Low cost cpap flow generator and humidifier assembly

• US 20090229606A1
• Filed: 08/15/2006
• Published: 09/17/2009
• Est. Priority Date: 08/15/2005
• Status: Active Grant

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Lee, Kenneth, Doudkine, Dmitri Anotolievich, Tarakci, Cem, Snow, John Michael, Smith, Ian Malcolm, Farrugia, Steven Paul, Tang, Zhuo Ran
• Granted Patent: US 8,739,780 B2
• Time in Patent Office: Days
• US Class Current: 128/203.140
• 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 CPAP device wherein humidification control is performed by a microprocessor of the CPAP device without requiring a separate humidification control chip.

2. The CPAP device according to claim 1, wherein motor control and display control are performed by the microprocessor without requiring a separate motor control IC and display control IC.

9. The CPAP device according to claim 1, wherein the microprocessor is configured to disable the CPAP device if a main power supply voltage is incompatible with the voltage rating of the CPAP device.

12. The CPAP device according to claim 1, wherein the microprocessor has a capacity of about 100-150 bytes.

3. A CPAP device comprising:

a flow generator including a microprocessor with an analog-to-digital converter (ADC);

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 via the ADC,

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

4. The CPAP device according to claim 3, wherein the humidifier control program includes 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.

5. The CPAP device according to claim 4, 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.

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

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

8. The CPAP device according to claim 4, 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.

10. The CPAP device according to claim 3, 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.

11. The CPAP device according to claim 10, 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.

13. The CPAP device according to claim 3, wherein the humidifier control program includes machine readable code configured to determine whether the humidifier is available.

14. The CPAP device according to claim 13, wherein the microprocessor executes a humidifier control program to:

receive output from the ADC, and

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

15. The CPAP device according to claim 14, wherein a signal is generated to indicate that the humidifier is not available if the output from the ADC is not within the possible range of operability of the humidifier.

16. The CPAP device according to claim 14, wherein a signal is generated to indicate that the humidifier is attached and operational if the output from the ADC is within the possible range of operability of the humidifier.

17. The CPAP device according to claim 15, wherein the possible range of operability is between about 5°

-70°

C.

18. The CPAP device according to claim 13, further comprising 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.

19. The CPAP device according to claim 18, 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.

20. The CPAP device according to claim 18, 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.

21. The CPAP device according to claim 3, further comprising a cradle to support the flow generator and the humidifier.

22. The CPAP device according to claim 21, 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.

23. The CPAP device according to claim 3, wherein the temperature sensor comprises a thermistor.

24. The CPAP device according to claim 3, wherein the flow generator includes main electrical components consisting essentially of the microprocessor, a motor, a power supply unit and a display.

25. The CPAP device according to claim 3, wherein the microprocessor is programmed with machine readable code to control the motor and the display.

26. A method for controlling a humidifier of a 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

supplying power to the humidifier in accordance with the digital signal.

27. The method according to claim 26, 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.

28. The method according to claim 27, 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.

29. The method according to claim 28, wherein the fraction is about 5-95% of the predetermined time period.

30. The method according to claim 28, wherein the predetermined time period is about 1-10 seconds.

31. The method according to claim 26, wherein the microprocessor has a capacity of about 100-150 bytes.

32. The method according to claim 26, further comprising determining whether the humidifier is available.

33. The method according to claim 32, wherein the humidifier availability is determined by:

receiving output from the ADC, and

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

34. The method according to claim 33, 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.

35. The method according to claim 33, 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.

36. The method according to claim 34, wherein the permissible range of operability is between about 5°

-70°

C.

37. The method according to claim 26, further comprising providing the flow generator with a pull-up resistor.

38. The method according to claim 37, 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.

39. The method according to claim 37, 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.

40. The method according to claim 26, further comprising programming the microprocessor with machine readable code to control motor and display functions.

41. A method for controlling a humidifier of a CPAP device including a controller comprising:

controlling a heating element in the humidifier with command signals from the controller;

sensing a temperature of a fluid in the humidifier with a sensor in the humidifier that transmits signals to the controller;

establishing an acceptable operating range for the signal transmitted to the controller;

determining whether the transmitted signal is within the acceptable operating range;

if the signal is within the acceptable operating range treating the signal as being indicative of the temperature of the fluid in the humidifier and using the signal to control the heating element, and

if the signal is outside of the acceptable operating range, the controller determines the humidifier to be unavailable.

