Parallelized multi-layered Monte Carlo Model for Evaluation of a Proximal Phalanx Photoplethysmograph

Blood pressure is a primary candidate to be remotely characterized by continuous monitoring devices, as high blood pressure is frequently a symptom of chronic conditions such as diabetes, obesity, and cardiovascular disease while also leading to morbidity itself. Much work has been done to characterize an electrocardiogram (EKG)-photoplethysmogram (PPG) continuous monitor, however a dual PPG continuous monitor may yield more accurate results due to the lack of the inherent pre-ejection period. To predict the anticipated signal of a remote dual-photoplethysmogram (PPG) blood pressure monitor, we utilized parallelized multi-layer Monte Carlo modelling to estimate light transport through the index finger at the proximal phalange. Monte Carlo models of the digital artery and surrounding tissue were created that represent various skin tones as well as the presence of arterioles. Additionally, the signal contribution by arteriole and artery was also determined. By varying incident wavelength, source-detector separation, skin tone, and arterial diameter as a function of pulse propagation; the feasibility of a proximal phalange PPG can be estimated and further optimized to aid development of a dual-PPG blood pressure monitor. The modelling results indicate that at a separation of 3.0mm, 700nm wavelength provides signal resolution that is indicative of contribution from the artery and not the arterioles, which could be beneficial for estimating pulse transit time toward calculating blood pressure. Further work should be completed to optimize source-detector separation for arterial contribution to signal and explore various locations on the body, as much optical property variation exists within literature.