Flow path sensing in flow therapy devices

Abstract

This invention provides flow path sensing for a flow therapy device, which includes a sensing chamber for measuring the flow rate of gas supplied to a patient. The sensing chamber may be located after a blower and / or a mixer. The sensing chamber may include an ultrasonic transducer, a temperature sensor, a heated temperature sensing element, and / or a gas concentration sensor. The gas flow path used in conjunction with the sensor system prevents the generation of undesirable vortices in the gas flow that could cause anomalies in flow measurement.

Description

[0001] Divisional Application Instructions

[0002] This application is a divisional application of Chinese invention patent application No. 201680079350.9, filed on December 2, 2016, entitled "Flow path sensing for a flow therapy device". Technical Field

[0003] This disclosure relates to methods and systems for flow path sensing in flow therapy devices used to deliver gas to patients. Background Technology

[0004] Respiratory assist devices are used in a variety of environments, such as hospitals, medical facilities, home care, or home settings, to deliver gas flow to a user or patient. Respiratory assist devices or flow therapy devices may include valves for delivering oxygen and gas flow, and / or humidifiers for delivering heated and humidified gases. Flow therapy devices allow for the regulation and control of airflow characteristics, including flow rate, temperature, gas concentration, humidity, pressure, etc. These gas properties are measured using sensors such as heated temperature sensing elements and / or thermistors. Summary of the Invention

[0005] This disclosure describes a flow therapy device in which gas flow rate is measured through at least a portion of a flow path. This portion of the flow path may be configured to be continuously curved, such that there are no significant angles. The flow path may include an inlet, a horizontal section, and an outlet, wherein the inlet and outlet may be positioned in opposite vertical directions, and the horizontal section is positioned between the inlet and outlet. The horizontal section may have a smooth curve along its entire length. The flow path may further include one or more sensors positioned within the flow path and configured to measure the flow rate of gas passing through that portion of the flow path. The one or more sensors may include one or more of an ultrasonic transducer or a gas concentration sensor. The one or more sensors may be configured to sense flow rate and / or oxygen concentration. The one or more sensors may be located within a sensor module.

[0006] The flow path can be further configured to have a total flow distance between 50 mm and 150 mm. The flow path can also be further configured to have an average cross-sectional diameter between 10 mm and 20 mm.

[0007] The flow path may further include a first cross-sectional area at a first end of the flow path; a second cross-sectional area at a second end of the flow path; and an intermediate cross-sectional area between the first end and the second end of the flow path, wherein the intermediate cross-sectional area may be smaller than the first cross-sectional area, and wherein the intermediate cross-sectional area may be smaller than the second cross-sectional area.

[0008] The one or more sensors may be located after the blower. The blower may be a mixer. The one or more sensors may further include a heated temperature sensing element and / or a pressure sensor configured to measure the flow rate of the gas, and / or temperature, humidity, and humidity.

[0009] A gas flow path is also described to prevent unwanted vortices from appearing in the gas flow rate that could cause abnormalities when measuring the flow rate. This flow path can be used with an ultrasonic sensor system.

[0010] This disclosure describes a flow therapy device that may include: an inlet port receiving gas flow rates from at least two different gas sources; a blower receiving the gas flow rates from the inlet port, wherein the blower is configured to mix the gas flow rates from the different gas sources to produce a mixed gas; a gas flow path receiving the mixed gas from the blower and directing the gas flow through a sensor chamber; and one or more sensors configured to measure one or more properties of the gas flow rates flowing through the gas flow path. The one or more sensors may be located after the blower. The blower may be a mixer. The one or more sensors may be located within a sensor module.

[0011] Different gas sources may include oxygen, and the inlet port may include a valve configured to deliver an oxygen flow rate to the blower. This valve may include a proportional valve.

[0012] The one or more sensors may include two or more ultrasonic transducers. The one or more sensors may also include a gas concentration sensor.

[0013] These ultrasonic transducers can be configured to determine gas concentration. These ultrasonic transducers can be configured to determine flow rate.

[0014] The one or more sensors may include a heated temperature sensing element configured to measure gas flow rate.

[0015] This disclosure describes a sensing chamber in a flow therapy device, which may include a flow path configured to accommodate a gas flow; and one or more sensors configured to measure the properties of the gas flow through the flow path, wherein the sensors may include a first ultrasonic transducer positioned at a downstream portion of the flow path and a second ultrasonic transducer positioned at an upstream portion of the flow path, and wherein the flow path may be configured to have a curved shape between the first and second ultrasonic transducers. This curved shape may be configured to reduce ineffective space in the gas flow.

[0016] These sensors may further include one or more temperature sensors configured to measure the temperature of the gas in the flow path.

[0017] The temperature sensor can be located in the flow path.

[0018] The sensing chamber further includes a sensing circuit board, wherein a first portion of the sensing circuit board is at least partially positioned within the flow path.

[0019] The sensing circuit board can be further configured to enable heat conduction between the airflow and the temperature sensor, and to impede heat conduction between the walls of the sensing chamber and the temperature sensor.

[0020] The sensing circuit board may further include at least a second portion of the sensing circuit board positioned outside the flow path.

[0021] The sensing chamber may further include a seal that separates a first portion of the sensing circuit board from a second portion of the sensing circuit board. This seal may be a pneumatic seal.

[0022] The flow path can be further configured to have a total flow distance between 50 mm and 150 mm.

[0023] The flow path can be further configured to have an average cross-sectional diameter between 10 mm and 20 mm.

[0024] The flow path can be further configured to have a constant cross-sectional shape along the length of the flow path.

[0025] The flow path may include a first cross-sectional area at a first end of the flow path; a second cross-sectional area at a second end of the flow path; and an intermediate cross-sectional area between the first and second ends of the flow path, wherein the intermediate cross-sectional area may be smaller than the first cross-sectional area, and wherein the intermediate cross-sectional area may be smaller than the second cross-sectional area. The flow path may be configured to bend entirely between the first and second ultrasonic transducers.

[0026] This disclosure describes a method for determining the characteristics of a gas flowing through a sensing chamber along a gas flow path from a first end to a second end of the sensing chamber, wherein the sensing chamber includes a first ultrasonic transducer positioned at the first end and a second ultrasonic transducer positioned at the second end, in a downstream direction defined along the gas flow path from the first end to the second end, and in an upstream direction defined along the gas flow path from the second end to the first end. The method includes emitting a downstream acoustic pulse from the first ultrasonic transducer and detecting the downstream acoustic pulse at the second ultrasonic transducer; determining a downstream time of flight based at least in part on the downstream acoustic pulse; emitting an upstream acoustic pulse from the second ultrasonic transducer and detecting the upstream acoustic pulse at the first ultrasonic transducer; determining an upstream time of flight based at least in part on the upstream acoustic pulse; and determining the characteristics of the gas by taking into account the ineffective space between the first and second ultrasonic transducers.

[0027] Determining the properties of a gas can include using the following equation to determine its velocity:

[0028] as well as

[0029]

[0030] Where c represents the speed of sound, D represents the distance between the first and second ultrasonic transducers where there is airflow, D0 represents the distance between the first and second ultrasonic transducers where there is no airflow, t1 represents the downstream flight time, and t2 represents the upstream flight time.

[0031] This disclosure describes a method for determining the characteristics of a gas flowing through a sensing chamber along a gas flow path from a first end to a second end of the sensing chamber, wherein the sensing chamber includes a first ultrasonic transducer positioned at the first end and a second ultrasonic transducer positioned at the second end, in a downstream direction defined along the gas flow path from the first end to the second end, and in an upstream direction defined along the gas flow path from the second end to the first end. The method may include emitting a downstream acoustic pulse from the first ultrasonic transducer and detecting the downstream acoustic pulse at the second ultrasonic transducer. The method may further include measuring the entire received ultrasonic waveform. The method may further include performing a cross-correlation between the received waveform and a reference to generate a time-of-flight measurement. The reference may be pre-recorded or predefined. The reference may be a single or previous waveform. The cross-correlation may include generating a differential time-of-flight, allowing the flow rate to be calculated. The gas may include helium oxide or carbon dioxide. The cross-correlation may include highlighting anomalies during operation.

[0032] This disclosure describes a system for calibrating a measurement module in a flow therapy device. The system may include a blower configured to deliver a gas flow rate at predetermined operating parameters; a first sensor configured to determine a first value of a gas characteristic; a first memory configured to store the first value; a control system configured to change the gas flow rate from the blower; and to adjust calibration parameters based at least in part on a comparison between the first value and a reference value at the predetermined operating parameters. The reference value may be obtained from one or more of a lookup table, user input, or calculated values.

[0033] The first sensor may include a pair of ultrasonic transducers.

[0034] The calibration system may further include a valve configured to deliver a flow rate of a second gas, wherein the control system may be further configured to change the flow rate of the second gas. The second gas may contain oxygen.

[0035] The system may further include a second sensor configured to determine a second value of the gas properties, wherein the control system may be further configured to compare the first value with the second value.

[0036] The second sensor may include a temperature sensor. The second sensor may include a heated temperature sensing element configured to measure gas flow rate. The second sensor may include a humidity sensor. The second sensor may further include a pressure sensor.

[0037] The gas characteristic can be flow rate. The gas characteristic can be oxygen concentration or other gas concentration. The gas characteristic can be temperature. The gas characteristic can be humidity. The gas characteristic can be pressure.

[0038] This disclosure describes a sensing chamber in a flow therapy device. The sensing chamber may include one or more sensors configured to measure gas properties, including a first ultrasonic transducer at a downstream portion of the flow path and a second ultrasonic transducer at an upstream portion of the flow path, and a heated temperature sensing element configured to measure the gas flow rate. The heated temperature sensing element can provide redundancy in flow measurement, including rapid flow measurement at low flow rates by the first and second ultrasonic transducers, and accurate flow measurement at low flow rates by the heated temperature sensing element. This redundancy can aid in flow rate calibration.

[0039] This heated temperature sensing element can adjust the calibration parameters of the ultrasonic transducer. The heated temperature sensing element can adjust the readings of the ultrasonic transducer. This adjustment can be continuous. The adjustment can be a predetermined amount, rate, or weighted flow rate, or other sensing parameter.

[0040] This disclosure describes a sensing chamber in a flow therapy device. The sensing chamber may include one or more sensors configured to measure gas properties, including a first ultrasonic transducer at a downstream portion of the flow path and a second ultrasonic transducer at an upstream portion of the flow path, wherein the one or more sensors may be directly mounted to a sensing circuit board. The sensing chamber may further include an ultrasonic circuit system positioned close to the ultrasonic sensors. The ultrasonic circuit system may be environmentally isolated from the one or more sensors. The chamber may further include a seal isolating the ultrasonic circuit system from the one or more sensors. The seal may be a pneumatic seal. At least one of the one or more sensors may be located on the sensing circuit board.

[0041] This disclosure describes a gas delivery system. The system may include one or more sensors configured to determine gas properties; a first pressure sensor configured to determine a first absolute pressure, wherein the first absolute pressure may be configured to determine an estimate of ambient pressure; and a second pressure sensor configured to determine a second absolute pressure, wherein the difference between the first and second absolute pressures may determine a calculated pressure differential, and wherein the calculation of gas properties may be adjusted at least in part based on changes in ambient pressure.

[0042] The system may further include a blower. The second absolute pressure sensor can be located downstream of the blower. The pressure generated by the gas source can be estimated from the calculated pressure difference.

[0043] One or more sensors configured to determine gas properties may include ultrasonic sensors. Ambient pressure readings allow for comparison of mass flow rate with volumetric flow rate. A first absolute pressure sensor may be located within the housing of the gas delivery system. A second pressure sensor may be located within a sensing chamber or sensor module and detects the pressure of the gas flow after the gas has been pressurized by a gas source. Attached Figure Description

[0044] Figure 1 The respiratory assist device, in the form of a flow therapy device, is shown in diagram form.

