 2016 / 050193, filed on December 2, 2016, entitled “Flow Path Sensing for Flow Therapy Apparatus” and International Application No. PCT / IB 2016 / 053761, filed on June 24, 2016, entitled “Breathing Assistance Apparatus”, which are incorporated herein by reference in their entirety. Figures 11 to 16 Examples of configurations of flow therapy devices that may be used with aspects of the present disclosure are discussed in further detail.

[0195] Control System

[0196] Reference again Figure 1A , the controller 13 can be programmed with or configured to execute a closed-loop control system for controlling the operation of the flow therapy device. The closed-loop control system can be configured to ensure that the patient's SpO2 reaches a target level and consistently remains at or near that level.

[0197] The controller 13 may receive input from the user that may be used by the controller 13 to execute a closed-loop control system. The target SpO2 value may be a single value or a range of values. The value may be preset, selected by a clinician, or determined based on a patient type, where the patient type may refer to a current ailment and / or information about the patient (e.g., age, weight, height, gender, and other patient characteristics). Similarly, the target SpO2 may be two values, each selected in any manner described above. These two values ​​will represent a range of acceptable values ​​for the patient's SpO2. The controller may target a value within the range. The target value may be the middle value of the range or any other value within the range, which may be preset or selected by the user. Alternatively, the range may be automatically set based on the target value of SpO2. The controller may be configured to have one or more set responses when the patient's SpO2 value moves outside the range. The response may include issuing an alarm, changing to manual control of FdO2, changing FdO2 to a specific value, and / or other responses. A controller may have one or more ranges, wherein when the controller is moved outside of each range, one or more different responses occur.

[0198] The graphical user interface of the flow therapy device can be configured to prompt the user to enter the patient type, and the SpO2 limits will be determined based on the content selected by the user. In addition, the user interface can include a customization option, wherein the user can define these limits.

[0199] In general, SpO2 will be controlled between about 80% and about 100%, or between about 80% and about 90%, or between about 88% and about 92%, or between about 90% and about 99%, or between about 92% and about 96%. SpO2 may be controlled between any two suitable values ​​from any two of the above ranges. The target SpO2 may be between about 80% and about 100%, or between about 80% and about 90%, or between about 88% and about 92%, or between about 90% and about 99%, or between about 92% and about 96%, or about 94%, or 94%, or about 90%, or 90%, or about 85%, or 85%. The SpO2 target may be any value between any two suitable values ​​from any two of the above ranges. For a defined range, the SpO2 target may correspond to the middle of the SpO2.

[0200] FdO2 can be configured to be controlled within a certain range. As previously discussed, as long as the flow rate meets or exceeds the patient's peak inspiratory demand, the oxygen concentration measured in the device (FdO2) will be substantially the same as the oxygen concentration (FiO2) breathed by the patient, and thus such terms can be considered equivalent. Each of the range limits can be preset, selected by the user, or determined based on a patient type, where the patient type can refer to the current ailment and / or information about the patient (e.g., age, weight, height, gender, and / or other patient characteristics). Alternatively, a single value of FdO2 can be selected, and the range can be determined at least in part based on the value. For example, the range can be above and below the selected FdO2 by a set amount. The selected FdO2 can be used as a starting point for the controller. If the controller attempts to move FdO2 outside the range, the system can have one or more responses. These responses can include sounding an alarm, preventing FdO2 from moving outside the range, switching to manual control of FdO2, and / or switching to a specific FdO2. A device may have one or more ranges, where when the device reaches the limits of each range, one or more different responses occur.

[0201] FdO2 can be controlled between about 21% and about 100%, or between about 21% and about 90%, or between about 21% and about 80%, or between about 21% and about 70%, or between about 21% and about 60%, or between about 21% and about 50%, or between about 25% and about 45%. FdO2 can be controlled between any two suitable values ​​from any two ranges described. The FdO2 target can be between any two suitable values ​​from any two ranges described. If the range is based on a single value, the upper and lower limits can be determined by adding / subtracting a fixed amount from the selected value. The amount added or subtracted can be about 1%, or about 5%, or 10%, or about 15%, or about 20%, or about 30%, or about 50%, or about 100%. The amount added / subtracted can be changed relative to the selected value. For example, the upper limit may be 20% higher than the selected value, so for the range of control, a selected value of 50% FdO2 will have an upper limit of 60%. The percentage used for the range may be about 1%, or about 5%, or 10%, or about 15%, or about 20%, or about 30%, or about 50%, or about 100%. The method used to calculate the lower and upper limits will not necessarily need to be the same. If a single value is used, the value may be between about 21% and about 100%, or between about 25% and about 90%, or between about 25% and about 80%, or between about 25% and about 70%, or between about 25% and about 60%, or between about 25% and about 50%, or between about 25% and about 45%.

[0202] A graphical user interface (GUI) 14 may be configured to display the range of values ​​that FdO2 and / or SpO2 are controlled within. The range may be displayed by having two limits set apart from each other on the GUI, with an indicator appearing within the range to graphically represent the position of the current value relative to the range limits.

[0203] The GUI may display a graph of the most recent FdO2 and / or SpO2 data. The GUI may display the level of each parameter on the same or different graphs over a defined time period (e.g., one or more hours). The length of time the data is displayed may match the length of time the data has been currently available.

[0204] The displayed FdO2 data may be at least one of a target FdO2 or a measured FdO2. The SpO2 data may include a line indicating a target SpO2. Additionally or alternatively, the SpO2 and / or FdO2 data may include one or more lines or one or more shaded areas indicating their respective control limits.

[0205] The graph may be displayed on a default display. Alternatively, the graph may be hidden, showing only the current data values. The graph may become available through interaction with the GUI (e.g., by selecting to view the graph for a defined parameter).

[0206] Bubble CPAP

[0207] Bubble CPAP therapy is another form of respiratory therapy that can be provided to newborns experiencing respiratory distress. Bubble CPAP therapy can cause variations or oscillations in the pressure of gas supplied to a patient connected to a positive pressure ventilation device. By immersing one end of the expiratory tubing in a column of water, the resulting bubbles cause variations or fluctuations in the pressure of the gas delivered to the patient. The Bubble CPAP system also provides a method for varying the mean pressure of the gas supplied to the patient by varying the level of liquid in the water column in which the end of the expiratory tubing is immersed. The immersion level of the end of the expiratory tubing can be kept constant in order to maintain the mean pressure of the gas supplied to the patient.

[0208] Figure 1G A breathing system for providing bubble CPAP therapy is shown that can provide humidified and pressurized gas to a patient 119 through a patient interface such as Figure 1G The hood 128 is connected to the inhalation conduit 121 in the device housing 114. The inhalation conduit 121 is connected to the outlet 112 of the humidification chamber 110 containing a volume of water 115. When the volume of water 115 in the humidification chamber 110 is heated by the heating plate 113 in the device housing 114, water vapor begins to fill the volume of the chamber 110 above the surface of the water. The water vapor can heat and humidify the air from the blower 118 (see Figure 1G) is provided to the chamber 110 through the inlet 116 of the chamber 110. The heated and humidified gas is passed from the outlet 112 of the humidification chamber 110 to the inhalation conduit 121. The inhalation conduit 121 may contain a heater, such as Figure 1G The heating wire 120 in the inhalation conduit 121 heats the wall of the conduit to promote a substantially constant humidity profile along the inhalation conduit 121 and thereby reduce condensation of humidified gas within the inhalation conduit 121. The device can be powered to heat the inhalation conduit 121 and the heating plate 113, such as by input from one or more sensors in the system.

[0209] The humidified gas can be delivered through the inspiratory conduit 121 to a patient interface, such as a mask 128, attached and / or sealed around the mouth, nose, and / or nostrils of the patient 119. The inspiratory conduit 121 provides a flow of gas to the patient 119, which can be ambient air, oxygen, a mixture of the two, or a mixture of ambient air and other auxiliary gases. The gas can include medications that can be added via aerosolization. In bubble CPAP, the gas flow through the inspiratory conduit 121 can be delivered at a substantially constant flow rate.

[0210] Excess gas can flow through the expiratory conduit 130 to a pressure regulator 134, which in the illustrated example is a bubbler. In a bubble CPAP system, the expiratory conduit 130 can terminate in an open terminal end 136. The terminal end 136 can be immersed in a volume of water 138 inside the bubbler 134.

[0211] The bubbler can regulate pressure through a terminal end 136 of the expiratory tube 130, which is submerged in a volume of water 138 at a desired depth below the water level 140. The terminal end 136 can also optionally be located on a short tube that can be integrated into the end of the expiratory tube 130. Whenever the pressure exceeds the desired level, the bubbler can act as a pressure regulator by exhausting gas to maintain the average or mean pressure at a target level. The bubble CPAP system can also include a pressure relief valve 146 for exhausting excess gas when the pressure exceeds the desired level. The bubbler can also provide pressure oscillations, which may have clinical benefits. Compared to intubation and / or mechanical ventilation, bubble CPAP therapy can reduce the incidence of acute lung injury and bronchopulmonary dysplasia.

[0212] Figure 1G The breathing system in can have a gas flow provided by a blower 118 integrated into the device housing 114. Figure 1GThe system in may also optionally include a supplemental gas source (such as an oxygen storage tank, an oxygen blender connected to a flow meter, etc.) for controlling the oxygen concentration in the airflow delivered to the patient 119. The supplemental gas source may be connected to the device housing 114 and / or the blower 118 (e.g., at the supplemental gas inlet). The supplemental gas flow provided to the device may be electronically controlled by the device at the supplemental gas inlet. For example, as described in the aforementioned disclosure of the flow therapy device. The supplemental gas source may also be configured to provide other types of auxiliary gases, such as nitrogen. The supplemental gas source may be connected to an internal blender that blends ambient air with the supplemental gas to provide the gas flow to the patient. The concentration of the supplemental gas introduced into or present in the airflow may be controlled. The system may include a temperature sensor 144 in the inspiratory conduit 121. The temperature sensor 144 may be connected to a controller located in the device housing 114, 117 and electrically communicate with the controller.

[0213] The breathing device may be switchable between a high flow therapy mode and a bubble CPAP therapy mode.

[0214] In high flow therapy mode, the breathing device is configured to provide high flow therapy.

[0215] In the Bubble CPAP therapy mode, the breathing apparatus is configured to provide Bubble CPAP therapy.

[0216] High flow therapy is a nasal high flow therapy.

[0217] In high flow therapy mode, the system includes an unsealed patient interface coupled to the inspiratory catheter 121 .

[0218] The unsealed patient interface may be a nasal cannula.

[0219] In use, the nasal cannula is positioned on the face of a user to provide gas to the user's nostrils.

[0220] In the bubble CPAP therapy mode, the system includes a sealed patient interface coupled to the inspiratory conduit 121 , and an expiratory conduit 130 coupled to the sealed patient interface.

[0221] Expiratory conduit 130 is coupled to a pressure regulator to regulate pressure within the patient interface and / or the patient's airway.

[0222] As described in more detail above, the pressure regulator includes a chamber having a water column, and the expiratory tube 130 is immersed in the water column. The pressure provided to the user is defined or set by the depth to which the expiratory tube 130 is immersed in the water column.

[0223] The inspiratory conduit 121 may be common between the high flow therapy mode and the bubble CPAP therapy mode.

[0224] The fact that the same suction catheter can be used for both modes reduces the number of parts that need to be interchanged when changing modes.

[0225] In addition, such a common inspiratory conduit allows the same respiratory device including a blower and humidifier integrated into the housing to be used for both the bubble CPAP mode and the high flow mode. In addition, integrating the humidifier and blower into a common housing makes transitioning between the bubble CPAP mode and the high flow mode simple because a single device can be used rather than a unique arrangement of several components as required in prior art systems.

[0226] The present system provides a single breathing apparatus that can be used to deliver both bubble CPAP therapy and high flow therapy, with only the interface requiring change. There is no change in components on the gas supply side (i.e., no change in gas supply components), because a common breathing apparatus can be used to deliver humidified gas.

[0227] The controller 13 may include a high flow therapy control program associated with the high flow therapy mode.

[0228] Controller 13 may include a bubble CPAP therapy control program associated with the bubble CPAP therapy mode.

[0229] In some embodiments, the high flow therapy mode may have a high flow therapy controller. Optionally, the high flow therapy controller may be configured to run a high flow therapy control program.

[0230] In some embodiments, the Bubble CPAP therapy mode may have a Bubble CPAP therapy controller. Optionally, the Bubble CPAP therapy controller may be configured to run a Bubble CPAP therapy control program.

[0231] The controller 13 is configured to select and apply a program corresponding to the selected operating mode.

[0232] Each of the high flow therapy control program and the bubble CPAP therapy control program defines corresponding operating parameters.

[0233] In some configurations, the operating parameters may include one or more motor speed or pressure limits (eg, upper pressure limits), as described in more detail below.

[0234] Closed-loop control

[0235] refer to Fig.10, illustrates a schematic diagram of a closed-loop control system 1000. The closed-loop control system may utilize two control loops. The first control loop may be implemented by an SpO2 controller. The SpO2 controller may determine a target FdO2 based in part on a target SpO2 and / or a measured SpO2. As discussed above, the target SpO2 value may be a single value or a range of acceptable values. The value may be preset, selected by a clinician, or automatically determined based on customer characteristics. In general, the target SpO2 value is received or determined before or at the beginning of a treatment period, but the target SpO2 value may be received at any time during the treatment period. During the treatment period, the SpO2 controller may also receive as input: a measured FdO2 reading from a gas composition sensor, and a measured SpO2 reading and a signal quality reading from a patient sensor. In some configurations, the SpO2 controller may receive a target FdO2 as an input, in which case the output of the SpO2 controller may be provided directly back to the SpO2 controller as an input. Based at least in part on these inputs, the SpO2 controller may output a target FdO2 to a second control loop.

[0236] The second control loop can be implemented by an FdO2 controller. The FdO2 controller can receive inputs of measured FdO2 and target FdO2. Then, the FdO2 controller can output an oxygen inlet valve control signal to control the operation of the oxygen valve based on the difference between these measured FdO2 and the target FdO2 value. When the flow therapy device is operated in automatic mode, the FdO2 controller can receive the target FdO2 value output from the first control loop. The FdO2 controller can also receive additional parameters, such as flow value or flow data, gas properties and / or measured FdO2. The gas properties can include the temperature of the gas at the O2 inlet and / or the oxygen content of the supply source. The gas supply source connected to the oxygen inlet valve can be an oxygen-enriched gas flow, wherein the oxygen content of the supply source can be less than pure oxygen (i.e., 100%). For example, the oxygen supply source can be an oxygen-enriched gas flow with an oxygen content less than 100% and greater than 21%.

[0237] In examples where the controller receives as input one or more of patient parameter data indicating the patient's oxygen saturation (SpO2) and flow data of a gas flow during treatment provided to the patient, the input is related to current operation of the respiratory therapy device. In some other examples, the controller may receive as input one or more of patient parameter data indicating the patient's oxygen saturation (SpO2) and flow data of a gas flow, wherein the one or more inputs are related to one or more previous operating states or treatment sessions of the respiratory therapy device.

[0238] The FdO2 controller can determine the oxygen flow rate required to achieve the target FdO2 from at least some of these inputs. The FdO2 controller can use the flow input to change the valve control signal. If the flow changes, the FdO2 controller can automatically calculate the new required oxygen flow rate required to maintain the target FdO2 at the new flow rate without having to wait for feedback from the gas concentration sensor (e.g., the measured FdO2 value). The FdO2 controller can then output the modified valve control signal to control the valve based on the new flow rate. In some configurations, the control signal of the FdO2 controller can set the current of the oxygen valve to control the operation of the oxygen valve. In addition or alternatively, the FdO2 controller can detect changes to the measured FdO2 and change the position of the valve accordingly. During manual mode, the second control loop can operate independently without receiving the target FdO2 from the first control loop. Instead, the target FdO2 can be received from a user input or a default value.

