Device for supplying gas to patient

Abstract

To provide a sensor mechanism or a device including a sensor mechanism that helps eliminate disadvantages of a conventional system for supplying a gas flow to a patient.SOLUTION: There is provided a device for supplying humidification gas to a patient that includes a gas supply passage downstream of a humidification gas supply source and upstream of a patient using the device, and in which at least one sensor is embedded in the wall of the passage or disposed outside the wall of the passage. In a preferred form, the wall of the passage separates the sensor and the gas flow in the passage. While the device is being used, a controller receives output from the sensor, and derives an estimate of characteristics of the gas flowing through the passage from the output of the sensor, or provides control output to the humidification gas supply source according to the output of the sensor.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to an apparatus for supplying a heated and humidified gas flow to a user for therapeutic purposes. In particular, the present invention relates to a sensor used in an apparatus for providing humidified air for respiratory humidification therapy, high-flow oxygen therapy, CPAP therapy, Bi-PAP therapy, OPAP therapy, etc., or for humidification of gases used in inhalation or keyhole surgery, for controlling the humidity of a gas flow.

Background Art

[0002] Apparatuses and systems for providing a humidified gas flow to a patient for therapeutic purposes are well known in the art. Systems for providing this type of therapy (e.g., respiratory humidification) have a structure in which gas is sent from a gas source to a humidification chamber. The gas becomes saturated with water vapor as it passes over water or through heated and humidified air within the humidification chamber. The heated and humidified gas is then sent from the humidification chamber downstream to a user or patient via a gas tube and a user interface.

[0003] The gas delivery system can be a modular system assembled from separate units, and the gas source can be a ventilator unit or a blower unit. That is, the humidification chamber / heater and the blower unit are separate (modular). The modules can be connected in series via connecting tubes during use to allow gas to pass from the blower unit to the humidification unit.

[0004] Alternatively, the ventilator can be an integrated system, and the blower unit and the humidification unit are contained within the same housing during use.

[0005] In both modular systems and integrated systems, the gas provided by the blower unit generally has the ambient atmosphere as a source.

[0006] Typically, a third common form of mechanical ventilation system used in hospitals is one in which the mechanical ventilation system generally receives at least a portion of the gas it uses from a central gas source that is external to the area of use (e.g., a hospital room). Gas tubing, for example, is connected between inlets mounted to the wall of the patient's room (or the like). The gas tubing can be directly connected to a humidification chamber in use, or, if necessary, a step-down control unit or the like can be connected in series between the gas inlet and the humidification chamber. This type of mechanical ventilation system is generally used when a patient or user may require oxygen therapy and oxygen is supplied from a central gas source. It is common to mix pure oxygen from the gas source with ambient air, for example, by using a venturi located within a step-down control unit, before delivering it to the patient or user. In systems of the type where at least some of the gas is sent from a central source, there is no need for a separate flow generator or blower - the gas is sent from the inlet under pressure and the step-down control unit changes the pressure and flow rate to the required levels.

[0007] An example of a prior art modular system that uses only ambient gas is shown in FIG. 1.

[0008] In typical integrated and modular systems, ambient gas is drawn into the main "blower" or ventilator unit or otherwise introduced, and the main "blower" or ventilator unit provides a gas flow at the outlet. The blower unit and the humidification unit are coupled or otherwise firmly connected to the blower unit. For example, the humidification unit is coupled to the blower unit by a slide-on or push-in connection, which ensures that the humidification unit is firmly connected to the main blower unit and held firmly in place on the main blower unit. An example of this type of system is the Fisher and Paykel Healthcare "slide-on" water chamber system shown and described in U.S. Patent No. 7,111,624. A variation of this design is a slide-on or clip-on design where the chamber is enclosed within a portion of the integrated unit during use. An example of this type of design is described in WO 2004 / 112873 pamphlet.

[0009] One problem faced by systems that provide a heated and humidified gas flow to a patient via a gas tube and an interface is the problem of appropriately controlling the characteristics of the gas. Clearly, in order to provide the required treatment, it is desirable to deliver to the patient (i.e., when the gas exits the user interface) a gas with precisely accurate temperature, humidity, flow rate, and oxygen percentage (if the patient is receiving oxygen therapy). The treatment regimen can be rendered ineffective if the gas delivered to the patient does not have the characteristics that are accurate or required. In many cases, the most desirable situation is to deliver to the user a gas that is completely saturated with water vapor (i.e., has a relative humidity of approximately 100%) at a constant flow rate. Other types or variations of treatment regimens may require a relative humidity of less than 100%. The breathing circuit is not a steady-state system, and it is difficult to guarantee that a gas with substantially accurate characteristics is delivered to the user. Achieving this result over a variety of ambient temperatures, ambient humidity levels, and various gas flows at the time of delivery can be difficult. The temperature, flow rate, and humidity of the gas flow are all interdependent characteristics. If one characteristic changes, the other characteristics will also change. Several external variables can affect the gas within the breathing circuit and make it difficult to deliver the gas to the user at substantially accurate temperature, flow rate, and humidity. As an example, the transport tube between the patient or user and the humidifier outlet is exposed to the ambient atmospheric conditions, and cooling of the heated and humidified gas within the tube can occur as the gas moves along the tube between the outlet of the humidification chamber and the user interface. This cooling can lead to "water droplet formation" within the tube (i.e., the formation of condensation on the inner surface of the tube). Water droplet formation is highly undesirable for reasons detailed in WO 01 / 13981 pamphlet.

[0010] To assist in achieving the delivery of a gas flow having a gas with the desired characteristics, prior art systems have used sensors (e.g., temperature sensors and humidity sensors) placed at various locations throughout the breathing circuit. Thermistors are commonly used as temperature sensors because they are reliable and inexpensive. Humidity sensors such as those described in U.S. Patent No. 6,895,803 are suitable for use in combination with systems that deliver heated and humidified gas to the user for therapeutic purposes.