[0045] Figure 2 This is a front view of a flow therapy device with the humidifier chamber in place and the raised handle / bar.

[0046] Figure 3 It corresponds to Figure 2 Top view.

[0047] Figure 4 It corresponds to Figure 2 The right-side view.

[0048] Figure 5 It corresponds to Figure 2 The left-side view.

[0049] Figure 6 It corresponds to Figure 2 Rear view.

[0050] Figure 7 It corresponds to Figure 2 Left front perspective view.

[0051] Figure 8 It corresponds to Figure 2 The right front perspective view.

[0052] Figure 9 It corresponds to Figure 2 A bottom view.

[0053] Figure 10 A first configuration of the air and oxygen inlet arrangement for the flow therapy device is shown.

[0054] Figure 11 A second configuration of the air and oxygen inlet arrangement for the flow therapy device is shown.

[0055] Figure 12 It is shown Figure 11 A cross-sectional view showing further details of the air and oxygen inlet arrangement.

[0056] Figure 13 It is shown Figure 11 Another cross-sectional view showing further details of the air and oxygen inlet arrangement.

[0057] Figure 14 It is shown Figure 11 A longitudinal cross-sectional view showing further details of the air and oxygen inlet arrangement.

[0058] Figure 15 This is an exploded view of the upper and lower housing components of the main casing of the flow therapy device.

[0059] Figure 16 This is a left front perspective view of the lower housing of the main housing, showing the housing for receiving the motor and / or sensor module sub-assemblies.

[0060] Figure 17A This is a first lower perspective view of the main housing of the flow therapy device, showing a recess inside the housing for the motor and / or sensor module sub-assemblies.

[0061] Figure 17B This is a second lower perspective view of the main housing of the flow therapy device, showing recesses for the motor and / or sensor module subassemblies.

[0062] Figure 18 A block diagram illustrating how a control system according to embodiments of this disclosure interacts with and / or provides control and guidance to components of a respiratory support system.

[0063] Figure 19 A block diagram of a controller according to an embodiment of this disclosure is shown.

[0064] Figure 20 A block diagram of an electric motor and / or sensor module according to embodiments of this disclosure is shown.

[0065] Figure 21 A sensing chamber according to an embodiment of this disclosure is shown.

[0066] Figure 22A A sensing circuit board within a sensing chamber according to an embodiment of this disclosure is shown.

[0067] Figure 22B A sensing circuit board within a sensing chamber according to another embodiment of this disclosure is shown.

[0068] Figure 22C A sensing circuit board within a sensing chamber according to another embodiment of this disclosure is shown.

[0069] Figure 23A A circuit representation of a transducer signal transmission according to an embodiment of this disclosure is shown.

[0070] Figure 23B A circuit representation of a bidirectional transducer signal transmission according to an embodiment of this disclosure is shown.

[0071] Figure 24A The transducer signal pulse is illustrated schematically.

[0072] Figure 24B The transducer signal is shown to propagate during transmission and reception.

[0073] Figure 24C An exemplary converter pulse designed to reduce ringing is illustrated.

[0074] Figure 25A A block diagram of the ultrasonic sensing model is shown.

[0075] Figure 25B A block diagram of an ultrasonic sensing model including invalid spaces is shown.

[0076] Figure 26A This is a flowchart illustrating a calibration system according to an embodiment of this disclosure.

[0077] Figure 26BThis is a flowchart illustrating a calibration system according to another embodiment of this disclosure.

[0078] Figure 27A The sensor circuit board with a trajectory is shown inside the sensing chamber.

[0079] Figure 27B A magnified portion of Figure 27a is shown, revealing further details of the trajectory.

[0080] Figure 28 This is a flowchart demonstrating the use of two absolute pressure sensors to determine gauge pressure.

[0081] Figures 29 to 33 Several different views are shown of other embodiments of the flow therapy device. Detailed Implementation

[0082] exist Figure 1 The image shows a flow therapy device 10. Generally, device 10 includes a main housing 100 containing a flow generator 11 in the form of an electric motor / impeller arrangement, an optional humidifier 12, a controller 13, and a user I / O interface 14 (including, for example, a display and one or more input devices, such as one or more buttons, a touchscreen, a combination of a touchscreen and one or more buttons, etc.). The controller 13 is configured or programmed to control components of the device, including: operating the flow generator 11 to generate a gas flow (airflow) for delivery to a patient; operating the humidifier 12 (if present) to humidify and / or heat the generated airflow; receiving user input from the user interface 14 for reconfiguration and / or user-defined operations of the device 10; and outputting information to the user (e.g., on the display). The user can be a patient, a medical professional, or anyone interested in using the device.

[0083] The patient breathing tube 16 is connected to the airflow outlet 21 in the housing 100 of the flow therapy device 10 and to the patient interface 17, such as a nasal cannula with a manifold 19 and a nose fork 18. Alternatively, the patient breathing tube 16 may be connected to a mask or tracheostomy interface. Humidified airflow generated by the flow therapy device 10 is delivered to the patient via the patient tube 16 through the cannula 17. The patient tube 16 may have a heater line 16a to heat the airflow flowing to the patient. The heater line 16a is controlled by a controller 13. The patient tube 16 and / or the patient interface 17 may be considered part of the flow therapy device 10, or alternatively, on its periphery. The flow therapy device 10, the breathing tube 16, and the patient interface 17 together form a flow therapy system.

[0084] The general operation of the flow therapy breathing device 10 will be known to those skilled in the art and therefore does not need to be described in detail here. However, in general, the controller 13 controls the flow generator 11 to generate an airflow at a desired flow rate, controls one or more valves to control the mixing of air and oxygen or other alternative gases, and / or controls the humidifier 12 (if present) to humidify the airflow and / or heat the airflow to an appropriate level. The airflow is directed to the patient through the patient catheter 16 and cannula 17. The controller 13 may also control the heating element in the humidifier 12 and / or the heating element 16a in the patient catheter 16 to heat the gas to a desired temperature to achieve the desired level of therapeutic and / or patient comfort. The controller 13 may be programmed to have or be able to determine a suitable target temperature for the airflow.

[0085] Operating sensors 3a, 3b, 3c, 20, and 25, such as flow sensors, temperature sensors, humidity sensors, and / or pressure sensors, can be placed in multiple different locations within the flow therapy device 10 and / or the patient catheter 16 and / or cannula 17. Outputs from the sensors can be received by a controller 13 to assist the controller in operating the flow therapy device 10 in a manner that provides appropriate treatment. In some configurations, providing appropriate treatment includes meeting the patient's inspiratory needs. The device 10 may have a transmitter and / or receiver 15 to enable the controller 13 to receive eight signals from the sensors and / or control multiple different components of the flow therapy device 10, including but not limited to the flow generator 11, humidifier 12, and heater line 16a, or accessories or peripherals associated with the flow therapy device 10. Alternatively or additionally, the transmitter and / or receiver 15 may transmit data to a remote server or enable remote control of the device 10.

[0086] The patient interface can be an unsealed interface, such as a nasal cannula.

[0087] An overview including the main casing description

[0088] Some embodiments of the flow therapy device are described in International Patent Application No. PCT / IB2016 / 053761, filed June 24, 2016, entitled “BREATHING ASSISTANCE APPARATUS,” which is incorporated herein by reference in its entirety. Figures 29 to Figure 33 Some of those embodiments are shown. Figures 2 to 17B Another embodiment of a flow therapy device 10 including a main housing 100 is shown. The main housing 100 has an upper housing 102 and a lower housing 202.

[0089] The upper housing 102 of the main outer casing has a peripheral wall arrangement 106. This peripheral wall arrangement defines a humidifier or humidification chamber compartment 108 for receiving a removable humidification chamber 300. The removable humidification chamber 300 contains a suitable liquid (e.g., water) for humidifying the gas to be delivered to the patient.

[0090] In the illustrated form, the peripheral wall arrangement 106 of the upper housing 102 includes a substantially vertical left outer wall 110 oriented in the longitudinal direction of the main housing 100, a substantially vertical left inner wall 112 oriented in the longitudinal direction of the main housing 100, and an interconnecting wall 114 extending between and interconnecting the upper ends of the left outer wall 110 and the left inner wall 112. The upper housing 102 further includes a substantially vertical right outer wall 116 oriented in the longitudinal direction of the main housing 100, a substantially vertical right inner wall 118 oriented in the longitudinal direction of the main housing 100, and an interconnecting wall 120 extending between and interconnecting the upper ends of the right outer wall 116 and the right inner wall 118. The interconnecting walls 114 and 120 are angled toward the respective outer edges of the main housing 100, but may alternatively be substantially horizontal or angled inwards.

[0091] The upper housing 102 of the main housing further includes a substantially vertical rear outer wall 122. The upper portion of the upper housing 102 includes a forward-angled surface 124. The surface 124 has a recess 126 for receiving a display and a user interface module 14. Interconnecting walls 128 extend between the upper end of the rear outer wall 122 and the rear edge of the surface 124 and interconnect them.

[0092] A substantially vertical wall portion 130 extends downward from the front end of surface 124. A substantially horizontal wall portion 132 extends forward from the lower end of wall portion 130 to form a wall shelf. A substantially vertical wall portion 134 extends downward from the front end of wall portion 132 and terminates in a substantially horizontal bottom portion 136 of humidification chamber compartment 108. The left inner wall 112, the right inner wall 118, wall portion 134, and bottom portion 136 together define humidification chamber compartment 108. The bottom portion 136 of humidification chamber compartment 108 has a recess 138 to receive a heater arrangement, such as a heating plate 140, or other suitable heating element, for heating the liquid in humidification chamber 300 for use during humidification.

[0093] The lower housing 202 of the main housing can be attached to the upper housing 102 by suitable fasteners or integrated attachment features (e.g., clips). The lower housing 202 includes a substantially vertical left outer wall 210 oriented in the front-rear direction of the main housing 100 and abutting the left outer wall 110 of the upper housing 102, and a substantially vertical right outer wall 216 oriented in the front-rear direction of the main housing 100 and abutting the right outer wall 116 of the upper housing 102. The lower housing 202 further includes a substantially vertical rear outer wall 222 abutting the rear outer wall 122 of the upper housing 102.

[0094] The lower housing 202 has a lip 242 that abuts against the lip 142 of the upper housing 102, and also forms part of a recess for receiving the handle portion 506 of the rod 500. The lower lip 242 includes a forward-pointing protrusion 243 that serves as a retainer for the handle portion 506 of the rod 500.

[0095] The lower side of the lower housing 202 includes a bottom wall 230. Various interconnecting walls 214, 220, and 228 extend between and interconnect the substantially vertical walls 210, 216, and 222 and the bottom wall 230. The bottom wall 230 includes a grille 232 with multiple openings to allow liquid to drain in the event of leakage from the humidification chamber 300 (e.g., from spillage). The bottom wall 230 also includes an elongated, forward- and backward-oriented slot 234. The slot 234 also allows liquid to drain without entering the electronics housing in the event of leakage from the humidification chamber 300. In the illustrated configuration, the heater plate 140 is not externally supported by the bottom wall 230, and therefore the slot 234 can be wide and elongated relative to the openings of the grille 232 to maximize liquid drainage.

