Source: https://patents.google.com/patent/US8733349B2/en
Timestamp: 2018-12-11 13:59:20
Document Index: 393809999

Matched Legal Cases: ['Application No. 587113', 'Application No. 596092', 'Application No. 610299', 'Application No. 596092', 'Application No. 600986', 'Application No. 2010206053']

US8733349B2 - Wire heated tube with temperature control system, tube type detection, and active over temperature protection for humidifier for respiratory apparatus - Google Patents
Wire heated tube with temperature control system, tube type detection, and active over temperature protection for humidifier for respiratory apparatus Download PDF
US8733349B2
US8733349B2 US12847021 US84702110A US8733349B2 US 8733349 B2 US8733349 B2 US 8733349B2 US 12847021 US12847021 US 12847021 US 84702110 A US84702110 A US 84702110A US 8733349 B2 US8733349 B2 US 8733349B2
US12847021
US20110023874A1 (en )
Timothy Nicholas Shadie
This application claims the benefit of U.S. Applications 61/230,128, filed Jul. 31, 2009, and 61/334,761, filed May 14, 2010, the entire contents of each incorporated herein by reference.
The entire contents of each of WO 2010/031126 A1 and U.S. Patent Application Publications 2008/0105257 A1, 2009/0223514 A1, and 2010/0116272 A1 are incorporated herein by reference.
None of these prior art devices provides an entirely satisfactory solution to the provision of comfortable humidified breathable gas to the patient, nor the ease of construction and hygiene requirements and the energy and patient comfort requirements at startup.
According to one aspect, a heated tube is provided to a respiratory apparatus to deliver the warm and/or humidified air and minimise condensation in the tube.
According to another aspect, a heated tube is provided that allows for measurement and/or control of the delivered air temperature.
According to yet another aspect, a failsafe mechanism may be provided to ensure the delivered air temperature does not exceed a safe temperature limit.
According to a further aspect, it is possible to automatically identify the size of the heated tube, e.g. whether the heated tube attached to the humidifier and/or has a 15 mm or 19 mm bore/internal diameter. Automatic adjustment of system performance with different tube sizes reduces need for clinician/patient adjustment of system settings.
According to a still further aspect, the pneumatic performance of the respiratory apparatus may be compensated, for example in the blower drive circuitry, depending on which heated tube is connected.
According to another aspect, it is possible to detect failures in the heated tube, such as high resistance hot spots in the wires or short circuits between the wires part way down the length of the tube.
According to still another aspect, the heated tube may be electrically and pneumatically connected to the humidifier and/or flow generator in a simple attachment process.
According to a further aspect, a heated tube is provided with an electrical circuit that provide a low profile tube and cuff mouldings.
According to yet another aspect, a tube configuration allows for high volume production. The electronic circuit may use standard components readily available for high production volumes.
As schematically shown in FIG. 1, a Positive Airway Pressure (PAP) system, for example a Continuous Positive Airway Pressure (CPAP) system, generally includes a PAP device 10, an air delivery conduit 20 (also referred to as a tube or tubing), and a patient interface 50. In use, the PAP device 10 generates a supply of pressurized air that is delivered to the patient via an air delivery conduit 20 that includes one end coupled to the outlet of the PAP device 10 and an opposite end coupled to the inlet of the patient interface 50. The patient interface comfortably engages the patient's face and provides a seal. The patient interface or mask may have any suitable configuration as is known in the art, e.g., full-face mask, nasal mask, oro-nasal mask, mouth mask, nasal prongs, etc. Also, headgear may be utilized to comfortably support the patient interface in a desired position on the patient's face.
As shown in FIGS. 4 and 5, the humidifier 15 is connectable to the flow generator 12 by connectors, or latches, 24. The latches 24 may be, for example, spring biased latches that engage corresponding recesses (not shown) in the flow generator 12. An electrical connector 26 is provided to electrically connect the flow generator 12 to the humidifier 14. Electrical power may be provided from the flow generator 12 to the humidifier 14, although it should be appreciated that the humidifier may be provided with its own power source. Control signals may also be provided from the flow generator 12 to the humidifier 14 through the electrical connector 26.
As shown in FIG. 4, the tub 14 comprises a tub lid 86 that is configured to direct a flow of breathable gas generated by the flow generator 12 along a channel 90 in the tub lid 86 and through an outlet 92 of the channel 90 into the tub 14. The humidifier chamber 16 includes an air inlet 22 configured to receive the flow of breathable gas generated by the flow generator 12 when the humidifier 15 is connected to the flow generator 12 by the latches 24. The inlet 22 directs the flow into the channel 90 in the tub top 86 of the water tub 20. The flow is directed by the channel 90 to the outlet 92 into the water tub 14. The tub 14 includes an outlet 88 for the humidified flow of breathable gas. A tube connector 70 with a scaling ring 76 (FIG. 7) is provided at a rear portion of the humidifier 15 in communication with the outlet 88. It should be appreciated that the tube connector 70 may be provided on a side, or the front, of the humidifier 15. The tube connector 70 is configured for connection to a hose, tube, or conduit to a tube that is configured to deliver the humidified flow to patient interface, e.g. a mask, as described in more detail herein.
It should be appreciated that the humidifier 15 may include its own control system, or controller, for example, a microprocessor provided on a printed circuit board (PCB). The PCB may be located in the wall of the humidifier chamber 16 and may include a light, e.g. an LED, to illuminate the contents of the tub 14 to permit visual inspection of the water level. It should also be appreciated that the flow generator 12 comprises a control system, or controller, that communicates with the controller of the humidifier 15 when the flow generator 12 and the humidifier 15 are electrically connected. It should be further appreciated that the flow generator and/or the humidifier may include a plurality of sensors, including for example, an ambient humidity sensor that may be configured to detect, for example, absolute ambient humidity and which may include an absolute humidity sensor or a temperature sensor to detect an ambient temperature and a relative humidity sensor to detect an relative humidity from which the ambient absolute humidity may be calculated. The plurality of sensors may also include, for example, an ambient pressure sensor to detect an ambient pressure, a flow sensor to detect a flow of breathable gas generated by the flow generator, and/or a temperature sensor to detect a temperature of a supply of water contained in the tub 14 of the humidifier 15 or the temperature of the heating plate of the humidifier 15. Such an arrangement is shown, for example, in U.S Patent Application Publication 2009/0223514 A1. The PAP system 10 may be operated according to various control algorithms stored in the controller(s) of the flow generator 12 and/or the humidifier 15. Such control algorithms are disclosed in, for example, U.S. Patent Application Publication 2009/02223514 A1.
