Measurement of Plethysmogram and Mechanomyogram Using Electret Sensor

ABSTRACT In this study, we attempted to estimate heart rate and blood pressure using an electret capacitor sensor (ECS) that measures pulse waves with high resolution. The ECS was attached to multiple areas of the body, and plethysmogram and mechanomyogram (pulse wave and muscle sound) were measured while blood pressure and pulse rate were measured. The results showed that the ECS had a signal‐to‐noise ratio more than 20 dB higher than that of the accelerometer (ACS), especially in the low‐frequency range. In pulse wave measurements, peaks derived from the first and second heart sound were identified; multiple regression analysis of the 6–50 Hz component of the peak of the first sound showed that correlations with R 2 values of 0.6 or higher were observed in systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse rate, even when a single first sound peak was used. In addition, ECS was able to detect muscle sounds during loading with a higher signal‐to‐noise ratio than ACS. Based on these results, it is expected that ECS is a sensor that can measure pulse wave and muscle sound with broadband frequency components and has the potential to estimate blood pressure and pulse rate from pulse wave in a short time.