[0096] As shown in Figures 17a and 17b, the lower housing 202 has a motor recess 250 for receiving a removable motor and / or sensor module. A recess opening 251 is provided in the bottom wall 230, adjacent to the rear edge of the bottom wall, for receiving the removable motor / sensor module. A continuous, airtight, and intact peripheral wall 252 is integrally formed with the bottom wall 230 of the lower housing 202 and extends upward from the outer periphery of the opening 251. The rear portion 254 of the peripheral wall 252 has a first height, and the front portion 256 of the peripheral wall 252 has a second height greater than the first height. The rear portion 254 of the peripheral wall 252 terminates at a substantially horizontal step 258, which in turn terminates at an upper auxiliary rear portion 260 of the peripheral wall 252. The front portion 256 and the upper auxiliary rear portion 260 of the peripheral wall 252 terminate at a top plate 262. Except for gas flow channels, all walls and the top plate 262 are continuous, airtight, and intact. Therefore, apart from the gas flow channel, the entire motor recess 250 is airtight and intact.

[0097] In an alternative configuration, the motor recesses, including items 252, 254, 256, 258, 260, and 264, can be formed separately from the lower housing 202. The motor assembly including the recesses can be inserted into the recess openings 251 and attached to the lower housing 202. When the motor assembly and the recesses are inserted into the lower housing 202, the airflow passage duct 264 extends through the downward extension duct 133 and is sealed by a soft seal.

[0098] Device 10 includes a connection manifold arrangement 320 for fluidly connecting a humidification chamber 300 to device 10. The humidification chamber 300 can be fluidly connected to device 10 from a position at the front of housing 100 in a rearward direction toward the rear of housing 100, along the rearward direction of the humidification chamber 300's entry chamber compartment 108, with linear sliding motion. The connection manifold arrangement 320 includes a manifold gas outlet port 322, which is in fluid communication with a gas flow channel from the motor / impeller unit 402 via a fixed L-shaped bend 324.

[0099] The manifold arrangement 320 further includes a manifold gas inlet port 340 (humidified gas return) embodied in a removable bend. The removable bend is L-shaped and further includes a patient outlet port 344 for coupling to the patient catheter 16 to deliver gas to the patient interface 17. The manifold gas outlet port 322, the manifold gas inlet port 340, and the patient outlet port 344 each include a soft seal, such as an O-ring seal or a T-seal, to provide a sealed gas passage between the device 10, the humidification chamber 300, and the patient catheter 16.

[0100] The humidification chamber gas inlet port 306 is complementary to the connecting manifold gas outlet port 322, and the humidification chamber gas outlet port 308 is complementary to the connecting manifold gas inlet port 340. The axes of these ports are preferably parallel so that the humidification chamber 300 can be inserted into the chamber compartment 108 with linear movement.

[0101] Device 10 has air and oxygen (or alternative auxiliary gas) inlets in fluid communication with a motor, enabling the motor to deliver air, oxygen, or a suitable mixture thereof to the humidification chamber 300 and thereby to the patient. Figure 10 As shown, device 10 may have a combined air / oxygen (or alternative auxiliary gas) inlet arrangement 350. This arrangement includes a combined air / oxygen port 352 entering housing 100, a filter 354, and a cover 356 having a laterally extending oxygen tube 358 in fluid communication with an oxygen source. Port 352 is fluidly coupled to motor 402. For example, port 352 may be coupled to motor and / or sensor module 400 via a gas flow passage between port 352 and an inlet or port in motor and / or sensor module 400 (which in turn leads to motor). This arrangement may have the type described in U.S. Patent Application No. 14 / 286,590, filed May 23, 2014, published as U.S. 2014 / 0345615, which is incorporated herein by reference in its entirety.

[0102] Alternatively, device 10 may have Figures 11 to 14The arrangement shown enables the motor to deliver air, oxygen (or an alternative auxiliary gas), or a suitable mixture thereof, to the humidification chamber 300 and thereby to the patient. This arrangement includes an air inlet 356' in the rear wall 222 of the lower housing 202 of the housing 100. The air inlet 356' includes a rigid plate with a suitable grille arrangement having holes and / or slots. Sound-absorbing foam may be provided adjacent to the plate on the inside side. An air filter housing 354' is positioned inside the main housing 100, adjacent to the air inlet 356', and includes an air outlet port 360 to deliver filtered air to the motor via the air inlet port 404 in the motor and / or sensor module 400. The air filter housing 354' may include a filter configured to remove particulate matter (e.g., dust) and / or pathogens (e.g., viruses or bacteria) from the airflow. A soft seal (e.g., an O-ring seal) is provided between the air outlet port 360 and the air inlet port 404 to seal between these components. Device 10 includes a separate oxygen inlet port 358' positioned adjacent to one side of the rear end of housing 100, the oxygen inlet port 358' for receiving oxygen from an oxygen source such as a canister or piped oxygen source. The oxygen inlet port 358' is in fluid communication with valve 362. Valve 362 may suitably be a solenoid valve, enabling control of the amount of oxygen added to the gas flow delivered to humidification chamber 300. It should be understood that, in alternative configurations, oxygen port 358' and valve 362 may be used with other auxiliary gases to control the addition of other auxiliary gases to the gas flow. Other auxiliary gases may include any one or more of a number of gases used for gas therapy, including but not limited to helium oxide and nitric oxide. Further details regarding the valve and filter are described in U.S. Provisional Application No. 62 / 409543, filed October 18, 2016, entitled “VALVE MODULE AND FILTER,” which is incorporated herein by reference in its entirety.

[0103] like Figures 13 to 16 As shown, the lower housing 202 carries a suitable electronic component board 272. This electronic component board can be positioned adjacent to corresponding outer sidewalls 210 and 216 of the lower housing 202. The electronic component board 272 may contain or be electrically connected to suitable electrical or electronic components (e.g., but not limited to, microprocessors, capacitors, resistors, diodes, operational amplifiers, comparators, and switches). Sensors may be used. Components of the electronic component board 272 (e.g., but not limited to one or more microprocessors) can act as the controller 13 of the device.

[0104] One or both of the electronic component boards 272 can be electrically connected to electrical components of the device 10, including the display unit and user interface 14, motor, valve 362, and heater board 140, to operate the motor to provide the desired gas flow rate, operate the humidifier 12 to humidify and heat the airflow to an appropriate level, and supply the airflow with an appropriate amount of oxygen (or, in an alternative configuration, supply an appropriate amount of alternative auxiliary gas).

[0105] The electronics board 272 can be electrically communicated with a connector arrangement 274 protruding from the rear wall 122 of the upper housing 102. The connector arrangement 274 can be coupled to a nurse alarm, a pulse oximetry port, and / or other suitable accessories. The electronics board 272 can also be electrically communicated with an electrical connector 276, also provided in the rear wall 122 of the upper housing 102, to provide mains power or battery power to the components of the device 10.

[0106] As described above, operating sensors such as flow sensors, temperature sensors, humidity sensors, and / or pressure sensors can be placed in multiple different locations within the flow therapy device 10 and / or patient catheter 16, and / or cannula 17. The electronics board 272 can be electrically connected to those sensors. Outputs from the sensors can be received by the controller 13 to assist the controller 13 in operating the flow therapy device 10 in a manner that provides optimal treatment, including meeting inspiratory requirements.

[0107] As described above, the electronics board 272 and other electrical and electronic components can be pneumatically isolated from the airflow path to improve safety and eliminate fire risk. This seal also prevents water ingress.

[0108] control system

[0109] Figure 18 A block diagram illustrating an embodiment of a control system 520 capable of detecting patient symptoms and controlling the operation of a flow therapy device including a gas source is shown. In this embodiment, the control system 520 manages the flow rate 532 of gas as it is delivered to the patient through the flow therapy device. The control system 520 can increase or decrease the flow rate by controlling the motor speed of a blower or valve in a stirrer. As described below, the control system 520 can automatically determine a setpoint or personalized flow rate value for a specific patient. In some embodiments, the flow rate can be optimized by the control system 520 to improve patient comfort and treatment.

[0110] The control system 520 can also generate audio and / or video output 534. For example, the flow therapy device may include a display 630 (see...). Figure 19The display may further include a speaker. The display 630 can indicate any warnings or alarms generated by the control system 520 to the physician. The display 630 can also indicate control parameters that can be adjusted by the physician. For example, the control system 520 can automatically recommend a flow rate for a specific patient. The control system 520 can also generate the patient's recovery status and send it to the display.

[0111] In some embodiments, the control system 520 may change the temperature setpoint 530 of one of the heating elements to control the output conditions of the gas delivered to the patient. The control system 520 may also change the operation or duty cycle of the heating element.

[0112] The control system 520 can determine outputs 530 to 534 based on one or more received inputs 502 to 510. Inputs 502 to 508 may correspond to sensor measurements automatically received by the controller 600. In the illustrated embodiment, the control system 520 receives sensor inputs corresponding to a transthoracic aspirator (TAA) sensor input 502, a respiratory rate sensor input 504, a work of breathing sensor input 506, and a CO2 sensor input 508, and / or other sensors in the aforementioned flow therapy device (pressure sensor, environmental sensor, pulse oximeter sensor). In an embodiment, the control system 520 may also receive inputs from the user or stored values ​​in memory 624. The control system 520 can dynamically adjust the flow rate 532 for the patient during treatment. In an embodiment, the control system 520 can continuously monitor system parameters and patient parameters.

[0113] controller

[0114] The control system 520 may include programming instructions for detecting input conditions and controlling output conditions. These programming instructions may be stored in the memory 624 of the controller 600, such as... Figure 19 As shown. In some embodiments, the programming instructions correspond to the methods, processes, and functions described herein. The control system 520 may be executed by one or more hardware processors 622 of the controller 600. The programming instructions may be implemented in C, C++, JAVA, or any other suitable programming language. In some embodiments, some or all of the control system 520 may be implemented in a dedicated circuit system 628, such as an ASIC and an FPGA.

[0115] like Figure 18 As shown, the control system 520 can receive inputs from multiple components of the flow therapy device. (Not...) Figure 18All inputs 502 to 510 shown may be present. Inputs 502 to 510 and outputs 530 to 534 may not necessarily appear in all embodiments. For example, in some embodiments, the control system 520 may only receive work of breathing (WOB) and / or respiratory rate sensor inputs 506 and generate flow control measurements 532. Depending on the configuration, some components corresponding to the inputs may not be included in the flow therapy device. The control system 520 may use the absence of an input itself to determine the input or system status.

[0116] Figure 19 A block diagram illustrating an embodiment of controller 600 is shown. The controller may include a hardware processor 622 capable of executing instructions stored in memory 626. In this embodiment, control system 520 is stored in memory 626 as programming instructions. The controller may also include circuitry 628 for receiving sensor signals. The controller may further include a display 630 for transmitting the status of the patient and the respiratory support system. Display 630 may also display warnings. The controller may also receive user input via a user interface (e.g., display 630). The user interface may alternatively or additionally include buttons or a dial pad. The user interface may alternatively or additionally include a touchscreen.

[0117] Motor and / or sensor modules

[0118] Figure 20 A block diagram shows a motor and / or sensor module 2000 received by a recess 250 in a flow therapy device. The motor and / or sensor module includes a blower 2001 that carries indoor air for delivery to the patient. In some embodiments, the blower 2001 is a centrifugal blower.

[0119] Indoor air enters through indoor air inlet 2002, which then enters blower 2001 through inlet port 2003. Inlet port 2003 may include valve 2004 through which pressurized gas enters blower 2001. Valve 2004 controls the flow of oxygen into blower 2001. Valve 2004 can be any type of valve, including proportional valves or dual valves. In some embodiments, the inlet port does not include a valve.

[0120] In some embodiments, blower 2001 may operate at a motor speed greater than 1,000 RPM and less than 30,000 RPM, greater than 2,000 RPM and less than 21,000 RPM, or between any of the foregoing values. The operation of blower 2001 will mix the gas entering blower 2001 through inlet port 2003. Using blower 2001 as a mixer can reduce the pressure drop that occurs in systems with independent mixers (e.g., static mixers including baffles) due to the energy required for mixing.