[0239] During the therapy session, the SpO2 controller and the FdO2 controller may continue to automatically control the operation of the flow therapy device until the therapy session ends or an event triggers a change from automatic mode to manual mode.

[0240] Closed-loop control using patient models

[0241] Figure 2Graphs 200 of SpO2 and FdO2 are provided, which illustrate the various operating stages of the flow therapy device during the treatment period. Although FdO2 (delivered oxygen fraction) is used in these graphs, as discussed earlier, FdO2 is substantially the same as FiO2 as long as the flow meets or exceeds the patient's peak inspiratory demand. Each operating stage includes a learning stage 210 and a control stage 220. During the learning stage, the controller generates a patient-specific model. Due to differences between individual patients, the way each patient's SpO2 responds to changes in FdO2 will vary. As a result, a patient-specific model can be generated to provide better control of the patient's SpO2. The learning stage 210 (also referred to as the model building stage) can include a waiting stage 212, a forward feeding stage 214, and a model generation or patient characterization stage 216. The patient characterization stage occurs simultaneously with at least a portion of the forward feeding stage 214. During the patient characterization stage, as data is collected during the forward feeding stage 214, the patient-specific model can be iteratively developed. After the patient-specific model is generated, the learning stage ends. After the learning phase, the flow therapy device operates in the control phase until the end of the treatment period. As described below, the flow therapy device can be configured to transition back to the learning phase during the treatment period. In some configurations, the learning phase is optional, and the patient-specific model can be generated without a defined learning phase. For example, in such a configuration, a default model can be used initially. Then, the default model can be updated to the patient-specific model during the treatment period. During the treatment period, the patient-specific model can be updated at defined intervals, defined events, periodically, aperiodically, and / or continuously.

[0242] Learning Phase

[0243] When the flow therapy device is initially turned on, the flow therapy device can start in manual mode or automatic mode. If the device is in manual mode, it can be switched to automatic mode. When starting in automatic mode or when switched to automatic mode, the flow therapy device can start a treatment period after the user provides one or more operating set values ​​(e.g., FdO2 limits, SpO2 limits, flow, etc.). When the treatment period begins, the controller can initiate a waiting phase 212. During the waiting phase 212, the position of the oxygen inlet valve is based on the FdO2 set value (e.g., an initial level or default value configured by a clinician) before the start of the learning phase, which can cause the valve to remain in the same position or cause the position of the valve to change (e.g., open or close). The patient's SpO2 may change in response to high flow therapy. FdO2 remains at a constant level and is not adjusted during the waiting phase 212. The controller can measure and record the patient's SpO2. Before proceeding to the forward delivery phase 214, the controller can wait until the SpO2 is stable and the SpO2 has stabilized at a reasonable constant value. The waiting phase 212 can last for a defined period of time. The controller may be configured to initiate the forward feed phase 214 without the wait phase 212 .

[0244] During the forwarding phase 214, the controller may change the level of FdO2, such as increasing or decreasing the level. The new FdO2 value may be preset or determined based on factors such as the patient's current SpO2. The new FdO2 may be selected by a clinician who selects the FdO2 based on their own expertise and knowledge. The selected FdO2 may bring the patient's SpO2 close to the target SpO2 level. FdO2 may be automatically determined by the controller 13.

[0245] During the forwarding phase 214, the controller measures and records the patient's SpO2. The controller may measure and record FdO2. The graph illustrates a step change in FdO2 to a target FdO2 value. The actual FdO2 may be ramped up to the target FdO2 over a defined period of time. The measured data of SpO2 and FdO2 may be incorporated to assess the relationship between SpO2 and FdO2 and generate a model. Signal quality indicators from the patient sensor 26 may also be recorded.

[0246] The forward delivery phase 214 can last at least a defined minimum time period and can automatically end after a defined maximum time period. In some configurations, the minimum time period can be about 30 seconds, about 1 minute, about 2 minutes, 3 minutes, or another value within the above values. The maximum time period can be about 3 minutes, about 4 minutes, about 5 minutes, about 6 minutes, or another value within the above values. The minimum and maximum values ​​can be a combination of any two suitable values ​​described above. After the minimum time period, the controller can determine whether the patient has been fully characterized based on an analysis of the defined patient characterization criteria. If the maximum time period is reached without fully characterizing the patient, the forward delivery phase will end and the default patient model will be used to start the control phase. The default model may depend on the patient type (e.g., normal, hypercapnic, user-defined, or other types). The default patient model may be based at least in part on one or more received characteristics of the patient. The reasons why the patient cannot be characterized are discussed in further detail below. In some configurations, the controller may be configured to bypass the forward delivery phase 214 after the waiting phase 212. In this case, the controller can analyze the measured data of SpO2 and FdO2 during the waiting phase in order to characterize the patient. The controller may initially use a default patient model based on known patient characteristics, and may continue to iteratively characterize the patient model based on measured data of SpO2 and FdO2 during operation, as discussed further herein, without initiating a defined feed-forward phase.

[0247] During the forward feed phase 214, the controller may analyze the relationship between FdO2 and SpO2. The controller may be configured to model the relationship using an exponential decay function, where the exponential decay constant is varied to best fit the model to the data. The initial and final FdO2 values ​​used in the exponential decay function may be set by the initial and final target FdO2 values. Fitting the model to the FdO2 data allows for analytical evaluation of the SpO2 model, which may be faster and less computationally demanding. Figure 3 An example of what two sets of trend fits might look like is shown in Optionally, the controller may determine a relationship between the measured FdO2 and the amount of time since the target FdO2 was changed.

[0248] Additional references Figure 3 , graph 301 illustrates the fitted trends of SpO2 graph 302 and FdO2 graph 305. The graphs also include a measure of the signal quality 304 of the patient monitor. In order to fit the trend to the SpO2 data, a model representing the behavior of the SpO2 data can be generated and at least one constant parameter of the model determined. The model can relate each change in FdO2 to a time-based change in SpO2.

[0249] After the change in FdO2, SpO2 does not show any change due to the change in FdO2 for a period of time, which can be called the delay time. The delay time is caused by a combination of various factors. One potential factor is the time it takes for the device to change FdO2, and it will be quite consistent. Another potential factor is the time it takes for the gas to travel from the device to the interface, which can depend on the selected flow rate. Another potential factor is the time it takes for the gas to travel from the user interface to the patient's lungs. This can depend on the selected flow rate, but can also depend on the restrictions of the patient's airway and the length of the passageway from the interface to their lungs. Another potential factor is the time it takes for oxygenated blood to travel from the patient's lungs to the measurement site (i.e., the location of the patent sensor). This depends on the speed of blood travel, which will vary based on the patient's physiology and heart rate. In addition, the length of time can depend on the distance between the patient's lungs and the type of patient sensor used. The distance can be changed by the location of the patient sensor. In addition or alternatively, the distance can be changed by the size of the patient.

[0250] After the delay time, SpO2 can exhibit an exponential decay curve in which SpO2 asymptotically approaches a new value with the total change being proportional to the total change in FdO2. In some embodiments, there are four parameters of the model that can affect the shape of the model (in addition to the effect of the change in FdO2 delivery). The first is the delay time between the change in FdO2 and the first change in SpO2. The second is the initial value of SpO2. The third is the magnitude of the total change in SpO2 relative to the magnitude of the change in FdO2. The fourth is the rate of exponential decay, which defines how fast SpO2 approaches its final value after the delay time.

[0251] Since FdO2 does not exhibit a single change but varies over time, the SpO2 model can be evaluated as an integral of the effects of various FdO2 changes over time. A model that can be used is shown below in equation (1).

[0252]

[0253] Equation (1) includes five parameters for the model that can be evaluated and determined when generating the model. FdO20, which is the initial FdO2; SpO20, which is the initial SpO2; DT, the delay time, which can be measured as the time (in seconds) between a change in FdO2 and the effect appearing in the measured SpO2 fraction; τ, which is the exponential decay constant; and a, the patient oxygen efficiency, the ratio between the change in SpO2 and FdO2, defined as FdO20 can be determined from the initial target FdO2. The remaining four parameters can be varied to find the model that best fits the data.

[0254] In one embodiment, the fit can be quantified by a method called least squares. The least squares method involves looking at each data point and calculating the error, where the error is based on the difference between the data point and the relevant point on the model. The errors for each data point can be added together to give an overall value for the error of the model.

[0255] The model can be determined by selecting the parameter set that results in the model having the smallest possible total error. The values ​​of the parameter set can be calculated using a suitable iterative method that aims to gradually get closer and closer to the ideal constant parameter set. One algorithm is the Levenberg-Marquardt algorithm. Additional reference is made to Figure 4 , illustrates both: a graph 401 illustrating iterations of a trend line before reaching a best fit 405; and a graph 404 of signal quality.

[0256] Additionally, when calculating the error, the error value for each data segment can be weighted according to the corresponding signal quality of the data segment. The signal quality of the patient sensor is illustrated in graph 404. When determining constant parameters and fitting trend lines, weighting the data points can give additional weight to more accurate data points. Without weighting, the error of the model's data points can potentially be greatly affected by inaccurate data points.

[0257] The results of the learning phase can be used to tune the controller to best suit the individual patient. An untuned controller that is not specifically modeled for the individual patient can exhibit a number of disadvantages. In general, a slow / overdamped controller will take longer to reach the target SpO2 and will be slow to react to any fluctuations. On the other hand, a fast / underdamped controller runs the risk of trying to move towards the target value too quickly and overshooting it. This can cause the controller to oscillate around the target and become unstable. Preferably, the controller is critically damped, meaning that the model can quickly reach the target SpO2 value, but not so fast that it substantially overshoots the target and becomes unstable. By using a model generated through patient characterization, an analytical solution to a critically damped control algorithm can be found.

[0258] Systems that utilize high nasal flow facilitate some of the analysis that can be performed during this learning phase. In other systems, such as ventilation via a mask or tracheostomy interface, the relationship between FdO2 and SpO2 is greatly affected by the patient's breathing rate. One of the reasons for this is that a portion of each breath is re-breathed exhaled gas. When a patient takes short, rapid breaths, most of the gas breathed is re-breathed gas, so the gas entering the patient's lungs is composed of a smaller portion of therapeutic gas. Similarly, when a patient takes slow, deep breaths, a smaller portion of the breath is re-breathed gas, so the gas entering the patient's lungs is composed of a larger portion of therapeutic gas. This affects the oxygen concentration in the patient's lungs, which in turn affects SpO2.

[0259] As described earlier, nasal high flow has the effect of flushing the patient's airways with therapeutic gas to greatly reduce rebreathing. This means that, regardless of the patient's breathing rate, rebreathing will be minimal and the gas entering the patient's lungs will be much more similar in composition to the therapeutic gas delivered by the device.

[0260] Since the effect of breathing rate on the FdO2 / SpO2 relationship is reduced, the device is able to utilize a learning phase at startup in which data analysis allows optimal tuning of the controller and / or implementation of patient-specific predictive control without computationally demanding ongoing learning.

[0261] When the characterization criteria have been met, the patient has been adequately characterized. After patient characterization 216, the learning phase 210 ends and the control phase 220 begins. The characterization criteria may define acceptable ranges for at least some of the parameters used to calculate the patient model. For example, the characterization criteria may include: a range of acceptable values ​​for a determined delay time between a change in FdO2 and a first change in SpO2; a range of acceptable values ​​for an initial value of SpO2; a range of acceptable values ​​for a rate of exponential decay, which defines how fast SpO2 approaches its final value after the delay time; a range of acceptable values ​​for a ratio between a change in SpO2 and a change in FdO2; and / or other parameters associated with the generation of the model. The characterization criteria may define only a minimum or maximum value for a parameter.

[0262] In some cases, patient characterization may fail. In such cases, the controller may either start the control phase with the default PID controller or switch back to automatically maintain FdO2 at a prescribed level. The default PID controller may be designed in such a way that it is critically damped or overdamped for most, if not all, patients. In general, an overdamped controller that moves slowly toward the SpO2 target is more desirable than an underdamped controller that oscillates and becomes unstable. Each patient type may have a different default PID controller.

[0263] Reasons for failure of patient characterization may include problems with the data set, such as low average signal quality, too small an increase in FdO2, and / or too small an increase in SpO2. Additionally or alternatively, a failure may occur due to reasons associated with modeling the data, such as certain parameters falling outside of a particular acceptable range. These parameters may include fit / error of the model, since a large error between the model and the data will reduce the effectiveness of the model. These parameters may include various parameters of the model discussed earlier (initial SpO2, delay time, exponential decay constant, and the ratio between the increase in FdO2 and the increase in SpO2), since an unrealistic value for any of these parameters will indicate an error in the model. Additionally or alternatively, a failure may occur during tuning of the PID if any of the tuned PID values ​​fall outside of a particular range.

[0264] Ideally, the clinician will be alerted by an alarm that this has occurred, and an option will be available to attempt another learning phase. Additionally or alternatively, the device itself may initiate another learning phase to attempt to characterize the patient. The number of automatic attempts may be limited to a defined number of times. Additionally or alternatively, a patient-specific model may be generated from a default model, and then optionally updated during a treatment session.

[0265] The learning phase may be repeated more than once during a treatment period. Even if the learning phase is successful, there may be conditions that arise during the treatment period that cause the controller to re-enter the learning phase. The controller may have a maximum amount of time that the patient model is valid. For example, in a hospital setting, the patient's condition may change over time in a way that affects the relationship between FdO2 and SpO2. Thus, it may be beneficial to end the control phase and / or automatically initiate a new learning phase to re-characterize the patient after a certain amount of time (e.g., one or more days). In addition or alternatively, the patient-specific model may be updated and re-characterized during the treatment period. For example, during the treatment period, the patient-specific model may be updated at defined intervals, defined events, periodically, aperiodically, and / or continuously.

[0266] The controller may test for errors between corresponding predicted and measured SpO2 values. A sufficiently large error (possibly spanning multiple error values ​​or a defined time period) may indicate an incorrect patient model, and the controller may be configured to initiate a new learning phase. In some cases, if the patient's SpO2 falls outside of a target range, the controller may end the control phase and trigger a new learning phase.

[0267] Predictive control during the control phase

[0268] Figure 5 A graph 500 of signal hysteresis between predicted SpO2 values ​​and SpO2 data is illustrated. One of the difficulties in controlling FdO2 based on the SpO2 signal is delay time and signal hysteresis. When the FdO2 is changed at the device, gas with the new oxygen concentration needs to travel through the catheter to the patient interface, down the patient's airway into their lungs, and perform gas exchange in the patient's lungs. The oxygenated blood must then travel through their blood vessels to the pulse oximeter site, be measured by the patient sensor, and then have the measurement data received by the controller. By the time the controller receives the measurement data, multiple additional cycles may have been processed, resulting in a substantial overshoot of the target SpO2, which in turn causes large oscillations in the patient's SpO2 and causes instability in control. In addition, another aspect of nasal high flow is the use of a humidifier during the treatment period. Without a humidifier, the patient's airway will dry out quickly. The humidification component will require sufficient residence time to function, thereby increasing the delay time. This additional delay will make the predictor increasingly important in considering the delay time.

[0269] Some ways to handle this problem include overdamping the controller, having low sensitivity, and / or by having a delay between each iteration of the control signal to allow previous changes in FdO2 to take full effect. Such delays may be based at least in part on data measured in the learning phase discussed earlier. Although such a system may handle signal delays appropriately, it may present new problems by being too slow and unresponsive to the patient's condition. For example, when the device is first turned on, it will greatly increase the time it takes to reach the target SpO2, or the controller may be too slow to react to sudden changes in the patient's SpO2.

