Using Bone Conduction Technology for Phonocardiogram Measurement Based on the Watch-Type Device: A Feasibility Study

Phonocardiogram (PCG) provides the most valuable information about the mechanical activity of the heart and has a significant role in postoperative out-of-hospital follow-up and cardiac health screening. Currently, the efficient heart disease diagnosis algorithms based on PCGs are proposed and are expected to be used for cardiac health routine screening. However, wearable PCG measurement devices still have limitations in routine monitoring. This study proposes a novel method for PCG measurement: using bone conduction sensors to measure PCG at the wrist dorsum and verifying the accuracy of PCG measurement in different body positions. First, the highly sensitive bone conduction sensor was integrated into the watch, which realizes bone conduction PCG measurement with the vibration transmission path of the body surface-wrist-watch. Second, photoplethysmogram (PPG) and the Hilbert envelope were utilized to assist the localization of S2, which significantly improved the S2 detection rate on the palmar side of the wrist. Finally, the anti-noise performance of the device was verified in different noise environments. The results show that the correlation coefficients of the wrist palm and dorsum side S1 intervals were 0.986 and S2 intervals were 0.976. The average detection rate of the wrist dorsum side S1 was 99.5% and the average detection rate of S2 was 95.5% in all body positions. Therefore, this article provides a practical foundation for the realization of routine cardiac health detection.