[0121] The mixed air exits the blower 2001 through duct 2005 and enters the flow path 2006 in the sensing chamber 2007. A sensing circuit board with a sensor 2008 is positioned in the sensing chamber 2007 such that the sensing circuit board is at least partially immersed in the airflow. The sensor 2008 on the sensing circuit board is positioned within the airflow to measure the gas properties within the airflow. After passing through the flow path 2006 in the sensing chamber 2007, the gas exits 2009 into the humidification chamber 300.

[0122] Positioning the sensor 2008 downstream of the combined blower and mixer 2001 can improve measurement accuracy, such as for measuring the fractional concentration of gas (including oxygen concentration) in systems where the sensor is positioned upstream of the blower and / or mixer. Such positioning provides repeatable flow profiles. Furthermore, positioning the sensor downstream of the combined blower and mixer avoids pressure drops that would otherwise occur, because in cases where sensing occurs before the blower, a separate mixer, such as a static mixer with baffles, is required between the inlet and the sensing system. The mixer introduces a pressure drop at this point. Positioning the sensor after the blower allows the blower to act as the mixer, whereas a static mixer would decrease pressure, whereas the blower would increase pressure. Additionally, immersing at least a portion of the sensing circuit board and sensor 2008 into the flow path increases measurement accuracy, as sensor immersion in the flow means they are more likely to be subjected to the same conditions (e.g., temperature and pressure) as the gas flow, and therefore provide a better representation of the gas characteristics.

[0123] Sensing chamber

[0124] The flow therapy device described herein is a modular system. The motor / sensing module, including some or all of the sensors, can be individually disassembled and replaced as needed. To improve modularity, some or all of the sensors can be positioned on a sensing circuit board within a sensing chamber, which can be at least partially placed within the flow path, and the control electronics on the control circuit board can be sealed away from the flow path. The code for the sensing algorithm (including conversion, memory and control, memory and calibration control) can be located on the sensing circuit board. For the purposes of this application, the sensing circuit board is defined as a circuit board positioned within the sensing chamber or sensor module.

[0125] During the use of a flow therapy device, water can come into contact with the sensing circuit board. For example, the device may be tilted, water from the humidifier chamber may move upstream or into the port, or the user may turn off the device before completing the drying mode. Water contact can damage the electronic components on the sensing circuit board and cause sensor corrosion and potential contamination of the airflow. To mitigate the effects of water contact with the sensing circuit board, a humidity sensor can be placed on the sensing circuit board to warn the user of the potential for water ingress or to initiate corrective measures. If the humidity sensor detects higher-than-expected humidity in the sensing module, corrective measures may include initiating a blower flow sequence to remove water from the sensing circuit board. This could include pulsed or other blower modes for drying the sensing circuit board. The corrective measures may also include activating the built-in or external heater in the humidity sensor. Furthermore, the sensing circuit board may be coated with a conformal coating to prevent or mitigate water ingress, as well as to mitigate the effects of oxygen ingress. This can be used in conjunction with sealing features around the electronics, as described below. Alternatively, closed-frame transducers (described below) can be used because they are less susceptible to damage from water ingress. A water barrier may also be introduced between the chamber and the sensing module. A non-limiting example is a one-way valve between the chamber and the sensing module.

[0126] Figure 21 An embodiment of a modular sensing chamber 2007 is shown. The sensing chamber 2007 can be positioned downstream of a blower 2001 within a motor and / or sensor module. The sensing chamber 2007 includes a flow path 2006 and is designed to hold a sensing circuit board 2200 (FIG. 22) within a housing 2101.

[0127] Airflow may experience pressure drops as it passes through a flow therapy device, which consumes power and thus affects the system's ability to achieve a specific flow rate. Pressure losses may be due to friction in the straight sections of the flow path or due to deviations from the straight path (e.g., bends, valves, constrictions, or expansions in the path).

[0128] The flow path 2006 has a curved shape. Gas flow enters at inlet 2103, flows along the curved flow path 2104, and exits on the opposite side of flow path 2105. In some embodiments, the inlet and outlet may be positioned in opposite vertical directions, and the airflow may enter the path vertically upwards, then curve to a horizontal direction, and then curve again to a vertically upwards direction. In some embodiments, the flow path does not have sharp bends. In some embodiments, the flow path has curved ends with a relatively straight middle portion. In some embodiments, the flow path maintains a constant cross-sectional shape throughout its length. In some embodiments, the flow path tapers slightly inwards from a first end and widens again to a second end, which can accelerate the flow for better measurement accuracy. In some embodiments, the surface of the flow path is lined with a surface modifier / lubricant to reduce friction within the flow path. A variety of different flow path configurations can be used. The curved flow path shape can reduce the pressure drop of the airflow without reducing the sensitivity of the flow measurement by aligning the measurement area with a portion of the flow path.

[0129] The sensing circuit board 2200 is positioned within the housing 2101 in the sensing chamber such that at least a portion of the sensing circuit board overlaps with the airflow in the flow path 2006. The opening 2102 can be positioned to hold the ultrasonic transducer 2204 along the flow path 2006. Figures 22A to 22B To measure the properties of the gas within the flow rate.

[0130] The flow path 2006 has a total distance between transducers. In some embodiments, the total distance of the flow path is between about 10 mm and about 1000 mm, between about 40 mm and about 200 mm, between about 50 mm and about 150 mm, between about 70 mm and about 120 mm, between 80 mm and 100 mm, or between any of the above values, or is about 95 mm.

[0131] The flow path 2006 has a total flow distance representing a portion of the flow path that coincides with the acoustic path. In some embodiments, the flow path has a total flow distance between about 1 mm and about 500 mm, between about 10 mm and about 200 mm, between about 50 mm and about 150 mm, between about 70 mm and about 100 mm, or between about 70 mm and about 88 mm, or between any of the foregoing values ​​or their equivalents, or about 75 mm. The total distance between transducers minus the total flow distance equals the ineffective space, which may be located at any or both ends of the ultrasonic path where there is no airflow.

[0132] The diameter of the flow path 2006 can be greater than about 2 mm and less than about 100 mm, between about 5 mm and about 50 mm, between about 10 mm and about 30 mm, between about 12 mm and about 25 mm, or between about 15 mm and 20 mm, or between any of the above values, or about 16 mm. Reducing the diameter of the flow path can increase the gas velocity at high flow rates beyond the useful velocity, can increase nonlinear effects in sensor measurements, can cause pressure drops, and can clamp / limit sensor arrangements and designs. Increasing the flow path diameter will occupy more system space and may lead to a decrease in flow sensitivity. Therefore, the optimal balance can be achieved according to the above ranges. The equivalent range can be used for devices with different flow configurations.

[0133] Flow path 2006 has a normalized flow distance, which means that the sensitivity of sensor 2204 equals the total flow distance across its cross-sectional dimension. Flow sensitivity is affected by the total flow distance and the gas velocity, which is influenced by the cross-sectional dimension. Assuming a circular cross-section duct, the flow sensitivity is proportional to...

[0134]

[0135] Where D represents the total flow distance and r represents the cross-sectional radius.

[0136] In some embodiments, the flow path 2006 has a normalized flow distance normalized to a radius of 8 mm, which is a cross-section of the flow path, and the radius is between about 1 mm and about 500 mm, between about 10 mm and about 200 mm, between about 50 mm and about 150 mm, between about 70 mm and about 100 mm, or between about 70 mm and about 88 mm, or between any of the foregoing values ​​or their equivalents, or about 75 mm. In some embodiments, the flow path 2006 has a normalized flow distance normalized to a radius of 6 mm, which is between about 1 mm and about 500 mm, between about 10 mm and about 200 mm, between about 20 mm and about 60 mm, between about 30 mm and about 50 mm, or between any of the foregoing values ​​or their equivalents, or about 40 mm. In some embodiments, the flow path 2006 has a normalized flow distance normalized to a radius of 10 mm, which is between about 10 mm and about 500 mm, between about 50 mm and about 200 mm, between about 100 mm and about 150 mm, between about 110 mm and about 130 mm, or between any of the foregoing values ​​or their equivalents, or is about 120 mm. In some embodiments, the flow path 2006 has a normalized flow distance normalized to a radius between 6 mm and 10 mm, and the normalized flow distance is between about 40 mm and 120 mm, or between any of the foregoing values ​​or their equivalents.

[0137] Figures 22A to 22C An embodiment of a sensing circuit board 2200 configured to be positioned within a sensing chamber is illustrated. In some embodiments, the sensing circuit board 2200 is a printed sensing circuit board (PCB). In some embodiments, the circuitry is constructed using wires connecting electronic components rather than being printed on a circuit board. In some embodiments, at least a portion of the sensing circuit board is mounted outside the flow path.

[0138] The sensing circuit board 2200 may include an ultrasonic transducer 2204 and one or more of the following: a separate gas temperature sensor 2205, a heated temperature sensing element 2206, a humidity sensor including a humidity-only sensor to be used with the separate temperature sensor, and a combined humidity and temperature sensor 2208, a sensor for measuring air pressure, a sensor for measuring differential pressure, and / or a sensor for measuring gauge pressure. The heated temperature sensing element may include a heated temperature sensing element, a hot-wire anemometer, such as a platinum wire or heated thermistor, and / or a negative temperature coefficient (NTC) thermistor. Other non-limiting examples of heated temperature sensing elements include glass or epoxy-encapsulated or unencapsulated thermistors. The heated temperature sensing element is configured to measure the flow rate of a gas. The sensing circuit board 2200 includes a first portion 2201 and a second portion 2202. The first portion 2201 is positioned within a gas flow path 2006, while the second portion 2202 is positioned outside the gas flow path 2006. Figures 22A to 22C Arrow 2203 indicates the direction of the airflow. The direction of the airflow is... Figure 22A Indicated as a straight line, and in Figure 22B and Figure 22C The direction of the air is indicated as curved. The general direction of the air is away from one upstream transducer 2204 and towards another downstream transducer 2204.

[0139] The first portion 2201 of the sensing circuit board 2200 may include an ultrasonic transducer, a transceiver, or a sensor at each end of the sensing circuit board to measure the properties of a gas along the flow path. Positioning the sensor within the flow path or module, rather than outside the flow path or module, allows a pair of transducers to operate within a smaller temperature range relative to each other, or both to be substantially at the same temperature (i.e., the temperature of the gas flow). Since transducers are temperature sensitive, placing them at substantially the same temperature improves accuracy. Furthermore, positioning the sensor along the flow path allows for measurements and calculations that take into account the effects of gas velocity, making it possible to remove the influence of gas velocity from the sensor measurements.

[0140] The distance between the ultrasonic transducers 2204 on opposite ends of the sensing circuit board 2200 can affect the measurement resolution. Increasing the distance between each ultrasonic transducer 2204 can reduce proportional or fractional errors because the length being measured will typically have a certain amount of error; therefore, if the length is increased, the proportion of error generated during measurement will be smaller than the proportion of error generated when measuring a shorter length. Thus, the overall measurement uncertainty decreases. The increased distance can also increase measurement resolution and accuracy because it allows for a longer time period for the acoustic signal between the ultrasonic transducers 2204. However, the increased distance may result in a weaker signal.

[0141] The ultrasonic transducers 2204 can be positioned such that the space between the ultrasonic transducers 2204 at least partially coincides with the flow path 2006. In some embodiments, the ultrasonic transducers are positioned at opposite ends of the sensing circuit board. Because the entire surface of the flow path is exposed to the acoustic path, sound waves propagate through all the gas in the flow path 2006. Waveform averaging can occur over the entire flow path, rather than just a portion of it. Averaging over a longer distance can reduce errors and decrease dependence on air-oxygen mixing.