[0270] The controller can be configured to implement predictive control as a PID controller during the control phase. The predictive control can be a Smith predictor. The predictive control can be determined based at least in part on one or more parameters analyzed during the learning phase 210. Using the data received during the learning phase 210 to design or modify the predictive controller allows patient-specific control to be much more effective. The purpose of the predictive control is to predict the SpO2 value taking into account the signal hysteresis and to control the FdO2 based on the predicted SpO2 value rather than the measured SpO2. This results in a control algorithm that can be highly sensitive and stable.

[0271] The predicted value of SpO2 may represent the SpO2 after a delay time has elapsed. The delay time is the time between when a change is made to FdO2 and when a response is seen in SpO2 (i.e., when a corresponding response is detected in the measured SpO2). Because any FdO2 change will not have any effect on SpO2 until after the delay time has elapsed, the currently available data for SpO2 and FdO2 may be used to fairly accurately predict the SpO2 until the end of the delay period. The predictor may generate data that is substantially the same as the measured SpO2 data, with the delay time removed, such as Figure 5 Although this prediction does not predict the disturbances shown in the real data, the overall shape of the curve matches.

[0272] The predictor may receive inputs including one or more measured FdO2 values, one or more target FdO2 values, one or more predicted SpO2 values, one or more measured SpO2 values, and / or one or more target SpO2 values. Each of these inputs may be a recent value and / or a previous value stored at least temporarily by the processor. Each of these inputs may be paired with any relevant data associated with the input data point, such as a signal quality measurement and / or a value relating to the time at which the measurement occurred.

[0273] From here, the PID controller will function essentially the same as described earlier, however, the PID controller uses an estimated SpO2 instead of a measured SpO2, and thus will instead calculate the difference between this estimate and the target. This value will represent the change in SpO2. Since a predictor is used, the change in SpO2 will take into account the previous change in FdO2 that has not yet taken effect. The change in SpO2 will be paired with the current FdO2 to determine a new target FdO2.

[0274] Figure 6A schematic diagram 600 of a Smith predictor utilized with a PID controller is illustrated. Initially, the PID controller receives an input of the difference between the predicted patient SpO2 and the target SpO2, and outputs a target FdO2 to the FdO2 controller to bring the patient SpO2 closer to the target SpO2. The FdO2 controller outputs instructions to control the valve of the flow therapy device based on the target FdO2 output by the PID controller.

[0275] This new FdO2 is delivered to the patient and combined with other disturbances, resulting in a patient response. These disturbances can include errors from any sensor or control mechanism in the machine (e.g., oxygen valve) that result in a changed FdO2. Additional changes in the patient's response can be caused by the patient's physiological and physical parameters (exertive activity, changes in breathing rate, etc.) that have an impact on the patient's SpO2. The SpO2 is then measured, and the value will be the patient's current SpO2 plus or minus any errors from the sensors. The disturbance information is carried in the feedback signal, and the controller can adjust the FdO2 level to account for any changes in the patient's effort or breathing pattern that require more or less oxygen. A signal quality indication is also output to the PID controller.

[0276] For reference, in a controller without a Smith Predictor, the measured SpO2 value is then compared to the target SpO2, and the difference between the two is fed back into the PID. Using the Smith Predictor model, first the controller makes a prediction for SpO2. This can be done using the same model generated during the learning phase or a default model (e.g., when the patient cannot be or is not characterized), where SpO2 is estimated by integrating the effects of all FdO2 changes over time and then adding them to the initial SpO2:

[0277]

[0278] Where DT, SpO20, a, τ, FdO20 are constant parameters of the model, which may be generated during the learning phase or may start as default values. These parameters may remain constant throughout the treatment period, or may be updated continuously, periodically, or aperiodically. Importantly, DT is the delay time between the change in FdO2 and the start of the SpO2 response. In a first step, this calculation is run assuming that DT is 0. This results in an estimate of the patient's SpO2 after the delay time has passed. This value may be referred to as the predicted SpO2 without the delay time.

[0279] Thereafter, the same equation is processed again using the estimate of DT from the learning phase. When using DT, the output of the model can be called the predicted SpO2 with delay time, which predicts the current reading from the pulse oximeter. The predicted SpO2 with delay time can also be calculated by referring back to the previous estimate of SpO2 without the delay time. For example, if the delay time is 90 seconds, the estimate of SpO2 with delay time is the estimate of SpO2 without delay time derived 90 seconds ago.

[0280] The difference between the SpO2 value without the delay time and the measured SpO2 value is then calculated. If the model is perfect, the difference will be 0. Typically, there will be some difference, and this represents both errors in the model and also the disturbances in the SpO2 mentioned earlier.

[0281] Figure 7 A graph 700 of the prediction with the delay time included is illustrated. The error and interference value is then added to the first prediction of SpO2 without the delay time and can be used to correct the predicted SpO2 using the measured error between the actual and predicted SpO2. The final value represents the predicted SpO2 without the delay time plus interference.

[0282] Then, the difference between the predicted SpO2 without the delay time plus disturbance and the target SpO2 is calculated, and the result is fed back into the PID controller, and the process starts again.

[0283] Assumptions can be made to reduce the computational load of modeling the SpO2 response. First, since FdO2 changes in step increments with each iteration of the control loop, the equation can be evaluated by using discrete time points. As such, the model can be further rearranged as an iterative process, where results from previous iterations of the model can be included in the current iteration of evaluating the model.

[0284] In some cases, the Smith Predictor can allow the PID controller to react to an expectation of an SpO2 reading, rather than reacting to it. For example, the Smith Predictor may predict that SpO2 will rise to a target level and stabilize at the target level. However, when the actual SpO2 measurements come into play, it may be shown that SpO2 is approaching the target faster than predicted, and is now on track to overshoot the target value based on the previous changes in FdO2 that have been made. Thus, the controller may quickly drop FdO2 to minimize or even prevent the overshoot from occurring. Without utilizing the Smith Predictor, the control system would not respond to the overshoot until it has already occurred.

[0285] Figure 8Different computational models for PID controllers are illustrated. To demonstrate the difference caused by the Smith predictor, a computational model is set to represent a COPD patient. The model involves a sudden drop from a healthy SpO2 reading along with random fluctuations in SpO2 that will normally occur. The purpose is to understand how quickly the control system can restore the patient to a healthy SpO2 reading and stabilize at that point and how well it handles random fluctuations. The same model with the same random fluctuations is tested on three different PID controllers: one is a PID controller with a Smith predictor 802, one is a normal PID tuned for a specific patient 804, and one is a PID controller tuned for a default patient 806. PID controllers can be tuned or untuned. An untuned PID controller can be referred to as a default PID or an untuned PID. An untuned controller refers to a PID controller that is not tuned according to a specific patient. However, an untuned controller can be tuned for stability or for a general patient type or a specific patient type (e.g., normal, hypercapnia, etc.), and is loaded onto the controller before operating the flow therapy device, and an example method thereof will be described. In addition, a tuned PID controller and a default PID controller may refer to a PID controller that does not incorporate a Smith Predictor. A Smith Predictor may be used to change a tuned PID.

[0286] As described above, the Smith PID 802 can recover to a healthy SpO2 reading approximately 4 times faster than the default PID 806 and is more accurate in maintaining the target SpO2. The tuned PID 804 is worse than the default PID 806, but not as good as the Smith PID 802.

[0287] Predictive control based on patient type

[0288] Closed-loop control of the system may encounter difficulties in estimating patient response in smaller patients, such as neonates and pediatrics. The control methods for determining and predicting SpO2 may be modified to take into account smaller patients. The controller may be configured to automatically determine the type of patient connected to the device based on one or more operating characteristics, such as measured flow or flow setting. This determination may allow the device to be used seamlessly with the full spectrum of patients, thereby improving clinical workflow by eliminating the need to select and potentially manually configure a separate control mode for patients requiring lower flow.

[0289] Lower flows are often associated with small patients, such as children and neonates, where higher flows may not properly take into account the physiology of such patients. Devices for providing high flow therapy to neonates and children are often configured to have flows significantly less than flows for larger patients. For example, high flow therapy is often provided to such patients at a rate set at or below 25 L / min. Estimation algorithms for larger patients may not be applicable to smaller patients. Smaller patients are often considered to be faster responding patients, and therefore require more aggressive and faster control of FdO2. Due to the smaller size of neonates and children, their SpO2 levels will respond significantly faster than in larger patients, because the distance that oxygenated blood travels to the patient's extremities (where the pulse oximetry monitoring site is typically located) is physically shorter.

[0290] The controller may use different methods to determine the timing parameters in order to estimate the SpO2 level in a smaller patient at a lower flow rate. While neonates and pediatric patients may be the primary subjects for a faster controller, in some cases, treatment may also be intentionally provided to adults at a lower flow rate. In the case of providing gas to adults at a lower flow rate, it may be appropriate to adjust the control method to provide faster control. When the flow rate of the nasal high flow rate is low or low, the entrainment of the therapeutic gas flow relative to the ambient air may be low, resulting in a reduced effect of FdO2 on FiO2. Due to this reduced effect, the SpO2 controller may need to respond more aggressively. In other words, when providing a lower flow rate of gas to an adult patient who will typically have a higher peak inspiratory flow rate than a pediatric patient (e.g., a pediatric, neonatal, or infant), they will entrain relatively more ambient air than at a higher flow rate. Such a higher level of entrainment of ambient air can result in a dilution of the oxygen concentration (FdO2) in the gas mixture inhaled by the patient, and therefore, the patient's SpO2 may not respond as expected, so a more aggressive control of FdO2 is required to ensure that SpO2 is maintained within or moved to the target range.

[0291] Delay time

[0292] The first time-related parameter that the controller uses to estimate SpO2 is the delay time (DT). The controller can determine DT using a delay time algorithm based on the flow rate of the gas flow measured or otherwise set or configured for the patient. For lower flows, for example, flows below 25 L / min, the controller can dynamically determine the value of the delay time constant. In some examples, the controller can evaluate the flow value and determine where it fits within a range of flow rates, rather than just checking whether it is below a specific value or threshold, as will be explained.

[0293] The controller may be configured to infer or determine whether the patient type is an adult patient or a pediatric patient. In another example, the controller may be configured to infer or determine whether the patient type is a particular type of pediatric patient. For example, the controller may be configured to determine whether the patient type is one of the following pediatric patient types: a premature patient, or a neonatal patient, or an infant patient, or a pediatric patient (e.g., 5 to 12 years old). The controller may be configured to determine the patient type based at least on the flow value.

[0294] In such examples, based at least on the flow rate of the gas stream, the controller can be configured to associate certain flow ranges with certain types of patients. For example, the controller can be configured to associate a flow range of 5L / min to 8L / min with a neonatal patient or an infant patient, and a flow range of 10L / min to 25L / min with a pediatric patient. These ranges are for illustrative purposes only, and it should be understood that different flow ranges can be used in other examples. Due to the significant changes between these patient characteristics, there may also be considerable overlap between the flow ranges prescribed for patients of different sizes and weights (for example, very large infants and very small toddlers can be prescribed similar flows). Therefore, in some configurations, it may be useful for the controller to consider other patient type standards.

[0295] In some further examples, additional inputs or estimated or measured parameters of the patient may also be used to determine the patient type. These additional inputs or estimated or measured parameters of the patient may be similarly evaluated or associated with certain ranges to determine the patient type. For example, the patient's heart rate and / or respiratory rate may additionally be used by the controller to evaluate or determine the patient type.

[0296] Once the controller identifies or determines the type of patient, the controller can select or determine an appropriate patient-specific model for the patient type, for example, if the controller determines that the patient is a neonatal patient, the controller can determine that a model for neonatal patients should be used. For example, different models can produce similar response speeds or response aggressiveness.

[0297] In some examples, the controller may display a request to confirm the determined patient-specific model on a display, and then be configured to receive user input related to the confirmation request, for example, through a user interface. For example, the controller may present the determined patient-specific model to the user on the display, while presenting a prompt to confirm or deny the use of the patient-specific model to deliver the gas flow using closed-loop control. Once the user confirms that the controller is applying the determined patient-specific model of the patient-specific model to continue, the controller is configured to initiate closed-loop control of the oxygen concentration of the gas flow using the confirmed patient-specific model.

[0298] The patient delay time may include device delay time (delay associated with the passage of gas through the device and / or breathing circuit (breathing tube and / or patient interface)) and patient delay time (delay associated with the delivery of oxygen within the body). The equation for determining DT may use one or more variables and / or constants, such as flow rate Q, measurement delay t measure , path volume V path , transmission delay t transport and the correlation coefficient z. Measurement delay t measure may have a time dimension and may be measured in seconds, milliseconds, minutes, or any other suitable units. measure Delays introduced by the measurement equipment, such as the pulse oximeter algorithm (which may involve a signal averaging process), may be taken into account. measure Signal transmission and / or other communication delays may also be included. Typically, t measure Various delays may be taken into account when electronically / algorithmically determining the patient's current SpO2 value. path V may have a volume dimension and may be expressed in liters or in another appropriate unit. Q is a flow value with a volume dimension over time, which is typically expressed in L / min. However, if DT is expressed in another time unit (e.g., seconds), then V path The and / or Q values ​​may be appropriately converted to account for this. The flow rate, Q, may be a flow setting as specified or configured by a user (e.g., using a user interface), or a flow rate measured by a device sensor (e.g., a flow sensor disposed in the gas flow). If the respiratory therapy device is a NIV device or has an NIV mode, Q may be the average flow rate of the gas flow delivered through the breathing circuit (e.g., the breathing tube and / or the patient interface) minus any mask leak flow. The delivery time, t transport Can have a time dimension. transport It can represent the delay caused by delivering oxygenated gas from the respiratory therapy device to the patient's lungs, and then the delay caused by delivering the oxygenated blood to the measurement site (e.g., most commonly a finger or toe). transport It may be closely related to the breathing tube length (and / or other physical tube characteristics) and the patient's height or length (or mass). The correlation coefficient z may represent the correlation between the delay time and the square root of the flow rate.

[0299] These constants can be determined through empirical testing on adult patients and patient models. These constants can be used to account for various delay time factors, such as pulse oximetry averaging / algorithm delay, estimated delivery delay of oxygenated blood to the measurement site, and estimated delivery time of oxygenated blood. However, using estimates (e.g., delivery delay) and flow-related terms derived from adult physiological data can make the output inappropriate for smaller patients.

[0300] In one embodiment, the equation for estimating the delay time for larger patients is as follows:

[0301]

[0302] In one embodiment, the equation for dynamically estimating the delay time for larger and smaller patients is as follows:

[0303]

[0304] in The items are the same for all patients, and The term Q is the patient-specific component of the delay time based on the minimum flow. max,infant represents the defined maximum acceptable therapeutic flow rate for infants. For high flow therapy, Q max,infant The value of is typically 25 L / min, but may have different values ​​greater or less than 25 L / min. For example, Q max,infant Can be configured by, for example, a biomedical technician according to preferred practices in the hospital. max,infant can be configured to be lower than 25 L / min. The minimum function (min()) serves to check whether the flow rate is above a defined limit. If the flow rate is above a defined limit, the output of the min() function will be the defined limit (e.g., 25). For example, if Q = 30, which is greater than the defined limit of 25, then the term will be equal to or 5z. The resulting delay time used by the controller will be equal to It will work for a normal adult controller. However, if the flow rate is set below a defined limit (e.g. 25 L / min), for example Q = 9 L / min, the delay time will be smaller and will be equal to

[0305] Determination of the delay time term causes the controller to automatically take into account that the device has a flow setting below a defined threshold. This can provide greater flow differentiation for smaller patients who require faster changes in FdO2 during treatment. The algorithm can be configured to take into account the relationship between weight and flow, and to take into account travel time delays due to system flow paths and transport delays associated with the patient's circulatory system. In one example, Q = 2 L / kg / min for patients up to 12 kg.

