Breathing aid

Abstract

To provide a respiratory assistance device with improved gas composition sensing capabilities. The respiratory aid device has a gas inlet configured to receive a gas supply, a blower unit configured to generate a pressurized gas flow from the gas supply, a humidification unit configured to heat and humidify the pressurized gas flow, and a gas outlet for the heated and humidified gas flow. A gas flow path extends through the respiratory device from the gas inlet, through the blower unit and the humidification unit, to the gas outlet. A sensor assembly is provided in the flow path prior to the humidification unit. The sensor assembly includes an ultrasonic gas composition sensor system for detecting the concentration of one or more gases in the gas flow.

Description

[Technical Field]

[0001] The present invention relates to a respiratory assistance device that provides a heated and humidified gas flow to a user for therapeutic purposes. In particular, but not exclusively, the respiratory assistance device may provide respiratory assistance to a patient or user requiring a supply of heated and humidified gas for respiratory therapies such as respiratory humidification therapy, high-flow oxygen therapy, positive airway pressure (PAP) therapy, including CPAP therapy, Bi-PAP therapy, and OPAP therapy, typically for the treatment of diseases such as obstructive sleep apnea (OSA), snoring, and chronic obstructive pulmonary disease (COPD). [Background technology]

[0002] Respiratory assistance devices or systems that provide a patient with a flow of humidified and heated gas for therapeutic purposes are well known in the art. Systems that provide this type of therapy (e.g., respiratory humidification) typically include a structure, such as a blower (also known as a compressor, ventilator unit, fan unit, flow generator, or pressure generator), that delivers gas from a gas source to a humidifier chamber. As the gas passes over hot water or through heated and humidified air in the humidifier chamber, it becomes saturated with water vapor. The heated and humidified gas is then delivered from the humidifier chamber to a downstream user or patient via a gas conduit and a user interface.

[0003] In one form, such a respiratory assistance system can be a modular system with a humidifier unit and a blower unit that are separate (modular) items. The modules are connected in series via connecting conduits to pass gas from the blower unit to the humidifier unit. For example, FIG. 1 shows a schematic diagram of a user 1 receiving heated and humidified air from a modular respiratory assistance system. Pressurized air is provided from a ventilator unit or blower unit 2a to a humidifier chamber 4a via a connector conduit 10. The humidified, heated, and pressurized airflow exits the humidifier chamber 4a via a user conduit 3 and is provided to the patient or user 1 via a user interface 5.

[0004] Alternatively, the respiratory assistance system can be an integrated system in which the blower unit and humidifier unit are contained within the same housing. A typical integrated system consists of a main blower unit or ventilator unit that provides the pressurized gas flow and a humidifier unit that fits or is otherwise securely connected to the blower unit. For example, the humidifier unit fits to the blower unit via a slide or push-fit connection, ensuring that the humidifier unit is securely connected to the main blower unit and held securely in place on the main blower unit. Figure 2 shows a schematic diagram of a user 1 receiving heated and humidified air from an integrated respiratory assistance system 6. The system operates in the same manner as the modular system shown in Figure 1, except that the humidifier chamber 4b is integrated with the blower unit to form the integrated system 6.

[0005] The user interface 5 shown in Figures 1 and 2 is a nasal mask that covers the nose of the user 1. However, it should be noted that in these types of systems, a mouth and nose mask, a full face mask, a nasal cannula, or any other suitable user interface may be substituted for the nasal mask shown. A mouth-only interface or mouth mask may also be used. The patient or user end of the conduit may also be connected to a tracheostomy fitting or endotracheal intubation.

[0006] U.S. Patent No. 7,111,624 contains a detailed description of an integrated system. In use, a "slide-on" water chamber is connected to the blower unit. A variation on this design is a slide-on or clip-on design where, in use, the chamber is enclosed within a portion of the integrated unit. An example of this type of design is shown in WO 2004 / 112873, which describes a blower or flow generator 50 and an associated humidifier 150.

[0007] For these integrated systems, the most common mode of operation is as follows: air is drawn by a blower through an inlet into a case that encloses and surrounds at least the blower portion of the system. The blower pressurizes the airflow from the flow generator inlet and passes it to the humidifier chamber. The airflow is heated and humidified in the humidifier chamber and exits the humidifier chamber via the inlet. A flexible hose or conduit is connected directly or indirectly to the humidifier outlet, and the heated and humidified gas is passed via the conduit to the user. This is shown schematically in Figure 2.

[0008] In both modular and integrated systems, the gas provided by the blower unit is typically sourced from ambient air. However, some forms of these systems may be configured to allow supplemental gas to be mixed with atmospheric air for specific treatments. In such systems, the gas conduit supplying the supplemental gas is typically connected directly to the humidifier chamber or elsewhere on the high-pressure (outlet) side of the blower unit, or alternatively, to the inlet side of the blower unit, as described in International Publication WO 2007 / 004898. This type of respiratory support system is typically used when a patient or user requires oxygen therapy and oxygen is supplied from a central gas source. Oxygen from the gas source is mixed with ambient air to increase the oxygen concentration before delivery to the patient. Such systems allow oxygen therapy to be combined with high-flow humidification therapy for the treatment of diseases such as COPD. In such therapy, it is important that the oxygen concentration being delivered to the patient is known and controlled. Currently, the oxygen concentration delivered to the patient is typically calculated manually or estimated based on printed look-up tables that provide various pre-calculated oxygen concentrations based on various oxygen flow rates supplied from a central gas source and various flow rates produced by a blower unit.

[0009] Where reference is made herein to patent specifications, other external documents, or other sources of information, it is generally for the purpose of providing a background for discussing features of the present invention. Unless specifically indicated otherwise, reference to such external documents should not be construed as an admission that such documents or such sources are prior art or form part of the general knowledge in any jurisdiction. Summary of the Invention [Problem to be solved by the invention]

[0010] It is an object of the present invention to provide a respiratory aid device with improved gas composition sensing capabilities, or at least to provide the public with a useful choice. [Means for solving the problem]

[0011] In a first aspect, the invention resides in a broad sense in a respiratory aid apparatus configured to provide a heated and humidified gas flow, the respiratory aid apparatus comprising: a gas inlet configured to receive a gas supply; a blower unit configured to generate a pressurized gas flow from the gas supply; a humidification unit configured to heat and humidify the pressurized gas flow; a gas outlet for the heated and humidified gas flow; a flow path for the gas flow through the respiratory apparatus from the gas inlet, through the blower unit and the humidification unit to the gas outlet; and a sensor assembly provided in the flow path prior to the humidification unit, the sensor assembly comprising an ultrasonic gas composition sensor system for detecting the concentration of one or more gases in the gas flow.

[0012] Preferably, the ultrasonic gas composition sensor system may comprise a transceiver pair of a transmitter and a receiver, the transceiver pair operable to transmit cross-flow acoustic pulses through the gas flow from the transmitter to the receiver to sense the speed of sound within the gas flow in the vicinity of the sensor assembly.

[0013] In one form, a transmitter-receiver pair may be positioned so that the acoustic pulse travels through the gas flow in a cross-flow, which is a direction substantially perpendicular to the direction of flow of the gas flow.

[0014] Alternatively, the transmitter and receiver pair may be positioned so that the acoustic pulse travels through the gas flow in a cross-flow that is oblique to, but not perpendicular to, the direction of flow of the gas flow.

[0015] In one form, a transmitter / receiver pair may include one transducer configured as a transmitter and the other configured as a receiver to transmit unidirectional acoustic pulses.

[0016] In another form, the transmitter and receiver transceiver pair may comprise a pair of transmitter-receiver transducers configured to transmit bidirectional acoustic pulses.

[0017] In one form, the transmitter and receiver may be aligned with one another relative to the direction of gas flow and may face one another across the flow path.

[0018] Alternatively, the transmitter and receiver may be displaced from each other in the direction of gas flow.

[0019] Preferably, the acoustic pulse may have a direct beam path between the transmitter and the receiver, or alternatively, the acoustic pulse may have an indirect beam path between the transmitter and the receiver, which involves one or more reflections.

[0020] In another form, the transmitter and receiver transducer pair may take the form of a single transmitter-receiver configured to transmit crossflow acoustic pulses and receive echo return pulses.

[0021] In another form, an ultrasonic gas composition sensor system may comprise a transmitter and receiver transducer pair operable to transmit flow-along acoustic pulses through the gas flow from the transmitter to the receiver to sense the speed of sound in the gas flow in the vicinity of the sensor assembly.

[0022] Preferably, the respiratory assistance device may further comprise a sensor control system operably connected to the transmitter and receiver transducer pair of the ultrasonic gas composition sensor system and configured to operate the transducer pair to sense the speed of sound through the gas flow and generate a sound speed signal indicative of the speed of sound.

[0023] Preferably, the sensor control system is configured to generate one or more gas concentration signals indicative of the concentration of gas within the gas stream based at least on the signal indicative of the speed of sound through the gas stream.

[0024] In one form, the sensor assembly may further include a temperature sensor configured to measure the temperature of the gas flow in the vicinity of the sensor assembly and generate a representative temperature signal, and the sensor control system configured to generate one or more gas concentration signals indicative of the gas concentration in the gas flow based on the sound speed signal and the temperature signal.

[0025] In another form, the sensor assembly may further include a humidity sensor configured to measure humidity of the gas stream in the vicinity of the sensor assembly and generate a representative humidity signal, and the sensor control system is configured to generate one or more gas concentration signals indicative of the gas concentration in the gas stream based on the speed of sound signal and the humidity signal. By way of example, the humidity sensor may be a relative humidity sensor or an absolute humidity sensor.

[0026] In another form, the sensor assembly may include both a temperature sensor and a humidity sensor that measure the temperature and humidity of the gas flow in the vicinity of the sensor assembly and generate representative temperature and humidity signals, respectively, and the sensor control system is configured to generate one or more gas concentration signals indicative of the gas concentration in the gas flow based on the sound speed signal, the temperature signal, and the humidity signal.

[0027] Preferably, the sensor control system may be configured to apply a temperature correction to the temperature signal to compensate for any expected temperature sensing error caused by heat within the respiratory apparatus affecting the temperature sensor.

[0028] Preferably, the sensor assembly may further comprise a flow sensor configured to sense a flow rate of the gas stream in the vicinity of the sensor assembly and generate a representative flow rate signal, and the system may further comprise a motor speed sensor provided configured to sense a motor speed of the blower unit and generate a representative motor speed signal, and the temperature correction is calculated by the sensor control system based on at least the flow rate signal and / or the motor speed signal.

[0029] In one form, the sensor control system may be configured to generate a gas concentration signal representative of the oxygen concentration within the gas stream.

[0030] In another form, the sensor control system may be configured to generate a gas concentration signal representative of the carbon dioxide concentration within the gas stream.

[0031] Preferably, the sensor assembly is removably mountable within the flow path.

[0032] Preferably, the flow path may have a shape or configuration that promotes a steady flow of gas stream through at least one section or portion of the flow path.

[0033] Preferably, the flow path may have a shape or configuration that promotes steady flow in the section or portion of the flow path that includes the sensor assembly.

[0034] Preferably, the flow path may include one or more flow directors at or towards the gas inlet, more preferably each flow director may be in the form of an arcuate fin.

[0035] In one form, the flow path may include at least one helical portion or section to promote a steady flow of gas. Preferably, the flow path may include an inlet section extending between the gas inlet and the blower unit, the inlet section including at least one helix.

