METHOD AND APPARATUS FOR IMPROVING THE COMFORT OF CPAP

• US 20070017518A1
• Filed: 09/26/2006
• Published: 01/25/2007
• Est. Priority Date: 06/20/2003
• Status: Active Grant

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Richard, Ron, Price, Andrew, Alder, Matthew, Farrugia, Steven
• Granted Patent: US 8,899,232 B2
• Time in Patent Office: Days
• US Class Current: 128/204.230
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/417 the bone marrow
• CPC Class Codes: A61M 16/0003 Accessories therefor, e.g. sensors, vibrators, negative pressure
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/021 operated by electrical means A61M16/202 – A61M16/205 take precedence
• CPC Class Codes: A61M 16/022 Control means therefor
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/026 specially adapted for predicting, e.g. for determining an information representative of a flow limitation during a ventilation cycle by using a root square technique or a regression analysis
• CPC Class Codes: A61M 16/06 Respiratory or anaesthetic masks
• CPC Class Codes: A61M 16/0666 Nasal cannulas or tubing devices for improving normal breathing through the nose A61F5/08; nose filters A62B23/06; outside holding devices A61M25/02
• CPC Class Codes: A61M 2016/0018 electrical
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2205/3334 Measuring or controlling the flow rate
• CPC Class Codes: A61M 2205/3365 Rotational speed
• CPC Class Codes: A61M 2205/3553 remote, e.g. between patient's home and doctor's office
• CPC Class Codes: A61M 2205/3584 using modem, internet or bluetooth
• CPC Class Codes: A61M 2205/502 User interfaces, e.g. screens or keyboards
• CPC Class Codes: A61M 2230/63 : Motion, e.g. physical activity

Abstract

A low-cost CPAP apparatus in which, upon detection of the transition from inhalation to exhalation, the blower motor is de-energized to allow it to freewheel. When the pressure in the patient mask (or whatever interface is utilized) reaches a minimum pressure level during exhalation, the motor is re-energized and its speed is controlled so to maintain the pressure at a level suitable for exhalation. Upon detection of the transition from exhalation to inhalation, the motor speed is increased to provide higher pressures in the patient mask suitable for inhalation.

Claims

1. In a CPAP apparatus having an electric motor, an impeller rotated by the motor, a patient interface, an air delivery conduit for delivering air from the impeller to the patient interface, a sensor for determining the pressure in the patient interface, and a control mechanism that causes air to be delivered at a desired pressure to the patient interface, and that detects transitions between inhalation and exhalation of a respiratory cycle of a patient;

a method of controlling the motor operation comprising the steps of;

(i) upon detection of the transition from inhalation to exhalation, de-energizing the motor to allow the motor to freewheel;

(ii) when the pressure in the patient interface reaches a minimum pressure level during exhalation, re-energizing the motor and controlling its speed so to maintain the pressure at a level suitable for exhalation while the motor is still being allowed to freewheel; and

(iii) upon detection of the transition from exhalation to inhalation, increasing the motor speed to provide higher pressures in the patient interface suitable for inhalation.

2. The method of claim 1 wherein in step (ii) the motor speed is controlled so as to maintain the pressure at said minimum level.

5. The method of claim 1 wherein the step of detecting the transition between at least one of inhalation to exhalation or exhalation to inhalation comprises the sub-steps of:

(iv) monitoring the respiratory air flow to the patient; and

(v) comparing the air flow to a threshold.

6. The method of claim 5 wherein said threshold is adjustable and when the air flow is smaller than said threshold, a transition is determined to have occurred, the threshold having the effect of adjusting the phase delay between the pressure and the air flow, the larger the threshold, the greater the confidence that a transition has been determined reliably at the expense of increased uncertainty in when the transition occurred, potentially leading to a phase delay and reduced synchronicity.

7. The method of claim 6 wherein said minimum pressure level during exhalation is adjustable to vary the comfort level for the patient.

8. The method of claim 1 wherein the step of detecting the transition between at least one of inhalation to exhalation or exhalation to inhalation comprises the sub-steps of:

(iv) monitoring the respiratory air flow to the patient; and

(v) comparing the air flow to a threshold.

9. The method of claim 8 wherein said threshold is adjustable and when the air flow is smaller than said threshold, a transition is determined to have occurred, the threshold having the effect of adjusting the phase delay between the pressure and the air flow, the larger the threshold, the greater the confidence that a transition has been determined reliably at the expense of increased uncertainty in when the transition occurred, potentially leading to a phase delay and reduced synchronicity.

10. The method of claim 9 wherein said minimum pressure level during exhalation is adjustable to vary the comfort level for the patient.

11. The method of claim 1 wherein said minimum pressure level during exhalation is adjustable to vary the comfort level for the patient.

12. The method of claim 1 further comprising the step of braking the motor in a dithered fashion during at least some of the time that it is freewheeling.

13. The method of claim 12 wherein braking of the motor occurs when the motor first starts to freewheel during a breathing cycle.

27. A CPAP apparatus having two modes of operation:

a) a first mode where the pressure during exhalation is reduced from a high level as claimed in claim 1, and

b) a second mode where the pressure remains substantially constant during a cycle of inhalation and exhalation;

and a controller adapted to detect the presence of an apnea and to switch the CPAP apparatus from the first mode of operation to the second mode of operation upon detection of an apnea.