Referring to FIG. 7, the humidifier comprises the tube connector 70 with the sealing ring 76 and a tube electrical connector 75. The tube connector 70 and the tube electrical connector 75 provide the ability to connect both a standard tube and a heated tube. As shown in FIG. 7, the tube electrical connector 75 comprises a plurality of contacts 78. The tube electrical connector 75 and the contacts 78 are provided separately from the tube connector 70. A heated tube having corresponding electrical connections, e.g. terminals, may be provided in a rotational snap fit with the tube electrical connector 75 as described in more detail below. This type of connection provides ease of connection and reduces the tolerance stack of the respiratory apparatus 10. A cover 132 may be connected to the back wall of the humidifier 15 to cover the tube connector 75 and the contacts 78 when a non-heated tube is connected to the tube connector 70. The cover 132 may be formed of a pliable rubber or other suitable flexible material. Alternatively the cover 132 may be a separate component, not attached to the humidifier that may be inserted over the tube electrical connector 75.
The opening of the cuff 330(1) includes a radial lip seal or sealing lip 331 along the interior surface thereof. As shown in FIG. 13, the radial lip seal 331, in its relaxed, undeformed shape, provides an internal diameter dl that is smaller than the external diameter of the tube connector 70. For example, the internal diameter may be less than about 22 mm (e.g., about 19-21 mm or less) for use with a standard 22 mm connector. In use, as best shown in FIG. 14, the sealing lip 331 is structured to resiliently deform upon engagement with the tube connector 70 so as to provide a gas tight seal against the exterior surface of the tube connector 70. For example, the sealing lip 331 provides a flexible protrusion structured to resiliently deflect from a first position (FIG. 13) and into a second position (FIG. 14) within a cut-out 335.
The sensor 45 is provided to a fixture 46 within the cuff. In the illustrated embodiment, the fixture 46 is wing-shaped (e.g. air-foil shaped) to optimize convective heat transfer over a range of flow rates, while minimizing noise or pressure drop. However, the fixture 46 may have other suitable shapes and/or textures. The cuff 330(2) may be formed by, for example, overmolding on a pre-block 47, or any method disclosed, for example, in U.S. Patent Application Publication 2008/0105257 A1, which is incorporated herein by reference in its entirety. The sensor 45 may be connected to the wires 504, 506, 508 in the heated tube 320 by a lead frame 48. The temperature sensed by the sensor 45 may be provided as a signal from the middle wire 504 through the lead frame 48 to a controller located in the humidifier 15 and/or the PAP system 10.
As shown in FIG. 18, the sensor 45 may take the form of a thermistor 410 formed of a Negative Temperature Coefficient (NTC) material. As described in more detail below, the middle wire 504 of the three wires 504, 506, 508 of the tube circuit 402 may be connected to the thermistor 410 and provide the temperature sensing signal to the controller. Two wires 506, 508 may be joined together at the lead frame 48 to complete the heating circuit. The third wire 504 provides a connection to the NTC thermistor which may be attached to the mid-point of the heating circuit. The two heating wires 506, 508 may be low ohmic value resistors to apply heat to the tube wall and therefore to the air being delivered to the patient. The signal wire 504 may be fitted with the thermistor 410 located at the patient interface end of the heated tube 320. The signal wire 504 monitors the temperature of the air at the patient interface end of the heated tube and detects any imbalance between the bridge formed by the two heater wires 506, 508. The imbalance may be used to detect a fault condition, for example high impedance or an open circuit and low impedance or a short circuit.
Referring to FIG. 20, a circuit configuration 400 according to a sample embodiment allows control of the tube air temperature using a sensor at the output (mask) end of the tube. The heated tube circuit 402 comprises the three wires 504,506, 508 and the temperature sensor, e.g. the NTC thermistor 410. The heater wires 404, 406, 408 are used in the sensing and control circuit to create a lower cost heating and sensing system with only three wires. As shown in FIG. 18, the three wires 504, 506, 508 of the heated tube circuit 402 are connected to different components of the sensing and control circuit to provide a sensing wire 404, a power supply wire 406 and a ground wire 408. The sensing and control circuit may be provided in a power supply and controller of the humidifier and/or flow generator. Such a power supply and controller is disclosed in, for example, U.S. Patent Application Publication 2008/0105257 A1.
Within the over-temperature control circuit is the heating control circuit which is designed to control the heating of the heated tube to obtain a desired temperature. The desired temperature may be set by the user or determined by the system. The heating control circuit switches the power supply 440 through the heated tube circuit 402 to a ground reference 412. Thus, the temperature sensor 410 moves between ground having 0V and half the supply voltage, e.g. 12V. Heating is supplied to the heated tube circuit 402 from power supply 440 through a second transistor switch 434. Transistor switch 434 is open and closed to turn heating on and off to the heated tube circuit 402 respectively. In one embodiment this transistor switch 434 is switched on and off very rapidly with changes in the duty cycle to control the heating of the tube. However, the switch 434 may be switched on to provide constant heating until a set temperature is reached and then turned off. The temperature of the heated tube is sensed by the temperature sensor 410 and is transmitted through sense wire 404 to sense resistor 426 and sensing circuit 428 comprising amplifier 430. A bias generator circuit 418 provides the source voltage Vcc for the sensing circuit 428 so that the temperature of the heated tube is determined whether the tube is being heated or not. The bias generator circuit 418 generates a reference voltage that is either the Vcc source voltage 414, shown as 5V in this embodiment although other voltages may be used, when the tube heating is off via switch 422 or provides half the voltage supply plus the Vcc source voltage 416, i.e. 5V, when the tube heating is on via switch 424. Thus a constant voltage of Vcc source voltage is provided across the sensing circuit 428 irrespective of the state of the heated tube. The switching of the bias switches 422, 424 is controlled by the transistor switch 434 of the heating control circuit, such that when the transistor switch 434 is closed the tube heating ON switch 424 is active and when the transistor switch 434 is open the tube heating ON switch 424 is inactive. Thus, it is the voltage that is supplied to the heated tube circuit 402 that provides the bias switch.