[0036] Preferably, the sensor assembly may be located in a helical portion of the flow path, more preferably the helical portion comprises one or more substantially straight sections and the sensor assembly is located in one of the straight sections.

[0037] Preferably, the sensor assembly may include a sensor housing having a body, the body being hollow and defined by a peripheral wall extending between a first open end and a second open end, thereby defining a sensing passage within the body between the walls and through which gas flow can flow in a direction of a flow axis extending between the first and second ends of the body, the transmitter and receiver transducer pair being disposed on opposite walls or sides of the sensing passage. More preferably, the sensor housing may include a body having two spaced-apart side walls and upper and lower walls extending between the side walls, defining a sensing passage along the body between the first and second ends, and a pair of transducer mounting assemblies disposed on opposite walls of the body, each configured to receive and hold a respective transducer of the transducer pair across the sensing passage of the body so that the transducers of the transducer pair are aligned and face each other.

[0038] Preferably, the blower unit may be operable to generate a gas flow at the gas outlet having a flow rate of up to 100 litres / minute.

[0039] In one form, the gas inlet may be configured to receive a supply of gas comprising a mixture of atmospheric air and pure oxygen from an oxygen source, hi another form, the gas inlet may be configured to receive a supply of gas comprising a mixture of atmospheric air and carbon dioxide from a carbon dioxide source.

[0040] Preferably, the flow path is within the bulk flow path of the device.

[0041] In a second aspect, the invention broadly resides in a sensor assembly for in-line flow path sensing of gas flow in a respiratory assistance device, the sensor assembly comprising a sensor housing having a body, the body being hollow and defined by a peripheral wall extending between a first open end and a second open end thereby defining a sensing passage within the body between the walls and through which gas flow can flow in the direction of a flow axis extending between the first and second ends of the body, the sensor assembly comprising an ultrasonic gas composition sensor system mounted in the sensor housing for sensing the concentration of one or more gases in the gas flow through the sensing passage, a temperature sensor mounted in the sensor housing for sensing the temperature of the gas flow through the sensing passage, and a flow sensor mounted in the sensor housing for sensing a flow rate of the gas flow through the sensing passage.

[0042] Preferably, the sensor housing may be configured to releasably engage a complementary retention aperture in the flow path of the respiratory assistance device.

[0043] Preferably, the ultrasonic gas composition sensor system may comprise a transmitter transducer and receiver transducer pair operable to transmit acoustic pulses from the transmitter to the receiver through the gas flow in a direction generally perpendicular to the flow axis of the gas flow flowing through the sensing passage.

[0044] Preferably, the transmitter and receiver transducer pairs may be located on opposite walls or sides of the sensing passageway.

[0045] Preferably, the body of the sensor housing includes two spaced-apart side walls and upper and lower walls extending between the side walls to define a sensing passageway along the body between the first and second ends, and the body may include a pair of transducer mounting assemblies disposed on opposing walls of the body, each of the pair of transducer mounting assemblies configured to receive and hold a respective transducer of the transducer pair so that the transducers of the transducer pair are aligned and face each other across the sensing passageway of the body.

[0046] Preferably, a pair of transducer mounting assemblies may be located on opposite side walls of the body, each transducer mounting assembly including a retention cavity for receiving and retaining a respective transducer of the pair therein.

[0047] Preferably, each transducer mounting assembly may include a cylindrical base portion extending from each side wall of the body and at least a pair of opposing clips extending from the base portion, the base portion and clips collectively defining a retention cavity.

[0048] Preferably, each side wall of the body may include a transducer aperture aligned with an associated transducer mounting assembly and through which the operating front face of the transducer may extend to access the sensing passageway.

[0049] Preferably, the transducer mounting assembly may be configured to position each transducer so that the operating surface of the transducer is substantially flush with the inner surface of each wall of the body of the sensor housing.

[0050] The second aspect of the invention may have any one or more of the features described in relation to the sensor assembly of the first aspect of the invention.

[0051] The phrase "stable flow" as used herein and in the claims, unless the context suggests otherwise, means a type of gas stream flow, whether laminar or turbulent, that promotes or causes the attribute or characteristic of the flow being measured or sensed to be substantially time invariant under a given set of conditions, on the scale at which the attribute or characteristic is being measured or sensed.

[0052] As used herein and in the claims, the phrase "crossflow beam" or "crossflow" refers to an ultrasonic pulse or beam transmitted with a beam path that is transverse to or across the main gas flow path direction or axis, as opposed to along the main gas flow path direction, unless the context indicates otherwise. For example, a crossflow beam may be transmitted across the gas flow path in a direction generally perpendicular to the main gas flow path direction or axis, although other crossflow angles are also contemplated and are covered by this term.

[0053] As used herein and in the claims, the phrase "along-flow beam" or "along-flow" refers to an ultrasonic pulse or beam transmitted with a beam path generally aligned with the main gas flow path direction or axis, whether parallel or coincident, unless the context suggests otherwise, and which may be transmitted either in the direction of gas flow or against it.

[0054] The term "comprises" as used in this specification and claims means "consisting of at least a portion of." When interpreting each sentence in this specification and claims containing the term "comprises," there may be features other than the feature or features followed by the term. Related terms such as "comprises" and "comprised" should be interpreted similarly.

[0055] Numeric range Reference to a numerical range disclosed herein (e.g., 1 to 10) is intended to incorporate reference to every relevant numerical value within that range (e.g., 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10), as well as any range of associated numerical values ​​within that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7); thus, every subrange of every range explicitly disclosed herein is also expressly disclosed. These are merely examples of what is specifically intended, and all possible combinations of numerical values ​​between the lowest and highest values ​​recited should likewise be considered to be expressly set forth herein.

[0056] As used herein, the term "and / or" means "and" or "or" or both.

[0057] As used herein, "(s)" following a noun refers to the plural and / or singular form of that noun.

[0058] While the invention is essentially as described above, other constructions are contemplated, of which the following are merely exemplary.

[0059] Preferred embodiments of the present invention will now be described, by way of example only, with reference to the drawings in which: [Brief explanation of the drawings]

[0060] [Figure 1] 1 is a schematic diagram of a known form of respiratory assistance device having a modularly configured blower unit connected to a humidifier unit; FIG. [Figure 2] 1 is a schematic diagram of another known form of respiratory assistance device in which the blower unit and humidifier unit are integrated into a single main housing; [Figure 3] 1 shows a perspective view of the main housing of a respiratory assistance device according to an embodiment of the present invention; [Figure 4] 4 shows a side elevational view of the respiratory assistance device of FIG. 3. [Figure 5] 5 shows a front elevational view of the respiratory assistance apparatus from direction A of FIG. 4. [Figure 6] 5 shows a rear elevation view of the respiratory assistance apparatus from direction B of FIG. 4. [Figure 7] 4 shows a bottom view of the respiratory assistance device of FIG. 3. [Figure 8] 4 shows a plan view of the respiratory assistance device of FIG. 3. [Figure 9] 4 shows a perspective view of the respiratory assistance device of FIG. 3 with the top of the main housing removed to expose the electronic control circuitry and blower unit compartment. [Figure 10] FIG. 10 shows a perspective view of the respiratory assistance device of FIG. 9 with the electronic control circuitry, outer blower unit case, and other components removed to expose the top side of the inner blower case for the motor and impeller. [Figure 10A] 4 shows a perspective view of the respiratory assistance device of FIG. 3 with the lower part of the main housing and base section removed, exposing the underside of the main outer blower unit case and the inner blower case. [Figure 11] 11 shows a perspective view of the respiratory assistance device of FIG. 10 with the internal blower case and humidification chamber inlet connector removed to expose the top side of the main housing base section. [Figure 12] FIG. 12 shows a perspective view of the respiratory assistance device of FIG. 11 with the bottom of the main housing removed to expose the base compartment and the humidifier unit compartment. [Figure 13] 13 shows a plan view of the respiratory assistance device of FIG. 12. [Figure 14] 13 shows a rear end view of the respiratory assistance device of FIG. 12 from direction C. [Figure 15] 13 shows a bottom view of the respiratory aid apparatus of FIG. 12 showing the sensor assembly and a first embodiment of an inlet section of a gas flow channel having a helical flow path. [Figure 16] 13 shows a perspective view of the underside of the respiratory assistance device of FIG. 12. [Figure 17] 13 shows an enlarged perspective view of the underside of the respiratory aid device of FIG. 12, in particular the inlet section of the gas flow path and part of the sensor assembly. [Figure 18A] 13 shows a bottom view of the respiratory apparatus of FIG. 12 showing the sensor assembly and a second embodiment of the inlet section of the gas flow channel having a direct flow path. [Figure 18B] 18B shows a rear end view of the respiratory assistance device of FIG. 18A with a direct inflow channel. [Figure 18C] 18B shows a perspective view of the underside of the breathing apparatus of FIG. 18A. [Figure 19] FIG. 2 shows a perspective view of a housing of a sensor assembly according to one embodiment of the present invention. [Figure 20] 20 shows a perspective view of the sensor assembly housing of FIG. 19 with the sensor arrangement mounted in the housing. [Figure 21] 20 shows a bottom view of the housing of the sensor assembly of FIG. 19. [Figure 22] 20 shows a plan view of the upper side of the housing of the sensor assembly of FIG. 19. [Figure 23] FIG. 20 shows a side view of the housing of the sensor assembly of FIG. 19. [Figure 24] 20 shows an end view of the housing of the sensor assembly of FIG. 19. [Figure 25] 1 shows a block diagram of a sensor control system for a respiratory assistance device according to an embodiment of the present invention; [Figures 26A-26E] 1A-1D show schematic diagrams of various ultrasonic transducer configurations for a sensor assembly using a crossflow beam. [Figures 27A-27C] 1A-1D show schematic diagrams of various ultrasonic transducer configurations for a sensor assembly using along-flow beams. DETAILED DESCRIPTION OF THE INVENTION

[0061] Overview The present invention relates primarily to a sensor assembly and associated sensor control circuitry for sensing various properties of a gas flow through a respiratory aid apparatus. By way of example, one embodiment of the sensor assembly and sensor control system will be described with reference to an integrated system type respiratory aid apparatus in which the blower unit is integrated with the humidification unit in a single housing. However, it will be appreciated that the sensor assembly and associated sensor control system may also be implemented in a modular type respiratory aid apparatus system in which the humidification unit is separate from the blower unit.

[0062] Furthermore, the described embodiments make particular reference to respiratory assistance devices used for high flow humidification and oxygen therapy, where the gas stream can be considered as a binary gas mixture of atmospheric air mixed with supplemental oxygen (O2), such that the oxygen concentration in the gas stream delivered to the end user has an increased oxygen concentration compared to atmospheric air. In the art, supplementing or mixing atmospheric gas with another gas is known as "augmentation," and is typically used to modify the concentration of a particular gas, such as oxygen or nitrogen, compared to its concentration in atmospheric air.

[0063] It will be appreciated that the sensor assembly and sensing circuitry may alternatively be implemented in other respiratory assistance devices that are specifically configured or specifically controlled for other respiratory therapies, such as PAP therapy, whether delivering a pressurized gas flow at atmospheric pressure only or of atmospheric air augmented with another particular gas, such as oxygen or nitrogen. It will be appreciated that while the sensor assembly and sensor control system are primarily configured to sense the oxygen concentration of a binary gas mixture including atmospheric gas augmented with oxygen, it may also be configured or adapted to sense properties of gas streams including other augmented air mixtures or binary gas mixtures, such as atmospheric air augmented with nitrogen (N) from a nitrogen source, atmospheric air augmented with carbon dioxide (CO) from a carbon dioxide source or any other suitable supplemental gas, helium augmented with oxygen, or any other suitable binary gas mixture.