[0306] Decay time constant

[0307] A second time-related parameter used by the controller that can be automatically modified to take into account smaller patients is the decay value (τ), also known as the decay time or (exponential) decay time constant. The decay time constant is related to the patient's response to oxygen, which takes into account the time it takes for SpO2 to decay to a stable value or a stable value range after the FdO2 changes and the delay time has passed. The decay time is a highly variable parameter (intra-patient and inter-patient). Intra-patient variability means that for the same patient, the decay time can be different at different time points. The intra-patient decay time can fluctuate or vary (short-term and / or long-term) based on the patient's condition and other factors. Inter-patient variability means that the decay time can vary between different patients due to various factors such as physiology, condition, intra-patient variations and differences in size. The means for estimating the time constant can involve changing the value of the time constant (in the PID-Smith Predictor controller tuning) until the best fit model is found.

[0308] In one embodiment, the equation for estimating the decay time constant is:

[0309]

[0310] This equation is similar to the delay time equation above, except that it includes a min() function. The min() function serves the same purpose. The correlation coefficient x can represent the correlation between the decay time and the square root of the flow rate. As described above, the measured delay t measure May have a time dimension and may take into account delays caused by measurement equipment, such as pulse oximetry algorithms (which may involve a signal averaging process). measure Signal transmission and / or other communication delays may also be included. Typically, t measure Various delays may be taken into account when electronically / algorithmically determining the patient's current SpO2 value. Take into account the patient's respiratory response.

[0311] In Q max,infant In the example equation with a limit of 25, if the flow rate is above 25 L / min, the decay constant will be t measure +5x. This value can then be adjusted as part of the best fit determination process. If the flow rate is 9 L / min, the decay constant will be t measure +3x (also best fit adjusted), and shorter times for larger patients with larger flows.

[0312] In some embodiments, the equations for delay time and decay time may be used to account for differences in flow only if one or more supplemental patient type criteria or criteria associated with one or more physical characteristics of the patient are met. In these cases, the flow-based timing parameter equations will be used, but only if the additional criteria are met. This can help ensure that the appropriate equations and controller functionality are used for the patient.

[0313] A supplementary criterion includes identifying the patient type based on the detected patient interface type. For example, the patient interface type (e.g., nasal cannula type) can be determined by measuring / estimating the flow resistance or conductivity of the respiratory therapy device (e.g., using a flow sensor inside the device, or alternatively, a patient proximal sensor). The patient interface type can be detected or identified as an adult-sized nasal cannula or a pediatric-sized nasal cannula. Further, the patient interface type can be detected or identified between several sizes of pediatric-sized nasal cannula. In such examples, each nasal cannula of different sizes will have a nasal prong with a narrower or wider inner diameter. Depending on the flow resistance or conductance estimate, the controller can determine the type of patient interface connected, for example, the controller can detect that an adult or pediatric-sized nasal cannula is connected. A nasal cannula with a narrower inner diameter nasal prong will exhibit a higher flow resistance than a nasal cannula with a wider inner diameter nasal prong, and can therefore be appropriately identified or detected. For example, this can be done by measuring the flow resistance and then comparing it with one or more thresholds or ranges to determine the possible nasal cannula connected. Alternatively, the user may manually enter or select the type of patient interface (eg, nasal cannula type) connected using the user interface 14 (eg, from a displayed list).

[0314] Another supplementary criterion includes identifying the patient type based on the detected tube type. For example, tubes for adults, pediatrics, infants, and neonates receiving high flow therapy may all have different inner diameters. The different diameters may be determined or detected using flow / aerodynamic resistance as seen by the respiratory therapy device using flow and / or pressure measurements. Thus, the controller may use flow and / or pressure measurements to identify whether an adult tube is connected, or even more specifically, which specific tube type is connected. Other methods known in the art (e.g., identifying resistors) may be used. Alternatively, the user may manually enter or select the type of type connected using the user interface 14 (e.g., from a displayed list).

[0315] Another supplementary standard includes identifying the patient type based on heart rate.Using the heart rate measured by the connected pulse oximeter (or a separate sensor or device), it can be determined that the infant or neonatal patient is using the therapeutic device.Infants and neonates typically have a relatively high heart rate compared to the resting heart rate of adults.For example, an infant or neonate can have a resting heart rate between 100bpm and 160bpm (some infants or neonates can have a heart rate slightly lower than 100bpm or even higher than 160bpm sometimes). This is in contrast to the normal resting heart rate of an adult typically between 60bpm and 100bpm.Therefore, the resting heart rate measured can be used as a supplementary standard for identifying the patient type.Even children under the age of 5 will usually show a higher resting heart rate, for example, 80bpm to 140bpm.The difference between children and adults usually becomes less obvious after the age of 5, but the resting heart rate of children under the age of 12 to 13 can be higher than the resting heart rate of a typical adult (for example, between 70bpm and 120bpm). However, some types of patients who do not necessarily require faster response times may also exhibit high heart rates (eg, post-cardiac surgery patients).

[0316] Another criterion includes using respiratory rate to distinguish neonatal patients from adults. Neonates typically exhibit higher respiratory rates, especially if the neonate is suffering from respiratory distress. For example, infants and neonates will typically have a resting respiratory rate between 30bpm and 60bpm (breaths per minute); and children under 5 years old may have a resting respiratory rate between 20bpm and 40bpm. For adults, the normal resting respiratory rate is between 12bpm and 20bpm. The difference gradually decreases for children aged 12 to 13 years old, and the resting respiratory rate of these children may be in the range of 16bpm to 30bpm. The patient's respiratory rate can be determined by a pulse oximeter using flow data / measurements and provided to the controller or determined by the controller itself. Therefore, the measured respiratory rate can be used as a supplementary criterion for identifying the patient type. Although the respiratory rate of a neonate with respiratory distress can be far beyond the adult range, there may be some overlap between adults and neonates with respiratory conditions.

[0317] In an alternative example, a user may use user interface 14 to manually enter or select values ​​for the patient's heart rate and / or breathing rate.

[0318] The controller may be configured to select the timing parameter equation to use based on a previous therapy type or mode (in the case of a multi-therapy mode device). For example, a respiratory therapy device may be able to provide bubble CPAP (BCPAP) therapy (with the correct device) as well as nasal high flow therapy (NHF). In such an example, if a switch from BCPAP to NHF occurs, the device's controller may elect to use the faster controller configuration in the therapy mode. In some examples, the output from the bubble detection algorithm may be stored (as part of a bubble CPAP therapy session) and later checked during startup of the closed-loop oxygen controller to identify whether the previous therapy session was indeed bubble CPAP, which would tell the controller that an infant may be connected to the device. In these examples, the indication of the previous therapy type may therefore be used as a supplemental criterion for determining or identifying the type of patient connected to the device.

[0319] An example bubble detection algorithm can use measurements of flow and / or pressure in a gas flow path to generate a flow and / or pressure waveform. Based on the identification of the presence of oscillations in the waveform, the algorithm can detect whether bubbles are occurring. For example, the algorithm can seek to identify the peak-to-peak amplitude of the waveform or the average of the amplitude over a time window. If the amplitude is above a threshold, this can confirm the presence of bubbles. The bubble detection algorithm can be any suitable bubble detection algorithm, and can be, for example, a bubble detection algorithm of the type described in published PCT specification WO 2022 / 058982A1 filed on September 21, 2021. The contents of that specification are incorporated herein by reference in their entirety.

[0320] Controller Tuning

[0321] As described herein, the PID-Smith Predictor controller is tuned with relevant parameters including delay time, exponential decay time constant, and patient oxygen efficiency. The first two parameters, once determined from the above expressions, are input to the PID and Smith Predictor tuning process.

[0322] Delay times and exponential decay time constants are involved in the learning phase.During the feed-forward phase, the controller determines the change / Δ in FdO2 to be used (ie, a step FdO2 change) appropriate for the patient.

[0323] Fig.29An example method 2900 for tuning a controller is shown in FIG. In the example method 2900, the tuning method 2900 first initiates closed-loop / predictive control at step 2902. The tuning method 2900 then proceeds to determine or identify the type of patient connected to the device, at step 2904, for example, the tuning method 2900 may determine or identify whether the patient is a pediatric patient or an infant patient. The patient type may be determined using one or more of the supplemental criteria as previously discussed. The tuning method 2900 then proceeds to determine an appropriate delay time (DT) at step 2906. The appropriate delay time may be determined using the methods previously described, for example, the tuning method may use a delay time algorithm to determine a DT based on a flow rate set for the patient. The tuning method 2900 then proceeds to determine or estimate an appropriate decay time constant (τ) at step 2908. For example, the controller may estimate the decay time constant using an equation as previously described. Once the patient type has been identified, the appropriate delay time has been determined, and the appropriate decay time constant has been determined / estimated, the tuning method proceeds to continue the PID and Smith Predictor tuning process at step 2910. In the PID and Smith Predictor tuning process, the patient type, delay time, and decay time constant are input to the PID and Smith Predictor tuning process, as will be described.

[0324] Signal weighting

[0325] refer to Figure 3 and Figure 4 , graphs 304 and 404 provide a signal quality indicator for a patient sensor. During use, the quality of the SpO2 signal from the patient sensor may change. Patient sensors (e.g., pulse oximeters) may be inaccurate in rare circumstances, such as when the pulse oximeter is moved around, which may result in poor quality data. Some patient sensors (e.g., pulse oximeters) may provide a signal quality indicator with each SpO2 reading. The signal quality indicator may be defined as a measure of the measurement accuracy of the patient sensor. The value of the signal quality indicator may be calculated on a defined scale, such as 0 to 1, where 0 represents no signal and 1 represents the strongest signal. The data representing the signal quality from the patient sensor may be processed in one or more ways, including fitting from a different scale (e.g., 0 to 5) to a defined scale of the system (e.g., 0 to 1).

[0326] When tuning a PID controller (whether it is default, patient specific, or predicted), the expected periodic disturbances can be analyzed. Periodic disturbances are fluctuations in SpO2 due to factors other than the controlled variable (FdO2) and can include errors in the SpO2 measurement. When tuning a PID controller, the expected periodic disturbances can be estimated, and in turn, the standard deviation of the SpO2 readings due to signal quality can also be estimated. The SpO2 readings will have a certain level of error between the measured value and the true value. This error can be represented by the measure of the standard deviation. The standard deviation will be inversely proportional to the signal quality.

[0327] Changes in signal quality can affect the error in the SpO2 measurement and thus the periodic disturbances to the system. This means that a previously tuned PID can go from being critically damped to being overdamped (the controller is unnecessarily slow) or overdamped (the controller becomes unstable). Signal quality can be accounted for by weighting the control algorithm based on the signal quality readings from the patient sensor. The control output can be multiplied by the signal quality to reduce the impact of data points with low signal quality. The goal: to dampen the PID controller as the signal quality decreases, effectively retuning the PID controller as the expected periodic disturbances change.

[0328] Weights may be applied to changes in FdO2 output by the PID control. Changes in FdO2 will be scaled relative to the most recent signal quality reading. For example, if FdO2 is at 30%, and the signal from the pulse oximeter indicates that the patient's SpO2 has dropped, the PID may indicate that FdO2 is increased by 4% to 34%. However, if the signal quality for the measurement is only 0.5, and linear weighting is being used, this increase may be attenuated to 2%, so that the new FdO2 will only be 32%. Weighting allows the controller to continue to control the patient's SpO2, but to do so slowly so as not to overcompensate for a poor quality measurement.

[0329] The relationship between signal quality and control algorithm weights may be defined by any function designed to represent increasing noise as signal quality decreases, and is not limited to a linear function as described above. The relationship between signal quality and control weights may be based on a correlation between signal quality and the standard deviation of the error.

[0330] By weighting the SpO2 measurement based on signal quality, the PID controller can be less affected by disturbances in the SpO2 measurement, such as motion artifacts and poor perfusion. Weighing the control algorithm by signal quality can result in a more robust, stable controller that can compensate for noisy data when signal quality degrades, while giving fast and accurate control when signal quality is high and the data is reliable.

[0331] Process for controlling flow therapy devices

[0332] 9A to 9C A flow chart of a method for controlling the operation of a flow therapy device during a high flow therapy period is illustrated. Process 900 and subprocesses 910 and 930 can be implemented by any system that can control the operation of a flow therapy device. For example, process 900 can be implemented in whole or in part by controller 13. Multiple different controllers can be configured to implement process 900. For example, different aspects of the process can be implemented by a controller. A remotely located system can be configured to implement a portion of the process. For example, a remotely located system can be configured to perform a learning phase 910 of the system, and a control phase 930 can be performed locally by controller 13. Although any number of systems can implement process 900 in whole or in part, to simplify the discussion, process 900 will be described with respect to specific components of controller 13 and flow therapy system 10.

[0333] In process 900, at box 902, a user can start a high flow therapy session on the flow therapy device 10. In order to start the therapy session, the flow therapy device may require a defined set of information about the patient. For example, the input may include one or more patient characteristics, such as patient type (e.g., normal, hypercapnic, or other type), age, weight, height, gender, and / or other patient characteristics. The flow therapy device 10 may also require the user to set a target SpO2 value or value range for the patient. The flow therapy device may automatically determine the target SpO2 value based at least in part on the received patient characteristics. After the information has been received, the therapy session can be initiated by the user and the process can proceed to box 910.

[0334] At block 910, the controller may execute a learning phase sub-process. The learning phase may generate a patient-specific model for use during the control phase. In some cases, the learning phase may fail, resulting in the use of a default patient model during the control phase 930. As discussed herein, a patient-specific model may be generated from a default model and then optionally updated during a treatment session without a defined learning phase.

[0335] Additional references Fig. 9B, further describing the learning phase in detail. At box 912, the controller performs a waiting phase until the patient's SpO2 value stabilizes. During the waiting phase 202, the oxygen inlet valve will default to the previous FdO2 set value, and the valve may be opened or closed as needed. The patient's SpO2 may change in response to high flow therapy, and thus the controller may wait until SpO2 has stabilized at a reasonably constant value before proceeding to box 914. Optionally, the waiting phase may be bypassed, and the process may proceed directly to box 914 without performing the waiting phase at box 912.

[0336] At box 914, the controller can increase the oxygen concentration of the gas flow to a new level based on the target SpO2 level. The new FdO2 value can be preset or determined based on various factors (such as the patient's current SpO2). The new FdO2 can be selected by a clinician who selects the FdO2 based on their own professional skills and knowledge. The selected FdO2 can bring the patient's SpO2 close to the target SpO2 level. FdO2 can be automatically determined by the controller 13.

[0337] At box 916, the controller measures and records patient parameters and device parameters. The patient parameter may be SpO2, and the device parameter may be FdO2. The controller may measure and record FdO2 and SpO2 data. The actual FdO2 may be ramped to the target FdO2 over a defined period of time. Signal quality indicators from the patient sensors may also be recorded.

[0338] At box 918, the controller can analyze the relationship between the patient and the device parameters and model the relationship. For example, the relationship can be between FdO2 and SpO2, and the controller can determine the relationship between the measured FdO2 and the amount of time since the target FdO2 change. The relationship can be modeled using an exponential decay function, where the exponential decay constant is changed to best fit the model to the data. The initial and final FdO2 values ​​used in the exponential decay function can be set by the initial and final target FdO2 values. Modeling the relationship can be performed as further described herein.

