Method and apparatus for providing positive airway pressure to a patient

• US 8,256,417 B2
• Filed: 11/22/2006
• Issued: 09/04/2012
• Est. Priority Date: 11/23/2005
• Status: Active Grant

• Current Assignee: Curative (Beijing) Medical Technology Co., Ltd.
• Original Assignee: Curative (Beijing) Medical Technology Co., Ltd.
• Inventors: Sun, Jianguo
• Primary Examiner(s): CROW, STEPHEN R
• Application Number:
  US12/094,876
• Publication Number:
  US 20090301488A1
• Time in Patent Office: 2,113 Days
• Field of Search: 128/204.18, 128/204.21, 128/204.22, 128/205.18, 128/205.24, 128/203.12, 128/203.16, 128/205.14
• US Class Current: 128/204.18
• 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 16/026 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 16/0858 Pressure sampling ports
• 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 2205/3351 Controlling upstream pump pressure
• CPC Class Codes: A61M 2205/52 with memories providing a history of measured variating parameters of apparatus or patient

Abstract

Methods and apparatus for treatment of medical disorders such as obstructive sleep apnea and congestive heart failure are disclosed. A method involves delivering pressurized air, oxygen or other breathing gas to a patient during a respiratory cycle, where pressure of the air is decreased according to an expiratory unloading factor during expiration. The timing and magnitude of the pressure change may be fully automated and responsive to feedback from a motor load sensor, optionally in combination with a pressure sensor.

Claims

1. A method for providing positive airway pressure to a patient, comprising:

sensing load on a motor that pressurizes flow of air to an airway of the patient, using a load sensor;

sensing pressure proximate the airway, using a pressure sensor

processing sensed pressure with a therapeutic pressure, to determine a difference between the sensed pressure and the therapeutic pressure;

automatically adjusting motor speed, based on motor load, so that the sensed pressure equals the therapeutic pressure; and

processing the therapeutic pressure with the motor load, to correlate the therapeutic pressure with the motor load.

2. The method of claim 1, further comprising:

sensing an expiratory phase of breathing, and

reducing motor speed, based upon motor load, to reduce pressure proximate the airway to an expiratory pressure.

3. The method of claim 2, the therapeutic pressure comprising a pressure selected to keep the airway open during inspiration and the expiratory pressure comprising a pressure selected to keep the airway open during expiration.

4. The method of claim 2, wherein reducing motor speed comprises:

determining an expiratory unloading factor for reducing motor speed; and

applying the expiratory unloading factor to reduce the pressure proximate the airway from the therapeutic pressure to the expiratory pressure.

5. The method of claim 2, the expiratory unloading factor comprising a gain factor, k, wherein applying the expiratory unloading factor comprises processing the gain factor k with the therapeutic pressure P_CPAP to provide the expiratory pressure P_EUT, by:

P_EUT(t)=P_CPAP+k*M(t),

M(t) comprising a normalized motor loading factor.

6. The method of claim 2, the expiratory unloading factor comprising a percentage x of the therapeutic pressure P.sub._CPAP, wherein applying the expiratory unloading factor comprises providing a fixed maximum expiratory unloading pressure P.sub._EUT—

_max by;

P<sub>EUT—

max</sub>=(1−

x)*P_CPAP.

7. The method of claim 2, further comprising:

sensing one or more additional expiratory phases;

averaging the expiratory phases;

estimating a portion of the expiratory phases for applying a maximum expiratory unloading pressure; and

during an expiratory phase, ramping pressure from the maximum expiratory unloading pressure to the therapeutic pressure, after the estimated portion and prior to commencement of an inspiratory phase of respiration.

8. The method of claim 7, wherein ramping pressure comprises increasing motor speed proportional to a difference between the expiratory and inspiratory pressures.

9. The method of claim 7, wherein ramping pressure comprises increasing motor speed based upon a motor load value.

10. Apparatus for providing positive airway pressure to a patient, comprising:

a flow generator having a motor and a blower for providing a flow of air at a selected inspiratory pressure;

a patient interface connected with the flow generator, for conducting the air to an airway of the patient;

a pressure sensor for monitoring pressure of the air at the interface and generating an interface pressure signal;

a load sensor for sensing load on the motor and generating a load signal;

a respiratory phase detector in communication with the load and pressure sensors, for processing the load signal with the interface pressure signal to determine a respiratory phase, and for generating a phase signal;

a processor in communication with the pressure sensor, load sensor and phase detector, for processing the phase, load and pressure signals with the inspiratory pressure and a selected expiratory pressure to determine an expiratory unloading factor, the expiratory unloading factor indicating a difference in motor load required for generating the inspiratory and expiratory pressures at the interface; and

a pressure controller in communication with the processor and the flow generator, for altering motor speed during an expiratory phase and according to the expiratory unloading factor, to achieve the expiratory pressure at the interface.

11. The apparatus of claim 10, the expiratory unloading factor indicating a change in a motor speed required for generating the inspiratory and expiratory pressures at the interface.

