Low cost CPAP flow generator and humidifier assembly

• US 8,739,780 B2
• Filed: 08/15/2006
• Issued: 06/03/2014
• Est. Priority Date: 08/15/2005
• Status: Active Grant

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Tang, Zhuo Ran, Tarakci, Cem, Snow, John Michael, Lee, Kenneth, Farrugia, Steven, Doudkine, Dmitri Anotolievich, Smith, Ian Malcolm
• Primary Examiner(s): DOUGLAS, STEVEN O
• Application Number:
  US11/988,934
• Publication Number:
  US 20090229606A1
• Time in Patent Office: 2,849 Days
• Field of Search: 128/203.14, 128/202.27, 128/204.17, 128/204.18, 128/204.21
• US Class Current: 128/203.14
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/0057 Pumps therefor
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/1075 by influencing the temperature A61M16/1045 takes precedence
• CPC Class Codes: A61M 16/109 the humidifying liquid or the beneficial agent
• CPC Class Codes: A61M 16/142 with semi-permeable walls separating the liquid from the respiratory gas
• CPC Class Codes: A61M 16/16 Devices to humidify the respiration air A61M16/1045 takes precedence
• CPC Class Codes: A61M 2205/3368 Temperature
• CPC Class Codes: A61M 2205/3561 local, e.g. within room or hospital
• CPC Class Codes: A61M 2205/3584 using modem, internet or bluetooth

Abstract

A CPAP device wherein humidification detection and/or control is performed by a microprocessor of the CPAP device without requiring a separate humidification control chip. The microprocessor may also control the flow generator motor and the flow generator display. Further, the microprocessor may include code to prevent ‘brown-out’, and/or to detect the availability (connection and/or operability) of the humidifier. Humidifier detection may be carried out using power consumption or temperature sensor signal analysis, e.g., facilitated by use of a pull-up resistor.

Claims

1. A continuous positive airway pressure (CPAP) device comprising:

a flow generator including a microprocessor;

a humidifier detachably coupled to the flow generator; and

a temperature sensor in communication with the humidifier and adapted to produce a voltage signal provided to the flow generator microprocessor,

wherein the microprocessor is programmed with a humidifier control program adapted to control power supply to the humidifier in accordance with output of the temperature sensor, and adapted to detect when the humidifier is substantially empty of water based on the output of the temperature sensor.

2. The CPAP device according to claim 1, wherein the humidifier control program includes machine readable code configured to:

compare the voltage signal of the humidifier temperature (T_H) to a maximum permissible temperature of the humidifier (T_MAX);

turn off power to the humidifier if the temperature is greater than T_MAX; and

turn on or keep on the power to the humidifier if the temperature is not greater than T_MAX.

3. The CPAP device according to claim 2, wherein the comparison of T_H to T_MAX is periodically carried out upon expiration of a predetermined time period and, if T_H is not greater than T_MAX, power is provided to the humidifier for only a fraction of the predetermined time period.

4. The CPAP device according to claim 3, wherein the fraction is about 5-95% of the predetermined time period.

5. The CPAP device according to claim 3, wherein the predetermined time period is in the range of about 1-10 seconds.

6. The CPAP device according to claim 3, wherein the flow generator is in communication with a main power voltage detector, and the fraction is determined in accordance with the detected main power voltage.

7. The CPAP device according to claim 1, wherein the humidifier control program includes machine readable code configured to:

compare the converted voltage signal of the humidifier temperature (T_H) to a temperature range (T_R), and

turn off or keep off power supply to the humidifier if T_H is within T_R.

8. The CPAP device according to claim 7, wherein, if T_H is not within T_R, the code is configured to:

turn off or keep off power supply to the humidifier if T_H is greater than a maximum allowable temperature (T_MAX), and if T_H is not greater than T_MAX, turn on or keep on the humidifier if T_H is less than a minimum temperature (T_MIN) and turn off or keep off the power supply to the humidifier if T_H is not less than T_MIN.

9. The CPAP device according to claim 1, wherein the humidifier control program includes machine readable code configured to determine whether the humidifier is available.

10. The CPAP device according to claim 9, wherein the microprocessor executes a humidifier control program to:

receive output, and

signal whether the humidifier is available based on the output.

11. The CPAP device according to claim 10, wherein a signal is generated to indicate that the humidifier is not available if the output is not within the possible range of operability of the humidifier.

12. The CPAP device according to claim 10, wherein a signal is generated to indicate that the humidifier is attached and operational if the output is within the possible range of operability of the humidifier.

13. The CPAP device according to claim 11, wherein the possible range of operability is between about 5°

-70°

C.

17. The CPAP device according to claim 1, further comprising a cradle to support the flow generator and the humidifier.

18. The CPAP device according to claim 17, wherein the cradle includes the temperature sensor and a heater plate with a heating element in communication with the humidifier, the temperature sensor being in thermal communication with the heating element.

19. The CPAP device according to claim 1, wherein the temperature sensor comprises a thermistor.

20. The CPAP device according to claim 1, wherein the flow generator includes main electrical components consisting essentially of the microprocessor, a motor, a power supply unit and a display.

21. The CPAP device according to claim 1, wherein the microprocessor is programmed with machine readable code to control the motor and the display.

41. The CPAP device according to claim 1, wherein the microprocessor determines whether the humidifier is substantially empty based upon a rate of change of temperature detected by the temperature sensor.