[0339] At box 920, the controller may determine whether the patient characterization criteria are met. The characterization criteria may define acceptable ranges for at least some of the parameters used to calculate the patient model. For example, the characterization criteria may include: a range of acceptable values ​​for the determined delay time between the change in FdO2 and the first change in SpO2; a range of acceptable values ​​for the initial value of SpO2; a range of acceptable values ​​for the rate of exponential decay, which defines how fast SpO2 approaches its final value after the delay time; a range of acceptable values ​​for the ratio between the change in SpO2 and the change in FdO2; and / or other parameters associated with the generation of the model. The characterization criteria may only define a minimum or maximum value for the parameter. If the criteria are met, at box 922, the controller outputs the patient-specific model for use during the control phase. If the patient characterization criteria are not met, the process proceeds to box 924, where the controller determines whether the maximum time for the learning phase has been exceeded. If the time has not been exceeded, the controller continues to iterate on the model. If the time has been exceeded, at box 926, the controller uses a default patient model for the patient. If the patient characterization criteria are not met, the controller may restart the learning phase subprocess 910 one or more times.

[0340] After the learning phase is complete, at subprocess 930, the model is output for use during the control phase. Fig. 9C To further describe the control phase sub-process.

[0341] At box 932, the controller executes a PID controller based on the patient model output during the learning phase. The PID controller can be configured to control FdO2 based on the target SpO2. At box 934, the PID can use a prediction algorithm (such as a Smith predictor) to predict SpO2. At box 936, the PID can determine the FdO2 value based on the predicted patient SpO2 value. At box 938, the PID controller can adjust the output of the FdO2 value based on a signal quality indicator associated with the patient sensor. At box 940, the model is adjusted based on the patient response. The difference between the predicted SpO2 and the target SpO2 is calculated, and the result is fed back to the PID controller. At box 942, the controller determines whether the treatment period is completed. If the treatment period is not completed, the process will start again. If it is completed, the treatment period ends.

[0342] Closed-loop control using oxygen efficiency

[0343] In use to achieve Fig.10 In another configuration of the closed-loop control system of the flow therapy device 10 illustrated in FIG. 1 , the flow therapy device 10 determines an oxygen efficiency associated with the patient. The flow therapy device 10 may generate a patient model that uses the patient's oxygen efficiency during a therapy session.

[0344] The oxygen efficiency can be calculated where Where FbO2 is the patient's blood oxygen fraction and FmO2 is the model-specific oxygen fraction parameter. The system can calculate the patient's oxygen efficiency (ξ O2 ) together with other parameters. The oxygen efficiency algorithm can use the equivalent SpO2 fraction to calculate the FbO2 fraction from a predefined hemoglobin saturation curve. And FmO2 can be considered equivalent to FdO2. In this case, the oxygen efficiency can be calculated based on the patient's measured SpO2 and the measured FdO2. In one configuration, the oxygen efficiency is determined based on the patient's measured SpO2 divided by the measured FdO2. In one configuration, the oxygen efficiency is determined based on a nonlinear relationship between the patient's measured SpO2 and the measured FdO2.

[0345] The oxygen efficiency of a patient requiring supplemental oxygen may be less than that of a healthy individual. For example, in a healthy individual, a change in FdO2 may cause a change in SpO2 that is twice as large as that of a patient with low oxygen efficiency. Measuring a patient's oxygen efficiency allows for more efficient implementation of a closed-loop oxygen control system.

[0346] like Fig.11 As shown in , the controller 13 can calculate the oxygen efficiency of the patient. The controller can receive a measured SpO2 value and a measured FdO2 value. The measured FdO2 value can be received from the gas composition sensor. Then, the instantaneous oxygen efficiency can be calculated based on the measured SpO2 and the measured FdO2 values. Then, the total oxygen efficiency of the patient can be estimated by applying a running filter to the instantaneous oxygen efficiency data. Filtering the instantaneous oxygen efficiency data can reduce fluctuations when estimating the total oxygen efficiency of the patient. The controller can also prioritize the latest data. The instantaneous oxygen efficiency data can be weighted according to the signal quality of the pulse oximeter, so that the measurement of the instantaneous oxygen efficiency based on the data with low signal quality will have a reduced impact on the estimation of the total oxygen efficiency of the patient. The instantaneous oxygen efficiency data can also be weighted based on the size of the recent change in FdO2, so that the measurement of the instantaneous oxygen efficiency based on the data after a large change in FdO2 has a reduced impact on the estimation of the total oxygen efficiency of the patient. This is due to the delay between when a change is made in FdO2 and when there is a change in the measured SpO2. The controller may also take into account whether the patient is wearing a cannula when estimating the patient's oxygen efficiency. For example, the controller may disregard efficiency data from periods when the patient is not wearing a cannula.

[0347] The device can continuously monitor and update an estimate of the patient's total oxygen efficiency. The patient's total oxygen efficiency can be used by multiple parts of the closed-loop control system, such as in a predictive model, tuning of PID coefficients, and / or step changes before the forward feed phase. The patient's total oxygen efficiency can be continuously updated as the estimate of the patient's instantaneous oxygen efficiency changes. The controller can start with an initial estimate of the patient's oxygen efficiency based on typical oxygen efficiencies for patients requiring supplemental oxygen. The total oxygen efficiency can then be updated as data is received. A higher estimate of the oxygen efficiency results in a smaller change in FdO2, which can reduce the risk of the patient receiving too much oxygen. A lower estimate results in a larger change in FdO2, which can allow the controller to achieve the target SpO2 more quickly, but may cause overshoot.

[0348] In some configurations, the flow therapy device 10 may have an initial oxygen efficiency calculation phase to determine the patient's oxygen efficiency. In some configurations, after the initial oxygen efficiency calculation, the oxygen efficiency is not updated.

[0349] Initiation of closed-loop control treatment

[0350] As described herein, a user may initiate a closed-loop control therapy session by interacting with a graphical user interface of the flow therapy device 10. Closed-loop control may require that a patient sensor 26 (e.g., a pulse oximeter) be connected to the patient and the flow therapy device 10, and that the signal quality of the patient sensor be at an acceptable level. Before closed-loop control begins, the user must set operating parameters for FdO2 and SpO2. Various methods for selecting these operating parameters are described herein.

[0351] The control range of FdO2 may have an upper control value and a lower control value. The user may select the upper and lower limits for the control range of FdO2. The difference between the upper and lower limits may be fixed. The control range may be fixed to a defined difference in oxygen concentration, such as a difference of 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% and 50% and / or any other range between the above values. The user may then be able to select a specific FdO2 range, such as, for example, 25%-45%, 52%-72%, 80%-100% or any other range. The user may be able to change the value of the FdO2 control limit in increments of 1%, 2%, 5%, or other increments.

[0352] The flow therapy device may have a lower limit of 21% and an upper limit of 100% for the FdO2 control range. The FdO2 control range may be truncated by the limit of the oxygen concentration that the device can feasibly deliver (e.g., 95%, 90% or lower values). For example, the gas supply source connected to the oxygen inlet valve may be an oxygen-enriched gas stream, wherein the oxygen content of the supply source may be less than pure oxygen (i.e., 100%).

[0353] The flow therapy device may include various configuration options for setting limits for the FdO2 control range. For example, the user may input the oxygen concentration of the oxygen source; the flow therapy device may be pre-programmed during manufacturing with an upper limit that cannot be changed; the upper limit may be changed by a technician but not by a normal user; the user may input the type of oxygen source (e.g., concentrator, oxygen cylinder, etc.) and the flow therapy device may determine the appropriate limits; and / or the flow therapy device may measure the oxygen concentration of the gas from the oxygen source.

[0354] Additionally, the flow therapy device can sound an alarm if the target oxygen concentration cannot be achieved. The alarm can be used as a failsafe for situations where a control range is selected that is higher than the oxygen source concentration. For example, if the control range is 80% to 100% when connected to a 90% source, the flow therapy device will not be able to exceed 90% and will trigger an alarm.

[0355] If the user attempts to reduce the control range of FdO2 above or below the upper or lower limit, respectively, the control range may be truncated. For example, if the user attempts to reduce the control limit of 21%-41%, the upper limit may continue to be reduced, but the lower limit will remain at 21%. This will result in a control range of less than 20% (e.g., 21%-35%). The control range may also have a lower limit on its size (e.g., 5%, 10%, 15%, etc.). The lower limit may be based on the size of the control range. For example, the lower limit may be half the size of the control range. Specifically, when one of the limits of the control range is at its physical limit (i.e., 21% or 100%), the other limit must be at least 10% above or below the limit. In such a configuration, the lowest and highest possible control ranges are 21%-31% and 90%-100%, respectively. The controller may change the FdO2 between the upper and lower limits of the control range in order to maintain the SpO2 within the patient's target range.

[0356] As described herein, a user can manually set a target range for SpO2. In some configurations, instead of manually selecting a target range for SpO2, a user can select a patient type, and the controller then selects a predetermined SpO2 control limit based on the patient type. Examples of patient types can include: "Normal," which has a defined SpO2 control range, such as 90%-98%, 92%-98%, 92%-96%, or another defined range; or "Hypercapnia," which has a defined control range, such as 88%-92%, 86%-90%, 88%-90%, or another defined range.

[0357] In order to maintain the patient's SpO2 within the target range, the controller can target the center of the patient's target range. In addition, the limits of the target range can act as alarm limits. For example, for a "normal" patient with an SpO2 target range of 92%-96%, the device will target an SpO2 value of 94%. If the patient's SpO2 value is outside the 92%-96% range, the device will then sound an alarm. The flow therapy device may have additional alarms set at defined limits that are independent of the selected SpO2 control range. For example, the flow therapy device may sound an alarm at 50%, 60%, 70%, 75% and / or 80% to indicate that the patient's saturation is decreasing.

[0358] The flow therapy device 10 may include a configuration menu in which some or all of these values ​​may be changed. The configuration menu may be protected by a PIN or similar password function; such that certain users are prevented from accessing the settings. For example, the configuration menu may be designed to be inaccessible to a normal user (e.g., a patient or nurse), but rather designed to be accessible to anyone who sets the device configuration (e.g., a technician or manufacturer).

[0359] In the configuration menu, the limits that may be selected for the FdO2 control range may be modified. For example, the device may be configured so that the upper limit of the FdO2 control range cannot exceed 90%. Setting limits on the control range may serve as a safety feature by preventing the device from delivering too high and / or too low an oxygen concentration. Additionally, limits may be set based on the substance that the device is likely to deliver. For example, if the device is connected to an oxygen-rich source that includes a gas with an oxygen concentration of 90%, it will be unlikely that the device will achieve 100% FdO2. In this case, the upper limit of the selectable FdO2 control range will need to be set at 90% or less.

[0360] In a higher level menu, it may also be possible to change the size of the control range for FdO2. For example, the size of the control range may be set to 10%, 15%, 20%, 27%, 30%, 36%, 40%, 50%, 60%, 70%, 80%, 90%, 100% or any other control range. When approaching one of the above limits, the control range will be able to be reduced, such as reduced by half. For example, if the range is set to 40% and the FdO2 lower limit is 21%, the lowest selectable range will be 21%-41%.

[0361] The SpO2 target range may be manually set by the user. The SpO2 target range for each patient type may also be changeable in the configuration menu. In addition, the device may have additional patient types that may be made selectable through the configuration menu. For example, the additional patient types may be labeled "Other" and may include customizable SpO2 target ranges. The upper and lower limits of the SpO2 target range for each patient type may be changed between 80% and 100% in 1% increments.

[0362] During a therapy session, the SpO2 controller and the FdO2 controller may automatically control the operation of the flow therapy device until the therapy session ends or an event triggers a change from automatic mode to manual mode.

[0363] During the treatment period, the graphical user interface can display a graphical indicator of oxygen efficiency. The oxygen efficiency characteristic displayed on the graphical user interface can be an output value based on SpO2 and FdO2. Another oxygen efficiency characteristic can be a function of the determined oxygen efficiency and the patient's respiratory rate. In the case where the oxygen efficiency characteristic is a function of the determined oxygen efficiency and the patient's respiratory rate, the oxygen efficiency characteristic can be calculated by dividing SpO2 by FdO2 and then dividing the value by the respiratory rate. The oxygen efficiency characteristic values ​​can be recorded and displayed in a graph or trend line format to show how these values ​​change over time. The graphical user interface can be configured to display each of the oxygen efficiency characteristic and the respiratory rate oxygen efficiency characteristic separately or together. For example, the values ​​associated with each characteristic can be displayed together on the same screen or on a separate screen (e.g., the user can switch to different screens within the interface to view different characteristics). The graph or trend line can be configured to display each characteristic separately or together on the same screen.

[0364] Fig.12 Graphs 1200 of SpO2 and FdO2 are provided that illustrate various stages of operation of a flow therapy device during a therapy session. Although FdO2 (fraction of delivered oxygen) is used in these graphs, as discussed earlier, FdO2 is essentially the same as FiO2 as long as the flow meets or exceeds the patient's peak inspiratory demand.

[0365] The various operating phases may include a waiting phase 1212, a step change 1214, a feed forward phase 1216, and a control phase 1220. Once the control limits have been set, the flow therapy device 10 may enter the waiting phase 1212. The waiting phase 1212 allows the SpO2 sensor to stabilize and allows for some initial data collection, such as SpO2, FdO2, signal quality, and other parameters. In particular, an initial estimate of the patient's oxygen efficiency may be determined. If the patient has been using the device in manual oxygen control mode with an SpO2 sensor attached, the device may already have an estimate of the patient's oxygen efficiency. In this case, the collected data may be used to continue to update this estimate.

[0366] In this configuration, the waiting phase 1212 can extend for a fixed predetermined amount of time. The amount of time can be between 1 second and 60 seconds, or between 2 seconds and 30 seconds, or between 3 seconds and 15 seconds, or between 4 seconds and 10 seconds, 5 seconds, or any other time period within the above range.

[0367] During the waiting phase 1212, the device may also evaluate data to determine what operations to perform during the subsequent forward feeding phase 1216. Prior to the forward feeding phase 1216, the controller may perform a step change 1214 in FdO2. The flow therapy device may make a step change in FdO2 to attempt to bring the actual SpO2 within or close to the target range. After making the step change in FdO2, FdO2 may remain constant for a defined duration during the forward feeding phase 1216 to allow the patient's SpO2 to stabilize.

[0368] Towards the end of the waiting phase 1212, data from several parameters may be evaluated to determine the size of a step change 1214 and whether a feed forward phase 1216 will be performed. First, the patient's SpO2 may be compared to a target SpO2 range. If the patient's SpO2 is within or above the target range, the step change 1214 and feed forward phase 1216 may be bypassed and the controller will transition directly from the waiting phase 1212 to the control phase 1220. If the patient's SpO2 is below the target range, the controller may determine whether a step change 1214 is needed. For example, a large recent change in FdO2 may mean that a step change 1214 in FdO2 is not needed. If a step change 1214 is needed, the device will proceed to the step change 1214 after the waiting phase 1212 ends.

[0369] For the step change 1214, the controller determines the change in FdO2 to be achieved. The size of the step change is based at least in part on the current SpO2, the target SpO2, and the oxygen efficiency.

[0370] Because of the delay between changing FdO2 and seeing the change in SpO2, there may be changes to FdO2 that have not yet taken effect when calculating oxygen efficiency. The flow therapy device 10 can take any recent changes in FdO2 into account when determining the predicted SpO2, oxygen efficiency, and the magnitude of the step change.

