Method and apparatus for optimizing the continuous positive airway pressure for treating obstructive sleep apnea

• US 6,488,634 B1
• Filed: 06/22/2000
• Issued: 12/03/2002
• Est. Priority Date: 05/07/1992
• Status: Expired due to Term

• Current Assignee: New York University
• Original Assignee: New York University
• Inventors: Norman, Robert G., Rapoport, David M.
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US09/602,158
• Time in Patent Office: 894 Days
• Field of Search: 600/529, 600/538, 128/204.23
• US Class Current: 600/538
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/6803 Head-worn items, e.g. helmets, masks, headphones or goggles
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• 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 16/0677 Gas-saving devices therefor
• 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
• CPC Class Codes: A61M 2230/005 Parameter used as control input for the apparatus
• CPC Class Codes: A61M 2230/04 Heartbeat characteristics, e.g. ECG, blood pressure modulation
• CPC Class Codes: A61M 2230/08 Other bio-electrical signals
• CPC Class Codes: A61M 2230/205 partial oxygen pressure (P-O2)
• CPC Class Codes: A61M 2230/62 Posture
• CPC Class Codes: A61M 39/228 with a tubular diaphragm constrictable by radial fluid force
• CPC Class Codes: G16H 20/40 relating to mechanical, radiation or invasive therapies, e.g. surgery, laser therapy, dialysis or acupuncture
• CPC Class Codes: G16H 40/63 for local operation
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment

Abstract

In the treatment of obstructive sleep apnea, a method and apparatus are disclosed for optimizing the controlled positive pressure to minimize the flow of air from a flow generator while still ensuring that flow limitation in the patient'"'"'s airway does not occur. In particular, the invention relates to a breathing device and method of use to adjust a controlled positive pressure to the airway of a patient by detecting flow limitation from analysis of an inspiratory flow waveform. Once the presence of flow limitation has been analyzed, the system determines an action to take for adjustment of the controlled positive pressure. The pressure setting is raised, lowered or maintained depending on whether flow limitation has been detected and on the previous actions taken by the system. The preferred breathing apparatus consists of a flow generator, a flow sensor, an analog to digital converter, a microprocessor, and a pressure controller, a patient supply hose, a nasal fitting, and, optionally, a pressure transducer. Using the method of the present invention, the microprocessor adjusts the air pressure in the patient supply hose when flow limitation is detected in the airway of the patient.

Claims

1. An apparatus for the treatment of an obstruction in the airway of a patient, comprising:

a source of breathing gas configured to provide breathing gas flow to a patient and to provide positive pressure in the airway of the patient;

a sensor to detect the flow of the breathing gas to the patient;

a signal processor operatively connected to the sensor and configured to define a waveform contour of an inspiratory flow of the breathing gas to the patient, and further configured to utilize the waveform contour to detect the presence or absence of an obstruction in the airway of the patient; and

a controller operatively connected to the signal processor, the controller being configured to adjust the positive airway pressure to the patient when the signal processor detects the presence or absence of an obstruction in the airway of the patient.

2. The apparatus of claim 1, wherein the controller is further configured to increase the airway pressure when the signal processor detects the presence of an obstruction, and the controller is further configured to decrease the airway pressure when the signal processor detects the absence of an obstruction.

3. An apparatus for optimizing the positive pressure in an airway of a patient, comprising:

means for providing positive pressure of a breathing gas to an airway of a patient;

means for generating a signal corresponding to a waveform contour of an inspiratory flow of breathing gas to the patient;

means for utilizing the wave form contour signal to detect a flow limitation in the airway of the patient; and

means for increasing the positive airway pressure when the means for utilizing detects a flow limitation in the airway of the patient.

4. The apparatus of claim 3, further including means for decreasing the positive airway pressure when the means for utilizing does not detect a flow limitation in the airway of the patient.

5. The apparatus of claim 4, wherein the means for utilizing is configured to generate data values representative of the signal corresponding to the inspiratory flow, to correlate the data values with a pure sine wave to determine a first index, to compare a regression fit of the data values with a regression fit of a pure sine wave to determine a second index, to compare a peak value of the data values with a peak value of a derivative of the data values to determine a third index, and to compare a peak value of the data values with an average of a plurality of peak flow values for flow limited breaths and with an average of a plurality of peak flow values for non-flow limited breaths to determine a fourth index.