12. The apparatus of claim 11, the change in motor speed comprising a reduction in motor speed for reducing the interface pressure to the expiratory pressure.

13. The apparatus of claim 10, the processor communicating with the pressure controller upon determining the expiratory phase, to reduce speed of the motor according to the expiratory unloading factor, the expiratory unloading factor comprising a reduction in motor speed based upon a motor load that is proportional to the expiratory pressure.

14. The apparatus of claim 10, wherein upon sensing an expiratory phase, the processor signals the pressure controller to reduce motor speed according to the expiratory unloading factor, and wherein upon sensing an inspiratory phase, the processor signals the pressure controller to increase motor speed, to increase interface pressure to the inspiratory pressure.

15. The apparatus of claim 10, wherein the expiratory pressure at the patient interface is directly proportional to the motor load.

16. The apparatus of claim 10, further comprising a timer for timing one or more of the expiratory phase, a portion of the expiratory phase for applying the expiratory unloading factor, and an inspiratory phase.

17. The apparatus of claim 10, further comprising a memory for storing one or more of the inspiratory pressure, interface pressure, load, phase, expiratory pressure and expiratory unloading factor.

18. The apparatus of claim 17, further comprising algorithms contained within the memory, the circuitry accessing the algorithms to determine the expiratory unloading factor.

19. A method of providing positive airway pressure to a patient, comprising:

supplying a flow of air to an airway of a patient at a selected inspiratory pressure;

determining an inspiratory phase of respiration;

monitoring pressure of the air proximate the airway;

monitoring load on a motor generating the flow of air;

processing the pressure proximate the airway, the load and the selected inspiratory pressure with a selected expiratory pressure that is lower than the inspiratory pressure, wherein processing comprises;

correlating the inspiratory pressure with an inspiratory motor load,

correlating the expiratory pressure with an expiratory motor load, and

determining, from the correlated pressures, an expiratory unloading factor for achieving the expiratory pressure proximate the airway;

determining an expiratory phase of breathing; and

automatically reducing speed of the motor according to the expiratory unloading factor, to reduce air pressure proximate the airway from the inspiratory pressure to the expiratory pressure.

20. The method of claim 19, wherein determining the expiratory unloading factor comprises determining a difference between the inspiratory pressure and the expiratory pressure, and calculating a motor load associated with the expiratory pressure.

21. The method of claim 20, wherein applying the expiratory unloading factor comprises reducing motor speed according to the percentage or proportional difference.

22. The method of claim 20, determining the expiratory phase of breathing comprising sensing a reduction in motor load correlated with the expiratory pressure, and applying the expiratory unloading factor comprising reducing motor speed based upon the reduced motor load.

23. The method of claim 19, determining the expiratory unloading factor comprising:

determining a percentage or proportional difference between the inspiratory and expiratory pressures; and

determining a percentage or proportional difference between the inspiratory and expiratory motor loads,

wherein the load difference is directly proportional to the pressure difference.

24. The method of claim 19, further comprising:

detecting termination of the expiratory phase; and

ramping pressure from the expiratory pressure detected at termination of the expiratory phase to the inspiratory pressure, prior to commencement of an inspiratory phase of respiration, by increasing motor speed.

25. The method of claim 19, further comprising:

timing the expiratory phase of respiration;

selecting a portion of the expiratory phase for applying the expiratory unloading factor;

applying the expiratory unloading factor during the selected portion; and

ramping pressure from the expiratory pressure to the inspiratory pressure upon termination of the portion and prior to commencement of an inspiratory phase of respiration.

26. A method for providing positive airway pressure to a patient, comprising:

with a load sensor, sensing load on a motor that pressurizes flow of air to an airway of the patient;

processing the sensed load with a pressure applied at the airway to correlate the sensed load with the applied pressure;

processing a desired therapeutic pressure with the correlated sensed load and applied pressure, to determine a therapeutic motor load associated with the desired therapeutic pressure, and

automatically adjusting motor speed, based on motor load, to achieve the desired therapeutic pressure and maintain functionality of the airway.

27. The method of claim 26, sensing load comprising sensing a reduced load correlated with an expiratory phase of breathing, and adjusting motor speed comprising applying an expiratory unloading factor to reduce motor speed;

wherein reducing motor speed reduces pressure at the airway.

28. The method of claim 27, further comprising:

sensing an increased load correlated with the therapeutic pressure, and

removing the expiratory unloading factor to increase motor speed to achieve the therapeutic pressure at the airway.

29. A method for providing positive airway pressure to a patient, comprising:

sensing pressure of air delivered to a patient airway, during an inspiratory phase of breathing;

with a load sensor, sensing load on a motor pressurizing the air to the patient, during an expiratory phase of breathing;

processing the sensed pressure with the sensed load and

automatically reducing speed of the motor according to the sensed load, to reduce pressure at the patient airway, wherein pressure during the expiratory phase is directly proportional to the motor load.

30. The method of claim 29, further comprising monitoring pressure at the airway during the expiratory phase, to insure that the pressure is sufficient to maintain the airway in an open position.