Contactless Cardiovascular Assessment by Imaging Photoplethysmography: A Comparison with Wearable Monitoring

Despite the notable recent developments in the field of remote photoplethysmography (rPPG), extracting a reliable pulse rate variability (PRV) signal still remains a challenge. In this study, eight image-based photoplethysmography (iPPG) extraction methods (GRD, AGRD, PCA, ICA, LE, SPE, CHROM, and POS) were compared in terms of pulse rate (PR) and PRV features. The algorithms were made robust for motion and illumination artifacts by using ad hoc pre- and postprocessing steps. Then, they were systematically tested on the public dataset UBFC-RPPG, containing data from 42 subjects sitting in front of a webcam (30 fps) while playing a time-sensitive mathematical game. The performances of the algorithms were evaluated by statistically comparing iPPG-based and finger-PPG-based PR and PRV features in terms of Spearman's correlation coefficient, normalized root mean square error (NRMSE), and Bland-Altman analysis. The study revealed POS and CHROM techniques to be the most robust for PR estimation and the assessment of overall autonomic nervous system (ANS) dynamics by using PRV features in time and frequency domains. Furthermore, we demonstrated that a reliable characterization of the vagal tone is made possible by computing the Poincare map of PRV series derived from the POS and CHROM methods. This study supports the use of iPPG systems as promising tools to obtain clinically useful and specific information about ANS dynamics.

Automated summary

Despite advancements in remote photoplethysmography (rPPG), extracting a reliable pulse rate variability (PRV) signal remains challenging. This study compared eight image-based photoplethysmography (iPPG) methods for pulse rate (PR) and PRV feature extraction. The algorithms were tested on a public dataset, and their performances were evaluated using statistical analysis. The study found that the POS and CHROM techniques were the most robust for PR estimation and assessing autonomic nervous system (ANS) dynamics. It also demonstrated that the Poincare map of PRV series derived from the POS and CHROM methods can reliably characterize vagal tone. This study supports the use of iPPG systems for obtaining clinically useful information about ANS dynamics.