Duration of photoplethysmographic signals for the extraction of Pulse Rate Variability Indices

Pulse rate variability (PRV) assesses the changes in pulse rate through time when pulse rate is extracted from pulsatile signals such as the photoplethysmogram (PPG). PRV has been used as a surrogate of heart rate variability (HRV), but there is evidence of differences between these two variables. It has been hypothesised that these differences may arise from physiological processes or from technical aspects that may affect the reliable extraction of PRV indices from PPG signals. Moreover, there are no guidelines for the extraction of PRV information from pulsatile signals, which hinders the comparison among PRV studies and the understanding of physiological changes that may affect PRV. In this study, the effects of using PPG signals with different duration for the extraction of time-domain, frequency-domain and Poincaré plot indices from PRV was studied. Using simulated PPG signals with known PRV content and varying duration, it was found that PRV indices can be reliably estimated from signals as short as 90 s. This indicates that PRV indices can be extracted from ultra-short PPG signals. Although further validation with real data is needed, it can be concluded that acquiring shorter segments of PPG can be used for PRV analysis, allowing for a more efficient acquisition and processing of this variable.