The circuit configuration may comprise a common ground referenced heating/sensing system with a supply voltage switching to the tube circuit for heating control. An alternative approach is to utilise the supply voltage as both the heating and sensing source voltage and control heating by switching to 0V the tube circuit.
Referring to FIG. 21, a sensing and control circuit configuration 450 according to another sample embodiment allows for discrimination between different values of the temperature sensor (e.g. thermistor value as an indicator of tubing type) to permit changes in system performance to compensate for changes in the characteristics of the tube types (e.g. pressure drop versus bore/internal diameter). For each tube type used within the system there should not be an overlap in the resistances obtained from using the different thermistors within the specified operating temperature range of the heated tube, for example between 0° C. and 45° C., preferably between −5° C. and 50° C. For example, a 15 mm internal diameter heated tube may include a temperature sensor with a thermistor value of 10 kΩ and a 19 mm internal diameter heated tube may include a temperature sensor with a thermistor value of 100 kΩ. FIG. 23 shows the characteristic curves for each of these example thermistor values. This allows the thermistor resistance value (or sensed voltage) to be used to detect the type of heated tube being used in the system. Thus, any compensation for air path performance can be adjusted automatically (without user intervention) for each tube type, if required. It should be appreciated that more than two types of tubes may be detected in the system by using multiple comparator and gains. Detection of the tube type can also be used to adjust the amplifier gain and increase the amplitude of the temperature sense signal for a lower sensitivity (higher value NTC thermistor) circuit.
The tube fault detection system is also able to detect the correct connection of the heated tube to the system. The control system has three connectors attached to the ends of wires 404, 406 and 408 that are adapted for connection with connectors on the ends of the three wires 504, 506 and 508 of the heated tube circuit 402. The connectors are arranged such that the last connectors to connect are those relating to the sensing wire 504. This ensures that if the heated tube is not correctly connected a fault will be detected in the control system as the voltage sensed by sense resistor 426 will be 0V. This fault detection system will detect faults such as short circuits, open circuits, wiring faults or connection faults.
Referring to FIG. 24, a control algorithm may be provided to prevent overheating of the humidifier heating plate. The control algorithm may be run concurrently with any of the PAP system control algorithms disclosed in U.S. Patent Application Publication 2009/0223514 A1. The control algorithm starts in S100 and proceeds to S110. In S110 it is determined if the heating plate temperature THP is lower than a first predetermined heating plate temperature THP1 and whether the sensed temperature TSEN detected by the humidity sensor is higher than a minimum sensed temperature TSENMIN. The first predetermined heating plate temperature THP1 may be the minimum temperature of the humidifier heating plate that is plausible. For example, very cold water may be placed in the humidifier, but ice should not be. So a first predetermined heating plate temperature THP1 may be, for example, between about 0° C. and 4° C., such as about 2° C. The minimum sensed temperature TSENMIN may be a minimum ambient temperature at which the PAP system is recommended to be used. For example, the minimum sensed temperature SENMIN may be between about 3° C. and 8°, such as about 5° C.
Referring to FIG. 29, the humidifier heating plate 900 may comprise a plate 902 formed of a heat conducting material. The heat conducting plate 902 may be made of, for example, metal, such as a nickel chrome alloy or anodized aluminum. A heating element 906 may be provided on the heat conducting plate 902. The heating element 906 may be formed from a resistive film, and may be formed by, for example, stamping or etching a resistive foil. An insulating layer 904 may cover the heating element 906. For stamping, the resistive film 906 is inserted between two insulating films 904. For etching, the resistive film 906, with an attached insulating film 904 on one of its sides, is covered by a second insulating film 904. The insulting film 904 may be formed of, for example, KAPTON®.
As noted with respect to FIG. 23, a 15 mm internal diameter heated tube may include a temperature sensor with a thermistor value of 10 kΩ and a 19 mm internal diameter heated tube may include a temperature sensor with a thermistor value of 100 kΩ The PAP system may be operated over a recommended temperature range. For example, the lowest recommended sensed (ambient) temperature at which the PAP system may be operated is 5° C., and the highest recommended sensed temperature at which the PAP system may be operated is 35° C. If the system is stored at the lowest recommended ambient temperature, e.g. 5° C., it is expected that the system will warm to above the lowest recommended ambient temperature in about 15 minutes. Over the recommended temperature range, the resistance values of the NTC temperature sensor in the heated tube will vary. For example, the temperature sensor in a 15 mm internal diameter heated tube may have a resistance ranging from about 8 kΩ to 28 kΩ, and the temperature sensor in a 19 mm inner diameter heated tube may have a resistance ranging from about 80 kΩ to 750 kΩ. These ranges can be reduced by the heated tube control shown in FIG. 25, in particular by the steps S210, S220, S230, S240, S245 and S250. If the temperature of the heated tube is below the lowest recommended sensed (ambient) temperature (i.e. TSENMIN) for operation of the PAP system, the control prevents heating of the heated tube. If this condition persists for more than 15 minutes (i.e. tMAX1), the control stops the PAP system and displays an unrecoverable error message (i.e. ERROR MESSAGE 4). Control of the heated tube in this manner reduces the resistance range at which the PAP system can heat the heated tube. For example, the 15 mm inner diameter heated tube may be heated across a resistance range of about 8 kΩ to 23 kΩ, and the 19 mm inner diameter heated tube may be heated across a resistance range of about 80 kΩ to 250 kΩ.