[0371] During the forward feed phase 1216, the controller maintains the FdO2 at the determined FdO2. In the absence of a step change 1214, the FdO2 may be maintained at the current FdO2 value. In the presence of a step change 1214, the determined FdO2 is the sum of the previously measured FdO2 and the magnitude of the step change. The forward feed phase 1216 may continue until a defined maximum time for the forward feed phase is reached (e.g., 60 seconds, 120 seconds, or another defined maximum duration), or until the measured SpO2 is within a target SpO2 value and / or within a target SpO2 range. After the forward feed phase 1216 ends, the control phase 1220 begins.

[0372] Predictive control during the control phase

[0373] During the control phase 1220, the controller varies FdO2 within the control range to achieve the target SpO2. The formula for determining the target FdO2 during the control phase is shown below in velocity form.

[0374]

[0375] Where E SpO2 is the error function, and K P , K I and K D are the PID coefficients. The error function represents how far the patient's SpO2 is from the target SpO2 and is calculated differently depending on whether a Smith predictor is used. In some configurations, the error function may also be filtered using a first-order low-pass Butterworth filter to remove random measurement errors.

[0376] As described herein, the PID coefficients may be tuned to better achieve the patient's target SpO2. In addition, the PID coefficients may also be weighted according to the inverse of the patient's oxygen efficiency, so that the controller will make larger changes to FdO2 for patients with low oxygen efficiency in order to achieve consistent changes in SpO2.

[0377] When using the default PID or a tuned PID, the error function is as follows.

[0378] E SpO2 (t) = SpO2 Measured (t)-SpO2Target

[0379] As discussed herein, the PID coefficients may be tuned based on patient characteristics. In addition, the Smith Predictor may be used to remove the pure time delay between when a change is made in FdO2 and when a corresponding change in SpO2 is detected. The delay time may be estimated based on the flow rate of the flow therapy device 10.

[0380] The Smith Predictor can use a model of the patient's SpO2 response based on the change in FdO2. Using this model, the Smith Predictor can make a prediction about how SpO2 will be after a delay time.

[0381] The predicted value is constantly corrected using an interference term, which represents the error between the modeled SpO2 and the measured SpO2. Once an initial SpO2 prediction is made, the prediction is then adjusted by incorporating the interference term. Combining these parameters gives the interference-adjusted predicted SpO2 value. This value is then used to calculate the error function. When the model and the estimated delay time are sufficiently accurate, the Smith Predictor PID can function similarly to a default or tuned PID used on a patient without a delay time.

[0382] As described herein, in some configurations, the Smith Predictor model can be evaluated in terms of SpO2 using the cumulative change in FdO2 multiplied by a coefficient that represents the relationship between the change in FdO2 and the change in SpO2. The coefficient is patient-specific and is generated using an initial estimate. The coefficient is then continuously updated based on real-time data (e.g., SpO2 and FdO2) received from the patient. The coefficient can be updated during all phases of the closed-loop control mode and is not limited to a specific learning phase.

[0383] The coefficient used in the Smith Predictor model may be the patient's oxygen efficiency. The patient's oxygen efficiency may be continually evaluated and updated in the model's algorithm. As stated herein, the oxygen efficiency estimate is updated throughout the waiting phase, the feed-forward phase, and the control phase, as well as during manual mode (if a pulse oximeter is being used).

[0384] PID controller weighting

[0385] As described herein, the control signal can be weighted according to the quality of the signal from the patient sensor 26. In addition, the control signal can be weighted depending on whether the measured SpO2 is above or below the target value. When the measured SpO2 is below the target, the weight can be equal to or greater than one, between 1 and 2, between 1.1 and 1.75, between 1.2 and 1.5, 1.25, or any value or range within the above range. When the measured SpO2 is above the target, the weight can be less than or equal to one, between 0.25 and 1, between 0.5 and 0.9, between 0.75 and 0.85, 0.8, or any value or range within the above range. This allows the controller to increase the oxygen concentration more quickly when the SpO2 is too low, while also reducing the chance of overshooting the SpO2 target and reducing the oxygen concentration when the SpO2 is too high. This weighting process can help reduce the amount of time that the patient receives a lower concentration of oxygen.

[0386] Process for controlling flow therapy devices

[0387] FIG. 13A to FIG. 13C A flow chart of a method for controlling the operation of a flow therapy device during a high flow therapy period is illustrated. Process 1300 and subprocesses 1310 and 1330 can be implemented by any system that can control the operation of a flow therapy device. For example, process 1300 can be implemented in whole or in part by controller 13. Multiple different controllers can be configured to implement process 1300. For example, different aspects of the process can be implemented by a controller. A remotely located system can be configured to implement a portion of the process. For example, a remotely located system can be configured to perform a setup phase 1310 of the system, and a control phase 1330 can be performed locally by controller 13. Although any number of systems can implement process 1300 in whole or in part, to simplify the discussion, process 1300 will be described with respect to specific components of controller 13 and flow therapy system 10.

[0388] In process 1300, at box 1302, a user can start a high flow therapy session on the flow therapy device 10. In order to start the therapy session, the flow therapy device may require a defined set of information about the patient. For example, the input may include one or more patient characteristics, such as patient type (e.g., normal, hypercapnic, or other type), age, weight, height, gender, and / or other patient characteristics. The flow therapy device 10 may also require the user to set a target SpO2 value or value range for the patient. The flow therapy device may automatically determine a target SpO2 value or value range for the patient based at least in part on the received patient characteristics. After the information has been received (if necessary), the therapy session can be initiated by the user and the process can proceed to box 1310.

[0389] At block 1310, the controller may perform a setup phase. Fig. 13B 13. The setup phase subprocess 1310 is described below. At block 1312, the controller waits for a defined period of time before proceeding. The wait time may provide a period of time for the patient's SpO2 value to stabilize. During the wait phase 1212, the oxygen inlet valve may default to a previous FdO2 set value, and the valve may be opened or closed as needed.

[0390] At box 1314, during the waiting stage, the controller measures and records patient parameters and device parameters. The patient parameter can be SpO2, and the device parameter can be FdO2. The controller can measure and record FdO2 and SpO2 data. The controller can determine oxygen efficiency based on SpO2 and FdO2.

[0391] At block 1316, the controller may determine whether the patient's SpO2 is within or above the target SpO2 range. If the target is already within or above the target SpO2 range, the process bypasses the step change and forward feed phases and proceeds directly to the control phase at block 1322. If the patient's SpO2 value is not within the target range, the process proceeds to block 1317.

[0392] At block 1317, the controller may determine whether FdO2 is at an acceptable level. If FdO2 is already at an acceptable level due to a recent change in FdO2, no further adjustment of FdO2 is required before advancing the stage, and the process bypasses the step change and proceeds directly to block 1320. If FdO2 is not at an acceptable level, the process proceeds to block 1318.

[0393] At box 1318, the controller can perform a step change in oxygen concentration. The controller can perform a step change to increase the oxygen concentration of the gas stream to a new level based on the target SpO2 level, FdO2, and oxygen efficiency. The new FdO2 value can be determined based on various factors (e.g., the patient's current SpO2). The new FdO2 can be selected by a clinician who selects the FdO2 based on their own professional skills and knowledge. The selected FdO2 can bring the patient's SpO2 close to the target SpO2 level. FdO2 can be automatically determined by the controller 13.

[0394] At box 1320, the controller may perform a feed forward phase. During the feed forward phase 1216, the controller maintains the FdO2 at a determined value for a determined amount of time. When the controller bypasses a step change, the controller may perform a feed forward phase without changing the FdO2. The feed forward phase 1216 may continue until a defined maximum time for the feed forward phase is reached (e.g., 120 seconds), or until the measured SpO2 is at a target SpO2 value and / or within a target SpO2 range. After the feed forward phase is complete, the process proceeds to box 1322 and begins the control phase subprocess 1330. Fig. 13C The control phase subprocess 1330 is further described.

[0395] At box 1332, the controller performs a control phase that uses a PID controller to control the execution of the flow therapy device 10. The PID controller can be configured to control FdO2 based on the target SpO2 and the measured SpO2. At box 1334, the controller can use a prediction algorithm (e.g., Smith predictor) to predict SpO2. At box 1336, the controller can determine the target FdO2 value based on the predicted patient SpO2 value. At box 1338, the controller can determine the oxygen efficiency based on the measured SpO2 value and the measured FdO2. At box 1340, the controller can adjust the output of the FdO2 value based on the signal quality indicator associated with the patient sensor. At box 1342, the controller control signal to the oxygen valve is adjusted. The difference between the predicted SpO2 and the target SpO2 is calculated, and the result is fed back to the PID controller to control the oxygen valve. At box 1344, the controller determines whether the treatment period is completed. If the treatment period is not completed, the process continues until the treatment period ends.

[0396] Motor and / or sensor module configuration

[0397] Figures 14 to 16 2. The configuration of the flow therapy device 10 is illustrated in FIG. The flow therapy device includes a main housing 100. The main housing 100 has a main housing upper chassis 102 and a main housing lower chassis 202.

[0398] like Fig.14 and Fig.15 As shown in FIG. 13 , the lower chassis 202 has a motor recess 250 for receiving a removable or non-removable motor and / or sensor module 400. Fig.15 A recessed opening 251 is provided in the bottom wall 230 adjacent its rear edge for receiving a removable or non-removable motor / sensor module 400, which is shown in FIG. 13 and FIG. Fig.15 and will be described in further detail below.

[0399] Figures 16 to 19 The motor and / or sensor module or subassembly 400 is shown in greater detail. As discussed above, the lower chassis 202 includes the recess 250 for receiving the motor and / or sensor module 400.

[0400] exist Figures 16 to 19 In the form shown in , the motor and / or sensor module 400 includes a stacked arrangement of three major components; a base 403 of the subassembly 400 (on which the motor 402 is positioned), an outlet gas flow path and sensing layer 420 positioned above the base 403, and a cover layer 440. The base 403, the sensing layer 420, and the cover layer 440 are assembled together to form a subassembly housing having a shape complementary to that of the recess 250 so that the subassembly 400 can be received in the recess 250. The base 403 is configured to close the recess opening 251 when the subassembly 400 is positioned in the recess 250. The subassembly 400 can be maintained in place in the recess in any suitable manner (e.g., using fasteners, clips, or a quick release arrangement), or can be fixed in an irremovable manner.

[0401] The sensing layer comprises a gas flow path having one or more sensors, the gas flow path being arranged to deliver gas to an outlet port of the housing.

[0402] The motor 402 has a body 408 that defines an impeller chamber that accommodates an impeller. The motor 402 may be any suitable gas blower motor, and may be, for example, a motor and impeller assembly of the type described in published PCT specification WO2013 / 009193. The contents of that specification are incorporated herein by reference in their entirety.

[0403] The gas outlet 406 is in fluid communication with the outlet gas flow path and the gas inlet of the sensing layer 420, which are stacked on top of the motor. This layer 420 includes a body 422, which includes a plurality of mounting legs 425 that can be inserted into a plurality of mounting slots (not shown) of the base 403 to secure the body 422 to the base 403. In one configuration, the body 422 defines a gas flow path that couples the gas outlet 406 with the gas flow path and the gas inlet of the sensing layer 420.

[0404] The body 422 defines a lower portion 426 of the sensing and gas flow path. The cover layer 440 has a body 442 defining an upper portion 446 of the sensing and gas flow path, wherein the shapes of the upper portion 426 and the lower portion 446 substantially correspond to each other.

[0405] like Fig.17 and Fig.18As shown in , the gas flow path includes a straight elongated gas flow portion 428, 448. The inlet is in fluid communication with a tangential inlet portion 430, 450 of the gas flow path, which is located at or adjacent to the inlet end of the straight elongated portion 428, 448 of the gas flow path. Recesses 433, 453 and 434, 454 may be provided at opposite ends of the straight elongated portion of the gas flow path.

[0406] The gas flow outlet port 452 extends vertically through the body 442 of the cover layer 440 and is located at or adjacent to the opposite outlet end of the linear elongated portions 428, 448 of the gas flow path. The gas outlet port 452 is in fluid communication with the upper portion of the motor recess 250, which in turn is in fluid communication with the gas flow channel. Likewise, due to the configuration of the walls 252 and top plate 262 of the recess 250, if gas leaks from the motor / sensor module 400, the gas will be exhausted to the atmosphere rather than into the portion of the main housing 100 that houses the bulk of the electronics and control equipment. The recess 250 may include spacers (such as Fig.15 262 ) to maintain proper spacing for gas flow from the gas outlet port 452 and the top plate of the recess 262 .

[0407] from Fig.17 It can be seen that at least a portion of the gas flow path through and out of the motor and / or sensing module 400 has a tortuous or serpentine configuration. For example, the direction of the gas flow traveling through the elongated portions 428, 448 is generally opposite to the direction of the gas flow traveling from the gas outlet port 452 to the inlet of the gas flow channel through the elbow 324.

[0408] like Fig.18 and Fig.19 As shown in , the cover layer 440 includes a sensing printed circuit board (PCB) 456. The cover layer 440 may also include one or more temperature sensors, such as thermistors seated in the elongated portions 428, 448 of the gas flow path. One sensor will measure the gas temperature, and the other sensor may be used as a redundant temperature sensor. Alternatively, one of the thermistors may be used as a reference flow sensor (e.g., via use as a constant temperature thermistor), and the measured temperature may be used to determine the gas flow through the portions 428, 448 of the gas flow path. One or more temperature sensors may be located on a portion of the sensing PCB 456 that faces the gas flow. In addition, the sensing PCB 456 may include other sensors, including but not limited to pressure sensors, humidity sensors, and dew point sensors.

[0409] One or both of electronic circuit boards 272 will be in electrical communication or coupling with the sensors to process information received from the sensors and to operate device 10 based on the information received from the sensors.

[0410] In an alternative configuration, the motor / impeller unit may be located remotely from the apparatus 10. In this configuration, the module received in the recess 250 may include only the gas flow path and various sensors to deliver gas to the fixed elbow 324 and thereby to the liquid chamber 300. In an alternative configuration, the module received in the recess 250 may include only the motor and the gas flow path, but no sensors.

[0411] In another alternative configuration, the motor and / or sensor module 400 may not be removable from the recess 250, but may be permanently mounted therein. In this configuration, the benefit of gas isolation from electrical / electronic components will still be provided.

[0412] The flow path is compact and has reduced turns / sharp turns, which reduces flow separation and lowers flow resistance.

[0413] The arrangement of the motor and flow path provides another layer of isolation due to the wall arrangement.

[0414] Having a modular motor and / or sensor module enables the various parts of the module to be disassembled if necessary for cleaning and / or maintenance.

[0415] There are advantageously no leak paths in the motor and / or sensor module.While the motor and / or sensor module may be a potential leak point, a leak in this area will result in oxygen being vented to the atmosphere or into the liquid chamber.

[0416] Valve module

[0417] Figures 20 to 28 A first configuration of valve module 4001 is shown. Valve module 4001 controls the flow of oxygen and / or other gases into the gas flow path of apparatus 10 and enables apparatus 10 to adjust the proportion of oxygen entrained in the air flow. The valve module is formed as a modular unit to facilitate manufacture, assembly, repair or replacement, such as in the event of a malfunction, routine maintenance or future upgrades / modifications.

[0418] The valve module 4001 is inserted vertically into the valve module receptacle 306 in the lower chassis 202 of the main housing in an upward direction. In alternative configurations, the valve module can be inserted into the housing in different directions, such as a forward direction, a downward direction, a rearward direction, or a lateral direction. The valve module 4001 can be removably engaged with the main housing of the device so that the valve module 4001 is substantially received in the housing and can be touched from the outside of the housing. In some configurations, the valve module 4001 can be fixed in the main housing and cannot be removed. A portion of the valve module 4001 is arranged to be substantially flush with the outer wall of the housing when the valve module is removably engaged with the housing.