[0011] Patent Gazette International Publication No. 2001 / 13981 pamphlet describes a system that uses the outputs of these sensors in the control aspect of a humidified gas supply system. Patent Gazette International Publication No. 2009 / 145646 pamphlet, another system that uses the outputs of sensors in the control aspect of a humidified gas supply system. The content of this publication is incorporated herein by reference.

[0012] A conventional method of providing a sensor within a gas flow is to provide a probe that penetrates the tube wall. The probe extends into the gas flow. A thermistor is provided at the tip of the probe and is typically positioned roughly in the center of the gas flow.

[0013] The probe can be fixed at a predetermined position (for example, a position provided at a permanent position within the gas supply source body), or it can be a removable probe (for example, positioned at a part of a replaceable component such as a breathing circuit). In the case of a removable probe, the component to which the probe is attached may include a suitable port, and the probe is pushed into the port and protrudes into the interior of the tube.

[0014] Positioning the sensor portion of the probe at the center of the gas flow is considered desirable to provide a representative reading of the characteristics of the gas flow (whether the characteristic is temperature, humidity, or flow). Unfortunately, at this position, the sensor is affected by the cleaning effort inside the gas passage using, for example, a small sponge at the end of a narrow handle. Furthermore, the protruding sensor can prevent the ability to completely clean the gas passage. This can especially apply when the protruding probe extends into the passage between the open end of the passage and the bend of the passage. It becomes difficult to access the area between the bend and the probe, especially the surface area directly behind the probe. Trying to access these areas can lead to damage to the probe. Summary of the Invention Problems to be Solved by the Invention

[0015] An object of the present invention is to provide a sensor mechanism or a device including the sensor mechanism that can at least help to eliminate the above drawbacks. **Means for Solving the Problem**

[0016] In one aspect, the essence of the present invention is a device for supplying humidified gas to a patient, comprising a humidified gas supply source, a gas supply passage downstream of the humidified gas supply source and upstream of the patient in use, a sensor embedded in the wall of the passage or disposed outside the wall of the passage, a controller that receives an output from the sensor and is adapted to derive an estimate of the characteristics of the gas flowing through the passage from the output of the sensor or provide a control output to the humidified gas supply source according to the output of the sensor, and the wall of the passage separates the gas flow in the passage from the sensor, and the device is provided.

[0017] According to a further aspect, the sensor is disposed in a groove on the outer surface of the wall of the tube.

[0018] According to a further aspect, the groove is about 30% or less of the diameter of the tube and protrudes into the flow path of the gas flowing through the tube.

[0019] According to a further aspect, the gas passage has a diameter of 10 mm to 30 mm.

[0020] According to a further aspect, the portion of the gas passage closest to the sensor is formed of a material having a thermal conductivity of less than 1 W / mK at 25°C, most preferably less than 0.4 W / mK.

[0021] According to a further aspect, the portion of the gas passage closest to the sensor is made of a plastic material such as polycarbonate or polypropylene.

[0022] According to a further aspect, the sensor is a thermistor.

[0023] According to a further aspect, a second sensor is provided at a position adjacent to the first sensor, and the second sensor is also disposed on a wall of a passage between the second sensor and the gas flowing in the gas passage. The controller receives an output from the second sensor, and from that output, the controller identifies the derivation of the physical properties of the gas flowing in the gas passage and is adapted to compare the derivation derived using the first sensor with the derivation derived using the second sensor.

[0024] According to a further aspect, the sensor is disposed in a portion of the gas passage adjacent to the humidified gas supply source.

[0025] According to a further aspect, the humidified gas supply source is included in a housing, the portion of the gas passage passes through the housing, and the sensor is disposed within that portion of the gas passage within the housing.

[0026] According to a further aspect, the controller estimates the physical properties of the gas flow based on the output of the sensor and based on the operating conditions of the humidified gas supply source.

[0027] According to a further aspect, the controller compensates for the situation of the humidified gas supply source including parameters indicating the power supplied to the humidified gas supply source, the ambient temperature inside the housing of the humidified gas supply source, the flow rate of the gas supplied by the humidified gas supply source through the gas passage, the power input to the flow generator within the humidified gas supply source, the power input to the humidifier within the humidified gas supply source, the power input to the controller within the humidified gas supply source, or any combination thereof.

[0028] According to a further aspect, the portion of the gas passage including the sensor is formed as a bend, and the sensor is disposed at or adjacent to the bent portion of the bend.

[0029] According to a further aspect, the sensor is disposed at a position where liquid can accumulate within the gas passage.

[0030] According to a further aspect, an additional sensor is provided spaced apart from the first sensor, one of the first sensor and the additional sensor being disposed at a position where liquid can accumulate within the gas passage, and the other being disposed at a position where liquid does not accumulate within the gas passage, the controller being adapted to calculate an estimate of the relative humidity of the gas flowing through the passage based on the outputs of the first and second sensors.

[0031] According to a further aspect, the sensor is disposed within a portion of the gas passage remote from a humidified gas supply source, such as a position along a gas supply tube to the patient, adjacent to the patient or directly along the passage.

[0032] According to a further aspect, the humidified gas supply includes a humidifier having a heater and a reservoir for containing an amount of water adjacent to the heater.

[0033] According to a further aspect, the humidifier comprises a heater plate and the reservoir comprises a removable container that contacts the heater plate during use.

[0034] According to a further aspect, the humidified gas supply source includes a blower and the output of the blower is provided to the inlet of the humidifier.

[0035] According to a further aspect, the blower and the humidifier heater are disposed within the same housing.

[0036] In a further aspect, the essence of the present invention is an apparatus for supplying humidified gas to a patient, comprising a gas supply passage defined by an inner surface of a passage wall, a sensor embedded in the passage wall of the passage or disposed on an outer surface of the passage wall of the passage, a controller adapted to receive an output from the sensor and derive an estimate of a characteristic of the gas flowing through the passage or a control output for the humidified gas supply source from the output of the sensor, the wall of the passage separating the gas flow within the passage from the sensor.

