Distance-related consistency of imaging photoplethysmogram dynamics

A photoplethysmogram (PPG) is an optical biomedical signal measuring changes in the amount of light reflected or transmitted through the skin. In recent years, imaging PPG(iPPG), which can measure pulse waves through video recordings by conventional cameras in a similar way as conventional PPG devices, has been attracting attention. In this study, we investigated the effect of measurement distance on the dynamic properties of iPPG and verified whether the dynamic properties remain. Using recurrence quantification analysis and the Wayland test on data from twelve healthy subjects, we found that iPPG maintains deterministic properties within 0.0 to 0.6 cm measurement distance. Also, while some measures of periodicity and regularity showed distance-dependent changes, we confirmed that the fundamental chaotic dynamics were maintained. These findings show that iPPG is feasible for non-contact health monitoring applications with advanced analysis, thus contributing to the improvement of biomedical sensing technology.