Changes in the Shape of the Photoplethysmographic Signal in Response to the Active Orthostatic Test

Mateusz Pałasz1, Marek Żyliński2, Gerard Cybulski1
1Department of Mechatronics, WUT, 2Warsaw University of Technology


The aim of the study was to check if the shape of photopletysmographic signal (PPG) is modified by the active orthostatic maneuver. We hoped to verify if such a preliminary analysis could provide any information on the condition of the cardiovascular system and its regulation. We recorded simul-taneously ECG (as a reference gating signal) and PPG. Signals were sampled at the rate of 1000 Hz in 6 male and 1 female subjects, who changed posi-tion from supine to standing (remaining 3 minutes in each). The procedures, written in Python environment, were used to analyze the data. We used the indices of the shape of PPG signals known from literature (area under the curve – AUC, rise time-RT) and proposed two other: the time of the maxi-mum derivative occurrence on ascending slope (Tmax) and the time of oc-currence of the minimal derivative on descending slope (Tmin) of the ple-thysmographic curve. The indices obtained in two positions were compared using t-Student test). It was found that RT, AUC and Tmax, were significant-ly higher in standing position than in supine, whereas Tmin was lower. Bas-ing on this very preliminary results we could conclude that some indices characterizing the shape of the PPG signal are modified by the changing of the position of subject. We could only speculate that such indices might be used for noninvasive assessment of cardiovascular system.