Metrological characterization and signal processing of a wearable sensor for the measurement of heart rate variability

This paper presents a methodology for the processing of the Photoplethysmography (PPG) signal measured using a smartwatch during motion tests. For statistical validation, signals from 15 healthy subjects have been collected while the subjects are walking on a treadmill. The motion artifacts (MAs) of the PPG signal have been removed demonstrating that the 37% of the signals are affected by MAs. Then, the experimental performance assessment of the PPG signal, from which the heart rate variability (HRV) has been extracted, by measuring the RR intervals, is compared to the RR intervals extracted from ECG signals measured using a multi-parametric chest belt that is considered as a reference sensor. The uncertainty of the PPG sensor in the measurement of the RR intervals is ± 169 ms, (with a coverage factor k = 2) if compared to the reference method, which in percentage is 30%.