Sequential Validation of a Cuffless Photoplethysmography-Based Wristband for Blood Pressure Measurement: Algorithm Building to Regulatory Standard Trial
Introduction
Hypertension increases cardiovascular risk. Measuring reliable blood pressure (sBP and dBP for systolic and diastolic BP) is challenging. A photoplethysmography (PPG)-based wristband with a custom BP algorithm could provide continuous BP. The algorithm was made by PPG channel aggregation, band-pass filtering and segment creation and evaluated the different PPG colors. Noise and interference were removed. PPG segments were created with a quality factor based on pulse quality. The AI model learned patterns from structured data, including pre-processed features and initialization measurements, ranking their importance.
Hypothesis
cuffless PPG-based-wristband method for continuous BP monitoring is compatible with ISO 81060-2:2019.
Methods
Compare PPG-guided BP algorithm predictions with subclavian arterial reference measurements during cardiac catheterization. Consecutive patients meeting ISO 81060-2:2019 criteria were included. Reference measurements used a validated invasive BP device (100Hz). PPG signals were collected at 128Hz using six light emission diodes and two photodiodes. Three initialization measurements with a validated cuff were taken before catheterization. Machine learning-based BP algorithm utilized 100+ features. Correlation, mean error, and standard deviation (SD) and sBP and dBP were determined.
Results
97 patients provided 420 samples. Mean age, weight, and height were 67 years, 183.7 lbs, and 5'8.5" respectively. sBP swas ≤100mmHg (11%) and ≥160mmHg (25%). dBP was ≤70mmHg (53%) and ≥85mmHg (24%). BP algorithm predictions correlated strongly with reference measurements for sBP (r = 0.985) and dBP (r = 0.961) BP. Mean error was ±3.7mmHg (SD 4.4 mmHg) for sBP and ±2.5mmHg (SD 3.7 mmHg) for dBP. Results were consistent across gender and skin color categories (Fitzpatrick I-VI), but also for different strata of BP values.
Conclusions
Wristband-based PPG with the developed BP algorithm provides accurate continuous BP monitoring across various BP ranges. It offers a valid and less burdensome alternative to cuff BP measurements for in-hospital and at-home monitoring. Further research is needed to evaluate algorithm precision during movement and for long-term prediction stability.