[0064] Integrated high-flow humidification and oxygen therapy respiratory support device Referring to Figure 3, the main housing of an integrated respiratory assistance device 10 (breathing device) according to one embodiment of the present invention is shown. The breathing device 10 includes a blower unit that generates a pressurized or high-flow gas flow, which is then heated and humidified by a humidification unit as described above. Although not shown in Figure 3, the gas flow generated by the breathing device 10 is typically delivered to the patient by a patient interface that includes a flexible delivery conduit or tube connected at one end to a gas outlet 12 of the breathing device 10 and at the other end to a user interface, which is typically a nasal cannula, or alternatively may be a nasal mask, a full-face mask, a tracheostomy fitting, or any other suitable user interface.

[0065] In this embodiment, the respiratory apparatus 10 is provided with a humidification unit 15, for example of the type described above with reference to FIG. 2. The humidification unit 15 comprises a humidified water chamber 17 and a heater plate 19, which are located within a humidification unit compartment, generally designated 14, at or toward the front end 11 of the main housing. With reference to FIGS. 3 and 5, the humidification chamber 17, if provided, is provided with an inlet port 16 and an outlet port 18 for connecting the chamber to a fluid path of the respiratory apparatus. For example, the inlet port 16 is connected to a fluid path after a blower unit, such that the humidification chamber 17 receives a pressurized or high-flow gas flow through an inlet from a blower unit located at or toward the rear end 13 of the main housing. Once heated and humidified, the gas flow exits the humidification chamber via the outlet port 18, which is fluidly connected to the gas outlet 12 of the respiratory apparatus 10.

[0066] 6, the gas inlet assembly 20 of the respiratory apparatus 10 is shown at the rear end 13 of the main housing. In this embodiment, the gas inlet assembly 20 includes one or more atmospheric air inlet valves 22 through which ambient atmospheric air is drawn into the apparatus by a blower unit, and a supplemental gas connection inlet 24, which may be connected to a central gas source of supplemental gas, such as an oxygen stream, that mixes with the atmospheric air to increase the oxygen concentration. As described in more detail below, the binary gas mixture of air and oxygen is drawn or aspirated by the blower unit and pressurized into a gas stream at a desired flow rate that is subsequently delivered to a humidification unit where it is heated and humidified before being delivered to the end user via a patient interface to complete the breathing circuit.

[0067] 3, in this embodiment, the main housing of the respiratory apparatus 10 is of two-part construction, including a lower housing portion 26 that is removably coupled or mated to an upper housing portion 28 that, when assembled together, form an overall main housing or case that encloses the blower unit and provides a humidification unit compartment that receives the humidification chamber. However, it will be appreciated that a multi-part housing structure of three or more parts or a single, integral main housing may alternatively be utilized. In this embodiment, the housing parts are molded from plastic, although it will be appreciated that one or more components or parts of the housing may be formed from other materials if desired.

[0068] Referring to Figure 7, there is shown a main base or lower portion 26a of the lower housing portion 26. Referring to Figure 8, a user control interface 30 is provided on the main top portion 28a of the upper housing portion 28, and may include user controls and / or a user display for controlling the breathing apparatus 10.

[0069] Referring to FIG. 9, the respiratory apparatus 10 is shown with the housing top 28 removed, exposing the main or outer blower unit case 32 of the blower unit section housed, in this embodiment, toward the rear end 13 of the main housing. The front circuit board 31 containing the control system electronics for the respiratory apparatus 10 and mounted along the blower unit case 32 is also visible in FIG. 9. Also more clearly visible are the connectors and / or conduits 23, 25 that fluidly connect the inlet port 16 and outlet port 18 of the humidification chamber 17 to the blower unit and gas outlet 12, respectively. FIG. 10 shows the inner blower case 34, which houses the blower unit motor and impeller. The blower unit gas outlet is generally designated 35. The inner blower case 34 is mounted or housed within the main blower unit case 32 shown in FIG. 9.

[0070] 10A, the blower unit's gas flow outlet 35 can be seen more clearly. The blower unit is also provided with a central gas inlet aperture or port 37 through which gas is drawn by the blower unit's rotating impeller. In this embodiment, the blower unit's inlet port 37 is fluidly connected to the gas inlet assembly 20 by a flow path.

[0071] Referring to FIG. 11 , the base section 36 is located at or toward the rear end 13 of the main housing, behind the blower unit. In this embodiment, the base section 36 is mounted to or housed within the lower housing section 26. The base section 36 includes an outlet port or aperture 38 in its top or lid 36 a, which is fluidly connected by a conduit and / or connector to the inlet port 37 of the blower unit so that, in operation, gas flows from the base section 36 through the blower unit after entering the gas inlet assembly 20. FIG. 12 more clearly shows the base section 36 with the lower housing section 26 of the main housing omitted from the view. The humidification unit section 14 is also more clearly visible in FIG. 12 .

[0072] Gas flow path In operation, a flow or stream of gas is transported via a flow path through the respiratory apparatus 10 from the gas inlet assembly 20 to the gas outlet 12. In this embodiment, the flow path begins at the gas inlet assembly 20, where a gas stream, such as atmospheric air mixed with supplemental oxygen, enters the respiratory apparatus 10 and is channeled or transported through an inlet section of the flow path in the base compartment 36 before entering the blower unit compartment described above. After exiting the inlet section of the flow path, the gas stream enters the blower unit, where the gas is pressurized or accelerated into a high-flow gas stream having a controllable flow rate, typically a high flow rate for high-flow humidification therapy. In such applications, the flow rate may range from about 1 L / min to about 100 L / min, more preferably from about 2 L / min to about 60 L / min. The flow path exits the blower unit and enters a fluidly connected (e.g., via conduits, connectors, and / or ports) humidification unit, where the gas stream is heated and humidified. The flow path terminates where the gas flow is transported from the outlet 18 of the humidification unit to the gas outlet 12 of the respiratory apparatus 10 .

[0073] It will be appreciated that certain portions or sections of the gas flow path may be completely sealed, for example, the flow path after the humidifier unit. Additionally, the flow path may be sealed between the humidifier unit and the blower unit, and the inlet section of the flow path before the blower unit may also optionally be substantially sealed along a large portion of the flow path after the gas inlet assembly 20. It will be appreciated that the flow path transporting the gas flow may be defined by conduits, ports, and / or connectors that fluidly connect various components, such as fluidly connecting the blower unit to the humidifier unit, and / or may generally be defined by the formation of a housing and case within the respiratory apparatus, which may, for example, constitute an enclosed channel or passage formed from interior walls or surfaces that direct the gas flow through the respiratory apparatus.

[0074] Spiral Inlet Channel - First Embodiment Figure 14 shows an inlet aperture 58 formed at the rear of the base section 36. The inlet aperture 58 is located behind the gas inlet assembly 20. A first embodiment of the inlet section of the gas flow path will now be described with reference to Figure 15. The inlet section of the gas flow path is provided within the base section 36 of the main housing and extends from the gas inlet assembly 20 at the rear of the respiratory apparatus 10 to the outlet port 38 of the base section and then into the inlet port 37 of the blower unit described above. As shown in Figure 15, the inlet section of the path shown generally follows the path indicated by arrow XX.

[0075] In this embodiment, at least a portion of the inlet section of the flow path has a shape or configuration that promotes a steady flow of air as it reaches the outlet port 38 and before entering the blower unit compartment through the outlet port 38. The steady flow of air helps reduce noise and increase the accuracy of the sensed gas characteristic measured by the sensor assembly in the sensor zone of the flow path. In this embodiment, the steady flow is generated or provided by at least a portion of the inlet section of the flow path that is helical or provides a helical course or path. For example, as shown in FIG. 15 , at least a portion of the flow path indicated by arrow XX is in the form of a gradually tightening path. The terms “helical” or “spiral” are intended to mean any form of flow path that is continuous and gradually winds in one or more turns from a starting point to an end point. Any uniform or non-uniform helical path is intended to be encompassed, whether it is a continuous, gradually tightening curve with a decreasing radius relative to a center point or central axis, where the rate of radius reduction may be constant or variable, or a helical path of any shape shown in FIG. 14 in which the flow path is wound (i.e., in at least one turn) such that it spirals toward a reference point located within the outermost turn of the path, regardless of whether the reference point is located in the center.

[0076] The spiral portion of the flow path may form a majority of the entire inlet section of the flow path, or alternatively, a small portion of the inlet section of the flow path, depending on design requirements. In this embodiment, the spiral portion of the flow path begins generally at 42 and ends after one inward spiral turn generally at 44. The inlet section of the flow path begins with an initial section or portion, before the start of the spiral 42, at an inlet zone generally indicated at 46, and ends with an ending section or portion, after the end of the spiral 44, generally indicated at 48. In this embodiment, the end of the inlet section of the flow path is in the form of a gradually spiraling flow path that opens into a larger transition zone 48 within which the outlet port 38 to the blower unit is located. The transition zone 48 has a generally curved peripheral wall that may generally conform to at least a portion of a circumference or be otherwise curved or concave when viewed in a plan view. In FIG. 15 , the circumferential wall section of the transition zone is defined between 50 and 52 about a center point Y within the transition zone 48. The wall shape within the transition zone is configured to continue to promote a steady flow of the gas stream as it exits the inlet section of the flowpath and enters the blower unit.

[0077] As discussed above, the flow path within the respiratory apparatus 10 may be formed from a combination of conduits, tubing, housings, or cases of the respiratory apparatus, including connectors, ports, and / or other connections that fluidly connect various sections of the flow path. In this embodiment, the inlet section of the flow path is generally defined by two coextensive walls 54 and 56 that are spaced apart and enclosed within the base compartment to form a conduit, channel, or passageway bounded by horizontally extending upper and lower walls or surfaces, such as the top cover 36a of the base compartment and the base or lower side 26a of the lower housing section 26 of the main housing (see FIG. 7 ). As shown in this embodiment, the walls 54, 56 are upright and extend generally perpendicular or substantially perpendicular to the generally horizontal, enclosing top cover 36a of the base compartment and the lower side 26a of the lower housing section 26. It will be understood that the coextensive walls 54 and 56 may alternatively be bounded from above and / or below by one or more flat plates or members. In this embodiment, the flow path, at least the flow path within the spiral portion of the inlet section, has a generally rectangular or square cross-sectional shape, although it will be understood that this is not required. In alternative embodiments, the flow path may be configured to have any other desired cross-sectional shape, including circular, oval, or other shapes, and the shape may be uniform along the length of the flow path or may vary between two or more shapes and / or sizes. It will also be understood that the inlet section, and particularly the spiral portion of the inlet section of the flow path, may be formed from a rigid shaped conduit or tube that is formed to extend in a desired spiral shape.

[0078] In this embodiment, the cross-sectional area of ​​the spiral portion of the inlet section of the flow channel is generally uniform along the length of the spiral, although in alternative embodiments, the cross-sectional area may be non-uniform along the length of the spiral. In particular, the width (W) between coextensive walls 54 and 56 is generally constant throughout the entire spiral portion of the inlet section in this embodiment, but may be variable along the length of the spiral in alternative embodiments, if desired. Referring to FIG. 17, the wall height (H) is also preferably constant at least along the spiral portion of the inlet section of the flow channel, but may be configured to be variable in other embodiments, if desired.