[0037] To those skilled in the art related to the field of the present invention, many modifications of the structure of the present invention, as well as widely different embodiments and applications, will be apparent without departing from the scope of the present invention defined in the appended claims. The disclosure and description herein are purely exemplary and are not intended to be limiting in any sense.

[0038] As used herein, the term "comprising" means "comprising at least in part", that is, when interpreting a sentence containing this term in this specification, all of the features preceded by this term in each sentence must be present, but other features can also be present.

[0039] A preferred form of the present invention will be described hereinafter with reference to the accompanying drawings.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2a

Figure 2b

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0041] Detailed Description of the Preferred Embodiment The present invention provides an improved sensor mechanism that is less likely to be damaged and enables more efficient cleaning of the tube in which the sensor is disposed. The sensor mechanism is shown in FIGS. 8-11 and will be described in detail hereinafter with respect to these mechanisms. The sensor operates in conjunction with a controller that estimates the thermal characteristics of the gas flow based on the sensor output and the dominant conditions of the system. In some embodiments, the controller also controls aspects of the operation of the system such as the gas flow rate and the power supplied to the heater of the humidifier. In that case, the output of the temperature sensor can be supplied directly to the control algorithm without any intermediate steps of converting the sensor output to an estimated temperature. Instead of intermediate steps, the control algorithm directly compensates for the dominant system conditions.

[0042] A general system configuration in which the sensor mechanism according to the present invention can be incorporated will first be described with reference to FIGS. 2-4.

[0043] Schematic views of a user 2 receiving air from a modular ventilator unit and a humidifier system according to a first system configuration example are shown in FIGS. 2a and 2b. System 1 provides a pressurized heated and humidified gas flow to user 2 for therapeutic purposes (e.g., to reduce the occurrence of obstructive sleep apnea, to provide CPAP therapy, to provide humidification for therapeutic purposes, etc.). System 1 will be described in detail hereinafter.

[0044] The ventilator unit or blower unit 3 has an internal compression unit and a flow generator or fan unit 13 - generally, this can be referred to as a flow control mechanism. Air from the atmosphere enters the housing of the blower unit 3 through the ambient air inlet 40 and is drawn through the fan unit 13. The output of the fan unit 13 is adjustable - the fan speed is variable. The pressurized gas flow exits the fan unit 13 and the blower unit 3 and moves through the connecting tube 4 to the humidification chamber 5 and enters the humidification chamber 5 through the inlet port or inlet port 23.

[0045] The humidification chamber 5 in use contains a certain volume of water 20. In a preferred embodiment, the humidification chamber 5 in use is disposed on a humidifier base unit 21 having a heater plate 12. The heater plate 12 is powered to heat the base of the chamber 5 and thus the contents of the chamber 5. The water in the chamber 5 evaporates when heated, and the gas (above the surface of the water 20) in the humidification chamber 5 is heated and humidified. The gas flow entering the humidification chamber 5 through the inlet port 23 passes over (or through these heated and humidified gases - applicable in the case of a large chamber and flow rate) the heated water and is heated and humidified as it passes through. The gas flow then exits the humidification chamber 5 through the outlet port or outlet port 9 and enters the transport tube 6.

[0046] When the "humidification unit" is referred to herein with reference to the present invention, this should be construed to mean at least the chamber 5 and, where applicable, the base unit 21 and the heater plate 12.

[0047] The heated and humidified gas is passed along the length of the transport tube 6 and provided to the patient or user 2 through the user interface 7. The tube 6 may be heated via a heater wire (not shown) etc. to assist in avoiding water droplet formation. The tube typically has a circular internal cross-section. The inner diameter of the tube is typically about 20 mm, but can be from 10 mm to 30 mm. These typical dimensions apply to both the flexible portion of the gas flow path and the rigid components such as bends and connectors, as well as the portion integrated into the components of the humidified gas supply source.

[0048] The user interface 7 shown in FIG. 2a is a nose mask that surrounds and covers the nose of user 2. However, it should be noted that a nasal cannula (such as that shown in FIG. 2b), a full face mask, a tracheal opening fitting, or any other suitable user interface may be used in place of the shown nose mask. The central controller or control system 8 is disposed within the blower case (controller 8a) or within the humidifier base unit (controller 8b). In this type of modular system, it is preferred that separate blower controller 8a and humidifier controller 8b be used, and most preferably that controllers 8a, 8b be connected (e.g., by cable, etc.) and be able to communicate with each other during use.

[0049] The control system 8 receives user input signals via a user control device 11 disposed on the humidifier base unit 21, or the blower unit 3, or both. In a preferred embodiment, the controller 8 also receives inputs from sensors disposed at various points throughout the system 1.

[0050] FIG. 7 shows a schematic representation of some of the inputs to and outputs from the controller 8. Note that not all possible connections and inputs / outputs are shown - FIG. 7 is representative of some of the connections and is a representative example.

[0051] The sensors and their locations will be described in more detail later. In response to user input from the control device 11 and signals received from the sensors, the control system 8 determines control outputs, and in a preferred embodiment, the control system 8 transmits signals to adjust the power to the humidification chamber heater plate 12 and the speed of the fan 13. The programming by which the controller determines how to determine the control outputs will be described in more detail later.

[0052] A schematic diagram of user 2 receiving air from the integrated blower / humidifier system 100 according to the second form of the present invention is shown in FIG. 3. This system operates in a manner very similar to the modular system 1 shown and described above in FIG. 2, except that the humidification chamber 105 is integrated with the blower unit 103 to form an integrated unit 110. The pressurized gas flow is provided by a fan unit 113 disposed inside the case of the integrated unit 110. The water 120 in the humidification chamber 105 is heated by a heater plate 112 (which is an integral part of the structure of the blower unit 103 in this embodiment). Air enters the humidification chamber 105 through the inlet port 123 and exits the humidification chamber 105 through the outlet port 109. The gas flow is provided to the user 2 through the transport pipe 106 and the interface surface 107. The controller 108 is included within the outer shell of the integrated unit 100. The user control device 111 is disposed on the outer surface of the unit 100.