[0142] A first portion 2201 of the sensing circuit board 2200 may include a temperature sensor, such as a thermistor 2205 within the flow path 2006. Immersing the temperature sensor within the gas flow path increases thermal conductivity between the gas and the sensor, allowing for more accurate sensing of the gas temperature and a faster response from the temperature sensor. Furthermore, positioning the temperature sensor within the flow path minimizes parasitic heat sources and heat sinks (e.g., thermal conduction from the module walls). In some embodiments, the thermistor 2205 is a negative temperature coefficient (NTC) thermistor. In some embodiments, the thermistor 2205 is a digital sensor.

[0143] In some embodiments, the sensing circuit board within the sensing chamber includes traces (e.g., copper traces) arranged to reduce thermal conduction between the chamber walls and the sensing circuit board. Figure 27A An embodiment of a sensing circuit board 2200 with trace 2701 is shown, and Figure 27B A magnified portion of the sensing circuit board 2200 with traces 2701 shown in Figure 27A is illustrated. In some embodiments, traces 2701 are located on the outer layer of the sensing circuit board to facilitate heat transfer to the air. Typically, due to the high thermal conductivity of copper or other similar conductive materials, the traces on the sensing circuit board can provide most of the heat conduction for the entire sensing circuit board. Due to the high planar density of copper, longer, curved tracks can reduce heat conduction but can also increase the volumetric conductivity of the sensing circuit board. In some embodiments, the tracks are thin and long, and not arranged very densely. This configuration can reduce heat conduction caused by the tracks without substantially increasing the volumetric conductivity.

[0144] A first portion 2201 of the sensing circuit board 2200 may include a heated temperature sensing element 2206. The temperature of the heated temperature sensing element may be selectable. As described herein, the heated temperature sensing element 2206 is a variable temperature sensor configured to sense gas flow rate. Figure 22C A cutout 2012 is shown around the heated temperature sensing element 2206. Similarly, but compared to the wiring described above, the cutout 2012 can reduce the temperature impact on the heated temperature sensing element 2206.

[0145] In some embodiments, the sensing chamber includes a seal separating a first portion 2201 of the sensing circuit board 2200 from a second portion 2202 of the sensing circuit board 2200. The seal may include O-rings and grooves on either side of the intermediate portion of the sensing circuit board to provide a soft surface for sealing the rigid portion. In some embodiments, the seal may include co-molding, wherein a soft layer is molded onto the rigid portion of the device to provide a sealing element. The seal may close off a high-pressure region of the flow path, wherein a sensor on the first portion of the circuit measures the characteristics of the airflow. The seal may prevent gas from escaping from the high-pressure region of the flow path and moving toward the electronics of the flow therapy device, and may prevent water from contacting the second portion of the sensing circuit board.

[0146] The second portion 2202 of the sensing circuit board 2200 may include a driver, a microcontroller, and / or other circuitry 2207. In some embodiments, the second portion 2202 includes circuitry for each ultrasonic transducer 2204 to control the pulses of the ultrasonic transducers. Positioning the circuitry of the ultrasonic transducers 2204 close to them reduces noise and increases the ability to compensate for temperature effects in the circuitry. This reduces noise because only a short analog portion is needed to transmit the signal from the ultrasonic transducers 2204 to the sensing circuit board processing circuitry 2207 due to the extreme proximity, and this analog portion, which would be sensitive to noise from surrounding components, is sandwiched between two ground planes (e.g., planes made of copper) in the sensing circuit board 2200. Once the signal has reached the sensing circuit board processing circuitry 2207, any further transmission is via a noise-robust digital signal. The proximity of the ultrasonic transducer 2204 to the circuit system 2207 means that the circuit system 2207 is more likely to be at a similar temperature to the gas, thereby compensating for inaccuracies in the readings of the ultrasonic transducer 2204 caused by the temperature difference between the circuit system 2207 and the gas. In some embodiments, the circuitry for the two ultrasonic transducers is located at opposite ends of the second portion 2202 of the sensing circuit board 2200. Positioning the circuitry at opposite ends avoids electrical interference between the transmitted and received signals.

[0147] Next, we will combine Figure 22C Further details describe the sensing circuit board 2200. The features described below can be combined with... Figure 22A and Figure 22B In the illustrated embodiment. As shown Figure 22CAs shown, the sensing circuit board 2200 includes a first portion 2201 and a second portion 2202. A pneumatic seal surrounding the first portion 2201 is configured to prevent gas leakage outside the first portion 2201. The pneumatic seal can be configured to seal each surface (upper and lower) of the sensing circuit board 2200. The pneumatic seal on each surface of the sensing circuit board 2200 can be an O-ring seal. Additional sealing features can be used. A non-limiting example is an additional plug added to the screw protrusion, which will be inserted into the hole 2216 to mount the sensing circuit board 2200 in the chamber 2101. The plug can reduce the possibility of gas (including oxygen) leaving the sensing module or sensing chamber or sensing circuit board 2200 via the screw. The plugs and O-ring seals used to seal the flow path and circuit system 2207 can be replaced with co-molded washers, which allows for the use of fewer parts, reduces assembly time, and reduces the possibility of operator error.

[0148] The first portion 2201 of the sensing circuit board 2200 includes an ultrasonic transducer 2204 on opposite ends of the sensing circuit board 2200. The ultrasonic transducer 2204 can measure gas properties such as oxygen concentration and flow rate. As described below, the ultrasonic transducer 2204 can be an open frame or a closed frame. Figure 22C As shown, the ultrasonic transducer 2204 is directly mounted on the sensing circuit board 2200. This arrangement suppresses acoustic coupling, which occurs when the ultrasonic transducer is first connected to the housing and then assembled onto the sensing circuit board 2200. Another advantage of direct mounting is that fewer steps are required to install the ultrasonic transducer. Furthermore, the distance between the transducers 2204 is fixed, which reduces the possibility of physical drift over time. Figure 22C A heated temperature sensing element 2206 is also shown, which is configured to measure flow rate and is located approximately midway between the temperature sensor 2205 and the humidity and temperature sensor 2208 in the flow path 2203. The combination of the ultrasonic transducer and the heated temperature sensing element for flow rate measurement facilitates rapid and accurate flow rate measurement over a wide flow rate range, as will be described in detail below.

[0149] Figure 22C The sensing circuit board 2200 further includes a temperature sensor 2205 and a temperature and humidity sensor 2208. The temperature and humidity sensor 2208 can monitor the dew point. Figure 22CAs shown, temperature sensor 2205 is located upstream of temperature and humidity sensor 2208. Temperature sensor 2205 is closer to the inlet of flow path 2203, and temperature and humidity sensor 2208 is closer to the outlet of flow path 2203. Temperature sensor 2205 and temperature and humidity sensor 2208 are each very close to one of the ultrasonic transducers 2204. For example, temperature sensor 2205 and temperature and humidity sensor 2208 are each located between approximately 10 mm and 50 mm from one of the ultrasonic transducers 2204. In some embodiments, temperature sensor 2205 and temperature and humidity sensor 2208 are each located between approximately 20 mm and 45 mm from one of the ultrasonic transducers 2204. In some embodiments, temperature sensor 2205 and temperature and humidity sensor 2208 are each located between approximately 30 mm and 40 mm from one of the ultrasonic transducers 2204. Figure 22A and Figure 22B The fingers shown are different from those used to keep the sensor straight. Figure 22C The first portion 2201 of the sensing circuit board 2200 includes a bent finger 2010 to position the temperature sensor 2205 and the humidity and temperature sensor 2208 close to the center of the flow path 2203 to improve reading accuracy. The temperature sensor 2205 and the humidity and temperature sensor 2208 allow the system to measure the temperature at two locations within the flow path 2203. The first location is closer to the inlet of the flow path, and the temperature is measured by the temperature sensor 2205. The second location is closer to the outlet of the flow path 2203, and the temperature is measured by the humidity and temperature sensor 2208. The two temperature readings provide an approximation of the temperature gradient along the flow path 2203. This method works well if there is no large temperature gradient within the flow path. For example, as those skilled in the art will understand from the disclosure herein, the bulk gas temperature can be calculated using mathematical formulas (e.g., weighted sums or other formulas) based on the two readings. Furthermore, since temperature sensor 2205 and temperature and humidity sensor 2208 are close to ultrasonic transducer 2204, the two temperatures provide a good approximation of the temperature of the ultrasonic signals emitted and received by ultrasonic transducer 2204. This allows for edge detection methods (described below in the "Ultrasonic Sensing" section) designed to reduce dependence on the transducer itself, such that only the gas temperature along flow path 2206 is relevant to oxygen concentration and flow rate calculations.

[0150] Alternatively, in cases with large gradients within the flow path, the following techniques can be used. A temperature gradient can be obtained between the temperature sensor on the pressure sensor 2209 (described in more detail below in the section on dual absolute pressure sensors) and the temperature and humidity sensor 2208, and this gradient can be used in conjunction with the gradient between the temperature sensor 2205 and the temperature and humidity sensor 2208 to approximate the temperature of the ultrasonic transducer 2004 closer to the temperature and humidity sensor 2208. The same technique can be used to estimate the temperature of the ultrasonic transducer 2004 closer to the temperature sensor 2205. A temperature gradient can be obtained between the temperature sensor on the pressure sensor 2209 and the temperature sensor 2205, and this gradient can be used in conjunction with the gradient between the temperature sensor 2205 and the temperature and humidity sensor 2208 to approximate the temperature of the ultrasonic transducer 2004 closer to the temperature sensor 2205.

[0151] Since the dew point inside the device is substantially the same as the dew point outside the device, the humidity sensor 2208 can be placed anywhere inside or outside the device if it provides dew point measurement. However, it is advantageous to place the humidity sensor in a location where it measures humidity after the gas has been mixed by the blower. One advantage of this configuration is that the humidity measurement responds quickly to changes in humidity. Another advantage is that if the device is used with an oxygen concentrator, the ultrasonic measurement will be independent of the concentrator's efficiency, whereas measuring the humidity of ambient air before mixing would result in a small error based on the concentrator's efficiency.

[0152] The second portion 2202 of circuit board 2200 may include a driver, a microcontroller, non-volatile memory such as EEPROM, and / or other circuitry 2207. The use of a microcontroller allows for sensor fusion between the heated temperature sensing element and the ultrasonic transducer, while the system operates to correct for the flow rate rapidly determined by the ultrasonic transducer, which has a more accurate heated temperature sensing element. In some embodiments, the microcontroller is incorporated into the non-volatile memory. Using this non-volatile memory offers the following features and advantages: Calibration parameters and limits of these parameters can be stored, allowing for modularity of the system as described above. More details are provided in the “Calibration” section below. A unique ID for each module can also be stored, which can be used, for example, for tracking modules during manufacturing and / or in the field. The non-volatile memory also allows errors to be logged during operation, which can aid in fault diagnosis.

[0153] Ultrasonic sensing

[0154] The following describes a model of a sensing system utilizing the speed of sound (denoted by c) and the gas velocity (denoted by v), and... Figure 25AThe image shows two transducers 2204 facing each other at a distance D, each generating a pulse that travels a distance (“acoustic path” 2501) between the two transducers and is received by the other transducer 2204. If the sensor is arranged with some components parallel to the airflow along the acoustic path 2501, the signal travels with the flow rate at a speed of c+v in a first direction, and against the flow rate at a speed of cv in a second direction. The sensor measures the time of flight of these two signals. Using this time of flight, c and v can be calculated, and the gas flow rate can be determined.

[0155] The measured flight time in the first direction is The flight time in the second direction is The solution can be obtained using the speed of sound and the velocity of the gas.

