Influence of gravitational offset removal on heart beat detection performance from android smartphone seismocardiograms

Abstract

Seismocardiography (SCG) is a non-invasive method of analyzing and recording cardiovascular vibrations on the chest wall. Mobile devices offer the possibility to monitor cardiac activity. Accelerometers used in such analysis register gravitational offset because the effects of gravity on an object are indistinguishable from acceleration. Our aim is to investigate the influence of gravitational offset removal on heart beat detection from smartphone seismocardiograms. We registered SCG signals from two subjects (male and female) in supine position before and after enabling gravitational offset removal to analyze its influence on beat detection algorithm performance. Our algorithm consists of signal preprocessing, calculating analytical envelope and RMS envelope and peak finding. The influence of gravitational offset on heart beat detection is insignificant due to band-pass filtration. Offset removal slightly increased PPV for male subject and sensitivity for female subject. We observed beat detection quality improvement when using RMS envelope. The best performance was achieved using RMS envelope on signal from male subject. This study proves insignificant influence of gravitational offset on our heart beat detection algorithm. Very high performance on analyzed signals (Se = 0.990, PPV = 0.948 for all beats, Se = 1.000, PPV = 0.962 for the best case) encourages studies on another SCG data sets or experiment set-ups.