[0079] In this embodiment, the entire inlet section of the flow path extends in approximately the same plane within the base section 36, such that there is no vertical shift or displacement of the flow path within the inlet section, at least within the spiral portion of the inlet section, until the flow path transitions to the outlet port 38, where the flow path extends vertically into the blower unit case 32 above the base section 36.

[0080] In this embodiment, there is a single spiral section located substantially before the transition zone of the flow path where the flow path enters the blower unit section 32. However, it will be appreciated that in alternative embodiments, the flow path may include two or more separate spiral sections located in series within the flow path. If there are multiple spiral sections, they may all be located before the blower unit, or they may be located in the flow path after the blower unit and before the humidifier unit, or alternatively, at least one spiral section may be provided in each region. In preferred embodiments, one or more spiral sections are preferably provided before the flow path enters the humidifier unit, and more preferably before the flow path enters the blower unit or any other section of the flow path where promoting stable flow is beneficial for noise reduction or gas flow characteristic sensing accuracy.

[0081] Sensor Assembly With reference to FIGS. 15-17, the respiratory apparatus 10 includes a sensor assembly 60 positioned or installed along the flow path prior to the humidification unit to sense various characteristics or parameters of the gas flow. In this embodiment, the sensor assembly 60 is provided in a sensor zone in the inlet section of the flow path, preferably within the spiral portion of the inlet section of the flow path if the gas flow has steady flow characteristics. The sensor assembly 60 includes a sensor housing, shown in FIGS. 16 and 17, configured or adapted to receive and hold one or more sensors, sensor components, or sensor devices that detect or sense one or more characteristics of the gas flow flowing through the flow path. For clarity, FIGS. 16 and 17 show the housing of the sensor assembly 60 without any sensors. The housing and sensors are described in further detail with reference to FIGS. 19-24.

[0082] In this embodiment, the sensor housing is a modular component that is removably secured, mounted, engaged, retained, or fitted within the flow path so that it can be removed for replacement, maintenance, or repair, if desired. In this embodiment, the flow path walls 56 and 54 at the inlet section are discontinuous within a generally straight section 61 of the flow path, thereby providing a receiving or mounting slot, aperture, groove, or gap that may receive and retain the sensor housing of the sensor assembly 60. When installed, the sensor assembly housing bridges the retention gap provided by the discontinuous walls 54, 56 to complete the flow path. Using this configuration, the sensor assembly 60 is configured to provide sensing of one or more characteristics of gas flow within a bulk or main flow path of the respiratory apparatus. In other words, the sensor assembly 60 is not disposed in a separate chamber or auxiliary flow path relative to the bulk or main flow path through the respiratory apparatus.

[0083] In this embodiment, the sensor housing is configured to be received and retained within the mounting aperture of the flow channel via a friction fit, although it will be appreciated that any other releasable mounting configuration or retention system may alternatively be used, including a clip system, a latch system, a snap fit, or any other releasable configuration.

[0084] The sensor assembly 60 may be configured or adapted to carry one or more sensors that sense one or more characteristics of the gas stream in the flow path. Any suitable sensor may be mounted in the sensor housing, as will be appreciated. In this embodiment, the sensor assembly includes at least a gas composition sensor that senses or measures the gas composition or concentration of one or more gases in the gas stream. In this embodiment, the gas composition sensor is in the form of an ultrasonic gas composition sensor system that utilizes ultrasound or sound waves to determine gas concentrations. In particular, the ultrasonic gas composition sensor utilizes two-component gas detection or analysis to determine the relative gas concentrations of two gases in a two-component gas mixture. In this embodiment, the gas composition sensor is configured to measure the oxygen concentration in a bulk gas stream flow, which consists essentially of atmospheric air augmented with supplemental oxygen, a two-component gas mixture of nitrogen (N) and oxygen (O). It will also be appreciated that the ultrasonic gas concentration sensor may be configured to measure the gas concentration of other augmented gases mixed with atmospheric air in the gas stream, including nitrogen (N) and carbon dioxide (CO), or any other ratio of the two gases. For example, an ultrasonic gas concentration sensor may be configured to measure carbon dioxide (CO2) and deliver a controlled carbon dioxide level to a patient to control the patient's breathing pattern. By adjusting the carbon dioxide level to the patient, the patient's Cheyne-Stokes breathing can be controlled. Controlling a patient's breathing pattern may be useful in some situations, such as athlete training to mimic high altitude conditions.

[0085] As mentioned above, in this embodiment, the respiratory apparatus 10 includes a gas inlet assembly 20 configured to receive ambient atmospheric air and a supplemental gas, such as oxygen, from an oxygen supply line or gas bottle. However, it will be appreciated that the air supply need not be ambient; air may be supplied to the gas inlet assembly from an air supply line or gas bottle. Furthermore, it will be appreciated that the respiratory apparatus 10 need not necessarily receive a supply of air. The respiratory apparatus 10 may be configured to receive any two or more supplies of gases suitable for mixing and subsequent delivery to an end user via a patient interface. Gases may be supplied to the respiratory apparatus' gas inlet assembly by any suitable means, including from a central gas supply line, from a gas bottle, or in other manners.

[0086] In this embodiment, the sensor assembly 60 also includes a temperature sensor configured to measure the temperature of the gas stream, and a flow sensor configured to sense the flow rate of the gas stream in the flow path.

[0087] Direct Inlet Channel - Second Embodiment 18A-18C, a second embodiment of the inlet section of the gas flow path within the base compartment 36 is described. Like reference numerals in the drawings represent similar components to the spiral inlet flow path of the first embodiment described with reference to FIGS. 14-17. In this second embodiment, the inlet section of the flow path is a shorter, more direct flow path between the inlet aperture 58 and the outlet port 38 of the base compartment 36. The shorter, more direct flow path reduces gas residence time in the base compartment, thereby reducing heating of the gas due to surrounding electronic components.

[0088] In this embodiment, the inlet flow path may be defined by three main zones or regions extending between the inlet aperture 58 and the outlet port 38. The three regions are the inlet zone 39, the sensor zone 41, and the transition zone 43.

[0089] 18A , inlet zone or region 39 extends between inlet aperture 58 and approximately transition line EE before sensor zone 41. In this embodiment, inlet zone 39 of the inlet flow path is defined between two walls 45 and 47, which extend at or toward inlet aperture 58 and then into sensor assembly 60. In this embodiment, the cross-sectional area of ​​inlet zone 39 gradually decreases or diminishes from inlet aperture 58 toward transition line EE to sensor zone 41, such that the wall profile at the inlet zone forms a funnel-like configuration. For example, side walls 45 and 47 have a wider displacement from each other at inlet aperture 58 relative to their displacement from each other at or toward transition line EE. In other words, this distance or displacement between side walls 45 and 47 decreases from inlet aperture 58 toward transition line EE such that inlet zone 39 begins with a wide opening at inlet aperture 58 and the flow path gradually narrows toward transition line EE before sensor zone 41. This funnel-like configuration of the inlet zone creates an accelerating gas stream flow, promoting a more stable gas flow in the subsequent sensor zone.

[0090] Optionally, inlet zone 39 may be provided with one or more flow directors 49. In this embodiment, inlet zone 39 comprises a curvature in that it is not a direct, straight flow path from the gas inlet assembly to the sensor zone, which may create uneven flow or velocity gradients across the inlet flow path in one or more regions of the inlet flow path. To counteract this, inlet zone 39 is provided with multiple flow directors 49, in the form of arcuate or curved fins (as shown more clearly in FIG. 18C ) that are not biased toward any particular wall of the flow path and that are configured or provided with a profile or shape that helps promote uniform airflow to sensor zone 41. It will be appreciated that the number and shape or geometry of flow directors 49 may be varied to help direct airflow at a desired angle to sensor zone 41, but are preferably configured so that bulk flow enters the sensor zone in a direction that is generally perpendicular to transition line EE or the front opening of sensor assembly 60. In this embodiment, fins 49 assist in providing a steady flow through sensor zone 41. Referring to FIG. 18B , fins 49 may also function as a tamper or protective guard to prevent user access to sensor assembly 60, which may include delicate or calibrated sensor components. In this embodiment, fins 49 are integrally formed with top cover 36 a of base section 36 and suspended downwardly from top cover 36 a into the inlet zone, although it will be appreciated that the fins may alternatively be integrally formed with base or lower portion 26 a of lower housing section 26 or attached to extend upwardly from base or lower portion 26 a into the inlet zone. It will also be appreciated that the fins need not necessarily be oriented vertically, but may alternatively be oriented horizontally, extending from the sidewall of the inlet zone of the inlet flow path, or oriented at any other suitable angle or mixture of angles.

[0091] Sensor zone 41 is defined between the end of the inlet zone at approximately transition line EE and the beginning of transition zone 43 at approximately transition line FF. The sensor zone comprises a modular, removable sensor assembly 60 of the type described above with reference to FIGS. 15-17 and disposed in the bulk flow path to sense various characteristics or parameters of the gas flow. As shown, the terminations of side walls 45, 47 extend into the open front side of sensor assembly 60, and the termination of loop wall 51 of transition zone 43 extends to the opposite rear outlet side of sensor assembly 60. As with the embodiment described with reference to FIGS. 15-17, sensor assembly 60 is removably retained within a retention gap provided or formed between the terminations of side walls 45, 47 and loop wall 51.

[0092] The transition zone 43 is defined by a generally curved peripheral or loop wall 51, which may generally conform to at least a majority of a circumference or may be otherwise curved or concave when viewed in a plan view. In this embodiment, the loop wall 51 may extend circumferentially about a center point 53. An opening to the transition zone 43 is defined by an end of the loop wall that extends outward relative to the center point 53 and engages the outlet side of the sensor assembly 60. As shown, the generally circular or spherical transition zone 43 provides an outlet for airflow through the outlet port 38 in the top cover 36a of the base section 36.

[0093] Similar to the spiral inlet flow path embodiment described with reference to Figures 14-17, the shorter direct inlet flow path of Figures 18A-18C is bounded from above and below by horizontally extending upper and lower walls or surfaces to form an enclosed channel or airflow passage. The flow path is primarily defined by coextensive side walls 45, 47 and loop wall 51, which are bounded from above and below by, for example, the top cover 36a of the base section and the base or lower side 26a of the lower housing section 26 of the main housing (see Figure 7). As shown, in this embodiment, side walls 45, 47, 51 are upright and extend generally perpendicular or substantially perpendicular to the generally horizontal enclosing top cover 36a of the base section and the lower side 26a of the lower housing section 26.

[0094] Sensor housing and location In the above embodiment, the sensor assembly 60 is located in the sensor zone, and the inlet section of the flow path is before the blower unit. However, the sensor assembly may alternatively be located in the sensor zone in any other suitable portion of the flow path before the humidifier unit. In particular, the flow path sensor zone may be located anywhere in the flow path upstream (i.e., before) the humidifier unit, including before or after the blower unit.

[0095] The sensor housing and sensors of the sensor assembly 60 will now be described in further detail. The sensor assembly may be utilized in either the spiral or direct inlet flow path embodiments described with reference to FIGS. 14-18C. Referring to FIGS. 19-23, the sensor assembly 60 includes a sensor housing 62 that carries one or more sensors for measuring various characteristics of gas flow in the bulk flow path. In this embodiment, the sensor housing 62 includes a central body 63 extending between a first end 74 and a second end 76. The body 63 is hollow and has openings at both ends, thereby providing a passageway or sensing passageway 86 for gas flow from the first end 74 to the second end 76 of the body 63. In particular, the gas flow generally flows in the direction of a flow axis 110, shown in FIG. 20, that extends from the first end 74 to the second end 76 of the body 63.