[0156]

[0157]

[0158] During implementation, "ineffective space" usually exists at either end of the ultrasonic path where there is no airflow. Figure 25B A model incorporating ineffective spaces 2502 is presented. Generally, these ineffective spaces 2502 are not explicitly defined, and the component of the flow path 2503, which coincides with the ultrasonic path 2501, may vary along the length of the sensing region. However, the smooth, tortuous flow path disclosed herein reduces the variation in the flow profile, which in turn reduces the ineffective spaces. Because the ineffective spaces are very small, therefore... Figure 25B The approximation shown is very good, and the invalid space can be considered as a well-defined region. For the average distance D0 of the invalid space 2502 separated between the two ends of the ultrasonic path 2501 and the distance D where airflow 2503 exists, the measured time of flight becomes...

[0159] and

[0160] For the exact solution to C, we can obtain:

[0161]

[0162] The gas velocity is given by the following formula:

[0163]

[0164] The expression can be simplified based on the assumption that the speed of sound will be significantly higher than the speed of gas, so by approximating c 2 >>v 2 The expression simplifies to:

[0165]

[0166]

[0167] Volumetric flow rate can be obtained by multiplying the gas velocity v by the effective cross-sectional area A: Q = vA. If the flow rate forms an angle with the acoustic path, then the volumetric flow rate can be expressed as...

[0168]

[0169] The effective cross-sectional area can be considered as a lumped parameter that fully represents the combination of known and unknown parameters.

[0170] In some embodiments, the equations given above are simplified to other forms.

[0171] Figure 23a illustrates a circuit representation of transducer signal transmission during transducer sensing according to an embodiment of the present invention. A transmitter driver 2301 drives a transmitter 2302 to emit a signal, which propagates through the air 2303 to a receiver 2304. An amplifier 2305 amplifies the waveform, detects 2306 edges or delays, and a microcontroller 2307 provides a drive signal and captures the edges. Figure 23b illustrates a circuit representation of signal transmission in two directions by superimposing the paths of Figure 23a in both directions. Various topologies can be implemented.

[0172] The transmitter driver 2302 may include four transistors used as an inverter, the first two transistors for level shifting, and the latter two transistors forming a half-bridge driving the transducer. Separating the transmitter driver 2302 from the transmitter / transducer 2303 allows for isolation between the transducer 2303 and the driver 2302 when the transducer 2303 is used as a receiver 2304 during the transmission of an acoustic signal in the opposite direction. In some embodiments, the transmitter driver is an integrated driver chip. In some embodiments, the transmitter driver transistor is a MOSFET, which can exhibit low delay and good stability over a wide temperature range. In some embodiments, the transmitter driver transistor is a bipolar junction transistor.

[0173] In some embodiments, transmitter 2303 may include an “open-frame” piezoelectric transducer operating at 25 kHz, 40 kHz, or any other frequency. In some embodiments, transmitter 2303 may include a “closed-frame” piezoelectric transducer operating at low voltages (e.g., below about 20 V). Low voltage is ideal for oxygen safety. On the one hand, open-frame transducers offer greater amplitude, better sensitivity, and signal-to-noise ratio, and operate at lower voltages, making them more suitable for use with the flow therapy devices described herein. However, open-frame transducers may be less reliable because they are not sealed, making them more susceptible to damage from water ingress and mechanical damage, such as when the cone separates. On the other hand, closed-frame transducers are less susceptible to water ingress or mechanical damage because they do not have a cone. However, closed-frame transducers typically require higher voltages than the common operating voltage of flow therapy devices.

[0174] Receiver 2304 may include an "open-frame" piezoelectric transducer operating at 25 kHz, 40 kHz, or any other frequency. In some embodiments, receiver 2304 may include a "closed-frame" piezoelectric transducer operating at low voltages (e.g., below about 20 V). In some embodiments, transmitter 2303 and receiver 2304 are transducers of the same type.

[0175] Figure 24a schematically illustrates the signals transmitted and received in opposite directions, and Figure 24b illustrates the propagation signal 2303 during transmission and reception. A pulse train is applied to the transducer / transmitter 2302 and can be a pulse or pulse group 2401 or a square wave. Since the piezoelectric transducer may be highly resonant, the signal generated by the transducer / transmitter 2303 may not be a square wave, but can be an envelope sine wave. Similarly, the waveform 2402 received by the transducer / receiver 2304 may not be exactly the transmitted sound wave, but rather a combination of the transmitted wave and the resonance of the transducer / receiver. After the recovery phase 2403, another pulse train 2401 is applied to the transducer / receiver 2304 and received by the transducer / transmitter 2303.

[0176] The time interval between pulse trains can vary; however, reducing this interval (e.g., by moving the pulse trains closer together in time) can cause interference between subsequent pulse trains due to transducer ringing. For example, if the time between pulse trains is reduced, a new pulse train may begin before the signal from the previous pulse train has stabilized. Therefore, measurements determined from a specific point in the pulse train may overlap with the end of the signal from the previous pulse train (when that signal has stabilized). Ultrasonic transmitters can have features designed to reduce ringing. Figure 24CAs shown, the ultrasonic transmitter can extend pulse 2405 to bring it closer to the drive signal or separate its phase by 180° to quickly reduce pulse ringing. Only a few additional out-of-phase pulses are needed to help reduce ringing, as too many out-of-phase pulses will cause ringing to restart. In some embodiments, the pulse can be modified so that its phase difference is less than or greater than 180 degrees. In other embodiments, one or more pulses can be omitted to reduce ringing.

[0177] Any number of pulses can be emitted in each pulse train. However, increasing the number of pulses increases echoes, which can make the sensor's behavior unpredictable. Reducing the number of pulses may result in insufficient amplitude for accurate measurements. In some embodiments, the total transmission time of the pulse train is less than the flight time. A longer transmission time may lead to measurement errors, such as interference from signals interfering with each other, interference from echoes in the gas, electrical noise from the pulses, or sound passing through the housing. In some embodiments, the number of emitted pulses is between 1 and 50, between 1 and 10, 5 pulses, or any other number of pulses. The frequency of the pulses can vary. The frequency of the pulses can be the same as, lower than, or higher than the frequency of transmitter 2303.

[0178] Amplifier 2305 may include a common-emitter bipolar junction emitter (BJT) amplifier without decoupling capacitors. Such amplifiers can achieve low phase delay and good frequency response. In other embodiments, amplifier 2305 may include an operational amplifier or other integrated amplifier.

[0179] The edge / delay 2306 can be measured by measuring the zero-crossing points of the received waveform, i.e., by detecting points on the 'RX' curve 2402 that exceed zero, such as... Figure 24B As shown. During implementation, when the receiver has just begun to "ring," the signal-to-noise ratio is very low, making it difficult to detect the first few edges of the waveform. Typically, the starting point of the measurement will be one or more edges after the actual start, and the true time of flight must be calculated from this. In a simple linear regression system, at least two edges are measured and the period of the waveform is calculated, allowing the measured points to be extrapolated back by an appropriate number of periods to find the starting point of the waveform. If many edges are measured, linear regression can be used to calculate the time offset at the zero edges. The peak value of the waveform can be calculated first by taking the arithmetic mean of adjacent edges (and then used for the same type of calculation). The arithmetic mean calculation mitigates the influence of the zero-point offset in edge detection, which could otherwise slightly bias the results.

[0180] In practice, these linear regression methods have fundamental limitations. Both the transmitter and receiver have non-zero phase responses, and as mentioned above, most piezoelectric transducers are highly resonant. Furthermore, the accurate phase response and resonant frequency of each transducer can vary between components, with temperature, and over time. The actual received waveform is then a driving waveform convolved with both the transmitter and receiver impulse responses. Therefore, the received waveform is not a true envelope sine curve, but rather has a complex phase delay at its starting point and a frequency that varies as the waveform “sounds,” potentially resulting in partial or full beats depending on the difference between the resonant frequencies of the driving waveform and the TX and RX transducers, or more generally, the impulse responses. The shape of the received waveform also shifts due to the shift in the fundamental resonant frequency under different temperature and other waveform offset conditions. Any simple linear regression at the edges will be negatively affected by this shift, as simple linear regression assumes that the waveform period does not change from the measured edge to the extrapolated edge. This necessitates adding temperature and other empirical calibrations to the linear regression or similar calculations to account for these additional temperature and similar waveform offset effects. These calibrations may, in turn, become inaccurate over time or in different transducers.

[0181] Another method to mitigate other similar effects of temperature drift or waveform shift is to adjust the drive frequency. As mentioned above, many transducers have a certain degree of uniform shift in their resonant frequency across the entire temperature range, and therefore the drive frequency can be varied accordingly. In an alternative embodiment, the resonant frequency of the transducer can be estimated based on the sensed waveform, and the drive frequency can be adjusted accordingly to allow the system to dynamically match the drive frequency to the resonant frequency and minimize spurious phase delays.

[0182] In some embodiments, to better illustrate these differences, especially mismatches between the transmitter and receiver that cannot be directly adjusted, a more general expression weighting each edge can be used. For example, a weighted vector can be used, such as t = δ + ∑ i w i E i position w of flight time t i is i th Edge weights and E i is i th Edge-time calculations. By selecting an appropriate set of weights, expressions very close to the inversion of the convolution process can be generated even for reasonable variations in the TX and RX resonant frequencies. This allows for minimal or no empirical temperature calibration in time-of-flight calculations.

[0183] In some embodiments, edge / delay can be measured by measuring an amplified waveform. The amplified waveform is actually... Figure 24BThe image shows the captured and stored RX wave. Measuring the amplified waveform allows for improved fault detection because the actual waveform is observed, and it can also be used for more detailed time delay estimation. For example, a cross-correlation can be performed between the received waveform and a reference (whether earlier recorded or previously defined) to generate a time-of-flight measurement. This reference can be a separate or previous waveform. Because the cross-correlation is performed over complex shapes, this method does not rely on the “windowing” performed in edge detection, which requires knowing exactly where an edge must fall within a predefined window to determine if a correct edge has been detected. The absence of “windowing” allows for a wider range of sound velocity sensing. Even if the sound velocity range causes edges to fall outside the window, the cross-correlation can still correctly measure the time of flight, which can then be used to define new edge windows for edge-based measurements. Thus, gases that might not be usable for a particular system due to their high sound velocity range can become available, such as helium-oxygen mixtures or carbon dioxide, which produce sound velocity variations several times greater than oxygen. Comparing the waveform to a reference can also highlight anomalies during operation, such as low signal amplitude, interference, unacceptable offsets in transducer frequencies, etc. The waveforms in each direction can also be cross-correlated to each other to generate differential time of flight, from which the flow rate can be calculated.

[0184] The microcontroller 2307 provides drive signals and captures edges. The microcontroller can operate at any frequency, but higher frequencies can improve resolution. The microcontroller 2307 can operate at 24MHz, 48MHz, 72MHz, 120MHz, or any other frequency.

[0185] calibration

[0186] In some embodiments, sensors may be used in combination to provide redundancy and calibrate the flow therapy device. For the purposes of this specification, calibration refers to checking the variable and / or adjusting the system, measurement, and / or display if a measured variable differs from an expected or reference variable. Compared to ultrasound, heated temperature sensing elements have a logarithmic response that produces increased sensitivity at low flow rates. Heated temperature sensing elements can provide improved accuracy in low flow rate measurements, but ultrasonic transducers can provide rapid measurements. The control system may shut down the blower and oxygen flow to create a situation with known values ​​and compare readings from different types of sensors to determine if the sensed values ​​are acceptable. The control system may then change the blower speed and oxygen flow rate and use or compare readings from different types of sensors and perform appropriate calibrations.

[0187] Calibration can be the adjustment of parameters in a mathematical model used to calculate gas properties, including gas velocity, flow rate, gas temperature, humidity, pressure, and / or oxygen concentration. Specifically, when calculating gas properties based on a mathematical model, the model parameters in the relationships can exhibit unknown variations. By using sensors to take measurements under known conditions, these measurements can be used to solve for one or more unknown parameters in the model.

