Comparative Waveform Analysis of Nose and Finger PPG Signals for Non-Invasive Blood Pressure Estimation

Continuous, non-invasive Blood Pressure (BP) monitoring is crucial for managing cardiovascular health, but traditional cuff-based devices are impractical for daily use. This feasibility study investigates the use of smart eyewear to acquire photoplethysmography (PPG) signals from the nose, for BP estimation via pulse wave analysis.We compared the performance of nose PPG against standard finger PPG in estimating systolic (SBP) and diastolic (DBP) BP. Data was collected from 8 healthy volunteers during a dynamic cycling protocol to induce cardiovascular changes. Subject-specific regression models were trained using features from both nose and finger PPG signals. Our results show the nose site provides performance comparable, to the finger. For DBP, the nose model yielded a higher correlation (R=0.83 vs. 0.79) and lower Mean Absolute Error (MAE) (4.54 mmHg vs. 4.67 mmHg). A similar trend was observed for SBP, with a marginally higher correlation for the nose site (R=0.74 vs. 0.72). These findings suggest nose PPG via smart glasses is a viable and robust alternative for non-invasive BP monitoring, opening new possibilities for wearables health-tracking solutions