[0053] A schematic diagram of user 2 receiving air from a further form of the artificial respiration system 200 is shown in FIG. 4. The system 200 is generally characterized as a remote source system and receives air from a remote source through a wall flow inlet 1000.

[0054] The wall flow inlet 1000 is connected to a control unit 202 via an inflow pipe 201, and the control unit 202 receives gas from the inlet 1000. The control unit 202 has sensors 250, 260, 280, 290, and each of the sensors measures the humidity, temperature, pressure, and flow rate of the incoming gas flow.

[0055] Next, the gas stream is provided to the humidification chamber 205, heated and humidified, and provided to the user in the same manner as outlined above. It should be noted that when a "humidification unit" is referred to in relation to a remote source system such as system 200, this should be interpreted as meaning something that incorporates the control unit 202 - the gas from the remote source may be directly connected to the inlet, or connected via the control unit 202 (to reduce pressure etc.), but the control unit and the humidification chamber should be interpreted as belonging to the overall "humidification unit".

[0056] If necessary, system 200 can have a central source as an O2 source, or provide O2 or a proportion of O2 by mixing O2 flowing in from the central source with ambient air via a venturi 90 etc. disposed in the control unit 202. It is also preferable for the control unit 202 to have a valve or a similar mechanism that operates as a flow control mechanism for adjusting the flow rate of the gas passing through system 200.

[0057] Sensor The modular systems and integrated systems 1, 100, and 200 shown in FIGS. 2, 3, and 4 have sensors disposed at points throughout the system. These will be described later in relation to the artificial respiration system 1.

[0058] A preferred form of the modular system 1 shown in FIG. 2 has at least the following sensors in the following preferred positions. 1) An ambient temperature sensor 60 disposed within, in the vicinity of, or on the blower case, configured or adapted to measure the temperature of the incoming air from the atmosphere. It is most preferable for the temperature sensor 60 to be disposed within the gas stream after (downstream of) the fan unit 13 and as close as possible to the inlet or entrance to the humidification chamber. 2) A humidifier unit outlet port temperature sensor 63 that is disposed at the chamber outlet port 9 or at the end of the device of the transport tube 6 (opposite to the patient side end). The outlet port temperature sensor 63 is configured or adapted to measure the temperature of the gas flow when the gas flow exits the chamber 5 (in any configuration, the outlet port temperature sensor 63 can be considered to be close to the chamber outlet port 9).

[0059] The sensor 63 is preferably provided according to the present invention, and the sensor is separated from the gas flow by the wall of the tube and does not substantially protrude into the gas flow.

[0060] Similarly, the sensors are disposed at substantially the same positions in the integrated system 100 shown in FIG. 3 and the system 200 of FIG. 4. For example, in the integrated system of FIG. 3, the ambient temperature sensor 160 is disposed in the gas flow within the blower case immediately before (upstream of) the humidification chamber inlet port 123. The chamber outlet port temperature sensor 163 is disposed at either the chamber outlet port 109 and is configured to measure the temperature of the gas flow when the gas flow exits the chamber 105 (in any configuration, the outlet port temperature sensor 163 can be considered to be close to the chamber outlet port 109). Alternatively, in any embodiment, this sensor can be disposed at the end of the device of the transport tube 106 (opposite to the patient side end). A similar numbering scheme is also used in the artificial respiration system shown in FIG. 4 - the ambient temperature sensor 260, the fan unit 213, the chamber outlet port temperature sensor 263 disposed at the chamber outlet port 209, etc.

[0061] It is also preferred that the artificial respiration systems 1 (and 100, 200) have a heater plate temperature sensor 62 disposed adjacent to the heater plate 12 and configured to measure the temperature of the heater plate. An artificial respiration system having a heat plate temperature sensor is preferred for providing an immediate indication of the state of the heater plate. However, it is not absolutely necessary for the system to have a heater plate temperature sensor.

[0062] Most preferably, in the flow probe - system 1, which is arranged upstream of the fan unit 13 and is configured to measure the gas flow, the flow probe 61 is included. The preferred position of the flow probe is upstream of the fan unit, but the flow probe may be arranged downstream of the fan or at any other suitable position. Here too, it is preferred that the flow probe forms part of the system, but it is not absolutely necessary for the flow probe to form part of the system.

[0063] The layout and operation of the artificial respiration system 1 will be described in more detail hereinafter. The operation and layout of systems 100 and 200 are substantially the same and will not be described in detail except where necessary.

[0064] In the artificial respiration system 1, readings from all sensors are fed back to the control system 8. The control system 8 also receives input from the user control device 11.

[0065] Additional alternative and further sensors and their layouts will be described in more detail hereinafter.

[0066] Temperature Sensor Arrangement According to the present invention, the temperature sensor 63 (or 163, or 263) is arranged such that the wall of the tube separates the gas flow from the temperature sensor.

[0067] Preferably, the sensor is embedded in a recess on the outer surface of the wall of the tube. The recess may extend so as to protrude into the gas flow. For example, the inner surface of the tube wall near the recess may bulge or protrude into the gas flow. Alternatively, the recess can be contained within the general thickness of the tube wall, and thus the inner surface of the tube wall in the immediate vicinity of the recess does not need to protrude relative to the surrounding inner surface. Alternatively, the sensor may be fixed to the outer wall surface without a recess for accommodation.

[0068] When a depression is formed on the inner surface of the pipe wall and protrudes into the gas flow, the degree of protrusion is preferably limited to less than 1 / 3 of the diameter of the pipe at that position. In the case of a bulge that conforms to a depression protruding beyond this, the substantial benefits associated with housing the sensor outside the pipe wall are not achieved. Most preferably, there is no bulge or protrusion in the gas flow related to the sensor position. This is because the complexity of the plastic mold is usually lower, making manufacturing easier than an arrangement with some protrusion in the flow path.