[0419] Because the valve module is modular and accessible from the outside of the housing, the valve module can be replaced without significantly disassembling the device 10 and without damaging the seals of the housing of the device. Since the valve module 4001 is substantially received within the housing, when the valve module is engaged with the housing, it becomes integrated with the housing and does not increase the size or volume of the housing. In addition, the components of the valve module (e.g., the valve 4003 and valve manifold 4011 described below) are protected during use because they are positioned within the valve support 4051 and the main housing of the device during use. If the device 10 is accidentally bumped or dropped, this configuration significantly reduces the possibility of damaging the valve module and valve module components.

[0420] The valve module includes a flow control valve 4003 arranged to control the gas flow through the valve manifold 4011. The valve is arranged to control the gas flow in a part of the device. For example, the valve can be arranged to control the gas flow to the filter module 1001. Alternatively, the valve 4003 can be arranged to control the gas flow to another part of the device. The valve module 4001 and the filter module 1001 are positioned upstream of the blower 402 and the motor and / or sensor module 400. In some embodiments, the valve module 4001 and the filter module 1001 are positioned downstream of the blower 402.

[0421] The valve 4003 comprises a cylindrical body 4005 and a valve member therein.

[0422] For example, the flow control valve may be a solenoid valve, may be motor driven, or may be piezo-electrically operated.

[0423] In a solenoid valve, a valve member is actuated between an open position and a closed position. A solenoid valve may be a proportional valve. The range of gas flow through the valve (ie, due to the size of the valve opening) is relative to the current supplied to the valve.

[0424] Alternatively, the solenoid valve may be controlled with a modulated input signal such that the valve is modulated between an open position and a closed position.

[0425] The valve 4003 may be a needle valve, a plunger valve, a gate valve, a ball valve, a butterfly valve, a stop valve, etc. The valve may be a pressure-compensated type.

[0426] In some configurations, the valve is a normally closed valve; that is, the valve is closed when power is removed. This will prevent the connected gas supply line from continuously releasing oxygen or other gas when the device is powered off. In some alternative configurations, the valve is a normally open valve.

[0427] In some configurations, valve 4003 is an electrically actuated proportional solenoid valve. For example, the valve can be a μProp valve available from Staiger GmbH & Co. KG of Erligheim, Germany, an Asco 202 Series Preciflow valve available from Emerson / Asco Valves of New Jersey, or any other suitable type of valve.

[0428] The valve may have a coaxial inlet-outlet configuration.

[0429] The valve module 4001 includes a valve manifold 4011 having a body 4013 defining a gas flow path 4015 between a valve manifold gas inlet 4017 and one or more valve manifold gas outlets 4019. The gas inlet 4017 of the valve manifold is axially positioned at or toward the end of the valve manifold. In some configurations, the valve manifold 4011 has a single gas outlet 4019 radially positioned on the valve manifold. In some configurations, the valve manifold 4011 includes a plurality of valve manifold gas outlets 4019 radially positioned around the valve manifold. The valve manifold outlets 4019 are arranged to deliver gas from the valve manifold gas inlet 4017 to the gas inlet of the filter module 1001. The radial arrangement of the outlets 4019 helps direct oxygen (or other gas) toward the filter module, thereby minimizing the loss of oxygen and improving entrainment efficiency. The valve 4003 is arranged to control the flow of gas from the valve manifold gas inlet 4017 to the valve manifold gas outlet 4019. When the valve is "closed", the flow of gas from the gas inlet 4017 to the gas outlet 4019 is blocked. When the valve is "open", the flow of gas from the gas inlet 4017 to the gas outlet 4019 is enabled.

[0430] The end 4018 of the valve manifold 4011 opposite the gas inlet receives the valve 4003 and sealingly engages with it so that the valve and the valve manifold are in fluid communication. The end 4018 includes a flange 4023 to be mounted to the valve. The flange 4023 has apertures for receiving fasteners 4024, 4025 to fasten the manifold to the valve 4003. An O-ring may be provided around the periphery of the interface between the valve 4003 and the valve manifold 4011 to sealingly engage the valve with the valve manifold.

[0431] The valve manifold 4011 directs / disperses oxygen from the valve via radially positioned gas outlets 4019. In some embodiments, a single gas outlet 4019 is provided in the valve manifold. As oxygen passes through the outlet, noise is generated. Because the device may be used in a medical and / or home environment in close proximity to a patient, it is desirable to minimize the noise generated.

[0432] Additionally or alternatively, a hood, duct or channel may be formed around, near or in fluid communication with the valve manifold outlet 4019 to reduce noise. Additionally and / or alternatively, foam or the like may be placed around the valve manifold, near the valve manifold outlet, to reduce noise.

[0433] A small filter may be provided inside the inlet of the valve manifold gas inlet 4017 to prevent the introduction of dust or particles into the valve.

[0434] The end of the valve manifold corresponding to the gas inlet 4015 is arranged to receive and connect to a connector 4031. In the form shown, the connector 4031 is a rotary connector. Alternatively, the connector 4031 may be arranged so that the gas inlet 4033 of the connector can be moved in a different manner, such as, for example, translational movement or pivotal movement.

[0435] Valve module 4001 is located at the beginning of the flow path of the device. If valve 4003 were to become blocked (i.e., blocked by dust, particles, etc.) such that it would remain open, excess pressurized oxygen or other gas would flow in from the ambient air inlet opening in valve support 4051 (e.g., Fig.26 This will prevent any excessive pressure from reaching the patient. Thus, the system can be considered inherently pressure limited without the use of a pressure relief valve.

[0436] An opening 4052 is provided in the valve support 4051 to allow ambient air to be drawn into the gas flow path of the device. The ambient air flow path passes near or adjacent to the valve. In the form shown, the opening 4052 is located around the gas inlet of the rotary connector. In addition or alternatively, the opening may be located elsewhere in the valve support. When the blower motor 402 of the device is operated, suction through the filter module and the valve module will be generated to draw ambient air into the device. The ambient air flow path passes through the valve module and allows ambient air to be entrained by the gas flow from the flow control valve. The ambient air flow path has a gas outlet adapted to convey ambient air so that it flows through one or more temperature sensors of the device for conveying gas flow.

[0437] The device may simultaneously draw in gas from the gas inlet of the valve manifold and draw in ambient air, or pressurization of the gas from the gas inlet may force the gas through the filter. The gas will exit the valve module and enter the gas inlet in the filter. The device may be configured such that gas from the gas inlet and ambient air are dynamically entrained / mixed in the device before being delivered to the gas outlet of the device.

[0438] The valve module can be configured to minimize pressure drop across the valve module by one or more of the following: having large openings 4052 for ambient air around the rotary connector and / or elsewhere; having radiused / rounded / slanted edges in the flow path (i.e., for example, inside the valve manifold) to minimize turbulence and smooth flow.

[0439] The valve module 4001 described herein is arranged to be directly coupled to the filter 1001 to provide a gas flow path from the valve module to the filter. No hose connection is required between the valve module and the filter module. This minimizes the size of the components and makes it easy to connect and disconnect the modular valve module and the filter module.

[0440] The filter modules and valve modules described herein can provide a variable gas flow path for the device. For example, the valve module can control the oxygen flow into the gas flow path of the device via the valve module and the filter module. Alternatively, by means of a first sub-compartment gas inlet (e.g., Fig.24 The inlet 1011 of the filter module directly connects the alternative oxygen source to the filter module, bypassing the valve module. This is practical in the case where the user may wish to manually adjust the oxygen supply (i.e., such as through a wall supply rotor flow meter).

[0441] It will be appreciated that the filter modules and valve modules described herein may be used separately in an apparatus for delivering a gas flow. Alternatively, the filter and valve modules may be used together as a filter and valve assembly for improved functionality.

[0442] In the configuration shown, the device 10 receives oxygen in at least one of the following ways: via a valve module (for automatic oxygen regulation of the device); or via an alternative gas inlet provided on top of the filter (allowing attachment of a manually adjustable oxygen supply - i.e., such as via a wall supply rotameter).

[0443] The various configurations described are merely exemplary configurations. Any one or more features from any of these configurations may be used in combination with any one or more features from any of the other configurations.

[0444] For example, a rotary connector used in a valve module may have additional functionality. In some configurations, the rotary connector may be arranged to rotate about more than one axis; and may, for example, have two adjacent rotary connection parts with rotation axes that are transverse to each other, so that the gas inlet of the rotary connector can rotate about two axes. In some configurations, the rotary connector may include a ball and socket arrangement or a similar arrangement so that the gas inlet of the rotary connector can rotate in substantially any direction. In some configurations, the rotary connector may be arranged to provide both rotational and translational movement; so that the gas inlet of the rotary connector can rotate about one or more axes and, for example, can move in a straight line. This may be practical for translating the gas inlet from one part of the device to another, such as, for example, translating from one side of the device to the other side of the device. In some configurations, the gas inlet may be arranged to translate rather than rotate.

[0445] As another example, while the motor and / or sensor subassembly recess is described as being located in the bottom side of the main housing, it may alternatively be located in the rear, side, front, or top of the housing. In the case of such variations, the air and / or oxygen inlet may also be positioned differently as desired.

[0446] As another example, instead of the liquid chamber and chamber compartment being configured so that the liquid chamber is inserted into and removed from the chamber compartment from the front of the housing, the configuration may allow the liquid chamber to be inserted into and removed from the chamber compartment from the side, back, or top of the housing.

[0447] As another example, although the filter module is described as being inserted into the housing from above and the valve module is inserted into the housing from below, either or both of these components may be inserted into any suitable portion of the housing, such as an upper portion, a lower portion, a side portion, a front portion, or a rear portion.

[0448] The filter module and valve module are described with reference to a flow therapy device capable of delivering heated and humidified gas to a patient or user. The device may be suitable for treating chronic obstructive pulmonary disease (COPD). The device may be configured to deliver gas to a patient interface at a high flow rate (high flow therapy), particularly nasal high flow therapy.

[0449] Alternatively, the filter module and / or valve module may be used in a device for a different purpose. The device may be a high flow therapy device, or may be a low flow therapy device. Features may also be provided in a device for providing continuous positive airway pressure (CPAP), which may deliver gas (humidified or otherwise) under positive pressure.

[0450] Alternatively, the filter module and / or valve module may be used with devices that do not require a humidifier and therefore do not require the features of the liquid chamber 300 or chamber compartment 108. For example, it will be appreciated that a configuration that isolates the motor and gas flow path from electrical and electronic components has broad application in other types of gas delivery devices.

[0451] The “flow therapy device” language is intended to cover all such variations.

[0452] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that the prior art forms part of the common general knowledge in the relevant field in any country in the world.

[0453] Where references are made to directional terms such as "upward", "downward", "forward", "rearward", "horizontal", "vertical", etc., these terms refer to the device when it is in a typical in-use position and are used to illustrate and / or describe relative directions or orientations.

[0454] Unless the context clearly requires otherwise, throughout the specification and claims, the words "comprising," "including," and the like are to be interpreted in an inclusive sense and not in an exclusive or exhaustive sense, that is, in the sense of "including, but not limited to."

[0455] As used herein, the terms "substantially," "approximately," and "substantially" represent an amount that is close to the stated amount and still performs a desired function or achieves a desired result. For example, in some embodiments, the terms "substantially," "approximately," and "substantially" may refer to an amount within a range of less than or equal to 10%, less than or equal to 5%, and less than or equal to 1% of the stated amount, as the context may permit.

[0456] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that the prior art forms part of the common general knowledge in the relevant field in any country in the world.

[0457] The disclosed apparatus and systems may also be broadly said to reside in the parts, elements and features referred to or indicated in the specification of this application, either individually or collectively, and in any or all combinations of two or more of the parts, elements or features.

[0458] Where in the foregoing description, reference has been made to integers or components having known equivalents thereof, such integers are incorporated herein as if individually set forth.

[0459] Depending on the embodiment, certain actions, events, or functions of any algorithm, method, or process described herein may be performed in a different sequence, may be added, combined, or omitted entirely (e.g., not all described actions or events are necessary for the practice of the algorithm). In addition, in some embodiments, actions or events may be performed simultaneously rather than sequentially, for example, through multithreading, interrupt handling, or multiple processors or processor cores or on other parallel architectures.

[0460] It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the disclosed apparatus and system, and without diminishing its attendant advantages. For example, various components may be repositioned as desired. It is therefore contemplated that such changes and modifications are included within the scope of the disclosed apparatus and system. In addition, not all of these features, aspects, and advantages are necessary to practice the disclosed apparatus and system. Therefore, the scope of the disclosed apparatus and system is intended to be limited only by the appended claims.

Claims

1. A respiratory apparatus for providing a flow of gas to a patient, the respiratory apparatus comprising: a gas composition sensor configured to determine at least an oxygen content (FdO2) of the gas flow during operation of the breathing apparatus; a controller configured to control delivery of the flow of gas to the patient using closed loop control, wherein the controller is configured to: receiving patient parameter data indicative of oxygen saturation (SpO2) of the patient from at least one sensor; receiving data indicative of a measured delivered oxygen fraction (FdO2) of the gas flow from the gas composition sensor; receiving flow data corresponding to or indicative of a flow rate of the flow of gas provided by the breathing apparatus; determining at least one time-related parameter, the or each time-related parameter being based at least in part on the flow data; and generating a patient-specific model, the patient-specific model being based at least in part on the at least one time-dependent parameter; wherein the patient-specific model is used to predict changes in the oxygen saturation (SpO2) of the patient in response to changes in the measured delivered oxygen fraction (FdO2) of the gas flow.

2. A breathing apparatus as claimed in claim 1, wherein: The determination of the at least one time-dependent parameter is based at least in part on whether the flow rate is below a defined threshold.

3. A breathing apparatus as claimed in any one of claims 1 to 2, wherein: The at least one time-related parameter is a device-specific delay time associated with the delivery delay time of oxygen from the respiratory apparatus to the patient.

4. A breathing apparatus as claimed in any one of claims 1 to 3, wherein: The at least one time-related parameter is a patient-specific delay time associated with a delivery delay time of oxygen from the patient's upper airway to a tissue perfusion monitoring site.

5. A breathing apparatus as claimed in any one of claims 1 to 4, wherein: The at least one time-dependent parameter is a decay value associated with the time it takes for the patient's SpO2 level to decay to a stable range of values ​​after a change in FdO2 by the controller.

6. A breathing apparatus as claimed in any one of claims 1 to 5, wherein: The flow data indicates or corresponds to a specified flow configured by a user.

7. A breathing apparatus as claimed in any one of claims 1 to 5, wherein: The flow data indicates or corresponds to a measured flow of the gas provided by the breathing apparatus.

8. A breathing apparatus as claimed in claim 7, wherein: The flow rate is received from a flow sensor disposed in the gas flow.

9. A breathing apparatus as claimed in any one of claims 1 to 8, wherein: The determination of the at least one time-related parameter is based at least in part on at least one criterion associated with one or more physical characteristics of the patient.

10. A breathing apparatus as claimed in claim 9, wherein: The determination of the at least one time-related parameter is based at least in part on at least one criterion associated with the patient's size.

11. A breathing apparatus as claimed in claim 9 or claim 10, wherein: The at least one criterion associated with the one or more physical characteristics of the patient is flow rate.

12. A breathing apparatus as claimed in claim 9 or claim 10, wherein: The at least one criterion associated with the one or more physical characteristics of the patient is a detected patient interface type.

13. A breathing apparatus as claimed in any one of claims 9 to 12, wherein: The at least one criterion associated with the one or more physical characteristics of the patient is a patient interface type configured by a user.

14. A breathing apparatus as claimed in any one of claims 9 to 13, wherein: The at least one criterion associated with the one or more physical characteristics of the patient is heart rate.

15. A breathing apparatus as claimed in any one of claims 9 to 14, wherein: The at least one criterion associated with the one or more physical characteristics of the patient is breathing rate.

