Key result
Multi-wavelength PPG combined-feature models estimate cuff SBP with ~13 mmHg error.
Why the study?
Cuffless blood pressure estimation from photoplethysmography remains challenging, motivating an exploratory evaluation of whether curvature-derived waveform features and amplitude ratios across multiple wavelengths are associated with cuff-based blood pressure readings.
Do curvature-derived waveform features from multi-wavelength PPG signals accurately estimate cuff-based systolic and diastolic blood pressure in physician-screened volunteers?
Cross-Sectional (n=48)
Do curvature-derived waveform features from multi-wavelength PPG signals accurately estimate cuff-based systolic and diastolic blood pressure in physician-screened volunteers?
Multi-wavelength PPG amplitude ratio features involving the dicrotic notch correlate with cuff-based blood pressure readings, though substantial error in systolic blood pressure estimation currently limits clinical utility.
Exploratory PPG features may aid cuffless BP research; leaves open validation in larger cohorts before clinical consideration.
Background: Cuffless blood pressure (BP) estimation from photoplethysmography (PPG) remains challenging. This exploratory study investigated whether curvature-derived waveform features from multiple PPG wavelengths, particularly amplitude ratios, are associated with cuff-based BP readings. Methods: Red, infrared, and green PPG signals were recorded for 90 s from 48 physician-screened volunteers (23 males and 25 females; mean age, 63.41 ± 14.20 years). A single automated upper-arm cuff BP measurement was initiated approximately 2 s after each PPG recording. A curvature-based procedure identified pulse valleys, systolic peaks, dicrotic notches, and diastolic peaks, from which timing, amplitude, and amplitude ratio features were extracted. Separate linear regression models for systolic BP (SBP) and diastolic BP (DBP) were evaluated using participant-level ten-fold cross-validation. In each iteration, feature selection and model fitting were performed using only the nine training folds, and the fitted model was evaluated on the held-out fold. Results: In the descriptive analysis across all 48 participants, amplitude ratio features involving the systolic peak and dicrotic notch showed stronger associations with cuff-based BP readings than most individual timing and amplitude features. For green-light PPG, the systolic-peak-to-dicrotic-notch amplitude ratio (RatioSN) had a correlation of approximately 0.56 with SBP and 0.48 with DBP. Based on out-of-fold predictions, the best combined-feature models achieved root mean square errors of 12.87 mmHg for SBP and 7.17 mmHg for DBP, with corresponding R2 values of 0.87 and 0.83. Conclusions: Multi-wavelength PPG amplitude ratio features, particularly those involving the dicrotic notch, warrant further investigation for cuffless BP estimation. The substantial SBP error, small cohort, and use of a single cuff measurement obtained after each PPG recording limit interpretation. These findings do not establish clinical measurement accuracy or continuous BP tracking.
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Chang et al. (2026) conducted a cross-sectional in Blood pressure estimation in physician-screened volunteers (n=48). Multi-wavelength (red, infrared, green) PPG curvature-derived waveform and amplitude ratio features vs. Single automated upper-arm cuff BP measurement was evaluated on Association and estimation error (RMSE and R2) for cuff-based systolic blood pressure (SBP) and diastolic blood pressure (DBP) (RMSE 12.87 mmHg for SBP (R2=0.87) and 7.17 mmHg for DBP (R2=0.83)). Multi-wavelength PPG combined-feature models estimated cuff BP with RMSE of 12.87 mmHg (R2=0.87) for SBP and 7.17 mmHg (R2=0.83) for DBP.
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