Investigation of optical heart rate sensors in wearables and the influence of skin tone and obesity on photoplethysmography (PPG) signal

Wearable devices, with Photoplethysmography (PPG)-based sensors, are helping patients to monitor chronic health conditions outside the clinic. The prime source of PPG signals is the blood volume change in the dermal vasculature. Here, we present a novel approach of using a skin model, containing double vascular layer within the dermis to investigate the pulsatile contribution from the region. Finite Element Method (FEM) is used to design vessels and PPG signals from the wrist are extracted by studying light transport through Monte Carlo simulations. By assessing PPG sensors in common wearables, the influence of obesity on the PPG signals are also investigated.