To detect the subtle cases, a condition that occurs when the heated tube temperature is unresponsive to significant applied power may be observed. The PAP system may be designed to distribute power between the heating plate of the humidifier and the heated tube. For example, the heated tube may have priority over, for example, 60% of the available power. In the embodiments described in FIGS. 20-22, 36 W are available to the heated tube. The criteria for the decision in S215 of the control algorithm of FIG. 25 may be set based on tests conducted at the extremes of the recommended ambient temperature operating range of the PAP system. At the minimum recommended sensed (ambient) operating temperature of 5° C. and supplying full power to the heated tube, the temperature of the heated tube rose above 15° C. within 3 minutes. A 15° C. temperature increase corresponds to 15 kΩ, for a 15 mm tube and 150 kΩ for a 19 mm tube. Therefore, if the temperature of the heated tube has not risen above 15° C. (i.e. THT1) after 3 minutes (i.e. tMAX2) of 36 W (i.e. PHT1), the control can stop heating the heated tube before the heated tube is in danger of being damaged. It should be appreciated that other times and corresponding temperature measures may be used.
Alternatively, or in addition, to the modem 708, a multiplexor may be provided in order to combine multiple signals onto a single line. The signal wire 404 of the patient interface may be used to encode and decode data for reading sensors and operating controllers by adding a multiplexing circuit to modulate data for the controllers of the patient interface and demodulating signals from the sensor(s) of the patient interface device. A multiplexor 431 may be provided to multiplex the output of the amplifier 430 so that false temperature control or over temperature cut out does not occur. A multiplexor 433 may also be provided to multiplex power onto the signal wire 404. The multiplexor may also handle the de-multiplexing of an incoming signal into the original respective signals. A multiplexor may also be added to circuit configuration 700 to multiplex incoming signals from data 704 and the temperature reading from the NTC sensor 410.
Data 704 can include passive data. Such data, may include, for example the ambient air temperature within a patient interface or the amount of pressure and flow in the patient interface. Data 704 may additionally include commands. For example, the commands may include, an instruction that a particular sensor is to take a measurement or turn off/on, that an active vent on the patient interface is to be controlled, e.g., opened and/or closed or proportionally opened and/or proportionally closed to actively control respiratory pressure and flows. Circuit configuration 700 may provide an encoding feature that encodes data and/or commands before they are sent along the signal wire 404. Similarly, data and/or commands received by circuit configuration 700 may be decoded.
1. A control system for a heated conduit for use in a respiratory apparatus, the control system comprising:
an over-temperature control circuit to prevent overheating of the heated conduit;
a heating control circuit configured to control heating of the heated conduit to obtain a predetermined temperature;
a sensing circuit including a sensing resistor configured to indicate the temperature of a sensor positioned in the heated conduit; and
a bias generator circuit configured to provide a first source voltage to the sensing circuit so that the temperature of the heated conduit is monitored whether the heated conduit is being heated or not.
2. A control system according to claim 1, wherein the over-temperature control circuit comprises a first transistor switch that is turned on when the temperature is below the predetermined temperature and is turned off when the temperature is at or above the predetermined temperature.
3. A control system according to claim 2, wherein the predetermined temperature is within a range of about 30° C. to about 45° C.
4. A control system according to claim 2, wherein the over-temperature control circuit further comprises a first comparator that controls switching of the first transistor switch by comparing a reference voltage representing the predetermined temperature to a voltage determined from a first amplifier of the sensing circuit.
5. A control system according to claim 4, further comprising a multiplexer to multiplex an output of the first amplifier.
6. A control system according to claim 1, wherein the heating control circuit is configured to switch the power supply from the power supply and controller through a tube circuit of the heated conduit to a ground reference so that a temperature sensor of the tube circuit receives between zero volts and half a supply voltage of the power supply.
7. A control system according to claim 6, wherein power is supplied to the tube circuit from the power supply through a second transistor switch that is switched on and off to turn heating on and off, respectively, to the tube circuit.
8. A control system according to claim 7, wherein the second transistor switch is switched on and off with changes in a duty cycle.
9. A control system according to claim 7, wherein the second transistor switch is switched on to provide constant heating until the predetermined temperature is reached and is then switched off.
10. A control system according to claim 7, wherein when the second transistor switch is closed the first source voltage and half the supply voltage is applied to the sensing circuit and when the second transistor switch is open the first source voltage is applied to the sensing circuit.
11. A control system according to claim 7, wherein a signal from a temperature sensor of the tube circuit is provided to a first amplifier of the sensing circuit and the first amplifier produces a voltage that represents the temperature of the flow in the heated conduit, and the second transistor switch is open and closed to modulate the power supplied to the tube circuit to maintain the predetermined temperature.
12. A control system according to claim 11, further comprising a multiplexer to multiplex the output of the first amplifier.
13. A control system according to claim 1, wherein the control system is configured to detect an internal diameter of the heated conduit connected to the respiratory apparatus.
14. A control system according to claim 13, wherein the control system detects the internal diameter of the heated conduit based on a resistance value of a temperature sensor of a tube circuit of the heated conduit.
15. A control system according to claim 14, wherein the resistance values of the temperature sensor for differing internal diameters do not overlap within a specified operating temperature.
16. A control system according to claim 15, wherein the specified operating temperature is within a range of about −5° C. to about 50° C.
17. A control system according to claim 11, further comprising a second comparator configured to compare the voltage across the sensing resistor sensed by the first amplifier with a reference voltage that identifies a heated conduit having a predetermined internal diameter corresponding to a predetermined resistance of the temperature sensor.