16. A breathing apparatus as claimed in any one of claims 9 to 15, wherein: The at least one criterion associated with the one or more physical characteristics of the patient is a measure of breathing intensity and / or volume.

17. A breathing apparatus as claimed in any one of claims 9 to 16, wherein: The at least one criterion associated with the one or more physical characteristics of the patient is a previous treatment type or mode.

18. A breathing apparatus as claimed in any one of claims 9 to 17, wherein The controller is further configured to select a first algorithm or a second algorithm to determine the at least one time-related parameter based at least in part on whether the flow rate satisfies a defined threshold.

19. A breathing apparatus as claimed in claim 18, wherein Selecting the first algorithm or the second algorithm to determine the at least one time-related parameter is further based at least in part on the at least one criterion associated with the one or more physical characteristics of the patient.

20. A breathing apparatus as claimed in any one of claims 1 to 19, wherein: The closed-loop control includes using a first closed-loop control model configured to determine a target delivered oxygen fraction (FdO2) for the gas flow.

21. A breathing apparatus as claimed in claim 20, wherein: The target FdO2 for the gas flow is determined based at least in part on a target SpO2 and the patient parameter indicative of the oxygen saturation (SpO2) of the patient.

22. A breathing apparatus as claimed in claim 21, wherein The target FdO2 for the gas flow is further based at least in part on the received data indicative of a measured delivered oxygen fraction (FdO2) of the gas flow.

23. A breathing apparatus as claimed in any one of claims 21 to 22, wherein: The target FdO2 is further based at least in part on a previously determined target FdO2.

24. A breathing apparatus as claimed in any one of claims 1 to 23, wherein: The closed-loop control includes using a second closed-loop control model configured to determine a control signal for an oxygen inlet valve based at least in part on a difference between a target FdO2 for the gas flow and the received data indicative of the measured delivered oxygen fraction (FdO2) of the gas flow.

25. A breathing apparatus as claimed in claim 24, wherein: The control signal for the oxygen valve is determined based at least in part on the target FdO2 and the received data indicative of the measured delivered oxygen fraction (FdO2) of the gas flow.

26. A breathing apparatus as claimed in claim 25, wherein: The control signal for the oxygen valve is further determined based at least in part on the received flow data.

27. A breathing apparatus as claimed in claim 26, wherein: The received flow data corresponds to or is indicative of a total gas flow provided by the breathing apparatus.

28. A breathing apparatus as claimed in any one of claims 1 to 27, wherein: The patient-specific model is generated during a current treatment session.

29. A breathing apparatus as claimed in claim 28, wherein The patient-specific model is generated during the current treatment session based at least in part on a default model.

30. A breathing apparatus as claimed in any one of claims 1 to 29, wherein: The patient-specific model is updated during the current treatment session.

31. A breathing apparatus as claimed in any one of claims 1 to 30, wherein: The patient-specific model includes the patient's oxygen efficiency.

32. A breathing apparatus as claimed in claim 31, wherein The oxygen efficiency is determined based at least in part on the received data indicative of the oxygen saturation (SpO2) of the patient and the received data indicative of the measured delivered oxygen fraction (FdO2) of the gas flow.

33. A breathing apparatus as claimed in any one of claims 31 to 32, wherein: The oxygen efficiency is determined based at least in part on the received data indicative of the oxygen saturation (SpO2) divided by the received data indicative of the measured fraction of delivered oxygen (FdO2).

34. A breathing apparatus as claimed in any one of claims 31 to 33, wherein: The oxygen efficiency is determined based at least in part on a non-linear relationship between the received data indicative of the oxygen saturation (SpO2) of the patient and the received data indicative of the measured fraction of oxygen delivered (FdO2).

35. A breathing apparatus as claimed in any one of claims 1 to 34, wherein: The controller is configured to predict the SpO2 of the patient based at least in part on the received data indicative of the measured fraction of oxygen delivered (FdO2).

36. A breathing apparatus as claimed in claim 35, wherein: One or more previous predictions of the SpO2 are compared to currently received data indicative of the oxygen saturation SpO2 to calculate a model error.

37. A breathing apparatus as claimed in claim 36, wherein: The model error is weighted according to a signal quality of the at least one sensor.

38. A breathing apparatus as claimed in any one of claims 36 to 37, wherein The model error is used to correct the current SpO2 prediction.

39. A breathing apparatus as claimed in any one of claims 36 to 38, wherein The predicted SpO2 is based at least in part on a Smith predictor.

40. A breathing apparatus as claimed in any one of claims 1 to 39, further comprising: A patient interface, wherein the patient interface is selected from at least one of the following: a face mask, a nasal mask, a nasal pillow mask, a tracheostomy interface, a nasal cannula, or an endotracheal tube.

41. A breathing apparatus as claimed in claim 40, wherein: The nasal cannula is a non-sealing nasal cannula.

42. A breathing apparatus as claimed in any one of claims 1 to 41, wherein: The respiratory apparatus is configured to deliver a nasal high flow (NHF) flow of gas to the patient.

43. A breathing apparatus as claimed in any one of claims 1 to 42, wherein: The at least one sensor includes a pulse oximeter configured to determine or provide patient parameter data indicative of at least an oxygen saturation (SpO2) of the patient.

44. A breathing apparatus as claimed in any one of claims 1 to 43, wherein: The controller is configured to receive device parameter data indicative of an oxygen concentration of the gas flow.

45. A breathing apparatus as claimed in any one of claims 1 to 44, further comprising: Supplement gas inlet valve.

46. ​​A breathing apparatus as claimed in claim 45, wherein The controller is configured to control operation of the supplemental gas inlet valve.

47. A breathing apparatus as claimed in any one of claims 45 to 46, wherein The make-up gas inlet valve is a proportional valve.

48. A breathing apparatus as claimed in any one of claims 45 to 47, wherein The supplementary gas inlet valve is an oxygen inlet valve.

49. A breathing apparatus as claimed in any one of claims 45 to 48, wherein The supplemental gas inlet valve includes a swivel connector.

50. A breathing apparatus as claimed in any one of claims 1 to 49, further comprising an ambient air inlet.

51. A breathing apparatus as claimed in claim 50 as appended to claim 48, wherein The oxygen inlet valve is in fluid communication with a filter module, wherein the respiratory apparatus is configured to entrain oxygen received from the oxygen inlet valve with ambient air from the ambient air inlet into the filter module.

52. A breathing apparatus as claimed in any one of claims 1 to 52, wherein: The gas composition sensor is positioned downstream of a blower module of the respiratory apparatus.

53. A breathing apparatus as claimed in claim 52 as appended to claim 51, wherein The filter module is positioned upstream of the blower module of the respiratory apparatus.

54. A breathing apparatus as claimed in any one of claims 52 to 53, wherein The blower module mixes ambient air and oxygen.

55. The breathing apparatus of any one of claims 1 to 54, further comprising a humidifier.

56. A breathing apparatus as claimed in any one of claims 1 to 55, further comprising an integrated blower and humidifier.

57. A breathing apparatus as claimed in any one of claims 1 to 56, wherein: The breathing apparatus is configured to be portable.

58. A breathing apparatus as claimed in any one of claims 1 to 57, wherein: The breathing apparatus is configured to have a controlled variable flow.

59. The breathing apparatus of any one of claims 1 to 58, further comprising a heated breathing tube.

60. A breathing apparatus as claimed in any one of claims 1 to 59, wherein: The ultrasonic sensor system includes a first ultrasonic transducer and a second ultrasonic transducer.

61. A breathing apparatus as claimed in claim 60, wherein: Each of the first ultrasonic transducer and the second ultrasonic transducer is a receiver and a transmitter.

62. A breathing apparatus as claimed in claim 61, wherein The first ultrasonic transducer and the second ultrasonic transducer transmit pulses bidirectionally.

63. A breathing apparatus as claimed in claim 62, wherein: The first ultrasonic transducer is a transmitter and the second ultrasonic transducer is a receiver.

64. A breathing apparatus as claimed in any one of claims 60 to 63, wherein At least one of the first ultrasonic transducer or the second ultrasonic transducer transmits pulses across the gas flow.

65. A breathing apparatus as claimed in any one of claims 1 to 64, wherein: The controller is configured to display a first oxygen efficiency characteristic on a display of the respiratory apparatus.

66. A breathing apparatus as claimed in any one of claims 1 to 65, wherein: The controller is configured to display a second oxygen efficiency characteristic on a display of the respiratory apparatus, wherein the second indication of oxygen efficiency is based at least in part on the oxygen efficiency and the measured breathing rate of the patient.

67. A breathing apparatus as claimed in claim 66, wherein The second oxygen efficiency characteristic is calculated by dividing the received patient parameter data indicative of the oxygen saturation (SpO2) of the patient by the received data indicative of the delivered oxygen fraction (FdO2) of the gas flow and dividing the resulting value by the measured respiratory rate.

68. A breathing apparatus as claimed in any one of claims 66 to 67, wherein The controller is configured to display a graph or a trend line indicating at least one of the first oxygen efficiency characteristic or the second oxygen efficiency characteristic over a defined time period.

69. A breathing apparatus as claimed in any one of claims 1 to 68, wherein The respiratory device is capable of changing between operating in a high flow therapy mode and a bubble CPAP therapy mode.

70. The breathing apparatus of claim 69, wherein In the high flow therapy mode, the respiratory device is configured to provide high flow therapy.

71. The breathing apparatus of claim 69, wherein: In the Bubble CPAP mode, the respiratory device is configured to provide Bubble CPAP therapy.

72. A breathing apparatus as claimed in any one of claims 1 to 71, wherein: One or more of the patient parameter data indicative of oxygen saturation (SpO2) and the flow data are received during provision of therapy to the patient and are related to current operation of the respiratory therapy device.

73. A breathing apparatus as claimed in any one of claims 1 to 71, wherein: One or more of the patient parameter data indicative of oxygen saturation (SpO2) and the flow data are associated with one or more previous operating states or therapy sessions of the respiratory therapy device.

74. A respiratory apparatus for providing a flow of gas to a patient, the respiratory apparatus comprising: a gas composition sensor configured to determine at least a delivered oxygen fraction (FdO2) of the gas flow during operation of the breathing apparatus; a controller configured to control delivery of the flow of gas to the patient using closed loop control, wherein the controller is configured to: receiving patient parameter data indicative of oxygen saturation (SpO2) of the patient from at least one sensor; receiving data indicative of a measured delivered oxygen fraction (FdO2) of the gas flow from the gas composition sensor; receiving flow data corresponding to or indicative of a flow rate of the flow of gas provided by the breathing apparatus; comparing the flow data with a defined flow threshold; determining a set of time-dependent parameters using a first model or a second model based at least in part on a result of said comparison of said flow data to said defined flow threshold; and A patient-specific model is generated based at least in part on the set of time-dependent parameters, wherein the patient-specific model is used to predict changes in the oxygen saturation (SpO2) of the patient in response to changes in the measured delivered oxygen fraction (FdO2) of the gas flow.

75. A breathing system for providing a flow of gas to a patient, the breathing system comprising: a gas composition sensor configured to determine at least a delivered oxygen fraction (FdO2) of the gas flow during operation of the breathing system; a patient sensor configured to at least determine an oxygen saturation (SpO2) of the patient; a controller configured to control delivery of the flow of gas to the patient using closed loop control, wherein the controller is configured to: receiving patient parameter data indicative of oxygen saturation (SpO2) of the patient from the patient sensor; receiving data indicative of a measured delivered oxygen fraction (FdO2) of the gas flow from the gas composition sensor; receiving flow data corresponding to or indicative of a flow rate of the flow of gas provided by the breathing system; and A patient-specific model is generated based at least in part on the flow data, wherein the patient-specific model is used to predict changes in the oxygen saturation (SpO2) of the patient in response to changes in the delivered oxygen fraction (FdO2) of the gas flow.

76. A method for controlling gas flow delivery to a patient using closed loop control, the method comprising: receiving patient parameter data indicative of oxygen saturation (SpO2) of the patient from at least one sensor; receiving data indicative of a measured delivered oxygen fraction (FdO2) of the gas flow from a gas composition sensor; receiving flow data corresponding to or indicating a flow rate of the gas flow; determining at least one time-related parameter, the or each time-related parameter being based at least in part on the flow data; as well as generating a patient-specific model, the patient-specific model being based at least in part on the at least one time-dependent parameter; wherein the patient-specific model is used to predict changes in the oxygen saturation (SpO2) of the patient in response to changes in the measured delivered oxygen fraction (FdO2) of the gas flow.

77. A respiratory apparatus for providing a flow of gas to a patient, the respiratory apparatus comprising: a supplemental gas inlet valve configured to receive oxygen from an oxygen supply; a flow generator operatively connected to the supplemental gas inlet valve and configured to generate a gas flow; a user interface, the user interface comprising a display; and a controller configured to control delivery of the flow of gas to the patient using closed loop control, wherein the controller is configured to: determining a patient type based on one or more input or estimated or measured parameters of or associated with the patient; determining a patient-specific model, the patient-specific model being based at least in part on the determined patient type; and Closed-loop control of the oxygen concentration of the gas flow is initiated using the validated patient-specific model.

78. A breathing apparatus as claimed in claim 77, wherein The controller is further configured to display on the display a request to confirm the determined patient-specific model and receive user input related to the request.

79. A breathing apparatus as claimed in claim 78, wherein The controller is further configured to initiate closed-loop control of the oxygen concentration of the gas flow using the confirmed patient-specific model based on the received user input indicating confirmation of the patient-specific model.

80. A breathing apparatus as claimed in any one of claims 77 to 79, wherein The patient-specific model is used to predict changes in the patient's oxygen saturation (SpO2) in response to changes in a measured delivered oxygen fraction (FdO2) of the gas flow.

81. The respiratory apparatus of any one of claims 77 to 80, further comprising a gas composition sensor configured to determine at least a delivered oxygen fraction (FdO2) of the gas flow during operation of the respiratory apparatus.

82. A breathing apparatus as claimed in claim 81, wherein The controller is further configured to receive data indicative of a measured delivered oxygen fraction (FdO2) of the gas flow from the gas composition sensor.

83. A breathing apparatus as claimed in any one of claims 77 to 82, wherein The controller is further configured to receive patient parameter data indicative of an oxygen saturation (SpO2) of the patient from at least one sensor.

84. A breathing apparatus as claimed in claim 83, wherein Closed-loop control of the oxygen concentration of the gas flow using the confirmed patient-specific model includes adjusting the supplemental gas inlet valve based on the received patient parameter data indicative of the patient's oxygen saturation (SpO2) and changes in the patient's oxygen saturation (SpO2) as predicted by the patient-specific model.

85. A breathing apparatus as claimed in any one of claims 77 to 84, wherein The patient type is determined to be one of: an adult patient or a pediatric patient.

86. A breathing apparatus as claimed in claim 85, wherein The pediatric patient can be further identified as one of: an infant patient, or a neonatal patient, or a pediatric patient.

87. A breathing apparatus as claimed in any one of claims 77 to 86, wherein The one or more input or estimated or measured parameters of or associated with the patient include the size of the patient.

88. A breathing apparatus as claimed in claim 87, wherein The patient's size is their height.

89. A breathing apparatus as claimed in any one of claims 77 to 88, wherein The breathing apparatus further comprises a flow sensor.

90. The breathing apparatus of claim 89, wherein: The one or more input or estimated or measured parameters of or associated with the patient are estimated via the flow setting.

91. A breathing apparatus as claimed in any one of claims 77 to 90, wherein The one or more input or estimated or measured parameters of or associated with the patient are a measured or estimated heart rate of the patient and / or a measured or estimated breathing rate of the patient.

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