[0096] In this embodiment, the body 63 is defined between a first end 74 and a second end 76 by two spaced apart vertical side walls 64, 66 and a top wall 68 and a bottom wall 70 extending horizontally between the vertically extending side walls 64, 66, which collectively form and define a sensing passageway. The body is open at both ends 74, 76, which, in use, are aligned with the flow path direction so that gas flow travels through a hollow interior or cavity of the body defined by the inner surfaces of the side, top, and bottom walls. In this embodiment, the width W between the side walls 64, 66 and the height (H) between the top wall 68 and bottom wall 70 generally correspond to the cross-sectional dimensions of the portion or section of the flow path immediately surrounding either side of the sensor assembly.

[0097] Sensor installation Temperature and flow sensors 19, 20, and 22, this embodiment of the sensor assembly is provided with mounting apertures 78, 80 that receive and retain a temperature sensor 82 and a flow sensor 84. For example, the temperature sensor mounting aperture 78 is provided in the top wall 68 of the body of the sensor housing and is configured to receive and retain a temperature sensor. Similarly, a separate flow sensor mounting aperture 80 is provided in the top wall 68 of the body 63 of the sensor housing 62 and is shaped or configured to receive and retain a flow sensor. The sensors 82, 84 may be retained within the respective mounting apertures 78, 80 with a friction fit, a snap fit, or any other coupling or fastening configuration. The temperature sensors may also optionally be provided with infrared radiation shielding components.

[0098] Referring to FIG. 20 , the temperature sensor 82 and the flow sensor 84 are mounted so as to be suspended downwardly from the top wall 68 of the body 63 into the sensing passage 86. Preferably, the temperature sensor 82 and the flow sensor 84 are suspended approximately centered between the ends 74 and 76 of the body. The sensors 82, 84 do not necessarily have to be suspended from the top wall, and they do not necessarily have to be oriented vertically. In other embodiments, the sensors 82, 84 may be mounted or secured to any of the top, bottom, or side walls of the body 63 of the sensor housing. Furthermore, the orientation of the sensors 82, 84 from the support or mounting wall to the sensing passage may be vertical, horizontal, or at any other suitable angle. The sensors 82, 84 do not necessarily have to be centered relative to the support wall, but may be located in any suitable, central, or other position within the sensing passage. The sensors 82, 84 may also extend from the same or different support walls.

[0099] In this embodiment, the temperature sensor 82 may be a monolithic, digital, IC, temperature transceiver, although any alternative type of temperature sensor, whether analog or digital, may be utilized. In this embodiment, the temperature sensor 82 is a silicon bandgap temperature transceiver.

[0100] In this embodiment, the flow sensor 84 comprises a hot wire anemometer (HWA) flow detector. In one form, the flow sensor 84 is a constant resistance HWA, in which case the detector comprises a temperature-controlled heated bead thermistor disposed in the sensing passage, from which the flow rate can be determined based on the energy (current) required to maintain the bead at a preset temperature. The preset temperature is preferably configured to be set at a level that does not significantly alter the local temperature of the gas flow through the sensing passage in the context of an O2 measurement. It will be appreciated that in other forms, the flow sensor 84 may comprise a constant current HWA, in which case the flow rate is determined from changes in the resistance of the heated bead. It will be appreciated that any other suitable form of flow sensor or detector may be used, if desired.

[0101] Ultrasonic Gas Composition Sensor System In this embodiment, an ultrasonic gas composition sensor is implemented and configured to sense the relative gas concentrations of a binary gas mixture in a gas stream using non-invasive cross-flow beam, pulse or wave based binary gas analysis of ultrasonic energy, as described in more detail below.

[0102] The sensor housing includes transducer mounting assemblies, generally designated 90 and 92, that receive and hold the ultrasonic transducer components of the ultrasonic gas composition sensor system. In this embodiment, the transducer mounting assemblies 90, 92 are provided on opposite sides of the body 63, thereby supporting or mounting a pair of transducers on opposite sides of the sensing passage 86. The transducers are aligned with and face each other across the sensing passage 86. The transducer mounting assemblies 90, 92 are mounted or secured to each of the body's side walls 64, 66. Each transducer mounting assembly or formation is configured to provide a receiving cavity 90a, 92a sized and shaped to receive and hold a complementary sized and shaped transducer component of the gas composition sensor system. In this embodiment, the receiving cavities 90a, 92a are generally cylindrical and aligned with or coaxial with a circular transducer aperture provided through each of the body's side walls 64, 66. 19 shows the transducer aperture 66a in the side wall 66; the side wall 64 similarly has a corresponding transducer aperture, which is not visible. It will be appreciated that in alternative embodiments, the transducer pairs can be mounted on the top and bottom walls 68, 70 of the body, with the remaining temperature and flow sensors 82, 84 mounted to extend into the sensing passages from either side wall 64, 66.

[0103] 23 and 24, in this embodiment, each transducer mounting assembly 90, 92 has a cylindrical base portion 90b, 92b that is secured or mounted at one end to the respective exterior surfaces of the side walls 64, 66 of the body 63 and is provided at the other end with at least a pair of opposing clips, clip portions, or fingers 90c, 92c extending from the cylindrical base portion. The cylindrical base portions, in combination with the extension clips, collectively define retention cavities 90a, 92a within which the transducer components are securely received and retained. In this embodiment, each transducer mounting assembly is provided with a circular array of clips or clip portions 90c, 92c spaced around the entire circumference of the cylindrical base portion 90b, 92b. In this embodiment, six clip portions 90c, 92c forming three opposing pairs are provided, although it will be understood that the number of pairs of clip portions may be varied as desired.

[0104] The clip portions 90c, 92c may be resiliently flexible, allowing them to flex slightly outward relative to the axis of each receiving cavity 90a, 92a, indicated at 90d, 92d, respectively. The clip portions 90c, 92c may also be configured to taper in a direction toward the respective cavity axis 90d, 92d as they extend away from the respective cylindrical base portions 90b, 92b. This provides cylindrical retaining cavities with a decreasing diameter or gradually tapering dimensions as they extend away from the base portions 90b, 92b. As shown in FIG. 24 , each clip portion 90c, 92c, when viewed in cross section along its length extending away from the associated cylindrical base portion 90b, 92b, is generally arcuate or concave, thereby conforming to the circumference of a cylinder. 23, by way of example, each clip portion extends between a first end 94 disposed on the cylindrical base portion 90b and a second or terminal end 96 that defines the end of the transducer receiving cavity 90a. In this embodiment, the inner surface of each clip portion toward the terminal end 96 is provided with a ridge or shoulder 97 that extends into the retention cavity and is configured to act as a stop or grip formation to secure the transducer component within the retention cavity.

[0105] Upon installation of a typically cylindrically shaped transducer component within each transducer mounting assembly 90, 92, the clip portions 90c, 92c flex slightly outward as the transducer component is partially inserted and then return to their respective resting states once the transducer is fully engaged within the cavity, thereby firmly gripping or retaining the transducer within its respective retaining cavity.

[0106] It will be appreciated that other transducer mounting assemblies may alternatively be used to receive and retain the transducer element within the sensor housing, if desired. Preferably, the transducer mounting assembly is configured to releasably secure the transducer component, so that the transducer can be removed from the sensor housing for replacement or repair, if required.

[0107] In this embodiment, the body 63 and transducer mounting assembly are integrally formed from a suitable material such as plastic, although it will be appreciated that parts of the sensor housing may be formed separately and then secured or connected together.

[0108] Referring to FIG. 20 , transducers 100, 102 are shown mounted in respective transducer mounting assemblies 90, 92 of the sensor housing. In this embodiment, the transducers and transducer mounting assemblies are configured to cooperate such that the front faces of the transducers extend into the respective transducer apertures in the side walls 64, 66 of the body 63, thereby lying flush with the remaining inner surfaces of the side walls. For example, referring to FIG. 20 , the front face 102b of the transducer 102 is shown to be generally flush with the inner surface 66b of the side wall 66. The same configuration is provided for the opposing transducer component 100.

[0109] As shown, this configuration provides a pair of transducers 100, 102 that are aligned with each other and face each other across the sensing passage 86 of the body 63 so that ultrasonic waves are transmitted in a direction generally perpendicular to the direction or flow axis 110 of gas flow moving through the passage 86 from the first end 74 to the second end 76 of the body.

[0110] The distance between a pair of transducers 100, 102 (e.g., designated W in FIG. 19), which defines the acoustic beam path length, is selected to be large enough to provide the desired sensitivity, but short enough to avoid phase wrap-around ambiguity. For example, the distance between the transducers is selected to be large enough to increase sensitivity, but limited based on the total phase shift expected for the range of gas compositions and temperatures being sensed.

[0111] Sensor control system and circuit 20, the electrical terminals or connectors 100a, 102a of the transducers 100, 102 protrude from the side of the body 63 of the sensor housing, and the electrical terminals 82a, 84a of the temperature sensor 82 and flow sensor 84 are accessible at the exterior surface of the top wall 68 of the body 63. A flexible wiring fabric or tape 112 may extend across the sides and top of the sensor housing to provide wiring connections to the electrical terminals of the sensors. The wiring 112 extends to a sensor control system and circuitry in the respiratory apparatus 10 that is configured to control the sensors, as described further below.

[0112] Referring to FIG. 25 , an example of a sensor control system 150 electrically connected to sensor components 100, 102, 84, and 82 via wiring 112 is illustrated. It will be understood that the electronic sensor control system 150 may be implemented in software or hardware, including implementation in any programmable device, such as a microprocessor, microcontroller, digital signal processor, or the like, and may include memory and associated input / output circuitry, as appropriate. It will be understood that the various modules of sensor control system 150 may be various and further separate or integrated, and that FIG. 25 is described merely as an example of the general functionality of a sensor control system. Sensor control system 150 may be integrated with a main control system of a respiratory apparatus or may be a separate subsystem in communication with a main controller or control system. Sensor control system 150 is described with reference to a particular arrangement or configuration of sensors positioned to determine the gas composition or relative concentrations of gases in a binary gas mixture, such as an air / oxygen mixture that is substantially equivalent to a nitrogen / oxygen mixture. However, it will be understood that the sensor control system may be configured to provide information indicative of the concentrations of other gases in a gas stream.

[0113] Flow Module The flow sensor 84 is configured to sense the flow rate, e.g., in liters per minute, of the gas stream 110 flowing through a sensing passage 86 in the sensor housing and generate a representative flow rate signal 152, which is received and processed by a flow rate module 154 within the sensor control system 150. A motor speed sensor 120 is also preferably provided in the blower unit to sense the motor speed, e.g., revolutions per minute (rpm), of the blower unit motor. The motor speed sensor 120 generates a representative motor speed signal 156, which is received and processed by a motor speed module 158.

[0114] Temperature Module Temperature module 160 is configured to receive and process temperature signals 162 generated by temperature sensor 82 that represent the temperature of the gas stream flowing through sensing passage 86 of the sensor housing. In this embodiment, temperature sensor 82 is configured to sense the temperature of the gas stream in the vicinity of the acoustic beam path between transducers 100 and 102.