18. A control system according to claim 17, further comprising a second amplifier configured to add gain to the sensed voltage if the temperature sensor resistance corresponds to a first predetermined internal diameter and to add no gain to the sensed voltage if the temperature sensor resistance corresponds to a second predetermined internal diameter.
19. A control system according to claim 17, wherein the control system is configured to use a different reference voltage for each predetermined internal diameter.
20. A control system according to claim 18, wherein the first predetermined internal diameter is 19 mm and the second predetermined internal diameter is 15 mm.
21. A control system according to claim 17, wherein the control system is configured to control operation of a flow generator and/or a humidifier of the respiratory apparatus based on the detected internal diameter of the heated conduit.
22. A control system according to claim 21, wherein the control system is configured to adjust an amplitude of a signal generated by the temperature sensor based on the detected internal diameter of the heated conduit.
23. A control system according to claim 21, wherein the control system is configured to adjust a signal gain dependent on the detected internal diameter of the heated conduit to stop supplying power when the detected temperature exceeds the predetermined temperature.
24. A control system according to claim 1, further comprising a fault detection circuit configured to detect a fault in a connection of the heated conduit to the respiratory apparatus and/or a fault in a tube circuit of the heated conduit.
25. A control system according to claim 24, wherein the fault detection circuit comprises three resistors, a third comparator, a fourth comparator, and a second source voltage.
26. A control system according to claim 25, wherein the third and fourth comparators compare the voltage received from the first amplifier with threshold voltages across the three resistors.
27. A control system according to claim 24, wherein the fault comprises a) a discontinuity in any of at least three wires of the heated conduit and/or b) arcing and/or a bad connection between the heated conduit and a flow generator and/or a humidifier of the respiratory apparatus and/or between the heated conduit and a patient interface and/or c) low voltage.
28. A control system according to claim 24, wherein the power supply and controller is configured to cease supplying power in the event of a fault in the temperature sensor.
29. A control system according to claim 1, wherein the sensing circuit comprises a signal wire configured to receive signal data from the sensor in the heated conduit and transmit control signals to the heated conduit.
30. A control system according to claim 29, further comprising a modem to modulate the control signals and demodulate the signal data.
31. A control system according to claim 30, further comprising a multiplexer to multiplex the power supply to the signal wire.
32. A conduit for use in a respiratory apparatus for delivering breathable gas to a patient, the conduit comprising:
a helical rib on an outer surface of the tube;
a control system configured to control the conduit comprising:
a power supply to provide power to the conduit;
an over-temperature control circuit to prevent overheating of the conduit;
a heating control circuit configured to control heating of the conduit to obtain a predetermined temperature; and
a sensing circuit including a sensing resistor configured to indicate the temperature of a sensor positioned in the conduit; and a bias generator circuit configured to provide a first source voltage to the sensing circuit so that the temperature of the conduit is monitored whether the conduit is being heated or not;
a tube circuit comprising at least three wires supported by the helical rib in contact with the outer surface of the tube and a temperature sensor connected to at least one of the three wires to provide a signal to a power supply and the control system; and
a first cuff connected to a first end of the tube and a second cuff connected to a second end of the tube, the first cuff being configured to be connected to a patient interface of the respiratory apparatus and the second cuff being configured to be connected to a flow generator or humidifier of the respiratory apparatus.
33. A conduit according to claim 32, wherein the at least three wires are copper or enamelle copper.
34. A conduit according to claim 32, wherein the temperature sensor is provided in a fixture in the first cuff.
35. A conduit according to claim 34, wherein the fixture extends radially inward.
36. A conduit according to claim 34, wherein the fixture is airfoil shaped.
37. A conduit according to claim 32, wherein a first wire of the at least three wires connected to the temperature sensor comprises a sensing wire, a second wire is configured to be connected to a power supply of the flow generator or humidifier, and a third wire is configured to be a ground wire.
38. A conduit according to claim 37, wherein the first wire is between the second and third wires.
39. A conduit according to claim 32, wherein the temperature sensor comprises a thermistor.
40. A conduit according to claim 39, wherein the thermistor comprises a Negative Temperature Coefficient (NTC) material.
41. A conduit according to claim 40, wherein the tube has a diameter of about 15 mm and the thermistor has a resistance of 10,000Ω.
42. A conduit according to claim 40, wherein the tube has a diameter of about 19 mm and the thermistor has a resistance of about 100,000Ω.
43. A respiratory apparatus configured for delivering breathable gas to a patient, comprising:
a flow generator to generate a supply of breathable gas to be delivered to the patient;
a humidifier to vaporize water and to deliver water vapor to humidify the supply of breathable gas;
a first gas flow path leading from the flow generator to the humidifier;
a second gas flow path leading from the humidifier to a patient interface, at least the second gas flow path comprises a conduit according to claim 32; and
a power supply and controller configured to supply and control power to the conduit through the second cuff.
44. A respiratory apparatus according to claim 43, wherein the power supply and controller comprises an over-temperature control circuit to prevent overheating of the conduit.
45. A respiratory apparatus according to claim 44, wherein the over-temperature control circuit comprises a first transistor switch that is turned on when a temperature is below a predetermined temperature and is turned off when the temperature is at or above the predetermined temperature.
46. A respiratory apparatus according to claim 45, wherein the predetermined temperature is within a range of about 30° C. to about 45° C.
47. A respiratory apparatus according to claims 44, wherein the over-temperature control circuit further comprises a first comparator that controls switching of the first transistor switch by comparing a reference voltage representing the predetermined temperature to a voltage determined from a first amplifier of a sensing circuit.
48. A respiratory apparatus according to claim 47, further comprising a multiplexer to multiplex an output of the first amplifier.
49. A respiratory apparatus according to claim 47, wherein the power supply and controller further comprises a heating control circuit configured to control heating to obtain a desired temperature.
