New Ultrasound-Based Wearable System for Cardiac Monitoring

This work deals with the realization of an innovative wearable system for detecting current cardiac status. Signals acquired necessary to detect this status are the breathing signal, the heart apex pulse and the heart mechanical behavior. This system is based on a bi-modal sensor (an ultrasound transducer constituted by PVDF polymer) able to switch its sensitivity frequency range from low to high. The transducer, which has a low Q factor in order to exhibit a large broad bandwidth, is placed inside a textile belt. The wearable system is able to detect cardiac sounds from which the heart beat and the respiratory signal can be extracted, to generate ultrasound signals which can bounce off the heart, and to receive the back-propagated echoes. Innovative electronic tactics are implemented for maximizing sensor sensitivity at low frequency, saving power consumption and, at the same time, providing the right amount of energy for ultrasound investigation. The system is completely portable and wearable, powered by a rechargeable battery.