Wearable pulse wave velocity sensor using flexible piezoelectric film array

This report describes our proposed method of measuring pulse wave velocity (PWV) using a flexible piezoelectric film array. PWV is important cardiovascular information that can contribute to the early detection and treatment of hypertension and arteriosclerosis. Conventional methods used to calculate PWV measure the pulse transit time (PTT) between pulse waves measured at multiple positions of the body, or between an electrocardiogram (ECG) and a pulse wave. These methods require multiple devices to be worn on the body. By contrast, the proposed method realizes PTT measurement and PWV estimation using a single device incorporating a piezoelectric film array. Although it requires extraction of slight differences of pulse arrival times between pressure pulse waves with low signal-noise ratio (SNR), we introduce a signal processing method using cross correlation to resolve this difficulty. The proposed algorithm was applied to the pressure pulse wave measured using the prototype sensor at two points on the wrist. Measurements of four participants using the reference sensor confirmed that positive correlation was obtained with measured PTT. The correlation coefficient was as high as 0.94 with a low-noise condition.