Non-invasive Measurement of Pulse Rate Variability Signals by a PVDF Pulse Sensor

Pulse rate variability (PRV) is a small change in the heart beat cycle that can be obtained from the pulse signal. PRV has important application value in clinical diagnosis, disease monitoring, and prevention. PRV can be conveniently extracted from the fingertip pulse signal obtained by a photoplethysmography (PPG) pulse sensor. However, this method requires clamping the fingertip during the measurement, which is uncomfortable for the monitored person and is not conducive to continuous PRV detection in family monitoring or in a specific environment, such as driving. Thus, in this paper, we propose a pulse sensor with a soft polyvinylidene fluoride (PVDF) piezoelectric film. The non-invasive pulse signals can be collected by lightly pressing the fingertip on the sensor. In the experiment, two PVDF pulse sensors were used to collect the pulse waves from the left wrist and left forefinger; simultaneously, an infrared PPG pulse sensor measures the pulse wave of the right forefinger. The pulse waves measured by the three methods were further filtered to extract PRV signals and compare the differences. The results show that the PRV signal obtained by the PVDF sensor pressing measurement method has good consistency with the PRV signal obtained by PPG measurement, and the PVDF pulse sensor can be conveniently applied in wearable devices and portable medical devices to obtain the PRV.