[0115] Temperature module 160 is optionally configured to apply temperature compensation to temperature signal 162 to compensate for potential errors or offsets generated by temperature sensor 82. In particular, because sensor assembly 60 is located after the blower unit section and other electronic circuitry, heat from the circuitry and motor may affect the temperature sensed by temperature sensor 82 depending on the operating conditions. For example, due to heat above the sensor assembly, temperature signal 162 may indicate a higher gas flow temperature than the true temperature. To compensate for this potential error in certain operating conditions, temperature module 160 is configured to apply a temperature compensation factor or correction based on the following equation: T corrected =T sensor +ΔT. During the ceremony: T corrected is the corrected temperature after compensation, T sensor is the temperature sensed by temperature sensor 82, represented by signal 162; ΔT is the calculated or predicted temperature error based on the current operating conditions of the breathing apparatus. is.

[0116] The temperature error (ΔT) is modified in response to operating conditions of the respiratory apparatus 10. In this embodiment, the temperature error is calculated based on a proportional relationship between the current flow rate 152 of gas flow through the respiratory apparatus and the system conditions related to the current motor speed 156. Typically, an increase in flow rate has a cooling effect, while an increase in motor speed increases heating within the respiratory apparatus housing due to increased power usage. In operation, the temperature module is configured to continuously or periodically calculate the temperature error ΔT based on the current system operating conditions, particularly the current flow rate 152 and motor speed 156. The updated temperature error ΔT is then calculated based on the input temperature T sensed from the temperature sensor. sensor 162 and the corrected temperature T corrected Generate.

[0117] In one embodiment, ΔT = α × (motor speed / flow rate), where α is a constant. However, it will be appreciated that ΔT may alternatively be calculated based on a look-up table or other algorithm that takes into account one or more other operating conditions or system variables associated with the operation of the respiratory apparatus that affect temperature fluctuations likely to occur in the vicinity of the temperature sensor 82. In some embodiments, ΔT may incorporate time-dependent effects that have an impact on temperature fluctuations, such as heat stored in the respiratory apparatus over an extended run period. For example, ΔT may be expressed as an integro-differential expression that accounts for time-varying effects such as those due to the thermal capacitance of one or more parts of the respiratory apparatus.

[0118] Gas Composition Module The gas composition sensor system is configured as an ultrasonic two-component gas sensing system. As described above, the gas composition sensing system in this embodiment includes a pair of ultrasonic transducer elements 100, 102 disposed on either side of a sensing passage in a sensor housing. One of the transducer elements, 100, is configured as an ultrasonic transmitter that transmits unidirectional ultrasonic or acoustic beam waves or pulses across the sensing passage in a direction generally perpendicular to the direction of gas flow through the passage to the other ultrasonic transducer, which is configured as an ultrasonic receiver on the other side of the passage to receive the transmitted ultrasonic waves or pulses. In this embodiment, the transducer elements 100, 102 may typically be piezoelectric ceramic transducer elements operating at a narrow bandwidth or any other suitable operable ultrasonic transducer elements. In this embodiment, the transducer elements operate at a frequency of approximately 25 kHz, although this may be changed as desired. In a preferred form, the operating frequency is selected to be above the human audible sound spectrum so that gas composition detection is silent to the user, and / or to be at a frequency high enough to reduce or minimize interference from noise sources.

[0119] The ultrasonic transmitter 100 and receiver 102 are controlled by a driver circuit 170 and a receiver circuit 172, respectively, of a gas composition module 174. In particular, the driver circuit 170 provides a control excitation signal 176 to the ultrasonic transducer to drive it to transmit pulses of ultrasonic energy. The ultrasonic receiver 102 detects the pulses and generates a representative received signal 178, which is received and processed by the receiver circuit 172. In this embodiment, a pulsed system is utilized, although alternative embodiments may utilize continuous wave or standing wave techniques.

[0120] Binary gas analysis using ultrasound is based on detecting the velocity of an acoustic pulse through a gas sample, which in this case is the bulk or mainstream of the gas stream flowing through the sensing passage 86 of the sensor housing. The speed of sound is a function of the average molecular weight and temperature of the gas. In this configuration, the gas composition module 174 receives a temperature signal 164 from the temperature module 160, representing the indicated temperature of the gas flowing between the beam paths between the ultrasonic transducers. Knowledge of the detected speed of sound and the detected temperature can be used to identify or calculate the gas composition of the gas stream. In particular, measurements of the speed of sound across the sensing passage can be used to infer the ratio of two known gases by empirical relationships, standard algorithms, or data stored in the form of lookup tables, as is known in the field of ultrasonic binary gas analysis. Alternatively, if a temperature sensor is not utilized, it will be understood that an estimate of the temperature of the gas stream within the beam path of the ultrasonic transducer can be used in the binary gas analysis calculation. In such an alternative embodiment, the temperature of the gas stream can be adjusted or controlled to fall within a narrow temperature band so that the temperature estimate of the gas stream within the beam path can be used.

[0121] In some embodiments, the respiratory apparatus may also include a humidity sensor disposed in the flow path and configured to generate a humidity signal indicative of the humidity of the gas stream flowing through the sensor assembly. In such embodiments, the gas composition may be determined by the sensed speed of sound, the sensed temperature, and / or the sensed humidity. The humidity sensor may be a relative humidity sensor or an absolute humidity sensor. In some embodiments, the gas composition may be determined based on the sensed speed of sound and the sensed humidity without the need for a temperature sensor.

[0122] The gas composition sensing system can be used to measure the respective ratios of any two known gases in a gas composition. In this embodiment, the gas composition module is configured to determine the relative gas concentrations in a mixture of air mixed with supplemental oxygen, which is approximately equivalent to a nitrogen / oxygen mixture. In such a binary gas mixture, by monitoring the speed of sound and taking temperature into account, the average molecular weight of the gas can be determined, and therefore the relative concentrations of the two gases can be determined. From this ratio, the oxygen or nitrogen concentration of the gas stream can be extracted.

[0123] In this embodiment, the gas composition module 124 includes an analyzer or controller 180 configured to operate the ultrasonic transducers 100, 102 via respective driver and receiver circuits 170, 172 using control signals 171, 173. The analyzer 180 is also configured to receive and process the compensated temperature signal 164 from the temperature module 160. In operation, the analyzer 180 is configured to periodically transmit unidirectional ultrasonic or acoustic pulses at a desired frequency across a sensing path to determine the speed of sound of the acoustic pulse. The speed of sound measurements, along with knowledge of the temperature from the temperature module 160, are then used to determine the gas composition. The speed of the acoustic pulse may be determined in any desired manner, including using a timer circuit to measure the travel time of the acoustic pulse traveling across the path directly or indirectly from the transmitter 100 to the receiver 102 via phase detection. It will be appreciated that, if suitable signal processing is implemented, phase can be tracked to minimize the effects of "wraparound." The distance between transducer elements 100 and 102 is known, as is the width (W in FIG. 19 ) between sensor housing sidewalls 64 and 66; therefore, the speed of sound can be determined based on the travel time and the distance between the transducers (corresponding to the beam path length). In particular, the analyzer can be preprogrammed and calibrated with data representing the distance between the transducers and / or any other generally relevant or device-specific characteristics useful in determining gas composition via sound speed detection. Calibration can take into account changes in the distance between transducer elements 100 and 102 as a function of temperature. For example, the distance between sensor housing sidewalls 64 and 66 may increase or decrease as the temperature changes.

[0124] Optionally, the gas composition sensor module may be configured with a user-selectable or pre-programmed scaling or correction factor to take argon into account when determining the oxygen concentration to be used when oxygen is supplied to the respiratory device, preferably from a commercially available oxygen concentrator using pressure swing adsorption. For example, a user may activate the control system to utilize an argon scaling or correction factor to modify the sensed oxygen concentration to remove any argon components and result in a calculated oxygen concentration.

[0125] Sensor control system 150 may output data or signals indicative of various characteristics sensed by the sensor assembly or other sensors. For example, output signals or data 182, 184, and 186 from modules 154, 158, and 160 may represent sensed flow rate 182, motor speed 184, and temperature 186. Similarly, gas composition module 154 is configured to generate one or more output signals or data 188 indicative of the gas composition sensed by the ultrasonic gas composition sensing system. In this embodiment, output signal 188 may represent the oxygen percentage or oxygen (O2) concentration in the gas stream. Alternatively, the signal or additional signals may represent the concentration or percentage of nitrogen (N2). It will be understood that the system may be modified to provide signals indicative of other gas concentrations in the gas stream, including, but not limited to, carbon dioxide (CO2).

[0126] A main controller of the respiratory apparatus may then receive and process one or more gas concentration output signals 188. For example, the main controller may be configured to display the detected oxygen readings on an output display of the respiratory apparatus based on the oxygen signal 188. In one embodiment, the user control interface 30 (see FIG. 8) may be configured to display the gas concentration readings, e.g., oxygen concentration or one or more other gas concentration levels, detected by the ultrasonic gas composition sensor system.

[0127] In some embodiments, the main controller is configured to determine whether one or more gas concentration levels, e.g., oxygen concentration, remain within a user-defined range defined by a maximum and / or minimum threshold. For example, in such embodiments, the main controller may be configured to compare the detected gas concentration level based on the gas concentration output signal 188 with a user-defined or selected gas concentration level threshold. If the detected level is below a minimum threshold or above a maximum threshold, or is otherwise outside the user-defined range, the main controller may trigger or activate an alarm incorporated into the device, which may be audible, visual, tactile, or any combination thereof. The main controller may also optionally shut down the device or trigger any other operational function appropriate for each alarm that is triggered.

[0128] In some embodiments, the respiratory apparatus 10 includes a disinfection system and / or cleaning mode of the type described in International Publication No. WO 2007 / 069922, the contents of which are incorporated by reference. Such a disinfection system utilizes thermal disinfection by circulating heated dry gas through a portion of the gas flow path to the user interface. In such embodiments, the main controller is configured to determine, based on the sensed oxygen signal 188, whether the oxygen concentration level in the gas flow path is below a preset oxygen concentration level before initiating any disinfection system or cleaning mode. For example, the main controller may be configured to prevent initiation of any cleaning mode until the sensed oxygen concentration is within a safe range, preferably below about 30%, to minimize fire hazards.

[0129] The oxygen signal 188 can also be used to automatically control the motor speed of a blower unit to modify the flow rate of the gas stream, thereby changing or varying the oxygen concentration, or to shut down operation of the device should the oxygen concentration fall outside of a preset upper or lower threshold. Alternatively, a user of the respiratory device can manually control the oxygen supply flow rate from a central gas source connected to the respiratory device, thereby changing the oxygen concentration, based on real-time feedback from the displayed oxygen readings, without having to estimate the oxygen concentration based on a printed look-up table. In some embodiments, the respiratory device can have a valve that automatically changes or varies the oxygen supply flow rate from the central gas source, thereby changing the oxygen concentration. The main controller can receive the oxygen signal 188 and adjust the oxygen valve accordingly until a predetermined value of the oxygen signal 188 corresponding to the desired oxygen concentration is reached.

[0130] Alternative ultrasonic gas composition sensor system configurations 26A-26E, various alternative configurations of an ultrasonic transducer for a gas composition sensing system that senses the speed of sound through a gas flow by transmitting and receiving a cross-flow ultrasonic beam or pulse are described, with like reference numerals representing like components.

