Noninvasive Hemoglobin Measurements With Photoplethysmography in Wrist

This paper describes the application of multiwavelength photoplethysmography (MW-PPG) in reflectance mode for noninvasive measurements total hemoglobin concentration. Consumer wrist-wearable devices (smartwatches, wristbands) typically contain a sensor operating mode, as opposed to clinical pulse-oximetry sensors transmittance mode. We assume that generally accepted approach analysis transmittance-mode MW-PPG signal, based on direct implementation Beer-Lambert law, is not applicable reflectance-mode signals. propose shape signal carries information regarding distribution optical paths at different wavelengths within tissue, which crucial correct estimation absorption light probe volume. have developed and tested several machine-learning algorithms analyze estimate concentration this analysis. To train validate algorithms, we collected dataset 840 signals measured from 170 volunteers by using PPG sensor. Three reference were used label data test performance algorithms: an invasive laboratory blood test, minimally HemoCue Hb 201+, Masimo Radical-7 pulse-oximeter. The best achieved with algorithm, mean absolute error MAE ≈ 12.6±1.7 g/L correlation coefficient R 0.66±0.09, comparable device.