# US 2021/0275090 A1 · Sleep apena detection system and method

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- Number: US 2021/0275090 A1
- Document ID: US20210275090A1
- Status: Published application
- Kind: A1
- Application number: 17/190,471
- Filed: 2021-03-03
- Published: 2021-09-09
- Earliest claimed: 2020-03-03
- Assignees: Koninklijke Philips N.V.
- Applicants: Koninklijke Philips N.V.
- Inventors: GABRIELE PAPINI; PEDRO MIGUEL FERREIRA DOS SANTOS DA FONESCA
- Web page: https://patentgrep.com/patent/US20210275090A1

## CPC

- A61B 5/4818: {Sleep apnoea}
- A61B 5/0205: Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
- A61B 5/02416: {using photoplethysmograph signals, e.g. generated by infrared radiation (A61B5/14552 takes precedence)}
- A61B 5/14551: {for measuring blood gases}
- A61B 5/4812: {Detecting sleep stages or cycles}
- A61B 5/681: {Wristwatch-type devices}
- A61B 5/7267: {involving training the classification device}
- A61B 5/7278: {Artificial waveform generation or derivation, e.g. synthesizing signals from measured signals}
- A61B 5/7282: {Event detection, e.g. detecting unique waveforms indicative of a medical condition (cough events A61B5/0823; seizures A61B5/4094; sleep apnoea A61B5/4818)}
- G16H 40/67: for remote operation
- G16H 50/30: for calculating health indices; for individual health risk assessment
- A61B 5/02405: {Determining heart rate variability}
- A61B 5/0816: {Measuring devices for examining respiratory frequency (measuring frequency of electric signals G01R23/00)}
- A61B 2562/0219: Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G16H: HEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA

## Abstract

A system for detecting sleep apnea uses a PPG sensor for generating a PPG signal. An estimate of respiratory effort is derived from the PPG signal, and from this a respiratory effort signal is derived. Characteristic features are extracted from the respiratory effort signal, and sleep disordered breathing events are detected from the extracted characteristic features. This analysis can distinguish between sleep disordered breathing events and normal breathing during sleep.

## Claims

### Claim 1

A system for detecting sleep apnea, comprising:
a PPG sensor for generating a single-wavelength PPG signal for use in detecting sleep apnea; and
a processor, which is adapted to:
provide an estimate of respiratory effort from the PPG signal and thereby derive a respiratory effort signal;
extract characteristic features from the respiratory effort signal; and
detect sleep disordered breathing events from the extracted characteristic features and thereby distinguish between sleep disordered breathing events and normal breathing during sleep.

### Claim 2 (depends on 1)

The system as claimed in claim 1, wherein the processor is adapted to identify epoch periods during which sleep disordered breathing events are detected.

### Claim 3 (depends on 1)

The system as claimed in claim 1, wherein the processor is adapted to provide an estimate of respiratory effort by one or more of:
determining the amplitude of pulses in the PPG signal;
determining the distance between PPG pulses; and
determining the envelope of the peaks of the PPG pulses.

### Claim 4 (depends on 1)

The system as claimed in claim 1, wherein the processor is adapted to extract characteristic features by determining the signal power at the respiration frequency.

### Claim 5 (depends on 1)

The system as claimed in claim 1, wherein the processor is further adapted to extract cardiac features from the PPG signal.

### Claim 6 (depends on 5)

The system as claimed in claim 5, wherein the processor is adapted to extract cardiac features by one or more of:
determining the average heart beat interval;
determining a standard deviation of a heart beat interval;
determining a range of the heart beat interval; and
determining the nth percentile of the heart beat interval.

### Claim 7 (depends on 5)

The system as claimed in claim 5, wherein the processor is adapted to extract cardiac features by performing power spectral density analysis.

### Claim 8 (depends on 1)

The system as claimed in claim 1, wherein the processor is further adapted to extract cardiorespiratory coupling features from the PPG signal.

### Claim 9 (depends on 1)

The system as claimed in claim 1, wherein the processor is further adapted to derive sleep stages from heart rate variability information derived from the PPG signal.

### Claim 10 (depends on 9)

The system as claimed in claim 9, wherein the processor is further adapted to derive an estimated apnea-hypopnea index value based on a total sleep time obtained from the sleep stages and identified epoch periods during which sleep disordered breathing events are detected.

### Claim 11 (depends on 1)

The system as claimed in claim 1, wherein the processor is adapted to determine a severity level of the detected sleep disordered breathing events.

### Claim 12 (depends on 1)

The system as claimed in claim 1, further comprising an accelerometer for measuring body movements, wherein the processor is adapted to detect sleep disordered breathing events additionally taking account of body movements.

### Claim 13 (depends on 1)

The system as claimed in claim 1, wherein the processor is adapted to extract features by using a trained neural network.

### Claim 14

A computer-implemented method for detecting sleep apnea, comprising:
receiving a single-wavelength PPG signal;
providing an estimate of respiratory effort from the PPG signal and thereby deriving a respiratory effort signal;
extracting characteristic features from the respiratory effort signal; and
detecting sleep disordered breathing events from the extracted characteristic features.

### Claim 15 (depends on 14)

A computer program comprising computer program code means which is adapted, when said program is run on a computer, to implement the method of claim 14.