[0069] An appreciable advantage of the sensor arrangement according to the present invention is that the pipe component is easier to mold, easier to clean, and less prone to damage than a typical prior art sensor that includes a probe protruding into the gas flow path to place the sensor component approximately in the center of the gas flow. The inventors of the present invention have discovered that the temperature, dew point temperature, or humidity of the gas flow can be appropriately estimated using a sensor disposed outside the pipe wall or having the pipe wall between the sensor and the gas flow, and that an associated controller can compensate for the dominant system situation.

[0070] Preferred sensor embodiments are shown in FIGS. 8 and 9. FIG. 8 shows a pipe bend 800 that includes a portion of the gas flow path after the humidified gas exits the humidifier. The gas enters the pipe bend at end 814, flows in the direction indicated by arrow 816, and exits at end 818. The bend 800 can be constructed from any suitable plastic material. For example, the bend can be molded from polycarbonate. The outer surface of the connector is molded to include a groove 802. The groove 802 is aligned across the axis of the pipe, which is best seen in FIG. 9 and opens at least at one end. The outer surface of the groove of the bend bulges outwardly (820) to accommodate the groove. The groove is separated from the gas flow by approximately half the thickness of the wall 804 of the component. However, any separation that leaves sufficient thickness of plastic to maintain the integrity of the connector can be used.

[0071] The depression or groove extends across or along the outside of the component and serves as an efficient molding tool.

[0072] The temperature sensing component 806 is disposed within and secured to the groove 802. The temperature sensing component can be any electrical or electronic component having a measurable characteristic that varies according to temperature. A thermistor is an example of a suitable device. The sensor can be secured in place by any suitable method. Most preferably, the sensor 806 is secured by an adhesive such as an epoxy adhesive or a cyanoacrylate adhesive.

[0073] Leads 810 extend from the sensor.

[0074] At this location, the sensor is not in close thermal contact with the gas flow and is in close thermal contact with the wall of the tube.

[0075] The internal passage 812 is not blocked by any protruding probes and can be accessed over the entire range of the tube for cleaning, for example, by a sponge secured to a narrow rod. There are no protruding probes that could be damaged by cleaning attempts.

[0076] The temperature sensor is preferably disposed at the bottom of the bend. This location is an area that is likely to get wet by the humid air flow. This can improve heat transfer to the tube wall because the flow is fully or substantially saturated during normal use. The control algorithm presented below has proven to be robust to the sensor at this location.

[0077] In many applications, safety requirements determine the level of redundancy or the ability to check the integrity of the control system. Referring to FIG. 9, a second sensor 904 can be disposed beside the first sensor 806 and secured in place in the same manner as the first sensor 806. The second sensor can be present in the same groove as the first sensor. For example, each sensor can be disposed at slightly spaced positions within a groove extending across the outside of the tube. Alternatively, slightly spaced grooves 802, 902 can be formed in the tube (as shown), and the sensors are disposed and secured within each groove. Leads from each sensor extend from the groove.

[0078] In this dual-sensor embodiment, the controller can directly compare sensor outputs or calibrate and independently calculate the derivation of each sensor output based on the system situation and then compare the results. If the sensor outputs or the derivations of the sensor outputs are significantly different, the controller indicates an error, operates in a safe mode, or does both. Since the sensors are placed at slightly different positions, it is preferable to compare the derivations of each sensor output. Each derivation is calculated independently according to the system situation, and the calculation is calibrated according to the specific sensor position.

[0079] A further embodiment incorporating multiple sensors is shown in FIG. 10. According to the configuration of FIG. 10, the sensors are provided at spaced positions specifically aimed at seeing different operating situations. In particular, the configuration of FIG. 10 provides one temperature sensor 1002 at a position 1004 on the outer surface of the tube 1000 where it can be expected that the tube has no accumulated condensate, and another sensor 1006 is provided at a position 1008 on the outer surface of the tube where it can be expected that the inner surface of the tube accumulates condensate.

[0080] In a specific configuration, the sensor is provided in the vicinity of the flow bend, and the bend is arranged such that the curvature 1010 of the bend is slightly below 1012 the lower end of the two ends of the bend.

[0081] The second sensor 1006 is provided at a position outside the tube wall and at the lowest range of the inner surface of the tube wall. It is at that position 1008 where surface humidity is most likely to accumulate during the operation of the humid gas transport device.

[0082] The first sensor 1002 is provided at another position 1004 along the outer surface of the bend. The position of the first sensor is not very restricted, but for example, it can be a position where the inner surface of the tube is substantially vertical during use so that condensed droplets are unlikely to stop at that position. Thus, for example, the first sensor can be present at any position on the upward leg of the bend or at any position along the midpoint between the two sides of the downward leg of the bend.

[0083] The controller can be programmed to estimate the humidity of the gas flow using the outputs from the first and second sensors in this configuration. The controller program can use the first sensor to estimate the temperature of the gas flow. The second sensor can be affected by the evaporation of accumulated condensate due to the gas flow and can approximate a wet bulb within the humidity sensor. Each sensor is subject to external influences on the system, including the effects of gas flow rate and ambient heating. The controller can compensate for these effects in the same manner as described later in relation to a single temperature sensor.

[0084] If redundancy is required, multiple sensors can be provided at each location as described above in relation to FIG. 8.

[0085] Humidity control method The preferred control system 8 has at least one data set pre-loaded into the controller. The data forming the data set is pre-measured or pre-calculated under controlled conditions (e.g., in a test area or laboratory) in a specific system configuration having specific components (e.g., in particular, system 1, system 100, or system 200 where a specific blower unit and humidifier unit are used for data collection). The data is collected under several ranges of conditions typically encountered during use, and the pre-measured (pre-set) data is then loaded into the controller 8 as integrated software or hardware in the case of a production system, or as data to be used, for example, in a fuzzy logic algorithm for humidity control.

