Finger Versus Wrist Photoplethysmography Signals: Implications for Wearable Blood Pressure Monitoring

Blood pressure (BP) is a crucial indicator of cardiovascular health and provides essential information about the heart. Traditional cuff-based BP measurement with equipment like sphygmomanometers is uncomfortable and discontinued. Cuffless BP monitoring using photoplethysmography (PPG) signals has become an area of interest in the research community, particularly with the advent of wearables such as the Apple Watch and Xiaomi Band. While most wearable PPG signals are obtained from the wrist, the most widely used benchmark dataset, the MIMIC dataset, collects PPG signals from the finger. In this study, we collected PPG signals from both finger and wrist locations from 71 participants and compared their similarities and differences. Our results show that the quality of finger PPG signals is superior to that of wrist PPG signals. Additionally, transferring PPG signals from the finger to the wrist is more successful than transferring signals from the wrist to the finger. These findings make it possible to use the publicly available MIMIC dataset to predict BP from smartwatches. This study bridges the gap between academia and industry, and is an important step towards developing continuous BP monitoring for better management of cardiac health.