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

• US 5,546,933 A
• Filed: 06/07/1995
• Issued: 08/20/1996
• 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): Burr, Edgar S.
• Assistant Examiner(s): RACITI, ERIC
• Application Number:
  US08/475,227
• Time in Patent Office: 440 Days
• Field of Search: 128/204.18, 128/204.21, 128/204.23, 128/204.26, 128/205.18, 128/207.18, 128/716-726
• US Class Current: 128/204.23
• 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. A method for detecting flow limitations in the airway of a patient, comprising the steps of:

a) providing a nasal fitting in fluid communication with the airway of a patient, the nasal fitting having means for measuring the inspiratory flow of air to the patient;

b) measuring the inspiratory flow of air to the airway of the patient;

c) generating a curve of data values representative of the inspiratory flow of air to the patient for each breathing cycle;

d) processing such data values to generate a plurality of indices each independently descriptive of the shape of each such curve; and

e) combining such indices to determine whether a flow limitation in the patient is indicated.

2. The method of claim 1, further comprising the step of measuring the expiratory flow of ambient air from the patient, and generating second data values representative of the expiratory flow.

3. The method of claim 1, further comprising the step of prescribing a regimen of patient treatment when the combined indices indicate a flow limitation in the airway of the patient.

4. The method of claim 1, wherein generating said indices further comprises the steps of:

f) correlating the stored data values with a pure sine wave to create a first index;

g) comparing a regression fit of the stored data values with a regression fit of a pure sine wave to create a second index;

h) comparing a peak value of the stored data values with a peak value of a derivative of the stored data values to create a third index; and

i) comparing a peak value of the stored data values 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 to create a fourth index.

5. The method of claim 4, wherein combining said indices further comprises the step of calculating a fifth index as a mathematical function of the first index, the second index, the third index and the fourth index, wherein each index includes a weighted coefficient having a range including a value of zero.

6. A method for detecting flow limitations in the airway of a patient, comprising the steps of:

a) providing a nasal fitting in fluid communication with the airway of a patient, the nasal fitting having means for measuring the inspiratory flow of ambient air to the patient;

b) detecting the onset of an inspiratory flow of air to the airway of the patient;

c) storing data values representative of the inspiratory flow of breathing gas to the patient;

d) determining whether the stored data values indicate a flow limitation in the patient;

e) repeating steps b) through d) for a plurality of patient inspirations to create a plurality of peak flow values for flow limited breaths and to create a plurality of peak flow values for non-flow limited breaths;

f) correlating the stored data values with a pure sine wave to create a first index;

g) comparing a regression fit of the stored data values with a regression fit of a pure sine wave to create a second index;

h) comparing a peak value of the stored data values with a peak value of a derivative of the stored data values to create a third index; and

i) comparing a peak value of the stored data values 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 to create a fourth index.

7. The method of claim 6, further comprising the step of calculating a fifth index as a mathematical function of the first index, the second index, the third index and the fourth index, wherein each index includes a weighted coefficient having a range including a value of zero.