[0086] A data set particularly suitable for use in combination with system 1 is shown as a graph in FIG. 5. The X-axis represents the ambient temperature in the range of 18°C to 35°C. During use, the ambient temperature of the gas within the inlet respiratory system in front of or upstream of chamber 5 is measured by the ambient temperature sensor 60, and the ambient temperature data is relayed to the controller 8. It is most preferred that the temperature sensor 60 measures the ambient temperature of the gas immediately before it enters chamber 5. To create the data set, a typical system 1 is placed in an environment where the ambient temperature can be maintained at a known constant level over a range of temperatures.

[0087] In use, the user selects the flow rate by adjusting the control device 11. The controller 8 receives an input from the user control device 11 and adjusts the fan speed to substantially match this required flow rate (either by changing the fan speed to a speed known to substantially correspond to the flow rate required for a particular breathing circuit configuration, or by measuring the flow using the flow probe 61 and using a feedback mechanism via the controller 8 to adjust the flow rate to the required or demanded level). Seven different constant flow rates at seven different constant fan speeds are shown in the graph of FIG. 5. Lines 70 to 76 correspond to different flow rates as follows: Line 70 - flow rate 15 l / min. Line 71 - flow rate 20 l / min. Line 72 - 25 l / min. Line 73 - flow rate 30 l / min. Line 74 - flow rate 35 l / min. Line 75 - flow rate 40 l / min. Line 76 - flow rate 45 l / min.

[0088] The Y-axis indicates various target chamber temperatures. These temperatures may be stored as temperature sensor values and do not necessarily need to follow the actual calibrated temperature. That is, at any given fan speed (flow rate and pressure) and any given ambient temperature, there is a "best" or "ideal" target outlet temperature of the gas in the chamber 5 above the water 20 - the target outlet temperature shown on the Y-axis. This "ideal" temperature is the dew point temperature at a given constant flow rate and a constant ambient temperature. That is, the gas exits the chamber 5 at the required saturation (required humidity level), and then can be sent to the user 2 at the correct temperature and pressure for effective treatment. When the gas exits the chamber 5, the temperature is measured by the chamber outlet port temperature sensor 63. The controller 8 is adapted to receive the temperature data measured by the chamber outlet temperature sensor 63 and the data regarding the temperature of the gas entering the chamber 5 (measured by the ambient temperature sensor 60). Since the flow rate has been previously set to a constant value as outlined above, the controller 8 already "knows" the constant flow rate. Since the controller 8 "knows" both the flow rate and the ambient temperature, for example, it can look up the "ideal" target outlet temperature reading from within a range incorporated in a pre-loaded data set (e.g., the data graphically shown in FIG. 5). Next, the controller 8 compares the measured value of the chamber outlet temperature to the "ideal" target chamber temperature for a given known flow rate and ambient temperature. If the measured value of the target temperature does not match the "ideal" target value, the controller 8 generates or determines an appropriate control output and adjusts the power to the heater plate accordingly, increasing the power to increase the temperature of the gas in the chamber 5 or reducing the power to reduce the gas temperature. The controller 8 adjusts the power in this way to match the temperature measured at the outlet or outlet port to the required target temperature. In a preferred embodiment, the mechanism by which the controller 8 adjusts the output characteristics is via a proportional-integral-derivative controller (P.I.D. controller) or any one of several similar mechanisms known in the art.

[0089] The controller can also generate or determine a suitable control output, for example, by using a fuzzy logic control algorithm loaded into the controller 8 or a mathematical formula that uses the measured temperature and flow rate data as variables in the formula.

[0090] Examples of the mathematical formula are shown below. These generally correspond to the data graphically shown in Figure 5 in the flow rate range of 15 l / min to 45 l / min.

[0091] [Table 1]

[0092] Example: For the treatment regimen of User 2, a specific flow rate and pressure, for example, a flow rate of 45 l / min, are specified. The speed of the blower or fan unit 13 is set to send gas at this flow rate (via the control device 11). If the flow probe 61 is part of the system, this flow rate can be dynamically adjusted by feeding back real-time flow readings from the flow sensor or flow probe 61 to the controller 8, and the controller 8 adjusts the fan speed as needed. This can be done via a PID controller or the like that includes a part of the control device 8, as will be described in detail later. It is preferred that the flow rate be dynamically adjusted and monitored. However, if the flow probe is not part of the system, the flow rate is assumed or calculated from the fan speed and is assumed to be constant at a certain fan power level. The flow rate of 45 l / min is indicated by line 76 in the graph of FIG. 5. In this example, User 2 is sleeping in a bedroom with an ambient temperature of substantially 30°C. Air at 30°C enters the ventilator and is slightly warmed as it passes through the fan and connecting passages in the case. The temperature of the air just before entering the humidification chamber is measured by the ambient temperature sensor 60. Since the ambient temperature and flow rate are known, the controller 8 can calculate the required target temperature as shown on the Y-axis of the graph in FIG. 5. In this particular example, it can be seen that the chamber target temperature is 39.4°C. The chamber outlet temperature sensor 63 measures the temperature at the outlet of the chamber 5 (the gas temperature at the outlet point is approximately the same as the gas in the space above the contents 20 of the chamber). If the gas temperature measured by the chamber outlet temperature sensor 63 is not 39.4°C, the controller 8 determines and generates a suitable control output to change the power to the heater plate 12 accordingly. Similarly, if the ambient temperature measured by the ambient temperature sensor 60 changes, this can be fed back to the controller 8, and the output can be changed appropriately using a PID control algorithm or the like.

[0093] One of the advantages of this system over the systems disclosed in the prior art is as follows: In the systems according to the prior art, as the ambient temperature approaches the target dew point temperature, the power consumption of the heater plate decreases and does not raise the temperature of the water in the humidification chamber so much. Therefore, the gas tends not to be completely saturated when it exits the chamber. The method outlined above uses the value of the ambient temperature, or more preferably, the chamber inlet temperature, chamber outlet temperature, and flow rate of a system of known configuration to generate a target chamber outlet temperature at which the gas is saturated at a set flow rate and a specific ambient temperature, which is considered to be the substantially best or "ideal" temperature to be sent to the user, thereby solving this problem.

