Can PPG be used for HRV analysis?

Abstract

Heart rate variability (HRV) represents one of the most promising markers of the autonomic nervous system (ANS) regulation. However, it requires the acquisition of the ECG signal in order to reliably detect the RR intervals, which is not always easily and comfortably available in personal health applications. Additionally, due to progress in single spot optical sensors, photoplethysmography (PPG) is an interesting alternative for heartbeat interval measurements, since it is a more convenient and a less intrusive measurement technique. Driven by the technological advances in such sensors, wrist-worn devices are becoming a commodity, and the interest in the assessment of HRV indexes from the PPG analysis (pulse rate variability - PRV) is rising. In this study, we investigate the hypothesis of using PRV features as surrogates for HRV indexes, in three different contexts: healthy subjects at rest, healthy subjects after physical exercise and subjects with cardiovascular diseases (CVD). Additionally, we also evaluate which are the characteristic points better suited for PRV analysis in these contexts, i.e. the PPG waveform characteristic points leading to the PRV features that present the best estimates of HRV (correlation and error analysis). The achieved results suggest that the PRV can be often used as an alternative for HRV analysis in healthy subjects, with significant correlations above 82%, for both time and frequency features. Contrarily, in the post-exercise and CVD subjects, time and (most importantly) frequency domain features shall be used with caution (mean correlations ranging from 68% to 88%).

Clinical Validation of Heart Rate Apps: Mixed-Methods Evaluation Study

“…As such, PPG can be used to measure HR without the need for an ECG device. Furthermore, the HR derived from the PPG signal can be used in a series of calculations to determine the heart rate variability (HRV) [9]. …”

Can Wearable Devices Accurately Measure Heart Rate Variability? A Systematic Review

“…Finger tips have also been used as a measuring site but only in stationary conditions: it has been shown that HRV derived from fi ngertip PPG had an excellent correlation to ECG in stationary conditions. 38 However, a comparative study of fi nger derived PRV and HRV in healthy subjects 40 using a stationary equipment found a poor correlation and suggested that fi nger derived PRV might not be suitable to substitute ECG derived HRV, as has been mentioned by other authors, too 41 .…”

Relationships between resting heart rate, heart rate variability and sleep characteristics among female collegiate cross‐country athletes

“…Brandenberger, 2004). Pulse-rate variability via photoplethysmography (PPG) recordings at the wrist has been demonstrated to be a valid method for measurement of R-R intervals via electrocardiogram whilst at rest (Bolanos, Nazeran, & Haltiwanger, 2006;Lu, Yang, Taylor, & Stein, 2009;Pinheiro et al, 2016). (2017).…”