50. A respiratory apparatus according to claim 49, wherein the heating control circuit is configured to switch the power supply from the power supply and controller through the tube circuit to a ground reference so that the temperature sensor of the tube circuit receives between zero volts and half the supply voltage of the power supply and controller.
51. A respiratory apparatus according to claim 50, wherein power is supplied to the tube circuit from the power supply and controller through a second transistor switch that is switched on and off to turn heating on and off, respectively, to the tube circuit.
52. A respiratory apparatus according to claim 51, wherein the second transistor switch is switched on and off with changes in a duty cycle.
53. A respiratory apparatus according to claim 51, wherein the second transistor switched is switched on to provide constant heating until the desired temperature is reached and is then switched off.
54. A respiratory apparatus according to claim 49, wherein the sensing circuit further comprises a sensing resistor.
55. A respiratory apparatus according to claim 51, wherein when the second transistor switch is closed the source voltage and half the power supply voltage is applied to the sensing circuit and when the second transistor switch is open the source voltage is applied to the sensing circuit.
56. A respiratory apparatus according to claim 49, wherein the signal from the temperature sensor is provided to the first amplifier and the first amplifier produces a voltage that represents the temperature of the flow in the tube, and the second transistor switch is open and closed to modulate the power supplied to the tube circuit to maintain the desired temperature.
57. A respiratory apparatus according to claim 56, further comprising a multiplexer to multiplex the output of the first amplifier.
58. A respiratory apparatus according to claim 43, wherein the power supply and controller is configured to detect the internal diameter of the tube connected to the humidifier or flow generator.
59. A respiratory apparatus according to claim 58, wherein the power supply and controller detects the internal diameter of the tube based on a resistance value of the temperature sensor.
60. A respiratory apparatus according to claim 59, wherein the resistance values of the temperature sensor for differing internal diameters do not overlap within a specified operating temperature.
61. A respiratory apparatus according to claim 59, wherein the specified operating temperature is within a range of about −5° C. to about 50° C.
62. A respiratory apparatus according to claim 58, wherein the power supply and controller comprises a second comparator configured to compare the voltage across the sensing resistor sensed by the first amplifier with a reference voltage that identifies a tube having a predetermined internal diameter corresponding to a predetermined resistance of the temperature sensor.
63. A respiratory apparatus according to claim 62, wherein the power supply and controller is configured to use a different reference voltage for each predetermined internal diameter.
64. A respiratory apparatus according to claim 62, wherein the power supply and controller comprises a second amplifier configured to add gain to the sensed voltage when the temperature sensor resistance corresponds to a first predetermined internal diameter and to add no gain to the sensed voltage when the temperature sensor resistance corresponds to a second internal diameter.
65. A respiratory apparatus according to claim 64, wherein the first predetermined internal diameter is 19 mm and the second predetermined internal diameter is 15 mm.
66. A respiratory apparatus according to claim 58, wherein the power supply and controller is configured to control operation of the flow generator and/or humidifier based on the detected internal diameter of the conduit.
67. A respiratory apparatus according to claim 66, wherein the power supply and controller is configured to adjust the amplitude of the signal generated by the temperature sensor based on the detected internal diameter of the conduit.
68. A respiratory apparatus according to claim 66, wherein the power supply and controller adjusts a signal gain dependent on the detected internal diameter of the conduit to stop supplying power when the detected temperature exceeds the predetermined temperature.
69. A respiratory apparatus according to claim 43, wherein the power supply and controller is configured to detect connection of the conduit to the humidifier and/or flow generator.
70. A respiratory apparatus according to claim 69, wherein the conduit is configured to connect to the power supply and controller by rotating the second cuff relative to the humidifier and/or flow generator.
71. A respiratory apparatus according to claim 70, wherein the second cuff is configured to connect to the humidifier and/or flow generator by a bayonet connection.
72. A respiratory apparatus according to claim 69, wherein the first wire of the at least three wires that connects to the power supply and controller is grounded.
73. A respiratory apparatus according to claim 72, wherein the last wire of the at least three wires that connects to the power supply and controller is the wire connected to the temperature sensor.
74. A respiratory apparatus according to claim 73, wherein the last wire is configured to receive signal data from the temperature sensor and transmit control signals to the conduit.
75. A respiratory apparatus according to claim 74, wherein the power supply and controller further comprises a modem to modulate the control signals and demodulate the signal data.
76. A respiratory apparatus according to claim 48, wherein the power supply and controller comprises a multiplexer to multiplex the power supply.
77. A respiratory apparatus according to claim 73, wherein the power supply and controller comprises a tube fault detection circuit configured to detect a fault in the connection of the conduit to the flow generator and/or humidifier and/or a fault in the tube circuit of the conduit.
78. A respiratory apparatus according to claim 77, wherein the tube fault detection circuit comprises three resistors, a third comparator, a fourth comparator, and a second source voltage.
79. A respiratory apparatus according to claim 78, wherein the third and fourth comparators compare the voltage received from the first amplifier with threshold voltages across the three resistors.
80. A respiratory apparatus according to claim 77, wherein the fault comprises a) a discontinuity in any of the at least three wires of the conduit, b) arcing and/or a bad connection between the conduit and the flow generator and/or humidifier and/or between the conduit and the patient interface, and/or c) low voltage.
81. A respiratory apparatus according to claims 77, wherein the power supply and controller is configured to cease supplying power in the event of a fault in the temperature sensor.
82. A PAP system configured for delivering breathable gas to a patient, comprising:
a humidifier including a heating plate to vaporize water and deliver water vapor to humidify the supply of breathable gas;
a heated tube configured to heat and deliver the humidified supply of breathable gas to the patient; and
a control system comprising: a power supply to provide power to the heated tube; an over-temperature control circuit to prevent overheating of the heated tube; a heating control circuit configured to control heating of the heated tube to obtain a predetermined temperature; a sensing circuit including a sensing resistor configured to indicate the temperature of a sensor positioned in the heated tube; and a bias generator circuit configured to provide a first source voltage to the sensing circuit so that the temperature of the heated tube is monitored whether the heated tube is being heated or not,
wherein the power supply is configured to supply power to the heating plate and the heated tube, and
the control system is configured to control the power supply to prevent overheating of the heating plate and the heated tube.