[0094] Another advantage is that system 1 can accurately control the humidity level without the need for an accurate humidity sensor.

[0095] Another advantage is that when gas is sent from a compressor or blower to the humidification chamber and this incoming gas has a high temperature, the chamber temperature can be accurately compensated to achieve the desired dew point. This is particularly advantageous when the air or gas entering the chamber is warm and also in situations where the temperature increases as the flow rate increases. In operation, any flow generator increases the air temperature between the inlet and outlet from the atmosphere. This temperature change can be more pronounced with some types of flow generators. The temperature of the components of the system can change when the system first operates and then after some time has elapsed (for example, over a moderately long time period such as 1 - 2 hours, etc.). That is, the components of the system can get hot as the system operates and the system takes some time to reach a stable operating state. If these components are arranged within or adjacent to the air path between the point where air enters the system and the point where air enters the chamber, the temperature of these gases will change - as the gas moves along this path, some heat transfer from these components to the gas will occur. Therefore, when the system reaches a stable operating state, the gas temperature at the inlet point to the system can be different from the temperature of the gas at the inlet point to the chamber, so it can be seen that by measuring the gas temperature when the gas enters the chamber, the risk of introducing a temperature measurement error into the control calculation is reduced. However, although it is most preferable to measure the gas temperature at the inlet point to the chamber, it is generally also known that in most situations, measuring the atmospheric gas temperature is acceptable.

[0096] The method described above is substantially the same for the integrated device 100 or the device 200, but since the devices have slightly different configurations, the values preset or pre - measured and pre - loaded into the look - up table can be different. In other forms, the user can select a pressure ratio (and the dataset is changed with respect to pressure values rather than flow rate values).

[0097] Further alternative sensor layouts In a variation of the apparatus and method outlined above, the system (System 1, System 100, or System 200) also has additional sensors outlined below. 1) The patient-side end temperature sensor 15 (or 115, or 215) is disposed at the patient-side end of the transport tube 6 (or alternatively, within or on the interface 7). That is, at or near the patient or the transport point. As read herein, "patient-side end" or "user-side end" should be construed to mean near the user-side end of the transport tube (e.g., transport tube 6) or within or on the patient interface 7. This applies unless a specific location is otherwise stated. In any configuration, the patient-side end temperature sensor 15 can be considered to be at or near the user or patient 2.

[0098] These sensors are preferably provided in accordance with the configuration of the present invention. The sensors are separated from the gas flow by the wall of the tube and do not substantially protrude into the gas flow. As shown in FIG. 11, the temperature sensor 1115 can be provided such that the wall 1102 of the connector 1100 is between the temperature sensor and the gas flow using a structure equivalent to the structure described in FIGS. 8 and 9. Thus, for example, the connector shown includes a pair of grooves 1104 spaced apart across the outer surface. The sensors 1115, e.g., thermistors, are disposed in each groove. Each sensor 1115 is fixed in the groove by a suitable adhesive such as an epoxy adhesive.

[0099] According to this configuration, the interior of the tube is not blocked by any of the protruding probes. According to this configuration, since the sensor is not exposed to the gas flow, no subsequent sterilization or treatment is required. Further, the inner surface of the tube can be more easily cleaned. Alternatively, a peel away sleeve 1110 can be provided on the inner surface of the tube without being obstructed by the protruding sensor. The peel away sleeve can be peeled off from the tube after the first use, whereby a new peel away sleeve can be inserted (so that the tube can be used multiple times), or the tube can be reused without a peel away sleeve so that the tube can be used one more time. A multi-layer peel away sleeve can also be incorporated first, and accordingly the tube can be used multiple times.

[0100] Referring to FIG. 12, a sensor provided on the outside of the tube can be incorporated into a housing that is detachable from the tube wall. For example, the tube connector 1202 can include a recess suitable for accommodating the housing component 1206. Fixing features in the form of a taper, lip, or clip (1208) can place the housing component 1206 within the recess 1204. The sensor 1210 can be provided in the housing component at a position adjacent to the surface of the recess 1204 when the housing component is disposed in the recess. According to this configuration, the sensor can be reused even if the tube is disposable.

[0101] The reading value from the patient-side end temperature sensor 15 is fed back to the controller 8 and is used to ensure that the temperature of the gas at the transport point approximately matches the target patient temperature of the gas at the chamber outlet (the target patient temperature is the target dew point temperature at the chamber outlet). If the reading value from the patient-side end temperature sensor 15 indicates that the gas temperature is dropping as the length of the transport tube 6 is being moved, the controller 8 can increase the power to the tube heater wire (shown as wire 75 in FIG. 2a - not shown but present in the alternative preferred forms of the ventilator systems 200 and 400 shown in FIGS. 3 and 4 and the system shown in FIG. 2b) to maintain the gas temperature. If the power available to the tube heater wire 75 cannot equalize the gas at the transport point to the dew point temperature at the chamber outlet 9, the controller 8 lowers the target chamber outlet temperature (to a lower dew point temperature). The controller 8 lowers the chamber outlet temperature to the maximum gas temperature level or a level close thereto that the tube heater wire can deliver to the patient as measured by the patient-side end temperature sensor 15. A predetermined data set is loaded into the controller 8, and the controller 8 uses this data (similar to the data shown in graphical form in FIG. 5) to adjust the power to the heater plate, or the tube heater wire, or both. There is an ideal patient-side end temperature at a constant flow level and the ambient temperature (which can vary) measured by the ambient temperature sensor 60. The controller 8 adjusts the power output to the heater plate and the tube to match the temperature (measured by the temperature sensor 15) at the patient-side end of the tube to this ideal temperature.

