Beat-to-Beat Detection Accuracy Using the Ultra Low Power Senbiosys PPG Sensor

Abstract

Heart-rate variability (HRV) is a strong indicator of a healthy cardiovascular system. It is the physiological phenomenon defined by the variation of the duration between consecutive heartbeats. Consequently, for a proper and a reliable HRV analysis, it is essential to have an accurate estimation of the inter-beat intervals (IBI). In addition to accurate IBI detection, unobtrusive and low power consuming devices are important for long term HRV monitoring. In this study, we aim at evaluating the beat-to-beat detection accuracy of the ultra low power Senbiosys Photoplethysmography (PPG) sensor, the SB200. Eight male subjects (\(37.25 \pm 10.67\) years of age) participated in the study. The recordings include a finger PPG from the SB200, another finger PPG from the Shimmer3 optical development kit, and a reference ECG from the Shimmer3 ECG development kit. The study shows that the SB200 detects \(99.27\%\) of the beats with IBI values of mean absolute error (MAE) 6.58 ms compared to the R-to-R interval (RRI) values derived from the ECG and an average current consumption of less than \(190\,\upmu \text {A}\). Moreover, reducing the LED power consumption of the SB200 by 1/2 and 1/4 does not affect the detection rate, maintaining its value at \(99.25\%\) and \(99.22\%\), respectively. However, it does reduce the IBI estimation accuracy resulting in an MAE of 7.37 ms and 8.43 ms, respectively.