83. A PAP system according to claim 82, wherein the control system prevents heating of the heating plate when a temperature of the heating plate is less than a first predetermined heating plate temperature and a sensed ambient temperature is above a minimum sensed temperature for a time less than a first predetermined maximum time.
84. A PAP system according to claim 83, wherein the PAP system displays a first error message on a display on either the flow generator or the humidifier when the temperature of the heating plate is less than the first predetermined heating plate temperature and the sensed temperature is above the minimum sensed temperature for the time less than the first predetermined maximum time.
85. A PAP system according to claim 84, wherein the first error message is acknowledgeable by the patient or an operator through inputs on the flow generator or the humidifier.
86. A PAP system according to claim 84, wherein the control system stops the PAP system when the temperature of the heating plate is less than the first predetermined heating plate temperature and the sensed temperature is above the minimum sensed temperature for a time greater than the first predetermined maximum time.
87. A PAP system according to claim 86, wherein the PAP system displays a second error message on the display when the temperature of the heating plate is less than the first predetermined heating plate temperature and the sensed temperature is above the minimum sensed temperature for the time greater than the first predetermined maximum time.
88. A PAP system according to claim 87, wherein the second error message can not be acknowledged by the patient or operator.
89. A PAP system according to claim 83, wherein the first predetermined heating plate temperature is within a range of about 0° C. and about 4° C.
90. A PAP system according to claim 89, wherein the first predetermined heating plate temperature is about 2° C.
91. A PAP system according to claim 89, wherein the minimum sensed temperature is within a range of about 3° C. and about 8° C.
92. A PAP system according to claim 91, wherein the minimum sensed temperature is about 5° C.
93. A PAP system according to claim 91, wherein the first predetermined maximum time is between about 10 and 25 minutes.
94. A PAP system according to claim 93, wherein the first predetermined maximum time is about 15 minutes.
95. A PAP system according to claim 83, wherein the control system prevents heating the heating plate when the temperature of the heating plate is less than a second predetermined heating plate temperature and the sensed temperature is higher than a first maximum sensed temperature.
96. A PAP system according to claim 95, wherein the control system prevents heating the heating plate when the sensed temperature is higher than a second maximum sensed temperature that is higher than the first maximum sensed temperature.
97. A PAP system according to claim 95, wherein the control system stops the PAP system when, 1) the temperature of the heating plate is less than a second predetermined heating plate temperature and the sensed temperature is higher than the first maximum sensed temperature, or 2) the sensed temperature is higher than a second maximum sensed temperature that is higher than the first maximum sensed temperature.
98. A PAP system according to claim 95, wherein the PAP system displays a second error message when, 1) the temperature of the heating plate is less than a second predetermined heating plate temperature and the sensed temperature is higher than the first maximum sensed temperature, or 2) the sensed temperature is higher than a second maximum sensed temperature that is higher than the first maximum sensed temperature.
99. A PAP system according to claim 95, wherein the second predetermined heating plate temperature is within a range of about 22° C. and about 30° C.
100. A PAP system according to claim 99, wherein the second predetermined heating plate temperature is about 25° C.
101. A PAP system according to 99, wherein the second maximum sensed temperature is within a range of about 45° C. and about 55° C.
102. A PAP system according to claim 101, wherein the second maximum sensed temperature is about 50° C.
103. A PAP system according to claim 82, wherein the control system prevents heating the heated tube when a temperature of the heated tube is less than a minimum sensed temperature for a time less than a first predetermined maximum time.
104. A PAP system according to claim 103, wherein the control system displays a third error message on the display when the temperature of the heated tube is less than the minimum sensed temperature for the time less than the first predetermined maximum time.
105. A PAP system according to claim 104, wherein the third error message is acknowledgeable by the patient or operator through the inputs on the flow generator or the humidifier.
106. A PAP system according to claim 103, wherein the control system stops the PAP system when the temperature of the heated tube is less than the minimum sensed temperature for a time greater than the first predetermined maximum time.
107. A PAP system according to claim 106, wherein the PAP system displays a fourth error message when the temperature of the heated tube is less than the minimum sensed temperature for a time greater than the first predetermined maximum time.
108. A PAP system according to claim 103, wherein the control system prevents heating of the heated tube when a percentage of power supplied from the power supply to the heated tube is equal to or greater than a predetermined power percentage, the temperature of the heated tube is lower than a predetermined heated tube temperature, and an elapsed time is greater than a second predetermined maximum time that is less than the first predetermined maximum time.
109. A PAP system according to claim 108, wherein the control system stops the PAP system when the percentage of power supplied from the power supply to the heated tube is equal to or greater than the predetermined power percentage, the temperature of the heated tube is lower than the predetermined heated tube temperature, and the elapsed time is greater than the second predetermined maximum time.
110. A PAP system according to claim 109, wherein the PAP system displays the fourth error message when the percentage of power supplied from the power supply to the heated tube is equal to or greater than the predetermined power percentage, the temperature of the heated tube is lower than the predetermined heated tube temperature, and the elapsed time is greater than the second predetermined maximum time.
111. A PAP system according to claim 108, wherein the predetermined power percentage is about 60%.
112. A PAP system according to claim 111, wherein the predetermined heated tube temperature is about 15° C.
113. A PAP system according to claim 112, wherein the second predetermined maximum time is about three minutes.
114. A PAP system according to claim 82, wherein the heating plate comprises a plate formed of a heat conducting material, a heating element formed of a resistive foil provided on the plate, a thermistor formed of a resistive foil, and at least one insulating film that cover at least the heating element.