[0188] The calibration adjustment of an unknown parameter can account for more variations in the system than just the direct physical interpretation of that parameter (i.e., the adjustment can account for unknown variations among multiple parameters). This can occur in at least two cases. First, the two parameters may be inseparable, in which case the calibration adjustment can be viewed as a combination of the effects of both parameters. For example, in the previously described ultrasonic sensing model for gas velocity, the parameters of this term are grouped without variables to distinguish them.

[0189]

[0190] Therefore, for calibration purposes, their combined values ​​can be adjusted. Secondly, the system may not have enough calibration points to account for all parameters; in this case, calibration adjustments can approximate the variations of multiple parameters. For example, in the previously described ultrasonic model for sound velocity, parameters D+D0, t1, and t2 can exhibit significant variability, which can be clearly illustrated using multiple calibration points. However, in the simpler case using a single calibration point, a single parameter can be addressed to account for the total variability of all the aforementioned parameters. In the second case, additional measurements can be taken to validate the system and / or check if additional calibration points are needed.

[0191] For example, in the previously described sound speed model,

[0192]

[0193] Using known sound velocities and calibration points with ultrasonic flight times t1 and t2, the parameter to be calibrated can be D+D0.

[0194]

[0195] From the model above. Such calibration points can be taken at any flow rate because gas velocity will not appear in the model, but taking the calibration point at zero flow rate can reduce the residual cross-effect between gas velocity and sound velocity.

[0196] However, in the previously described model for flow,

[0197]

[0198] Similar calibrations cannot be performed at zero flow because of this item

[0199]

[0200] It might equal 0. However, a slight asymmetry between the two directions is generally expected, primarily due to transducer delay. This asymmetry can be modeled as:

[0201]

[0202] When using this asymmetric model, the gas velocity model can be adjusted as follows:

[0203]

[0204] The remaining values ​​in the model are based on the geometry of the flow path and are not easily affected by changes. Therefore, the adjusted gas velocity model can be used for calibration at zero flow.

[0205] In some embodiments, the calibration method does not depend on zero flow and can be applied to any flow. The calibration method can allow for individual delays, δ1 and δ2, in each time step of the flight direction, such that the speed of sound calculation becomes:

[0206]

[0207] The same applies to v, where the values ​​of c and v are known, and the delayed calculation is as follows:

[0208]

[0209]

[0210] In this scenario, the value of D+D0 can be fixed for all sensors or determined individually during manufacturing. If it is desired to calibrate c or v separately, the current calculated values ​​of the remaining variables can be substituted. For example, to calibrate flow rate without affecting the sound velocity reading, the current sensed value of c is used to produce values ​​of δ1 and δ2 that affect v, not c. In this way, flow rate can be calibrated with any known flow rate, and sound velocity can be calibrated in turn.

[0211] Similar calibration can be applied to other sensors. For example, heated temperature sensing elements can be modeled using King's Law or its derivatives, and unknown parameters can be adjusted based on measurements at calibration points. In some embodiments, redundancy provided by the ultrasonic transducer (fast but not always accurate at low flow rates) and redundancy provided by the heated temperature sensing element (slow but with good accuracy at low flow rates) can be combined during operation to provide continuous readings that are both fast and accurate at low flow rates. For example, low flow rates include flow rates less than about 25 L / min, or less than about 20 L / min, or less than about 15 L / min. For example, each time a flow rate reading is obtained from the heated temperature sensing element, it can be used to calculate or adjust the calibration parameters of the ultrasonic transducer, as described in the preceding paragraphs, thereby continuously calibrating any errors or drift in the ultrasonic transducer readings. Adjustments can be performed directly or filters can be used to adjust parameters only by a certain amount or at a certain rate, and / or the adjustment level can be weighted according to flow rate or other sensing parameters, or the optimal weights can be estimated using known system response characteristics, similar to a Kalman filter. Alternatively, the flow rate reading of the ultrasonic transducer can be adjusted directly, instead of adjusting the calibration parameters in a similar manner.

[0212] In some embodiments, system calibration can therefore be performed in the following steps, as illustrated in the flowchart of Figure 26A. First 2601, the control system can close the valve and adjust the blower to a fixed blower speed. Measurements from multiple different sensors (e.g., ultrasound, temperature, humidity, pressure) can be checked to ensure the system is operating correctly 2602. For example, the approximate flow rate from the ultrasonic transducer can be checked to ensure the flow path is not blocked, and / or the pressure can be measured by a pressure sensor and confirmed to be within acceptable values.

[0213] Next, the control system can shut off the blower and valve to generate zero flow 2603. As described above, the measurements from the ultrasonic transducers can be used to calibrate the total sensor distance (D+D0) and the zero flow offset 2605. The ultrasonic transducer readings can be used as a reference for calibrating heated temperature sensing elements. However, heated temperature sensing elements typically require two calibration points because they have more unknowns in the system (e.g., temperature sensitivity, temperature and / or power gradient). After calibrating the ultrasonic transducers, they can be used as a reference to generate at least one new condition to perform additional calibration, such as under zero flow or one or more non-zero flow conditions.

[0214] After calibrating the ultrasonic transducer 2612, the system can use the calibrated ultrasonic transducer to calibrate other sensors 2613. The blower 2606 can be turned on to allow flow through the system. With the valve closed, the known oxygen concentration is close to 20.9% (the oxygen concentration in the air). Measurements can be taken to check if the oxygen reading is within acceptable values ​​2607. Similarly, if the device is attached to a known oxygen source, the valve can be fully opened, and the blower set to a low flow rate, and measurements can be taken to check if the oxygen reading is close to 100% or within acceptable values, for example, if the oxygen concentrator only delivers approximately 100% oxygen. Furthermore, at 100% oxygen, measurements can be taken using a relative humidity sensor to check if the relative humidity reading is close to 0% or within acceptable values.

[0215] By utilizing both an ultrasonic transducer and a heated temperature sensing element to perform measurements and comparing those results 2608, the control system can calibrate the parameters 2609 of the heated temperature sensing element accordingly. The blower can be adjusted to create additional flow groups, which can be measured for additional calibration points.

[0216] Then, the control system can shut down the blower 2610 and verify the calibration 2611 of the ultrasonic transducer and the heated temperature sensing element at a known zero flow rate.

[0217] Figure 26B Another embodiment of the system's calibration steps is illustrated. In step 2620, the system generates a desired value for a given operating parameter. The desired value can be derived from a lookup table, user input, calculated values, etc. In step 2622, the system operates with the given and known operating parameters from step 2620. In step 2624, the system uses one of the sensors to measure a first value. In step 2626, the system compares the first value with the desired value from step 2620. In step 2628, the system can calibrate the measurement result based on the difference between the first value and the desired value. Measurement results that can be calibrated include sound velocity, flow rate when the blower is off (zero flow), or flow rate at a specific flow rate. Optionally, in step 2630, the system can repeat steps 2620 through 2628 once or several times as a check by operating with different operating parameters. In some embodiments, in step 2632, the system can optionally compare the first value with a factory setting. This comparison can be performed either after comparison step 2626 or after comparison step 2626 but before any calibration occurs. If the first value exceeds the limit, the system can stop the calibration process and output an alarm. This limit can be, for example, a factory tolerance or a predetermined calibration limit assumed for the equipment to operate under.

[0218] In some embodiments, the calibration system checks its parameters and adjusts them as needed to meet acceptable limits. In some embodiments, the calibration system checks its parameters to determine whether the sensed values ​​are acceptable without adjusting the parameters. System calibration can be performed during manufacturing to determine acceptable values ​​that will serve as a reference for later system calibration. Calibration can be performed in the factory, by the user, or automatically by the system. For example, the system may prompt the user for calibration, or an automatic calibration unit may calibrate the system when needed or only at appropriate times. In other instances, the user may initiate the calibration system.

[0219] Dual absolute pressure sensor arrangement

[0220] Flow therapy devices may include dual absolute pressure sensors, one of which is Figure 22C The pressure sensor 2209 is a metering sensor. Metering sensors are typically mounted on a sensing module to measure the difference between airflow pressure and ambient pressure. This difference is used to monitor how the user feels when the gas is delivered to the user in a flow therapy device. Metering sensors measure over a small range, thus offering advantages such as higher resolution, lower noise, and greater accuracy compared to absolute pressure sensors. However, metering sensors have several disadvantages. Metering sensors require the installation of two conduits. Problems with the conduits can arise for several reasons. For example, a conduit may detach, leading to oxygen leakage. Oxygen leakage is a safety hazard. Metering sensors are also sensitive to positioning because the sensor ports cannot face the flow or be in areas of stagnant pressure. Furthermore, the housing structure is less robust because the conduits need to pass through holes in the housing that houses the sensor.

[0221] Because the flow therapy device described herein controls the flow rate rather than the pressure delivered to the patient, the system is less affected by noise in the readings. This is helpful, for example, for synchronization with the patient's breathing. Noise can usually be filtered out. Therefore, an absolute pressure sensor in the therapy device can offer a simpler mechanical design than a metering sensor by eliminating the need for any tubing behind the seals without compromising the accuracy of the readings for flow control.

[0222] As described above, a pressure sensor is located in the flow path and is located in Figure 22C On the sensing circuit board 2200. Another pressure sensor can be positioned on a printed circuit board that is not located in the gas flow path or the pressurization area of ​​the device, but is exposed to ambient temperature. Therefore, as Figure 28 As shown in the flowchart, in step 2802, the air pressure sensor on the sensing circuit board within the flow path registers the absolute pressure P of the airflow. F Provided to the system's controller, for example Figure 1Controller 13 or Figure 19 The controller 600. In step 2804, another barometric pressure sensor will register the ambient pressure P. A The readings are provided to the controller. In step 2806, the controller calculates the difference P between the two values. F - P A In step 2808, the pressure difference is output as the metered pressure P in the system. G The system can use metered pressure P G This is used to adjust the motor speed profile and calibrate the control of oxygen or gas flow. For example, metering pressure P. G It is very helpful to synchronize with the patient's breathing.

[0223] In addition to the metered pressure P calculated in the system based on readings from two pressure sensors G Furthermore, by eliminating oxygen leakage and improving user safety, the dual absolute pressure sensor arrangement also offers the following applications and / or advantages.

[0224] Absolute pressure sensors in the flow path (e.g.) Figure 22C The pressure sensor 2209 allows for minor calibration of oxygen calculations. An absolute pressure sensor positioned in the flow path (e.g., Figure 22C The pressure sensor 2209 enables comparison between an ultrasonic flow sensor (volume flow rate) and a heated temperature sensing element (mass flow rate). Since the motor produces a constant volume flow rate, large variations in volume flow rate sensing are not expected in the device. However, for a constant motor, mass flow rate will vary with altitude, temperature, or oxygen fraction. An absolute pressure sensor helps calculate the gas density required to convert volume flow rate to mass flow rate, or vice versa, in order to compare readings between the ultrasonic flow sensor and the heated temperature sensing element. This allows the sensor's accuracy to be determined and appropriate calibration to be performed. For example, mass flow rate can be calculated as:

[0225] Mass flow rate = density × volumetric flow rate.

[0226] Even if the heating temperature sensing element is removed from the system, the mass flow rate can still be converted from the volumetric flow rate using the above equation. The metered pressure P in the system is calculated based on the readings of the two pressure sensors. GAnother application is the arrangement of algorithms by decomposing pressure measurements into more defined ranges for leak and blockage detection, or narrower leak and blockage alarms. The conversion between mass flow rate and volumetric flow rate is also useful for calibrating ultrasonic flow readings based on heated temperature sensing elements. Furthermore, the inclusion of an ambient pressure sensor allows for the conversion between mass flow rate and volumetric flow rate, enabling the system to redefine limits at different altitudes. Therefore, these limits are specific to environmental conditions, and a greater number of leak / blockage events can be captured with higher accuracy.

