Method and apparatus for providing positive airway pressure to a patient

• US 6,932,084 B2
• Filed: 11/26/2002
• Issued: 08/23/2005
• Est. Priority Date: 06/03/1994
• Status: Expired due to Term

• Current Assignee: RIC INVESTMENTS LLC (Respironics Incorporated)
• Original Assignee: RIC INVESTMENTS LLC (Respironics Incorporated)
• Inventors: Fiore, John, Mechlenburg, Douglas M., Ressler, Heather, Estes, Mark C., Kepler, Jeff
• Primary Examiner(s): Lewis, Aaron J.
• Application Number:
  US10/304,590
• Publication Number:
  US 20030121519A1
• Time in Patent Office: 1,001 Days
• Field of Search: 128/204.18, 128/204.21, 128/204.23, 128/204.26
• US Class Current: 128/204.18
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/0066 Blowers or centrifugal pumps
• 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 16/204 used for inhalation control
• CPC Class Codes: A61M 16/205 used for exhalation control
• 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 2016/0039 in the inspiratory circuit

Abstract

A system including methods and apparatus for treatment of a medical disorder such as obstructive sleep apnea or congestive heart failure. The system involves applying a gain to flow rate of pressurized gas delivered to a patient during inspiratory and/or expiratory phases of a respiratory cycle to deliver the pressurized gas in proportion to the respective gains during inspiration and/or expiration. A base pressure may be applied in addition to the gain-modified pressures and an elevated pressure profile may be employed to assist or control inspiration. The system may be fully automated responsive to feedback provided by a flow sensor that determines the estimated patient flow rate. A leak computer can be included to instantaneously calculate gas leakage from the system. The system may be utilized in connection with conventional continuous positive airway pressure treatments, such as CPAP or bi-level positive airway pressure equipment to effect various beneficial treatment applications.

Claims

1. An apparatus for delivering pressurized gas to an airway of a patient, the apparatus comprising:

a blower;

a conduit adapted to carry a flow of gas generated by the blower to the airway of the patient;

a sensor adapted to monitor a characteristic associated with the gas in the conduit or a flow of gas;

a signal related to the characteristic;

a pressure controller associated with at least one of the blower and the conduit to control a pressure of the gas in the conduit;

control means, responsive to the signal, for controlling the pressure controller so as to cause the gas to be delivered to a patient at a therapy pressure during at least a portion of a respiratory cycle, wherein the therapy pressure is a pressure sufficient to counter airway collapsing forces; and

a first selector unit, operatively connected to the control means, to select a first gain, wherein the control means controls the pressure controller so that the pressure of the gas in the conduit during at least a portion of a respiratory cycle is based on the first gain and the signal.

2. The apparatus of claim 1, wherein the control means controls the pressure controller so as to prevent pressure oscillations during expiration.

3. The apparatus of claim 2, wherein the control means controls the pressure controller to prevent pressure oscillations by causing the pressure controller to provide a pressure to such a patient during expiration after a maximum pressure reduction has been met at a greater of (1) the pressure that is determined based on the first gain and the signal, and (2) a current pressure being provided to such a patient.

4. The apparatus of claim 1, wherein the control means controls the pressure controller to provide a generally continuous positive pressure during at least a portion of an inspiratory phase of such a patient'"'"'s respiratory cycle and to provide the therapy pressure based on the first gain and the signal during an expiratory phase of such a patient'"'"'s breathing cycle.

5. The apparatus of claim 1, wherein the control means controls the pressure controller to provide a first pressure during at least a portion of an inspiratory phase of a patient'"'"'s respiratory cycle and to provide a second pressure during at least a portion of an expiratory phase of the respiratory cycle, wherein the second pressure is lower than the first pressure and is further reduced by an amount based on the first gain and the signal.

6. The apparatus of claim 1, wherein the control means also limits a rate of change for the pressure of the gas in the conduit.

7. The apparatus of claim 6, wherein the control means set a first rate of change limit for an increase in the pressure of the gas in the conduit and sets second rate of change limit for a decrease in the pressure of the gas in the conduit.

