Intrinsic PPG-ECG Coupling for Accurate and Low-Power Blood Pressure Monitoring

Long-term, continuous blood pressure (BP) monitoring is of great clinical importance for the early diagnosis and dynamic assessment of cardiovascular diseases. Conventional BP monitoring methods based on pulse transit time (PTT) typically rely on at least two independent signal channels. However, multi-signal processing introduces synchronization errors and inaccuracies in fiducial point detection, thereby limiting the accuracy and efficiency of BP estimation. In addition, recording and processing multiple signals increases circuit complexity and elevates system power consumption. To overcome these limitations, we propose an intrinsic signal synchronization strategy based on photoplethysmography-electrocardiogram (PPG-ECG) signal coupling. By fusing PPG and ECG signals into a unified waveform that preserves the essential features of both, intrinsic synchronization is inherently achieved. Compared with conventional independent signal processing, this approach reduces PTT error to less than 15 ms and achieves a PTT detection rate exceeding 98%. Furthermore, the data load is significantly reduced, resulting in a 43.75% decrease in system power consumption. Based on this principle, we developed a compact, lightweight, chest wearable sensor patch. The device demonstrates high BP measurement accuracy (ME ≤ 5 mmHg, STD ≤ 8 mmHg) across diverse scenarios, including both static and dynamic BP conditions. This strategy not only simplifies the design and manufacturing of BP monitoring devices but also enhances their performance in terms of accuracy, energy efficiency, and operational lifetime.