115. A PAP system according to claim 114, wherein the heating element and the thermistor are integrally formed.
116. A PAP system according to claim 114, wherein the heating element and the thermistor are separately formed.
117. A PAP system according to claim 116, wherein the heating element is formed of a first resistive material and the thermistor is formed of a second resistive material different from the first resistive material.
118. A PAP system according to claim 117, wherein at least one wire for delivering a signal to and from the thermistor is ultrasonically welded to the thermistor.
119. A PAP system according to claim 118, wherein the at least one wire is ultrasonically welded to the thermistor and the heating element.
120. A PAP system according to claim 114, wherein the at least one insulating film comprises two insulating films, a first insulating film that covers the heating element and a second insulating film that covers the thermistor.
121. A method of controlling a heated conduit connected to a respiratory apparatus, the method comprising:
supplying power to the heated conduit;
continuously monitoring a temperature of a sensor positioned in the heated conduit; and
controlling the power supply to the heated conduit via a control system to obtain a predetermined temperature, the control system comprising:
122. A method according to claim 121, wherein continuously monitoring the temperature of the sensor comprises continuously applying the first source voltage to the sensing resistor configured to indicate the temperature of the sensor positioned in the heated conduit.
123. A method according to claim 122, wherein controlling the power supplied to the heated conduit comprises turning on a first transistor switch when the temperature is below the predetermined temperature and turning off the first transistor switch when the temperature is at or above the predetermined temperature.
124. A method according to claim 121, wherein the predetermined temperature is between the range of about 30° C. and about 45° C.
125. A method according to claim 123, wherein turning the first transistor switch on and off comprises comparing a reference voltage representing the predetermined temperature to a voltage determined from a first amplifier connected to the sensing resistor.
126. A method according to claim 125, further comprising:
multiplexing an output of the first amplifier.
127. A method according to claim 121, further comprising:
switching the power supply through a tube circuit of the heated conduit to a ground reference so that the sensor receives between zero volts and half a supply voltage of the power supply.
128. A method according to claim 127, further comprising:
supplying power to the tube circuit through a second transistor switch; and
switching the second transistor switch on and off to turn heating on and off, respectively, to the tube circuit.
129. A method according to claim 128, wherein switching the second transistor switch on and off comprises changing a duty cycle of the power supply.
130. A method according to claim 128, wherein switching the second transistor switched on and off comprises switching the second transistor switch on to provide constant heating until the predetermined temperature is reached and then switching the second transistor switch off.
131. A method according to claim 128, wherein when the second transistor switch is on the first source voltage and half the supply voltage is applied to the sensing resistor and when the second transistor switch is off the first source voltage is applied to the sensing resistor.
132. A method according to claim 128, further comprising:
providing a signal from the sensor to the first amplifier;
producing a voltage with the first amplifier that represents the temperature of the flow in the heated conduit; and
opening and closing the second transistor switch to modulate the power supply to maintain the predetermined temperature.
133. A method according to claim 132, further comprising:
multiplexing the output of the first amplifier.
134. A method according to claim 121, further comprising:
detecting an internal diameter of the heated conduit connected to the respiratory apparatus.
135. A method according to claim 134, wherein detecting the internal diameter of the heated conduit comprises detecting a resistance value of the sensor.
136. A method according to claim 135, wherein the resistance values of the sensor for differing internal diameters do not overlap within a specified operating temperature.
137. A method according to claim 136, wherein the specified operating temperature is between the range of about −5° C. and about 50° C.
138. A method according to claim 122, further comprising:
comparing the voltage across the sensing resistor with a reference voltage that identifies a heated conduit having a predetermined internal diameter corresponding to a predetermined resistance of the sensor.
139. A method according to claim 138, further comprising:
adding gain to the voltage across the sensing resistor if the sensor resistance corresponds to a first predetermined internal diameter; and
adding no gain to the voltage across the sensing resistor if the sensor resistance corresponds to a second predetermined internal diameter.
140. A method according to claim 139, further comprising:
using a different reference voltage for each predetermined internal diameter.
141. A method according to claim 139, wherein the first predetermined internal diameter is 19 mm and the second predetermined internal diameter is 15 mm.
142. A method according to claim 134, further comprising:
controlling a flow generator and/or a humidifier of the respiratory apparatus based on the detected internal diameter of the heated conduit.
143. A method according to claim 142, further comprising:
adjusting an the amplitude of a signal generated by the sensor based on the detected internal diameter of the heated conduit.
144. A method according to claim 143, further comprising:
adjusting a signal gain dependent on the detected internal diameter of the heated conduit to stop supplying power when the detected temperature exceeds the desired temperature.
145. A method according to claim 121, further comprising:
detecting a fault in a connection of the heated conduit to the respiratory apparatus and/or a fault in a tube circuit of the heated conduit.
146. A method according to claim 145, detecting a fault comprises comparing the voltage from the first amplifier with threshold voltages across at least one resistor.
147. A method according to claim 145, wherein the fault comprises a) a discontinuity in any of at least three wires of the heated conduit and/or b) arcing and/or a bad connection between the heated conduit and a flow generator and/or a humidifier of the respiratory apparatus and/or between the heated conduit and a patient interface and/or c) low voltage.
148. A method according to claim 145, further comprising:
ceasing the power supply in the event of a fault in the sensor.
149. A method according to claim 121, further comprising:
receiving signal data from the sensor in the heated conduit; and
transmitting control signals to the heated conduit.
150. A method according to claim 149, further comprising:
modulating the control signals; and
demodulating the signal data.
151. A control system according to claim 1, wherein the bias generator circuit is configured to provide the first source voltage to the sensing circuit regardless of whether the power supply provides power to a heater in the heated conduit.
152. A control system according to claim 1, wherein a heating voltage supplied to the heating control circuit from the power supply provides a switch for the bias generator circuit.
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Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:BATH, ANDREW RODERICK;RICHMOND, DONALD ANGUS;ROW, NATHAN JOHN;AND OTHERS;SIGNING DATES FROM 20100806 TO 20100809;REEL/FRAME:024867/0283