Strain Plethysmography at the Radial Artery: A Promising Technique for Cuffless Blood Pressure Estimation.

This study introduces a novel framework based on radial strain plethysmography (SPG) for cuffless estimation of blood pressure (BP). For this purpose, a sensitive, custom-built micro-electromechanical systems (MEMS) strain sensor is used to capture pulse information at the radial artery. A comprehensive feature set consisting of the timing intervals between the fiducial points of the SPG segments, their derivatives, and integrals was extracted and concatenated with the demographic information of the subjects. An XGBoost regressor is then trained on the extracted features to estimate the systolic and diastolic blood pressures, SBP and DBP, respectively. The model is evaluated on 15 subjects using a 5-cross-validation (5-CV) approach. Mean error (ME), mean absolute error (MAE), and root mean square error (RMSE) of -0.22, 3.59, and 5.12 mmHg, respectively, are reported for the estimated DBP values, and ME, MAE, and RMSE of -1.00, 6.23, and 8.96 mmHg, respectively, are achieved for SBP estimation. It is also indicated that significant features for BP estimation encompass both demographic information and timing intervals, highlighting their combined importance. The results demonstrate that radial SPG is a reliable alternative to optical-based technologies for accurate BP estimation.