Unconstrained and non-invasive measurement of heart-beat and respiration periods using a phonocardiographic sensor
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Witthe rapid growth in the number of elderly people in the population, interest in health monitoring is increasing. Therefore the development of an unconstrained and non-invasive vital signs measurement system could be important for monitoring health status at home or in hospitals or nursing facilities. A simple system is proposed for measuring heart-beat and respiration periods for home healthcare. This was achieved with a phonocardiographic (PCG) sensor set on a water-mat or air-mat. The PCG sensor was an acceleration sensor that extracted the vibration of the mat caused by heart-beat and respiration. By calculating an autocorelation function of the fully rectifiedsensor output or by local pattern matching between the rectifiecbutput and a reference signal (pre-memorised for each subject), the system measured the average and instantaneous periods of both heart-beat and respiratin. Results showed that these periods were measured to a similar level of accuracy as for the electrocardiogram and thermistor respiration pickup. The comparative accuracies were within the following ranges: average heartbeat 0.19% to 0.67%, instantaneous heartbeat 0.53%to 1.15%, average respiration 0.51% to 2.17% and instantaneous respiration 2.51% to 5.20%.
KeywordsHeart-beat Respiration Phonocardiographic sensor Unconstrained Non-invasive Home healthcare
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