42. The method of claim 41 wherein the controller is separately housed from the humidifier and said method further comprises turning off a power to the humidifier if it is unavailable.

43. The method of claim 41 further comprising determining a target range for the signal which corresponds to an acceptable temperature range for the fluid, wherein the target range is within the acceptable operating range.

44. The method of claim 43 further comprising activating the heating element to heat the fluid when the signal is within the acceptable operating range and below the target range.

45. The method of claim 43 further comprising deactivating the heating element when the signal is within the acceptable operating range and above the target range.

46. A liquid crystal display (LCD) comprising:

a character domain including a plurality of segments, and

a control circuit to selectively energize one or more of the segments on a time share basis, at least two of the segments being driven serially.

47. The display of claim 46 wherein the LCD further comprises selectively energizing the segments based on a duty cycle.

48. The display of claim 47 wherein the duty cycle is divided into four periods and during each of said periods a different group of segments is driven.

49. The display of claim 46 further comprising a bias voltage applied to the segments.

50. The display of claim 46 further comprising a three resistors circuit having a current ratio of 1:

2;

1 to provide four different voltages to the segments.

51. The display of claim 50, wherein the four different voltages include 0, 1, 2 and 3 volts.

52. A controller and a liquid crystal display (LCD) for an electromechanical device comprising:

a control processor configured to control a plurality of functions in the device and one of said functions is driving the LCD;

said LCD having inputs receiving control signals from the control processor, wherein the LCD lacks a separate display driver processor;

a common domain in the LCD for displaying alphanumeric characters, wherein said common domain includes a plurality of segments and each segment is a liquid crystal sandwiched between a common electrode and a segment electrode, wherein said common electrode is electrically connected to the entire common domain and each segment has a corresponding unique segment electrode, and wherein said segment can be activated by applying voltages to the common electrode and segment electrode corresponding to the segment;

said common electrode having an input port on the LCD;

each of said segment electrodes having a corresponding input port on the LCD;

wherein the controller has a duty cycle for applying power to the common and segment electrodes for the segments, the controller applies power during the duty cycle sequentially to a first segment and then to a second segment.

53. The controller and a liquid crystal display (LCD) in claim 52 further comprising a plurality of common domains, each of which domains includes a unique common electrode.

54. The controller and a liquid crystal display (LCD) in claim 52 further comprising a voltage output lines from the controller connected to the input ports of the LCD for apply voltages to the common and segment electrodes.

55. The controller in claim 54 wherein the connection between the voltage output lines from the controller and the LCD ports comprises a first voltage output line connected to a first resistor in series with one of said LCD input ports, and a second voltage output line connected to a second resistor in series with said one of said common and segment electrodes, wherein the first resistor has a lower resistance value than the second resistor.

56. The controller of claim 55 wherein a unique voltage output line is connected to each first resistor and a single voltage output line, is connected to a plurality of the second resistors.

57. A method for controlling a CPAP device set to operate at predetermined voltage comprising:

monitoring a main power supply voltage;

comparing the monitored voltage to the predetermined voltage; and

producing a control signal based on the comparison to control operation of the CPAP device.

58. The method of claim 57, wherein the control signal disables the CPAP device if the monitored voltage is not equal to the predetermined voltage, and the method includes providing a warning signal via the CPAP device.

59. The method of claim 57, wherein the CPAP device includes a humidifier having a heating element that operates based on a duty cycle, wherein the method includes adjusting the duty cycle based on the comparison between the monitored voltage and the predetermined voltage.

60. A CPAP device comprising:

a flow generator including a microprocessor;

a motor provided to the said flow generator; and

a digital circuit to detect RPM of the motor, said digital circuit including a clock timer, a counter unit and a decoder, wherein the decoder is configured to generate a signal that is indicative of RPM as a function of time.

61. The CPAP device of claim 60, wherein the microprocessor is configured to compare the decoder signal to a predetermined value.

62. The CPAP device of claim 60, wherein the microprocessor is configured to vary the RPM of the motor based on the decoder signal.

63. The CPAP device of claim 60, further comprising a temperature sensor associated with a printed circuit board, the temperature sensor being configured to detect a temperature of the motor, said temperature signal being compared to a predetermined temperature and used to disable the motor in appropriate conditions.