28. A CPAP apparatus of claim 27 where the controller is further adapted to detect the resumption of normal breathing and to switch from the second mode of operation to the first mode of operation upon the detection of the resumption of normal breathing.

29. A CPAP apparatus of claim 27 where the controller is further adapted to switch from the second mode of operation to the first mode of operation upon the expiration of a predetermined period of time.

3. The method of claim I further comprising the step of braking the motor during at least some of the time that it is freewheeling.

4. The method of claim 3 wherein braking of the motor occurs when the motor first starts to freewheel during a breathing cycle.

14. A method of operating a CPAP apparatus in which a impeller-driven rotating impeller delivers air at a desired pressure to a patient interface, comprising the steps of:

(i) detecting the transition from inhalation to exhalation and in response thereto allowing the impeller to freewheel;

(ii) detecting when the pressure in the patient interface reaches a minimum pressure level during exhalation and in response thereto causing the motor to control the impeller speed so as to maintain the pressure at a level suitable for exhalation; and

(iii) detecting the transition from exhalation to inhalation and in response thereto causing the motor to control the impeller to operate at a higher speed to provide higher pressures in the patient interface suitable for inhalation.

15. The method of claim 14 wherein in step (ii) the impeller speed is controlled so as to maintain the pressure at said minimum level.

16. The method of claim 14 wherein the impeller is connected to a motor and further comprising the step of braking the motor during at least some of the time that the impeller is freewheeling.

17. The method of claim 16 wherein braking of the motor occurs when the impeller first starts to freewheel during a breathing cycle.

18. The method of claim 14 wherein detecting the transition between at least one of inhalation to exhalation or exhalation to inhalation comprises the sub-steps of:

(iv) monitoring the respiratory air flow to the patient; and

(v) comparing the air flow to a threshold.

19. The method of claim 18 wherein said threshold is adjustable and a transition is detected when the air flow is smaller than said threshold, the threshold having the effect of adjusting the phase delay between the pressure and the air flow, the larger the threshold, the greater the confidence that a transition has been detected reliably at the expense of increased uncertainty in when the transition occurred, potentially leading to a phase delay and reduced synchronicity.

20. The method of claim 14 wherein said minimum pressure level during exhalation is adjustable to vary the comfort level for the patient.

21. The method of claim 14 wherein the impeller is connected to a motor and further comprising the step of braking the motor in a dithered fashion during at least some of the time that the impeller is freewheeling.

30. A method of operating a CPAP apparatus having two modes of operation:

a) a first mode where the pressure during exhalation is reduced from a high level as claimed in claim 14, and

b) a second mode where the pressure remains substantially constant during a cycle of inhalation and exhalation;

and a controller adapted to detect the presence on an apnea and to switch the CPAP apparatus from the first mode of operation to the second mode of operation upon detection of an apnea.

31. A method of operating a CPAP apparatus as claimed in claim 30 where the controller is further adapted to detect the resumption of normal breathing and to switch from the second mode of operation to the first mode of operation upon the detection of the resumption of normal breathing.

32. A method of operating a CPAP apparatus as claimed in claim 30 where the controller is further adapted to switch from the second mode of operation to the first mode of operation upon the expiration of a predetermined period of time.

22. (canceled)

23. (canceled)

24. A CPAP apparatus for treatment of sleep disordered breathing by having a blower driven by a motor provide air at a desired pressure at the airway of a patient, in which the pressure during exhalation is reduced from a high level to a low level by allowing the motor to freewheel only during a pretreatment phase of use of the CPAP apparatus.

25. A CPAP apparatus of claim 24 where said pretreatment phase of use is a ramp phase.

26. A CPAP apparatus of claim 24 where said pretreatment phase of use is settling time.

33. In a CPAP apparatus having an electric motor, an impeller rotated by the motor, a patient interface, an air delivery conduit for delivering air from the impeller to the patient interface, a mechanism for determining the pressure in the patient interface, and a control mechanism that causes air to be delivered at a desired pressure to the patient interface, and that detects transitions between inhalation and exhalation of a respiratory cycle of a patient;

a method of controlling the motor operation during a sequence of respiratory cycles comprising the steps of;

(i) upon detection of the transition from inhalation to exhalation, de-energizing the motor to allow the motor to freewheel;

(ii) when the pressure in the patient interface reaches a minimum pressure level during exhalation, re-energizing the motor and controlling its speed so to maintain the pressure at a level suitable for exhalation while the motor is still being allowed to freewheel; and

(iii) upon detection of the transition from exhalation to inhalation, increasing the motor speed to provide higher pressures in the patient interface suitable for inhalation.

34. The method of claim 33 wherein during a ramp phase the motor speed is controlled in step (iii) so as to increase the pressure over successive respiratory cycles.

35. The method of claim 34 wherein during said ramp phase the motor speed is controlled in step (iii) so as to provide a substantially constant pressure during any single respiratory cycle while increasing the substantially constant pressure over successive respiratory cycles.

36. The method of claim 33 wherein at least one of the motor freewheeling in step (i) and the motor speed in step (iii) are controlled so as to decrease a pressure differential between inhalation and exhalation during the two steps over successive respiratory cycles.

37. The method of claim 36 wherein the cycles occur during a ramp phase.

38. The method of claim 37 wherein the ramp phase takes place while the patient is trying to fall asleep so that increased comfort is obtained during the ramp phase following which during patient therapy the pressure is more constant throughout a respiratory cycle.