# US 2014/0194780 A1 · Method and device for apnea and hypopnea detection

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- Number: US 2014/0194780 A1
- Document ID: US20140194780A1
- Status: Published application
- Kind: A1
- Application number: 14/117,922
- Filed: 2012-05-17
- Published: 2014-07-10
- Earliest claimed: 2011-05-17
- Assignees: University Health Network
- Inventors: Hisham Alshaer; Geoffrey Roy Fernie; T. Douglas Bradley
- Web page: https://patentgrep.com/patent/US20140194780A1

## CPC

- A61B 7/04: Electric stethoscopes
- A61B 5/4818: {Sleep apnoea}
- A61B 5/6803: {Head-worn items, e.g. helmets, masks, headphones or goggles}
- 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)}
- A61B 7/003: {Detecting lung or respiration noise}
- A61B 5/087: Measuring breath flow
- A61B 5/7257: {using Fourier transforms}
- A61B 2562/0204: Acoustic sensors
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

Disclosed herein is a method and device for apnea and hypopnea detection. In one embodiment, a method is provided for detecting apneas and hypopneas from a digitized breath sound recording acquired from a candidate suspected of sleep apnea. The method comprises scanning an amplitude profile of the digitized breath sound recording to identify a prospect event segment; evaluating characteristics of the prospect event segment for consistency with one or more preset apnea-specific criteria; classifying the prospect event segment as representative of an apnea upon it satisfying each of the one or more apnea-specific criteria; evaluating the prospect event characteristics for consistency with one or more preset hypopnea-specific criteria distinct from the apnea-specific criteria; and classifying the prospect event segment as representative of a hypopnea upon it satisfying each of the one or more hypopnea-specific criteria.

## Claims

### Claim 1

A method for detecting apneas and hypopneas from a digitized breath sound recording acquired from a candidate suspected of sleep apnea, the method comprising: scanning an amplitude profile of said digitized breath sound recording to identify a prospect event segment;
evaluating characteristics of said prospect event segment for consistency with one or more preset apnea-specific criteria;
classifying said prospect event segment as representative of an apnea upon it satisfying each of said one or more apnea-specific criteria;
evaluating said prospect event characteristics for consistency with one or more preset hypopnea-specific criteria distinct from said apnea-specific criteria; and
classifying said prospect event segment as representative of a hypopnea upon it satisfying each of said one or more hypopnea-specific criteria.

### Claim 2 (depends on 1)

The method of claim 1, said prospect event characteristics being evaluated for consistency with said one or more preset hypopnea-specific criteria only upon said characteristics failing to satisfy at least one of said one or more apnea-specific criteria.

### Claim 3 (depends on 1)

The method of claim 1, said scanning step comprising scanning said amplitude profile to identify multiple prospect event segments, the method further comprising sequentially repeating steps subsequent to said scanning step for each of said identified prospect event segments.

### Claim 4 (depends on 1)

The method of claim 1, further comprising increasing an apnea/hypopnea count for each said classified apnea and hypopnea, and outputting a severity index representative of a condition of the candidate as a function of said count.

### Claim 5 (depends on 1)

The method of claim 1, said one or more apnea-specific criteria comprising a minimum apnea event amplitude depth threshold, and said one or more
hypopnea-specific criteria comprising a distinct minimum hypopnea event amplitude depth threshold shallower than said minimum apnea event amplitude depth threshold.

### Claim 6 (depends on 5)

The method of claim 5, said hypopnea event amplitude depth threshold comprising both a minimum pre-apneic depth threshold and a distinct post-apneic depth threshold.

### Claim 7 (depends on 6)

The method of claim 6, said pre-apneic depth threshold being shallower than said post-apneic depth threshold.

### Claim 8 (depends on 5)

The method of claim 5, said scanning step comprising scanning said amplitude profile for segments satisfying a minimum prospect event depth threshold, said minimum prospect event depth threshold at least as shallow as said minimum hypopnea event amplitude depth threshold.

### Claim 9 (depends on 1)

The method of claim 1, said prospect event segment characterized by a falling edge and a rising edge temporally separated by a low-amplitude segment, said hypopnea-specific criteria comprising a minimum decreasing amplitude gradient for said falling edge.

### Claim 10 (depends on 1)

The method of claim 1, further comprising defining said amplitude profile as a breath-to-breath amplitude profile over time.

### Claim 11 (depends on 1)

The method of claim 1, further comprising extracting breath sounds associated with expiration, and defining said amplitude profile solely as a function of said extracted expiration breath sounds.

### Claim 12 (depends on 1)

The method of claim 1, further comprising recording said breath sounds via a microphone embedded within a face mask to be worn by the subject during sleep, the microphone disposed at a distance from a nose and mouth area of the candidate's face to be exposed to and thereby acquire expiratory airflow sounds.

### Claim 13 (depends on 1)

The method of claim 1, automatically implemented by one or more processors of a computing system, and further comprising outputting, via a user interface, an indication of a candidate's condition as a function of each said classified apnea and hypopnea.

### Claim 14 (depends on 1)

A computer-readable medium comprising statements and instructions stored thereon for implementation by one or more processors of a computing system to detect apneas and hypopneas from a digitized breath sound recording acquired from a candidate suspected of sleep apnea, in accordance with the steps of the method as claimed in claim 1.

### Claim at position 15

-20. (canceled)

### Claim 21 (depends on 1)

A system for detecting apneas and hypopneas from a digitized breath sound recording acquired from a candidate suspected of sleep apnea, the system comprising: one or more processors;
a computer-readable medium accessible by said one or more processors and having stored thereon statements and instructions executable thereby to operate on said recording in accordance with the method of claim 1.

### Claim 22 (depends on 21)

The system of claim 21, further comprising a face mask having a microphone mounted thereon and reproducibly disposable, upon the candidate wearing the mask, at a distance above a nose and mouth area of the candidate so to intercept and capture expiratory airflow sounds emanating therefrom to be digitized for processing.

### Claim 23 (depends on 22)

The system of claim 22, said mask further comprising a removable data storage medium operatively coupled to said microphone for storing recorded breath sounds thereon prior to processing.

### Claim at position 19

-25. (canceled)

### Claim 26 (depends on 14)

The computer-readable medium of claim 14, further comprising statements and instructions for increasing an apnea/hypopnea count for each said classified apnea and hypopnea, and outputting a severity index representative of a condition of the candidate as a function of said count.

### Claim 27 (depends on 14)

The computer-readable medium of claim 14, wherein said one or more apnea-specific criteria comprise a minimum apnea event amplitude depth threshold, and wherein said one or more hypopnea-specific criteria comprise a distinct minimum hypopnea event amplitude depth threshold shallower than said minimum apnea event amplitude depth threshold, said hypopnea event amplitude depth threshold comprising both a minimum pre-apneic depth threshold and a distinct post-apneic depth threshold, said pre-apneic depth threshold being shallower than said post-apneic depth threshold.

### Claim 28 (depends on 14)

The computer-readable medium of claim 14, wherein said prospect event segment is characterized by a falling edge and a rising edge temporally separated by a low-amplitude segment, said hypopnea-specific criteria comprising a minimum decreasing amplitude gradient for said falling edge.

### Claim 29 (depends on 22)

The system of claim 22, wherein said computer-readable medium further comprises statements and instructions for increasing an apnea/hypopnea count for each said classified apnea and hypopnea, and outputting a severity index representative of a condition of the candidate as a function of said count.