[0131] Referring to Figure 26A, a schematic diagram of a transducer configuration 200 of the embodiment described above with reference to Figures 19-25 is shown. As shown, this transducer configuration provides a pair of opposing transducers 202, 204 from either side of a sensing passageway 206, with the airflow path direction generally indicated at 208. In this configuration 200, each of the transducers 202, 204 is driven as either a dedicated transmitter or a dedicated receiver, whereby ultrasonic pulses 210 are transmitted unidirectionally across the airflow path from the transmitter transducer to the receiver transducer. As shown, the transducer pair are aligned with the airflow path direction 208 (i.e., upstream or downstream with no displacement from one another) and are configured to transmit cross-flow pulses generally perpendicular to the airflow path direction.

[0132] Referring to FIG. 26B, an alternative transducer configuration 220 is shown in which a pair of transducers 222, 224 are provided opposite each other on either side of the sensing passageway, but each transducer can operate as both a transmitter and a receiver. That is, each transducer is an ultrasonic transmitter-receiver or transceiver. In this configuration, bidirectional ultrasonic pulses 226 can be transmitted between the transmitter pair 222 and 224. For example, pulses can be transmitted back and forth between the transducers, or in any other order or pattern. Again, the transducer pair is aligned with the airflow direction and configured to transmit cross-flow pulses generally perpendicular to the airflow direction.

[0133] Referring to FIG. 26C, an alternative echo transducer configuration 230 is shown in which the transmitter and receiver transducer pair is provided in the form of a single ultrasonic transmitter-receiver transducer 232 located on one side of the detection passage and configured to transmit cross-flow acoustic pulses 236 across the detection passage 206 and receive reflected pulses or echoes reflected from the opposite side of the detection passage.

[0134] Referring to FIG. 26D , an alternative transducer configuration 240 is shown in which a transmitter transducer 242 and a receiver transducer 244 are displaced from one another relative to the airflow path (i.e., one upstream of the other) and are on opposite sides of the sensing path. While FIG. 26D shows the receiver upstream of the transmitter, the reverse configuration can also be utilized. With this configuration, the transmitter 242 can either transmit a crossflow pulse directly across the sensing path 206 to the receiver 244, as shown by beam 246, or create a longer indirect path length by a reflected path including at least two reflections, as shown by beam 248. As shown, with this displaced configuration, the acoustic pulse has a crossflow direction that is obliquely transverse to the airflow path direction 208, rather than generally perpendicular. While a unidirectional configuration is shown, it will be understood that the transducers 242, 244 may alternatively be ultrasonic transmitter-receivers, allowing bidirectional beam pulses to be transmitted back and forth between the transducers (i.e., both upstream and downstream relative to the airflow).

[0135] Referring to Figure 26E, an alternative transducer configuration 250 is shown that is a modification of the configuration of Figure 26D, in which the transmitter 252 and receiver 254 are again displaced from each other in the airflow direction 208, but are positioned on the same side of the sensing passageway, so that the transmitted crossflow pulse 256 comprises at least one reflection (or multiple reflections in the case of longer path lengths) from opposite sides of the sensing passageway 206. Otherwise, the same alternatives apply as those described with reference to Figure 26D, including bidirectional operation and swapping the locations of the transmitter and receiver.

[0136] 27A-27C, various additional alternative configurations of ultrasonic transducers for gas composition sensing systems that sense the speed of sound through a gas stream by transmitting and receiving ultrasonic beams or pulses along the flow, where like reference numerals refer to like components.

[0137] Referring to FIG. 27A , an alternative transducer configuration 260 is shown, in which a pair of transducers 262, 264 face each other from opposite sides of a sensing passageway 206, with the airflow direction or axis generally indicated at 208. In this configuration 260, each of the transducers 262, 264 is driven as either a dedicated transmitter or a dedicated receiver, such that ultrasonic pulses 266 are transmitted unidirectionally with a beam path between the transmitter and receiver generally aligned with or parallel to the gas flow axis 208 in the sensing passageway 206. In the illustrated embodiment, the transmitter is upstream of the receiver, but it will be understood that the reverse configuration can also be utilized. When using this configuration, a flow sensor is provided in the sensing passageway to provide a flow signal indicative of the flow rate of the gas flow in the sensing passageway. It will be understood that the speed of sound in the sensing passageway can also be derived or determined in a manner similar to that described above using the previous embodiment, and the flow signal can be used in signal processing to remove or compensate for the gas flow rate in the calculated sound speed signal.

[0138] Referring to FIG. 27B, an alternative transducer configuration 270 is shown in which a pair of transducers 272, 274 are positioned opposite each other on opposite sides of the sensing passageway, as in FIG. 27A, but each transducer can operate as both a transmitter and a receiver. That is, each transducer is an ultrasonic transmitter-receiver or transceiver. In this configuration, bidirectional flow-directed ultrasonic pulses 276 can be transmitted between the transducer pair 272 and 274. For example, pulses can be transmitted back and forth between the transducers, or in any other order or pattern. Again, the transducer pair is aligned with the airflow path axis 208 and configured to transmit flow-directed pulses in one or more beam paths generally aligned with or parallel to the airflow path axis 208 in the sensing passageway 206. With this configuration, a separate flow sensor is not necessarily required, as the flow component of the sound velocity signal can be derived or determined directly from processing of the transmitted and received acoustic pulses.

[0139] Referring to Figure 27C, an alternative echo transducer configuration 280 is shown in which the transmitter and receiver transducer pair is provided in the form of a single ultrasonic transmitter-receiver transducer 282 located at one side of the sensing passage (whether at the beginning or end) and configured to transmit along-flow acoustic pulses 286 along the sensing passage 206 with a beam path generally aligned with or parallel to the airflow axis 208, and to receive reflected pulses or echoes reflected from the opposite end of the sensing passage. In the embodiment shown, the transmitter-receiver 282 is shown at the end of the passage, but could alternatively be located at the beginning of the passage. As in the configuration of Figure 27A, a flow sensor is provided in the sensing passage to allow the speed of sound calculation to compensate for the airflow component.

[0140] It will be appreciated that the alternative configurations of Figures 26B-26E and 27A-27C can be used and the driver circuitry, receiver circuitry, and signal processing can be configured accordingly to sense the speed of sound in the sensing passage, which can then be used to determine the gas composition as described above.

[0141] Positive features 1. A respiratory aid apparatus configured to provide a heated and humidified gas flow, the respiratory aid apparatus comprising: a gas inlet configured to receive a gas supply; a blower unit configured to generate a pressurized gas flow from the gas supply; a humidification unit configured to warm and humidify the pressurized gas flow; a gas outlet for the heated and humidified gas flow; a flow path for the gas flow through the respiratory apparatus from the gas inlet, through the blower unit and the humidification unit to the gas outlet; and a sensor assembly provided in the flow path prior to the humidification unit, the sensor assembly comprising an ultrasonic gas composition sensor system for detecting the concentration of one or more gases in the gas flow.

[0142] 2. A respiratory assistance device according to paragraph 1, wherein the ultrasonic gas composition sensor system comprises a transmitter-receiver pair, the transmitter-receiver pair operable to transmit cross-flow acoustic pulses through the gas flow from the transmitter to the receiver to detect the speed of sound in the gas flow in the vicinity of the sensor assembly.

[0143] 3. A respiratory assistance device according to paragraph 2, wherein the transmitter-receiver pair is positioned so that the acoustic pulse travels through the gas flow in a direction substantially perpendicular to the direction of flow of the gas flow.

[0144] 4. A respiratory assistance device according to paragraph 2, wherein the transmitter-receiver pair is positioned so that the acoustic pulse travels through the gas flow in a cross-flow that is oblique to, but not perpendicular to, the direction of flow of the gas flow.

[0145] 5. The respiratory assistance device according to any one of paragraphs 2 to 4, wherein the transmitter-receiver pair includes a transducer configured as a transmitter and a transducer configured as a receiver to transmit unidirectional acoustic pulses.

[0146] 6. A respiratory assistance device according to any one of paragraphs 2 to 4, wherein the transmitter-receiver pair comprises a pair of transmitter-receiver transducers configured to transmit bidirectional acoustic pulses.

[0147] 7. A respiratory aid device according to paragraph 5 or 6, in which the transmitter and receiver are aligned with each other in relation to the direction of flow of the gas flow and face each other across the flow path.

[0148] 8. A respiratory aid device according to paragraph 5 or 6, in which the transmitter and receiver are displaced from each other in the direction of flow of the gas flow.

[0149] 9. A respiratory assistance device according to paragraph 8, in which the acoustic pulse has a direct beam path between the transmitter and the receiver.

[0150] 10. A respiratory assistance device according to paragraph 8, in which the acoustic pulse has a beam path that is indirect between the transmitter and the receiver and undergoes one or more reflections.

[0151] 11. A respiratory assistance device according to any one of paragraphs 2 to 4, wherein the transmitter transducer and receiver transducer pair are in the form of a single transmitter-receiver configured to transmit cross-flow acoustic pulses and receive echo return pulses.

[0152] 12. A respiratory assistance device according to paragraph 2, wherein the ultrasonic gas composition sensor system comprises a transmitter transducer and a receiver transducer pair operable to transmit flow-aligned acoustic pulses through the gas flow from the transmitter to the receiver to sense the speed of sound in the gas flow in the vicinity of the sensor assembly.

[0153] 13. A respiratory assistance device according to any one of paragraphs 2-12, further comprising a sensor control system operably connected to the pair of transmitter and receiver transducers of the ultrasonic gas composition sensor system and configured to operate the transducer pair to sense the speed of sound through the gas flow and generate a sound speed signal indicative of the speed of sound.

[0154] 14. A respiratory assistance device according to paragraph 13, wherein the sensor control system is configured to generate one or more gas concentration signals indicative of the gas concentration in the gas flow based at least on a signal indicative of the speed of sound through the gas flow.

[0155] 15. A respiratory assistance device according to paragraph 13 or 14, wherein the sensor assembly further comprises a temperature sensor configured to measure the temperature of the gas flow in the vicinity of the sensor assembly and generate a representative temperature signal, and wherein the sensor control system is configured to generate one or more gas concentration signals indicative of the gas concentration in the gas flow based on the sound speed signal and the temperature signal.

[0156] 16. A respiratory assistance device according to paragraph 13 or 14, wherein the sensor assembly further comprises a humidity sensor configured to measure humidity in the gas stream in the vicinity of the sensor assembly and generate a representative humidity signal, and the sensor control system is configured to generate one or more gas concentration signals indicative of the gas concentration in the gas stream based on the sound speed signal and the humidity signal.

[0157] 17. A respiratory assistance device according to paragraph 13 or 14, wherein the sensor assembly further comprises a temperature sensor configured to measure the temperature of the gas flow in the vicinity of the sensor assembly and generate a representative temperature signal, and a humidity sensor configured to measure the humidity in the gas flow in the vicinity of the sensor assembly and generate a representative humidity signal, and the sensor control system is configured to generate one or more gas concentration signals indicative of the gas concentration in the gas flow based on the sound speed signal, the temperature signal, and the humidity signal.

[0158] 18. A respiratory assistance device according to paragraph 15 or 17, wherein the sensor control system is configured to apply a temperature correction to the temperature signal to compensate for any predicted temperature sensing error caused by heat within the respiratory device affecting the temperature sensor.

[0159] 19. A respiratory assistance device according to paragraph 18, wherein the sensor assembly further comprises a flow sensor configured to sense a flow rate of the gas flow in the vicinity of the sensor assembly and generate a representative flow rate signal, and wherein the system further comprises a motor speed sensor provided configured to sense a motor speed of the blower unit and generate a representative motor speed signal, and wherein temperature compensation is calculated by the sensor control system based on at least the flow rate signal and / or the motor speed signal.

