Low-power, noninvasive measurement system for wearable ballistocardiography in sitting and standing positions

Ballistocardiography (BCG), the noninvasive measurement of the reaction forces of the body to the cardiac ejection of blood, is one of few methods available for unobtrusively assessing the mechanical aspects of cardiovascular health outside clinical settings. In this study, two sizes of piezoelectric film sensors were installed into the seat cushion of a chair and the foot insole, respectively, to acquire local BCG signals in sitting and standing positions. The design and engineering implementation of the signal processing circuit and data transmission system are discussed below. Although wearable BCG measurement devices have been extensively researched to date, to the authors' knowledge, they have never been tested in regards to power consumption and electrostatic discharge (ESD) immunity. In this work, comprehensive experiments were conducted to show the low power consumption and high reliability of the proposed system. The shapes and the amplitudes of measured signals were examined in detail. The results suggest that the proposed system can feasibly and reliably be used to continuously record and evaluate cardiovascular changes occurring throughout an individual's daily life.