14. A continuous positive airway pressure (CPAP) device comprising:

a flow generator including a microprocessor;

a humidifier detachably coupled to the flow generator;

a temperature sensor in communication with the humidifier and adapted to produce a voltage signal provided to the flow generator microprocessor, and

an analog-to-digital converter (ADC) and a pull-up resistor in communication with the ADC, wherein the ADC provides a signal to the microprocessor having a first value if the humidifier is not available and a second value, different from the first value, if the humidifier is connected and operable,

wherein the microprocessor is programmed with a humidifier control program adapted to control power supply to the humidifier in accordance with output of the temperature sensor.

15. The CPAP device according to claim 14, wherein the microprocessor includes code to signal availability of the humidifier in accordance with the signal provided from the ADC to the microprocessor via the pull-up resistor.

16. The CPAP device according to claim 14, wherein power is supplied to the humidifier, and if the converted voltage signal from the ADC to the microprocessor indicates power loss attributable only to the pull up resistor, then a signal is generated to indicate unavailability of the humidifier, and wherein if the converted voltage signal indicates power loss which is different from the power loss attributable only to the pull-up resistor, then a signal is generated to indicate availability of the humidifier.

22. A method for controlling a humidifier of a continuous positive airway pressure (CPAP) device, comprising:

monitoring a temperature of the humidifier;

generating a voltage signal representative of the humidifier temperature;

converting the voltage signal to a digital signal;

applying the digital signal to a microprocessor of a flow generator of the CPAP device,

supplying power to the humidifier in accordance with the digital signal, and

determining whether the humidifier is substantially empty of water based upon the digital signal.

23. The method according to claim 22, wherein the microprocessor includes a humidifier control program having machine readable code configured to:

compare the converted voltage signal of the humidifier temperature (T_H) to a maximum permissible temperature of the humidifier (T_MAX);

turn off power to the humidifier if the temperature is greater than T_MAX; and

turn on or keep on the power to the humidifier if the temperature is not greater than T_MAX.

24. The method according to claim 23, further comprising periodically comparing T_H to T_MAX upon expiration of a predetermined time period and, if T_H is not greater than T_MAX, providing power to the humidifier for only a fraction of the predetermined time period.

25. The method according to claim 24, wherein the fraction is about 5-95% of the predetermined time period.

26. The method according to claim 24, wherein the predetermined time period is about 1-10 seconds.

27. The method according to claim 22, wherein the microprocessor has a capacity of about 100-150 bytes.

28. The method according to claim 22, further comprising determining whether the humidifier is available.

29. The method according to claim 28, wherein the humidifier availability is determined by:

receiving output from an analogue to digital converter (ADC) and

signaling whether the humidifier is available based on the ADC output.

30. The method according to claim 29, further comprising generating a signal to indicate that the humidifier is not available if the output from the ADC is not within the permissible range of operability of the humidifier.

31. The method according to claim 29, further comprising generating a signal to indicate that the humidifier is attached and operational if the output from the ADC is within the permissible range of operability of the humidifier.

32. The method according to claim 30, wherein the permissible range of operability is between about 5°

-70°

C.

36. The method according to claim 22, further comprising programming the microprocessor with machine readable code to control motor and display functions.

42. The method according to claim 22, wherein the humidifier is determined to be substantially empty based upon a rate of change of the temperature.

33. A method for controlling a humidifier of a continuous positive airway pressure (CPAP) device, comprising:

monitoring a temperature of the humidifier;

generating a voltage signal representative of the humidifier temperature;

converting the voltage signal to a digital signal;

applying the digital signal to a microprocessor of a flow generator of the CPAP device,

supplying power to the humidifier in accordance with the digital signal, and

providing the flow generator with a pull-up resistor.

34. The method according to claim 33, further comprising providing the microprocessor with code to signal availability of the humidifier in accordance with the signal provided to the microprocessor via the pull-up resistor.

35. The method according to claim 33, wherein power is supplied to the humidifier, and if the converted voltage signal supplied to the microprocessor indicates power loss attributable only to the pull-up resistor, then a signal is generated to indicate unavailability of the humidifier, and wherein if the converted voltage signal indicates a power loss which is different from the power loss attributable only to the pull-up resistor, then a signal is generated to indicate availability of the humidifier.

37. A continuous positive airway pressure (CPAP) device comprising:

a flow generator including a microprocessor;

a humidifier detachably coupled to the flow generator; and

a temperature sensor in communication with the humidifier and adapted to produce a voltage signal provided to the flow generator microprocessor,

wherein the microprocessor is programmed with a humidifier control program adapted to detect when the humidifier is substantially empty of water based on the output of the temperature sensor.

38. The CPAP device according to claim 37, wherein the microprocessor determines whether the humidifier is substantially empty based upon a rate of change of temperature detected by the temperature sensor.

39. A method for controlling a humidifier of a continuous positive airway pressure (CPAP) device, comprising:

monitoring a temperature of the humidifier;

generating a voltage signal representative of the humidifier temperature;

converting the voltage signal to a digital signal;

applying the digital signal to a microprocessor of a flow generator of the CPAP device, and

determining whether the humidifier is substantially empty of water based upon the digital signal.

40. The method according to claim 39, wherein the humidifier is determined to be substantially empty based upon a rate of change of the temperature.