Using piezoelectric sensor for continuous-contact-free monitoring of heart and respiration rates in real-life hospital settings

In this paper we review over 1-million hours of experience with vital signs monitoring using piezoelectric sensor in real clinical settings. The sensor developed by EarlySense ltd is placed under the mattress and has no direct contact with the patient. The force exerted on the sensor is a summation of 3 sources, originating from gross body movement, chest wall movement due to respiration, and recoil of the body due to heart pulse (cardioballistic effect). The piezoelectric transducer generates a signal that can be separated into motion, respiration and ballistocardiogram (BCG) waveforms, from which movement, respiration rate (RR) and heart rate (HR) can be obtained respectively. Clinical trials to validate the extracted HR and RR values were performed with 16 adults and 37 children in real-life sleep lab settings and 42 ICU patients. The resulted absolute relative errors (aRE) over a wide range of values, including tachycardia, bradycardia, tachypnea and bradypnea, was 8% or lower. Controlled studies were used to validate movement against catigraph, and bed exit against visual inspection. In this work we also report some added values of this monitoring method to various irregular, yet hospital abundant, clinical cases; These include insights to end-of-life process, monitoring capabilities for patients with Left-Ventricular Assist Device, monitoring ventricular fibrillation during electrophysiological study, detecting apnea, and unique breathing patterns.