The minimal sampling frequency of the photoplethysmogram for accurate pulse rate variability parameters in healthy volunteers

• DOI: 10.1016/j.bspc.2021.102589
• Publication Date: 2021-04-08T17:53:59Z
• Authors: Szabolcs Béres; László Hejjel
• Keywords: Photoplethysmogram; Interpolation

Today mobile health-monitoring devices calculate heart rate and its variability mostly from the photoplethysmogram (PPG). Minimizing power consumption is crucial, one option optimizing signal sampling rate. Present study aimed to determine minimal frequency of PPG signal, which sufficient for accurate (HRV) analysis. 57 high-quality, 5-minute signals healthy volunteers sampled at 1 kHz (master) were decimated by a factor 2, 5, 10, 20, 50, 100, 200, 500, then cubic spline parabola interpolated back ms resolution. The mean pulse rate, standard deviation (SDNN), root square successive RR-differences (RMSSD), Porta Guzik indices (PI, GI) calculated. Their relative accuracy error (RAE) was determined, RAE<5% acceptable. Also, processing times measured. 200ms interval without interpolation with RAE<0.05%. SDNN RMSSD require least 20 (RAE: 1.28±0.96% 4.25±3.59%, respectively). By both interpolations, these intervals can be increased 100 50 ms, respectively. GI PI improved interpolation, here approximation better (GI: versus PI: ms). Parabola needs significantly less computation than interpolation. For monitoring average 5 Hz in subjects. Correct HRV analysis requires higher rates depending on parameter. Interpolation improve lower temporal resolution PPGs.