8. The apparatus of claim 1, further comprising means for smoothing transitions between changes in a pressure of the gas in the conduit.

9. The apparatus of claim 1, wherein the control means controls the pressure controller so that the pressure of the gas in the conduit during at least a portion of an expiratory phase of a respiratory cycle is based on the first gain and the signal.

10. The apparatus of claim 9, further comprising a second selector unit operatively connected to the control means to select a second gain, wherein the control means controls the pressure controller so that the pressure of the gas in the conduit during at least a portion of an inspiratory phase of the respiratory cycle is based on the second gain and the signal.

11. The apparatus of claim 1, wherein the first selector unit operatively is a manually actuated input device.

12. A method of providing pressured gas to an airway of a patient, the method comprising the steps of:

supplying a flow of gas to an airway of a patient from a source of gas via a conduit;

monitoring a characteristic associated with the flow of gas;

providing signal related to the characteristic;

selecting a first gain; and

controlling the flow of gas to such a patient during at least a portion of a respiratory cycle based on the signal and the first gain so as to deliver the flow of gas to a patient at a therapy pressure, wherein the therapy pressure is a pressure sufficient to counter airway collapsing forces.

13. The method of claim 12, further comprising a step of selecting a second gain, wherein the step of controlling the flow of gas to such a patient includes controlling the pressure based on the first gain and the signal during at least a portion of an inspiratory phase of a respiratory cycle and based on the second gain and the signal during at least a portion of an expiratory phase of a respiratory cycle.

14. The method of claim 12, wherein the controlling step includes controlling the pressure so as to prevent pressure oscillations during expiration.

15. The method of claim 14, wherein controlling the pressure so as to prevent pressure oscillations includes providing a pressure to such a patient during expiration after a maximum pressure reduction has been met at a greater one of (1) the pressure that is determined based on the first gain and the signal, and (2) a current pressure being provided to the airway of such a patient.

16. The method of claim 12, wherein the controlling steps includes (1) providing a generally continuous positive pressure during at least a portion of an inspiratory phase of a patient'"'"'s respiratory cycle and (2) providing the therapy pressure based on the first gain and the signal during at least a portion of an expiratory phase of such a patient'"'"'s respiratory cycle.

17. The method of claim 12, wherein the controlling steps includes (1) providing a first pressure during at least a portion of an inspiratory phase of a patient'"'"'s respiratory cycle and (2) providing a second pressure during at least a portion of an expiratory phase of a respiratory cycle, wherein the second pressure is lower than the first pressure and is further reduced by an amount based on the first gain and the signal.

18. The method of claim 12, wherein the controlling step includes limiting a rate of change for the pressure of the gas.

19. The method of claim 18, wherein the controlling step includes setting a first rate of change limit for an increase in the pressure of the gas and setting second rate of change limit for a decrease in the pressure of the gas.

20. The method of claim 12, further comprising smoothing transitions between changes in a pressure of the gas.

21. The method of claim 12, wherein controlling the flow of gas based on the signal and the first gain is done during at least a portion of an expiratory phase of a respiratory cycle.

22. The method of claim 12, wherein selecting the first gain is done manually.

23. An apparatus for delivering pressurized gas to an airway of a patient, comprising:

a gas flow generator;

a conduit coupled to the gas flow generator to communicate a flow of gas from the gas flow generator with an airway of a patient;

a sensor associated that monitors a characteristic associated with the gas or the flow of gas in the conduit;

a signal related to the characteristic;

a pressure controller associated with the gas flow generator or the conduit to control a pressure of the gas in the conduit;

an input device; and

processing means, responsive to the signal, a continuous positive airway pressure (CPAP) setting, and an expiratory gain Gain_Exp from the input device, for determining a pressure of the gas in the conduit during at least a portion of inhalation (Pinhalation) as;

Pinhalation=CPAP,

and for determining a pressure of the gas in the conduit during at least a portion of exhalation (Pexhalation) as;

Pexhalation=CPAP+Gain_Exp*(Flow−

FlowOffset),

where “

Flow”

is the chracteristic monitored by the sensor, where “

FlowOffset”

corresponds to a final value of the characteristic inspiration responsive to the final value being positive, otherwise FlowOffest is set to zero, and wherein the processing means controls the pressure controller so as to deliver a pressure of the gas in the conduit corresponding to Pinhalation during at least a portion of an inspiratory phase of a breathing cycle and corresponding to Pexhalation during at least a portion of an expiratory phase of a breathing cycle.

