Breathing sound analysis for estimation of airlow rate

Abstract

Apparatus for use detection of apnea includes a microphone mounted in the ear of the patient for detecting breathing sounds and a second external microphone together with an oximetric sensor. A transmitter at the patient compresses and transmits the signals to a remote location where there is provided a detector module for receiving and analyzing the signals to extract data relating to the breathing. The detector uses the entropy or range of the signal to generate an estimate of air flow while extracting extraneous snoring and heart sounds and to analyze the estimate of air flow using Otsu's threshold to detect periods of apnea and / or hypopnea. A display provides data of the detected apnea / hypopnea episodes and related information for a clinician.

Description

[0001] This invention relates to an apparatus for use in breathing sound analysis for estimation of airflow rate.

[0002] This application is related to a co-pending Application filed on the same day as this application under Attorney Docket No. 84201-1402 and entitled BREATHING SOUND ANALYSIS FOR DETECTION OF SLEEP APNEA / HYPOPNEA EVENTS.BACKGROUND OF THE INVENTION

[0003] Acoustical respiratory flow estimation has drawn much attention in recent years due to difficulties in airflow measurement. In clinical respiratory and / or swallowing assessment, flow is usually measured by spirometry devices, such as pneumotachograph, nasal cannulae connected to a pressure transducer, heated thermistor or anemometry. Airflow is also measured by indirect means, i.e., detection of chest and / or abdominal movements using respiratory inductance plethysmography (RIP), strain gauges, or magnetometers. The most reliable measurement of airflow is achieved by a mouth piece or facemask connected to a pneumotachogra...

Examples

example 1

[0141]Eight healthy subjects (3 males) aged 33.1±6.6 years with body mass index of 23.3±3.5 participated in this study. Tracheal sound was recorded using Siemens accelerometer (EMT25C) placed over supra-sternal notch using double adhesive tapes. Respiratory flow signal was measured by a mouth piece pneumotachograph (Fleisch No. 3) connected to a differential pressure transducer (Validyne, Northridge, Calif.). The subjects were instructed to breathe at very shallow flow rates with different periods of breath hold (2, 4, 6 sec) to simulate apnea. Tracheal sound and flow signals were recorded and digitized simultaneously at a 10240 Hz sampling rate.

Feature Extraction

[0142]Among several features of tracheal sound such as the sound's mean amplitude, average power and entropy used for flow estimation, entropy and the range of signal have been shown to be the best features following flow variation. Therefore, in this study tracheal sounds entropy was used to detect apnea (breath hold in th...

example 2

[0146]In this study 10 healthy subjects of the previous participated. Subjects were in two age groups: 5 adults (all female) 29±8 years old and 5 children (3 female) 9.6±1.7 years old. Respiratory sounds were recorded using Siemens accelerometers (EMT25C) placed over supra-sternal notch and the upper right lobe lung. Respiratory flow was measured by a pneumotachograph (Fleisch No. 3) connected to a differential pressure transducer (Validyne, Northridge, Calif.). Subjects were instructed to breathe at 5 different flow rates with 5 breaths at each target flow followed by a 10s of breath hold at the end of experiment. In this study the shallow (27 ml / s / kg) target flow rates were investigated. Tracheal sound signals were used for flow estimation while the lung sound signal in correspondence with tracheal sound signals were used for respiratory phase detection. The onsets of breaths were detected by running a threshold on the average power of the tracheal sounds and detecting the valleys...

[0001] This invention relates to an apparatus for use in breathing sound analysis for estimation of airflow rate.

[0002] This application is related to a co-pending Application filed on the same day as this application under Attorney Docket No. 84201-1402 and entitled BREATHING SOUND ANALYSIS FOR DETECTION OF SLEEP APNEA / HYPOPNEA EVENTS.BACKGROUND OF THE INVENTION

[0003] Acoustical respiratory flow estimation has drawn much attention in recent years due to difficulties in airflow measurement. In clinical respiratory and / or swallowing assessment, flow is usually measured by spirometry devices, such as pneumotachograph, nasal cannulae connected to a pressure transducer, heated thermistor or anemometry. Airflow is also measured by indirect means, i.e., detection of chest and / or abdominal movements using respiratory inductance plethysmography (RIP), strain gauges, or magnetometers. The most reliable measurement of airflow is achieved by a mouth piece or facemask connected to a pneumotachogra...

Examples

example 1

[0141]Eight healthy subjects (3 males) aged 33.1±6.6 years with body mass index of 23.3±3.5 participated in this study. Tracheal sound was recorded using Siemens accelerometer (EMT25C) placed over supra-sternal notch using double adhesive tapes. Respiratory flow signal was measured by a mouth piece pneumotachograph (Fleisch No. 3) connected to a differential pressure transducer (Validyne, Northridge, Calif.). The subjects were instructed to breathe at very shallow flow rates with different periods of breath hold (2, 4, 6 sec) to simulate apnea. Tracheal sound and flow signals were recorded and digitized simultaneously at a 10240 Hz sampling rate.

Feature Extraction

[0142]Among several features of tracheal sound such as the sound's mean amplitude, average power and entropy used for flow estimation, entropy and the range of signal have been shown to be the best features following flow variation. Therefore, in this study tracheal sounds entropy was used to detect apnea (breath hold in th...

example 2

[0146]In this study 10 healthy subjects of the previous participated. Subjects were in two age groups: 5 adults (all female) 29±8 years old and 5 children (3 female) 9.6±1.7 years old. Respiratory sounds were recorded using Siemens accelerometers (EMT25C) placed over supra-sternal notch and the upper right lobe lung. Respiratory flow was measured by a pneumotachograph (Fleisch No. 3) connected to a differential pressure transducer (Validyne, Northridge, Calif.). Subjects were instructed to breathe at 5 different flow rates with 5 breaths at each target flow followed by a 10s of breath hold at the end of experiment. In this study the shallow (27 ml / s / kg) target flow rates were investigated. Tracheal sound signals were used for flow estimation while the lung sound signal in correspondence with tracheal sound signals were used for respiratory phase detection. The onsets of breaths were detected by running a threshold on the average power of the tracheal sounds and detecting the valleys...

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