A Multimodal Transducer for Cardiopulmonary Activity Monitoring in Emergency

This paper is concerned with a new wearable system, which is able to monitor several vital signals and physiological variables in order to determine the cardiopulmonary activity status during emergencies. The innovative system consists of a multimodal broadband piezoelectric transducer based on polyvinylidene fluoride polymer integrated into a textile belt wrapped around the chest. An advanced electronic control unit, floating power supply, and wireless communication support make it suitable for portable monitoring during critical cardiopulmonary failures. The multimodal transducer is innovative in that only one sensitive element is employed to work as either an ultrasound (US) transceiver or piezoelectric sensor. The US transceiver is enabled to work at high frequency, i.e., it is excited by suitable pulses to emit an ultrasonic wave, which penetrates the body and receives the echo signals bouncing off the biological interfaces having different acoustic impedances. The piezoelectric sensor works at low frequency and acquires both signals generated by heart apex movements and the mechanical movement of the chest induced by respiration. This multimodality is allowed by a broadband of sensitivity jointly at a low value of the figure of merit (Q). Moreover, the transducer thickness is thin enough to assure a good adaptability to the biological site, and it is equipped with an advanced control unit enabling to switch from a high to a low working frequency. If jointly used along with an ECG wearable Holter, this transducer can be used to provide an exhaustive picture of the health status of the subject in the diagnostic and prognostic domains.