[0160] 20. A respiratory assistance device according to any one of paragraphs 13 to 19, wherein the sensor control system is configured to generate a gas concentration signal representative of the oxygen concentration in the gas stream.

[0161] 21. A respiratory assistance device according to any one of paragraphs 13 to 19, wherein the sensor control system is configured to generate a gas concentration signal representative of the carbon dioxide concentration in the gas stream.

[0162] 22. A respiratory assistance device according to any one of paragraphs 1 to 21, wherein the sensor assembly is removably mounted within the flow path.

[0163] 23. A respiratory aid device according to any one of paragraphs 1 to 22, wherein the flow path has a shape or configuration that promotes a steady flow of gas in at least one section or portion of the flow path.

[0164] 24. A respiratory assistance device according to paragraph 23, wherein the flow path has a shape or configuration that promotes steady flow in the section or portion of the flow path that includes the sensor assembly.

[0165] 25. A respiratory aid device according to paragraph 23 or 24, in which the flow path comprises one or more flow directors at or towards the gas inlet.

[0166] 26. An assisted breathing apparatus according to paragraph 25, in which each flow director is in the form of an arcuate fin.

[0167] 27. A respiratory assistance device according to any one of paragraphs 23 to 26, wherein the flow path comprises at least one spiral portion or section that promotes a steady flow of gas.

[0168] 28. A respiratory assistance device according to paragraph 27, wherein the flow path comprises an inlet section extending between the gas inlet and the blower unit, the inlet section comprising at least one spiral portion.

[0169] 29. A respiratory assistance device according to paragraph 27 or 28, wherein the sensor assembly is positioned in the spiral portion of the flow path.

[0170] 30. A respiratory assistance device according to paragraph 29, wherein the spiral portion comprises one or more substantially straight sections, and the sensor assembly is located in one of the straight sections.

[0171] 31. A respiratory assistance device according to any one of paragraphs 2 to 30, wherein the sensor assembly comprises a sensor housing having a body, the body being hollow and defined by a peripheral wall extending between a first open end and a second open end, thereby defining a sensing passage within the body between the walls, through which gas flow can flow in the direction of a flow axis extending between the first end and the second end of the body, and wherein the transmitter and receiver transducer pairs are disposed on opposite walls or sides of the sensing passage.

[0172] 32. A respiratory assistance device according to paragraph 31, wherein the sensor housing comprises a body having two spaced apart side walls and upper and lower walls extending between the side walls to define a sensing passageway along the body between a first end and a second end, and a pair of transducer mounting assemblies disposed on opposing walls of the body, each configured to receive and hold a respective transducer of the transducer pair such that the transducers of the transducer pair are aligned and face each other across the sensing passageway of the body.

[0173] 33. A respiratory assistance device according to any one of paragraphs 1 to 32, wherein the blower unit is operable to generate a gas flow at the gas outlet having a flow rate of up to 100 liters per minute.

[0174] 34. A respiratory assistance device according to any one of paragraphs 1 to 33, wherein the gas inlet is configured to receive a supply of gas comprising a mixture of atmospheric air and pure oxygen from an oxygen supply source.

[0175] 35. A respiratory assistance device according to any one of paragraphs 1 to 33, wherein the gas inlet is configured to receive a supply of gas comprising a mixture of atmospheric air and carbon dioxide from a carbon dioxide supply source.

[0176] 36. A respiratory assistance device according to any one of paragraphs 1 to 35, wherein the flow path is within the bulk flow path of the device.

[0177] 37. A sensor assembly for in-line flow path sensing of gas flow in a respiratory assistance device, comprising a sensor housing having a body, the body being hollow and defined by a peripheral wall extending between a first open end and a second open end, thereby defining a sensing passage within the body between the walls, and through which gas flow can flow in the direction of a flow axis extending between the first and second ends of the body, the sensor assembly comprising: an ultrasonic gas composition sensor system mounted to the sensor housing for detecting concentrations of one or more gases in the gas flow through the sensing passage; a temperature sensor mounted to the sensor housing for detecting a temperature of the gas flow through the sensing passage; and a flow sensor mounted to the sensor housing for detecting a flow rate of the gas flow through the sensing passage.

[0178] 38. A sensor assembly according to paragraph 37, wherein the sensor housing is configured to removably engage a complementary retention aperture in the flow path of the respiratory assistance device.

[0179] 39. A sensor assembly according to paragraph 37 or 38, wherein the ultrasonic gas composition sensor system comprises a transmitter transducer and a receiver transducer pair operable to transmit acoustic pulses from the transmitter to the receiver through the gas flow in a direction generally perpendicular to the flow axis of the gas flow flowing through the sensing passage.

[0180] 40. A sensor assembly according to paragraph 39, wherein the transmitter and receiver transducer pairs are positioned on opposite walls or sides of the sensing passageway.

[0181] 41. A sensor assembly according to paragraph 39 or 40, wherein the body of the sensor housing comprises two spaced apart side walls and upper and lower walls extending between the side walls to define a sensing passageway along the body between a first end and a second end, and the body may comprise a pair of transducer mounting assemblies disposed on opposing walls of the body, each of the pair of transducer mounting assemblies configured to receive and hold a respective transducer of the transducer pair across the sensing passageway of the body such that the transducers of the transducer pair are aligned and face each other.

[0182] 42. A sensor assembly according to paragraph 41, wherein a pair of transducer mounting assemblies are disposed on opposite side walls of the body, each transducer mounting assembly including a retaining cavity for receiving and retaining each transducer of the pair therein.

[0183] 43. A sensor assembly according to paragraph 42, wherein each transducer mounting assembly comprises a cylindrical base portion extending from each side wall of the body and at least a pair of opposing clips extending from the base portion, the base portion and clips collectively defining a retention cavity.

[0184] 44. A sensor assembly according to paragraph 43, wherein each side wall of the body is provided with a transducer aperture, the transducer aperture being aligned with an associated transducer mounting assembly, and through the transducer aperture an operating front face of the transducer may extend to access the sensing passageway.

[0185] 45. A sensor assembly according to paragraph 44, wherein the transducer mounting assembly is configured to position each transducer so that the operating surface of the transducer is substantially flush with the inner surface of each wall of the body of the sensor housing.

[0186] The above description of the invention includes preferred forms of the invention. Modifications may be made without departing from the scope of the invention, which is defined by the appended claims.

Claims

1. A respiratory support device configured to provide a heated and humidified gas stream containing a two-component gas mixture of atmospheric air mixed with supplemental oxygen, One or more gas inlets configured to receive atmospheric air, A supplemental gas connection inlet configured to receive a supply of oxygen from a supplemental gas source to mix with the atmospheric air to generate a gas flow containing the two-component gas mixture, and a valve operable to change or alter the flow rate of the supplemental oxygen supply, A blower unit configured to pressurize the gas flow, comprising a blower unit located downstream of the one or more gas inlets and supplemental gas connection inlets, A humidification unit configured to heat and humidify the gas flow, The gas outlet of the aforementioned gas flow, The gas flow path through the breathing support device is provided, from one or more gas inlets through the blower unit and the humidifier unit to the gas outlet, A sensor assembly comprising a gas composition sensor system for detecting the gas composition or concentration of one or more gases in the gas stream containing the two-component gas mixture, A controller operably connected to the sensor assembly, the controller generates one or more output signals or data indicating the oxygen ratio of the two-component gas mixture, A respiratory support device wherein the controller is configured to adjust the valve based on the one or more output signals or data.

2. The respiratory assist device according to claim 1, wherein the controller is configured to automatically adjust the valve until a predetermined or desired oxygen ratio is reached in the two-component gas mixture, and / or the supplemental oxygen gas supply is from a central gas source.

3. The respiratory assist device according to claim 1 or 2, wherein the pressurized gas flow is high flow rate, and / or the flow rate of the pressurized gas flow is in the range of 1 L / min to 100 L / min, and / or the flow rate of the pressurized gas flow is in the range of 2 L / min to 60 L / min.

4. The respiratory assistance device according to any one of claims 1 to 3, wherein the gas composition sensor system is an ultrasonic gas composition sensor system, and the ultrasonic gas composition sensor system comprises a pair of transmitters and receivers.

5. The respiratory assistance device according to any one of claims 1 to 4, wherein the sensor assembly further comprises a flow sensor configured to detect the flow rate of the gas flow near the sensor assembly and generate a representative flow signal, and optionally the flow sensor comprises a hot-wire anemometer flow detector.

6. The sensor assembly is provided in the flow path, either before or upstream of the humidifying unit, in the respiratory assistance device according to any one of claims 1 to 5.

7. The respiratory assistance device according to claim 6, wherein the sensor assembly is provided in the flow path behind or downstream of the blower unit.

8. The respiratory assist device according to any one of claims 1 to 7, further comprising a gas inlet assembly upstream of the blower unit in the flow path, the gas inlet assembly comprising the one or more gas inlets, the supplemental gas connection inlet, and the valve.

9. A respiratory assist device according to any one of claims 1 to 7, further comprising a gas inlet assembly upstream of the blower unit in the flow path, the gas inlet assembly comprising one or more gas inlets for atmospheric air and a supplemental gas connection inlet for supplemental oxygen, for mixing to produce the gas flow containing the two-component gas mixture.

10. The respiratory support device according to any one of claims 1 to 9, wherein the humidifying unit further comprises a heater plate and / or the humidifying unit further comprises a humidifying water chamber.

11. The flow path of the gas flow passing through the respiratory support device, Most of the inflow section of the flow path in front of the blower unit, The flow path between the blower unit and the humidifier unit, and / or The flow path after the humidification unit, A respiratory support device according to any one of claims 1 to 10, wherein one or more sections are sealed.

12. The respiratory assistance device according to any one of claims 1 to 11, wherein the humidifying unit comprises a humidifying unit compartment for receiving a humidifying water chamber having a heater plate, and the device comprises a main housing that surrounds the blower unit and provides the humidifying unit compartment for receiving the humidifying water chamber.

13. The respiratory assistance device according to any one of claims 1 to 12, wherein the sensor assembly is detachably mounted in the flow path.

14. The respiratory assistance device according to any one of claims 1 to 13, wherein the sensor assembly further comprises a temperature sensor, the temperature sensor is configured to measure the temperature of the gas flow near the sensor assembly and generate a representative temperature signal.

15. The respiratory support device according to any one of claims 1 to 14, further comprising an output display configured to display one or more gas concentration levels detected by the gas concentration sensor system.

16. The respiratory assist device according to any one of claims 1 to 15, wherein the controller is configured to compare a detected oxygen percentage represented by one or more output signals or data with a user-defined range defined by a maximum threshold and / or a minimum threshold, and further configured to trigger or activate an alarm of the device if the detected oxygen percentage is less than the minimum threshold, or greater than the maximum threshold, or otherwise outside the user-defined range.

17. The respiratory assistance device according to any one of claims 1 to 16, wherein the sensor assembly is provided in the flow path, and the flow path is the bulk flow path of the device.

18. The respiratory assistance device according to any one of claims 1 to 17, wherein the sensor assembly is configured to detect the oxygen ratio of the gas flow in the bulk channel of the device.

19. The respiratory support device according to any one of claims 1 to 18, wherein the device is operable to deliver a high-flow gas stream for high-flow therapy via a nasal cannula.

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