6. The apparatus of claim 5, wherein the means for utilizing is further configured to determine a fifth index as a function of the first index, the second index, the third index and the fourth index, wherein each index includes a weighted coefficient.

7. The apparatus of claim 3, wherein the means for utilizing is configured to generate data values representative of the signal corresponding to the inspiratory flow, to correlate the data values with a sinusoidal contour, to analyze the data values for flatness, to analyze the data values for respiratory effort, and to analyze the data values for relative flow magnitude.

8. An apparatus for optimizing the positive pressure in an airway of a patient, comprising:

a source of positive pressure of breathing gas provided to an airway of a patient;

a first sensor configured to generate a first signal corresponding to a waveform contour of an inspiratory flow of breathing gas to the patient;

a memory device configured to store the first signal generated by the first sensor;

a microprocessor configured to utilize the first signal to generate a second signal indicative of a flow limitation in the patient; and

a controller operably connected to the source of breathing gas and responsive to the second signal from the microprocessor so as to increase the positive pressure of the breathing gas in response to the second signal.

9. The apparatus of claim 8, wherein the microprocessor is further configured to generate a third signal when the first signal does not indicate a flow limitation in the patient, and wherein the controller is further configured to decrease the positive pressure of the breathing gas in response to the third signal.

10. The apparatus of claim 8, wherein the microprocessor is further configured to correlate the first signal with a pure sine wave.

11. The apparatus of claim 8, wherein the microprocessor is further configured to compare a regression fit of the first signal with a regression fit of a pure sine wave.

12. The apparatus of claim 8, wherein the microprocessor is further configured to compare a peak value of the first signal with a peak value of a derivative of the first signal.

13. The apparatus of claim 8, wherein the microprocessor is further configured to determine a plurality of peak flow values for flow limited breaths, to determine a plurality of peak flow values for non-flow limited breaths, and to compare a peak value of the first signal with an average of the plurality of peak flow values for flow limited breaths and with an average of the plurality of peak flow values for non-flow limited breaths.

14. A method for optimizing the positive pressure in an airway of a patient, comprising:

providing air at positive pressure to an airway of a patient;

monitoring the flow of air to the patient;

defining an inspiratory waveform contour of the flow of air to the patient;

analyzing the inspiratory waveform contour to determine the presence or absence of a patient airway obstruction; and

adjusting the positive pressure of air to the patient in response to the presence or absence of a patient airway obstruction.

15. The method of claim 14, wherein adjusting the positive pressure of air to the patient includes increasing the positive pressure of air to the patient when the inspiratory waveform contour indicates a patient airway obstruction, and further includes decreasing the positive pressure of air to the patient when the inspiratory waveform contour does not indicate a patient airway obstruction.

16. A method for optimizing the positive pressure of breathing gas to an airway of a patient, comprising:

applying breathing gas at positive pressure to an airway of a patient;

detecting an inspiratory flow of breathing gas to the patient;

generating a signal corresponding to a waveform contour of the inspiratory flow of breathing gas to the patient;

determining whether the waveform contour signal indicates a flow limitation in the airway of the patient; and

increasing the positive pressure of breathing gas when the signal indicates a flow limitation in the airway of the patient.

17. The method of claim 16, further comprising decreasing the positive airway pressure when the signal does not indicate a flow limitation in the airway of the patient.

18. The method of claim 17, further comprising:

calculating a first index by comparing the signal with a pure sine wave;

calculating a second index by comparing a regression fit of the signal with a regression fit of a pure sine wave;

calculating a third index by comparing a peak value of the signal with a peak value of a derivative of the signal;

determining peak flow values for a plurality of flow limited breaths;

determining peak flow values for a plurality of non-flow limited breaths; and

calculating a fourth index by comparing a peak value of the signal with an average of the peak flow values for the plurality flow limited breaths and with an average of the peak flow values for the plurality of non-flow limited breaths.

19. The method of claim 17, wherein determining whether the signal indicates a flow limitation in the airway of the patient further includes calculating a fifth index as a function of the first index, the second index, the third index and the fourth index, wherein the fifth index indicates the presence of flow limitation in the patient.

20. The method of claim 17, wherein determining whether the signal indicates a flow limitation in the airway of the patient further includes calculating a fifth index as a function of the first index, the second index, the third index and the fourth index, wherein the function includes a weighted coefficient for each of the first, second, third and fourth indexes.