[0227] Specifically, a blockage alarm will occur if the blower can only maintain flow by operating at a higher-than-expected speed. Therefore, as altitude increases, the mass flow rate decreases, meaning the blower speed must increase to deliver the required mass flow rate. Thus, the system can detect blockages because, using pressure sensors, it can adjust the blockage limit so that at higher altitudes, the system knows a higher motor speed is needed for a given mass flow rate, and similarly at lower altitudes, the system knows a lower motor speed is needed for a given mass flow rate.

[0228] Similarly, a leak alarm might occur if the blower doesn't need to operate at such high speeds to maintain the desired flow rate, for example, if the chamber is removed from the system (and therefore less restricted). Without pressure sensors, lower flow rates would be observed at lower altitudes for the same motor speed at higher altitudes with reduced mass flow, potentially confusing the system and requiring larger limits to be defined. Therefore, being able to redefine limits at different heights means that lower limits can be defined for higher heights, allowing for more leak / clogging conditions to be met.

[0229] More specifically, the absolute pressure sensor in the flow path allows for calibration in response to the partial pressure of water vapor in the gas. Knowing the moisture content of the incoming gas, which depends on the pressure, is useful in any humidity algorithm. Specifically, for a power-based humidity control algorithm, the gas characteristics are measured at the inlet before humidification, and the generated humidity is estimated based on the power input to the heater plate to heat the water and these gas characteristics. In this case, pressure significantly affects the accuracy of the humidity estimation because the amount of water required to reach a given dew point temperature depends heavily on the ambient pressure. Metered pressure can also affect humidity calculations, albeit to a lesser extent, based on the pressure drop to the patient outlet ports 21, 344 or to the patient, for example via patient interface 8, which produces a corresponding drop in dew point temperature.

[0230] Although only the raw ambient pressure value is measured and input into the device, various algorithms can be used to manually or automatically calculate the height and use it for system checks. For example, the device can calculate the height based on the pressure reading and display the calculated height to the user to determine if it is a true reading from the device. In another instance, the device can prompt the user to confirm that the displayed height is correct, or the device can request the user to input the height level.

[0231] In some embodiments, the system may use an absolute pressure sensor located outside the flow path or pressurization area and exposed to ambient temperature, or other locations suitable for reading ambient pressure using metering sensors between the control panel and the sensing module or sensing chamber. The system can determine the total pressure delivered to the patient by adding differential pressure readings from the metering sensor and the ambient pressure readings from the absolute pressure sensor.

[0232] Unless the context clearly specifies otherwise, throughout the specification and claims, the words “comprising”, “including”, etc., should be interpreted as inclusive rather than exclusive or exhaustive, that is, meaning “including but not limited to”.

[0233] The term “about” is used here to indicate within the standard measurement accuracy.

[0234] References to any prior art in this specification are not and should not be construed as an admission or suggestion in any form that such prior art forms part of common general knowledge in any country in the world.

[0235] The disclosed devices and systems may also be said in a broad sense to exist individually or collectively in any or all combinations of the components, elements and features mentioned or indicated in the specification of this application, as well as two or more of the said components, elements or features.

[0236] In the preceding description, references have been made to wholes or parts having their known equivalents, which are incorporated herein as if listed separately.

[0237] According to embodiments, certain actions, events, or functions, methods, or procedures of any algorithm described herein may be executed in a different order and may be added, combined, or omitted entirely (e.g., not all described actions or events are necessary for the practice of the algorithm). Furthermore, in some embodiments, actions or events may be executed simultaneously rather than sequentially, for example, through multithreading, interrupt handling, or multiple processors or processor cores or other parallel architectures.

[0238] It should be noted that various changes and modifications to the currently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the disclosed apparatus and system and without diminishing its associated advantages. For example, multiple different components may be repositioned as needed. Therefore, it is intended that such changes and modifications be included within the scope of the disclosed apparatus and system. Furthermore, not all features, aspects, and advantages are necessary for practicing the disclosed apparatus and system. Therefore, the scope of the disclosed apparatus and system is intended to be defined solely by the following claims.

Claims

1. A flow therapy device, comprising: The main housing includes a flow generator to produce airflow for delivery to the patient; A humidifier is used to humidify and / or heat the airflow generated; A sensing chamber includes a flow path and a plurality of sensors, the flow path being configured to receive generated airflow, the plurality of sensors being configured to measure the properties of the airflow flowing through the flow path, wherein the plurality of sensors include: A first ultrasonic transducer is positioned in the downstream portion of the flow path. A second ultrasonic transducer is positioned at the upstream portion of the flow path. A heating-type temperature sensing element is configured to determine the gas flow rate of the gas flow passing through the flow path. A temperature sensor is configured to determine the temperature of the airflow passing through the flow path. A humidity sensor configured to determine the humidity of the airflow passing through the flow path. A first pressure sensor is configured to determine the absolute pressure within the flow path, and A second pressure sensor, disposed within the main housing and configured to be exposed to ambient temperature, is configured to determine an estimate of the ambient pressure; and A controller configured to receive outputs from the plurality of sensors and to operate the flow generator and / or the humidifier based on the outputs from the plurality of sensors. The sensing chamber further includes a sensing circuit board, wherein a first portion of the sensing circuit board is at least partially located within the flow path of the sensing chamber, and wherein the sensing circuit board includes at least a second portion of the sensing circuit board located outside the flow path. The plurality of sensors in the sensing chamber are configured to be placed within the first portion of the sensing circuit board, and The first ultrasonic transducer and the second ultrasonic transducer are positioned at opposite ends of the sensing circuit board.

2. The flow therapy device according to claim 1, wherein, The sensing chamber is located downstream of the flow generator.

3. The flow therapy device according to claim 1 or 2, wherein, The flow therapy device also includes an inlet port that receives gas from at least two different gas sources, and the flow generator receives gas from the inlet port to generate the airflow.

4. The flow therapy device according to claim 3, wherein, The flow generator is configured to mix gases from the at least two different gas sources to produce a mixed gas.

5. The flow therapy device according to claim 1, wherein, The first ultrasonic transducer and the second ultrasonic transducer are positioned such that the space between the first ultrasonic transducer and the second ultrasonic transducer at least partially coincides with the flow path of the sensing chamber.

6. The flow therapy device according to claim 1 or 2, wherein, The first ultrasonic transducer and the second ultrasonic transducer are configured to determine the gas concentration of the gas flow passing through the flow path.

7. The flow therapy device according to claim 1 or 2, wherein, The first ultrasonic transducer and the second ultrasonic transducer are configured to determine the flow rate of the airflow passing through the flow path.

8. The flow therapy device according to claim 1, wherein, The sensing circuit board includes cutouts around the heated temperature sensing element.

9. The flow therapy device according to claim 1 or 2, wherein, The temperature sensor is a thermistor.

10. The flow therapy device according to claim 1 or 2, wherein, The humidity sensor and the temperature sensor are a combined humidity and temperature sensor configured to monitor the dew point of the airflow.

11. The flow therapy device according to claim 1 or 2, wherein, The plurality of sensors also include temperature and humidity sensors configured to monitor the dew point of the airflow.

12. The flow therapy device according to claim 11, wherein, The temperature sensor is configured closer to the inlet of the flow path in the sensing chamber, and the temperature and humidity sensors are closer to the outlet of the flow path in the sensing chamber.

13. The flow therapy device according to claim 11, wherein, The sensing circuit board includes a bent finger to position the temperature sensor and the humidity and temperature sensors closer to the center of the flow path to improve the accuracy of the readings.

14. The flow therapy device according to claim 11, wherein, The temperature sensor and the temperature and humidity sensor are respectively configured to be placed very close to one of the first ultrasonic transducer and the second ultrasonic transducer.

15. The flow therapy device according to claim 1, wherein, The sensing circuit board includes a track arranged to reduce thermal conduction between the chamber wall and the sensing circuit board.

16. The flow therapy device according to claim 1, wherein, The second portion of the sensing circuit board includes circuitry for the first ultrasonic transducer and the second ultrasonic transducer.

17. The flow therapy device according to claim 1, wherein, The sensing chamber includes a seal that separates the first portion of the sensing circuit board from the second portion of the sensing circuit board.

18. The flow therapy device according to claim 1 or 2, wherein, The plurality of sensors also includes a gas concentration sensor configured to determine the oxygen concentration or other gas concentration in the flow path.

19. The flow therapy device according to claim 17, wherein, The seal is configured to close the high-pressure area of ​​the flow path, wherein a sensor on the first portion of the sensing circuit board measures the characteristics of the airflow, the seal prevents gas from escaping from the high-pressure area of ​​the flow path and moving toward the electronics of the flow therapy device, and prevents water from contacting the second portion of the sensing circuit board.

20. The flow therapy device according to claim 1 or 2, wherein, The controller is configured to provide redundancy for flow measurement using outputs from the heated temperature sensing element and outputs from the first and second ultrasonic transducers. This redundancy includes rapid flow measurement at low flow rates by the first and second ultrasonic transducers, and accurate flow measurement at low flow rates by the heated temperature sensing element.

21. The flow therapy device according to claim 1 or 2, wherein, The difference between the first absolute pressure and the second absolute pressure determines the calculated pressure difference, and wherein the controller is configured to adjust the calculation of the property based at least in part on changes in the ambient pressure.

22. The flow therapy device according to claim 1 or 2, wherein, The controller is configured to compare mass flow rate with volumetric flow rate by using ambient pressure readings.

23. The flow therapy device according to claim 1 or 2, characterized in that, The flow therapy device is a modular system, and the sensing chamber is configured to be disassembled and replaced.

24. The flow therapy device according to claim 1 or 2, wherein, The humidity sensor is configured to warn the user to check whether the flow therapy device may have water ingress, or to take corrective measures.

25. The flow therapy device according to claim 1, wherein, The sensing circuit board is coated with a conformal coating to prevent water from entering the sensing circuit board or to mitigate the effects of water entering the sensing circuit board, and also to mitigate the effects of oxygen entering.

26. The flow therapy device according to claim 1 or 2, wherein, Positioning the plurality of sensors within the flow path configured to receive the generated airflow allows for measurements and calculations that take into account the effects of gas velocity, making it possible to remove the effects of gas velocity from the sensor measurements.

27. The flow therapy device according to claim 1 or 2, wherein, Positioning the temperature sensor within the flow path configured to receive the generated airflow increases thermal conductivity between the gas and the temperature sensor, and allows for more accurate sensing of the gas temperature, as well as a faster response from the temperature sensor.

28. The flow therapy device according to claim 1 or 2, wherein, The controller is also configured to use sensors to make measurements under known conditions and use the measurement results in a mathematical model to solve for one or more unknown parameters in order to calculate the characteristics of the airflow.

29. The flow therapy device according to claim 1 or 2, wherein, The controller is also configured to calculate the difference P between the absolute pressure and the ambient pressure. F -P A And outputs the pressure difference as the metering pressure P in the flow therapy device. G And wherein the controller is configured to use the metering pressure P G This is used to adjust the motor speed curve and calibrate the control of oxygen or gas flow rate.

30. The flow therapy device according to claim 1 or 2, wherein, The first pressure sensor, positioned in the flow path, enables comparison between the ultrasonic flow sensor that measures volumetric flow rate and the heated temperature sensing element that measures mass flow rate.

31. The flow therapy device according to claim 1 or 2, wherein, The controller is configured to control the flow generator based on the outputs from the plurality of sensors to generate an airflow with a desired flow rate.

32. The flow therapy device according to claim 1 or 2, wherein, The controller is configured to control the heating element in the humidifier to heat the airflow to a desired temperature based on the outputs from the plurality of sensors.

33. The flow therapy device according to claim 1 or 2, wherein, The controller is configured to be programmed to have or determine a suitable target temperature for the airflow.

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