# US 11,304,654 B2 · Method for detecting abnormal respiration using a photoplethysmography (PPG) signal

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- Number: US 11,304,654 B2
- Document ID: US11304654B2
- Status: Granted
- Kind: B2
- Application number: 15/696,428
- Filed: 2017-09-06
- Published: 2018-04-19
- Granted: 2022-04-19
- Earliest claimed: 2016-10-18
- Assignees: Electronics and Telecommunications Research Institute
- Applicants: Electronics and Telecommunications Research Institute
- Inventors: Hyun Soon Shin; Chan Young Hahm
- Web page: https://patentgrep.com/patent/US11304654B2

## CPC

- A61B 5/4818: {Sleep apnoea}
- A61B 5/0004: {characterised by the type of physiological signal transmitted}
- 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 5/0816: {Measuring devices for examining respiratory frequency (measuring frequency of electric signals G01R23/00)}
- A61B 5/6824: {Arm or wrist}
- A61B 5/0826: {Detecting or evaluating apnoea events (sleep apnoea A61B5/4818)}
- A61B 5/7225: {Details of analogue processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation (input circuits for detecting, measuring, or recording bioelectric or biomagnetic signals A61B5/30; specific diagnostic methods using bioelectric or biomagnetic signals A61B5/316)}
- A61B 5/725: {using specific filters therefor, e.g. Kalman or adaptive filters (specific diagnostics methods using using bioelectric or biomagnetic signals A61B5/316)}
- A61B 5/7278: {Artificial waveform generation or derivation, e.g. synthesizing signals from measured signals}
- A61B 5/742: {using visual displays (displays for heart-related electrical signals, e.g. ECG, A61B5/339)}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

An abnormal respiration detection apparatus includes a sensor for sensing a PPG signal from an optical signal reflected and received from a user's body; a band pass filter for extracting a signal of a required band from the PPG signal; an analog-to-digital converter for performing a digital conversion on the filtered PPG signal; and an abnormal respiration recognition unit deriving a respiration rate signal from the digital-converted PPG signal, deriving a plurality of respiration rate characteristic values through a time axis analysis on the derived respiration rate signal, and detecting an abnormal respiration using the derived plurality of respiration rate characteristic values. The embodiments can be utilized to monitor the survival of elders who live alone, soldiers isolated in a military operation, persons isolated in disaster and accident sites, thereby contributing to public and social safety and building of welfare society and nation.

## Claims

### Claim 1

An abnormal respiration detection method comprising:
sensing a photoplethysmography (PPG) signal from an optical signal reflected and received from a user's body;
performing a band pass filtering for extracting a signal of a required band from the sensed PPG signal;
performing a digital conversion on the filtered PPG signal; and
deriving a respiration rate signal from the digital-converted PPG signal, deriving a plurality of respiration rate characteristic values through a time-axis analysis on the derived respiration rate signal, and detecting an abnormal respiration using the derived plurality of respiration rate characteristic values,
wherein the plurality of respiration rate characteristic values include peak-to-valley values of the respiration rate signal expressed on the time axis and the number of peaks per unit time of the respiration rate signal,
wherein the detecting an abnormal respiration is performed by a first analysis using the peak-to-valley values of the respiration rate signal and then a second analysis using the number of peaks per unit time of the respiration rate signal, the second analysis being successively performed if the first analysis indicates the detection of abnormal respiration,
wherein the first analysis is performed according to Equation 1 by comparing a difference between a maximum peak-to-valley value of the peak-to-valley values during a current unit time and a previously-calculated moving average of the peak-to-valley values during a previous unit time with a first reference value,
{

PPcurrent
-
PP
⁢
average

PP
⁢
average
>
10
⁢
%
,
first
⁢
⁢
detection
⁢
⁢
of
⁢
⁢
apnea

PPcurrent
-
PP
⁢
average

PP
⁢
average
≤
10
⁢
%
,
normal
⁢
⁢
respiration
[
Equation
⁢
⁢
1
]
where PPcurrent represents the maximum peak-to-valley value during the current unit time, and PPaverage represents the previously-calculated moving average of the peak-to-valley values, and
wherein the second analysis is performed according to Equation 2 by comparing a difference between the number of peaks during the current unit time and a previously-calculated moving average value of the number of peaks during the previous unit time with a second reference value,
{

PNs
,
current
-
PNs
,
average

PNs
,
average
>
40
⁢
%
,
second
⁢
⁢
detection
⁢
⁢
of
⁢
⁢
apnea

PNs
,
current
-
PNs
,
average

PNs
,
average
≤
40
⁢
%
,
normal
⁢
⁢
respiration
[
Equation
⁢
⁢
2
]
where PNcurrent represents the number of peaks during the current unit time, and PNaverage represents the moving average of the number of peaks during the previous unit time which has been previously calculated through several unit times,
wherein the detecting an abnormal respiration further includes adding the maximum peak-to-valley value during the current unit time to the moving average of peak-to-valley to recalculate an updated moving average of peak-to-valley values, when the difference between the maximum peak-to-valley value during the current unit time and the previously-calculated moving average of peak-to-valley values does not exceed the first reference value, and
wherein the detecting an abnormal respiration further includes adding the number of peaks during the current unit time to the moving average of the number of peaks to recalculate an updated moving average of the number of peaks, when the difference between the number of peaks during the current unit time and the previously-calculated moving average of the number of peaks during a unit time does not exceed the second reference value.

### Claim 2 (depends on 1)

The abnormal respiration detection method according to claim 1, wherein the detecting an abnormal respiration further includes obtaining the respiration rate signal by performing a band pass filtering of a respiratory frequency band of 0.2 to 0.3 Hz frequency on the sensed PPG signal.

### Claim 3 (depends on 1)

The abnormal respiration detection method according to claim 1, wherein the abnormal respiration includes at least one of a central apnea, an obstructive apnea, and a mixed apnea.