[0102] The above method can be further improved in accuracy when other conditions of the gas within the system - the gas condition - are known. For example, when the humidity level of the input gas to the blower or the gas pressure of the input gas is known. To achieve this, alternative embodiments of the systems 1, 100, and 200 described above can have a gas condition sensor (e.g., a humidity sensor or a pressure sensor) disposed in the input gas path. In the modular system 1, a humidity sensor 50 is shown disposed near the air inlet 40. In the integrated system 100, this is shown as a humidity sensor 150 (and so on hereinafter). Similar to the control method outlined above, a humidity level data set is pre-loaded into the controller 8. At a constant flow rate and a known ambient or external humidity level, there is an ideal gas temperature at the chamber outlet (or the transport point to the user). The data set includes these ideal values for various ambient humidities and flow rates, similar to the values shown in graph form in FIG. 5. The controller 8 adjusts the power output of the heater plate, or the heater wire, or both, to match the measured chamber outlet temperature reading (or the patient-side end temperature) to the "ideal" temperature reading retrieved from the data set in the controller's memory. Similarly, placing a pressure sensor in the input gas path to the humidification chamber (pressure sensor 80 shown in the input gas path of FIG. 2 in the modular system, the pressure level of the input gas to the humidification chamber blower, if known, can improve the accuracy of the above method. Pressure sensor 180 is shown in the input gas path of FIG. 3 in the integrated system. Pressure sensor 280 is shown in the input gas path of FIG. 4 in the central gas source system). It should be noted that when the data of the data set is plotted in a graph in the context of a constant flow rate, ambient temperature, and another gas condition (e.g., humidity or pressure), the graph needs to be plotted with three axes - X, Y, and Z - when plotted, the graph becomes "three-dimensional".

Claims

1. An apparatus for supplying humidified gas to a patient, comprising: a humidified gas supply source; a gas supply passage downstream of the humidified gas supply source and upstream of the patient in use; a sensor embedded in the wall of the passage or disposed outside the wall of the passage, and a controller that receives an output from the sensor and is adapted to derive an estimate of the properties of the gas flowing through the passage from the output of the sensor or to provide a control output to the humidified gas supply source in accordance with the output of the sensor; characterized in that the wall of the passage separates the gas flow in the passage from the sensor.

2. The apparatus according to claim 1, wherein the sensor is disposed in a groove on the outer surface of the wall of the tube.

3. The apparatus according to claim 2, wherein the groove projects into the gas flow path of the gas flowing through the tube to an extent of 30% or less of the diameter of the tube.

4. The apparatus according to any one of claims 1 to 3, wherein the gas passage has a diameter of 10 mm to 30 mm.

5. The apparatus according to any one of claims 1 to 4, wherein the portion of the gas passage closest to the sensor is formed of a material having a thermal conductivity of less than 1 W / mK at 25°C, most preferably less than 0.4 W / mK.

6. The apparatus according to claim 5, wherein the portion of the gas passage closest to the sensor is made of a plastic material such as polycarbonate or polypropylene.

7. The apparatus according to any one of claims 1 to 6, wherein the sensor is a thermistor.

8. A second sensor is provided at a position adjacent to the first sensor, the second sensor is also disposed on the wall of the passage between the second sensor and the gas flowing in the gas passage, the controller receives an output from the second sensor, and from the output, the controller is adapted to identify the derivation of the physical properties of the gas flowing in the gas passage and compare the derivation derived using the first sensor with the derivation derived using the second sensor.

9. The apparatus according to any one of claims 1 to 8, wherein the sensor is disposed in a portion of the gas passage adjacent to the humidified gas supply source.

10. The apparatus according to claim 9, wherein the humidified gas supply source is contained in a housing, the portion of the gas passage passes through the housing, and the sensor is disposed in that portion of the gas passage within the housing.

11. The apparatus according to claim 10, wherein the controller estimates the physical characteristics of the gas flow based on the output of the sensor and based on the operating status of the humidified gas supply source.

12. The apparatus according to claim 11, wherein the controller compensates for the status of the humidified gas supply source including parameters indicating the power supplied to the humidified gas supply source, the ambient temperature inside the housing of the humidified gas supply source, the flow rate of the gas supplied by the humidified gas supply source through the gas passage, the power input to the flow generator in the humidified gas supply source, the power input to the humidifier in the humidified gas supply source, the power input to the controller in the humidified gas supply source, or any combination thereof.

13. The apparatus according to any one of claims 1 to 12, wherein the portion of the gas passage including the sensor is formed as a bent portion, and the sensor is disposed at the bent portion of the bent portion or adjacent to the bent portion.

14. The apparatus according to any one of claims 1 to 13, wherein the sensor is disposed at a position where liquid can accumulate in the gas passage.

15. An additional sensor is provided spaced apart from the first sensor, one of the first sensor and the additional sensor is disposed at a position where liquid can accumulate in the gas passage, and the other is disposed at a position where liquid does not accumulate in the gas passage, and the controller is adapted to calculate an estimate of the relative humidity of the gas flowing through the passage based on the outputs of the first and second sensors. The apparatus according to any one of claims 1 to 14.

16. The apparatus according to any one of claims 1 to 15, wherein the sensor is disposed adjacent to the patient or directly along the passage, in a portion of the gas passage remote from the humidified gas supply source, such as a position along the gas supply tube to the patient.

17. The apparatus according to any one of claims 1 to 16, wherein the humidified gas supply includes a humidifier having a heater and a reservoir for containing an amount of water adjacent to the heater.

18. The apparatus according to claim 17, wherein the humidifier includes a heater plate, and the reservoir includes a removable container that contacts the heater plate during use.

19. The apparatus according to claim 17 or 18, wherein the humidified gas supply source includes a blower, and the output of the blower is provided to the inlet of the humidifier.

20. The device according to claim 19, wherein the blower and the humidifier heater are arranged in the same housing.

21. A device for supplying humidified gas to a patient, comprising: a gas supply passage defined by an inner surface of a passage wall; a sensor embedded in the wall of the passage or arranged on an outer surface of the wall of the passage; a controller adapted to receive an output from the sensor and to derive an estimate of a characteristic of a gas flowing through the passage or a control output for a humidified gas supply source from the output of the sensor; and wherein the wall of the passage separates a gas flow in the passage from the sensor.

22. A humidified gas supply device for a patient as described herein with reference to FIGS. 2a to 12.

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