24. The apparatus of claim 23, wherein the pressure controller is a valve associated with the conduit that exhausts gas from the conduit to control the pressure of the gas-in the conduit.

25. The apparatus of claim 23, wherein the CPAP level is set via the input device.

26. The apparatus of claim 23, wherein the CPAP level is determined by the processing means based on an output of the sensor.

27. The apparatus of claim 23, wherein the processing means controls pressure controller so as to prevent pressure oscillations during expiration.

28. The apparatus of claim 27, wherein the processing means controls the pressure controller to prevent oscillations by causing the pressure controller to provide a pressure of the gas in the conduit during expiration after a maximum pressure reduction has been met at a greater of (1) Pexhalation and (2) a current pressure being provided to an airway of such a patient.

29. The apparatus of claim 23, wherein the processing means also limits a rate of change for the pressure of the gas in the conduit.

30. The apparatus of claim 29, wherein the processing means sets a first rate of change limit for an increase in the pressure of the gas in the conduit and sets second rate of change limit for a decrease in the pressure of the gas.

31. The apparatus of claim 23, further comprising means for smoothing transitions between changes in a pressure of the gas.

32. The apparatus of claim 31, wherein the means for smoothing comprises a filter for filtering a signal provided by the processing means to the pressure controller, wherein the signal corresponds to Pexhalation or Pinhalation determined by the processing means.

33. A method of delivering pressurized breathing gas to an airway of a patient, comprising:

generating a flow of gas;

sensing a characteristic associated with a current flow (Flow) of the gas;

providing a signal related to the characteristic;

selecting an expiratory gain (Gain_Exp);

setting a continuous positive airway pressure (CPAP) level;

controlling a pressure of the gas during at least a portion of inhalation (Pinhalation) as;

Pinhalation=CPAP;

and

controlling the pressure of the gas during at least a portion of exhalation (Pexhalation) as;

Pexhalation=CPAP+Gain_Exp*(Flow−

FlowOffset),

where “

FlowOffset”

corresponds to a final value of the characteristic during inspiration responsive to the final value being positive, otherwise FlowOffest is set to zero.

34. The method claim 33, wherein generating the flow of gas includes carrying the flow of gas to an airway of a patient via conduit, and wherein controlling the pressure of the gas includes exhausting gas from the conduit.

35. The method of claim 33, wherein setting the CPAP level is accomplished manually via an input device.

36. The method of claim 33, wherein setting the CPAP level is accomplished automatically based on an output of a sensor adapted to monitor a characteristic of such a patient or a characteristic associated with the gas flow of gas.

37. The method of claim 33, further comprising preventing pressure oscillations during an expiratory phase of a respiratory cycle.

38. The method of claim 37, wherein preventing oscillations includes providing a pressure of the gas during expiration after a maximum pressure reduction has been met at a greater of (1) Pexhalation, and (2) a current pressure of the gas.

39. The method of claim 33, further comprising limiting a rate of change for the pressure of the gas.

40. The method of claim 39, wherein limiting the rate of change includes providing a first rate of change limit for an increase in the pressure of the gas and a second rate of change limit for a decrease in the pressure of the gas.

41. The method of claim 33, further comprising smoothing transitions between changes in a pressure of the gas.

42. The method of claim 41, wherein smoothing transitions includes filtering the Pexhalation determinations made during the step of controlling a pressure.

43. The method of claim 33, wherein controlling a pressure of the gas during exhalation is done substantially continuously.