A dynamic optical phantom for PPG signal at the radial artery incorporation skin tone and obesity variations

Cardiovascular disease remains one of the leading causes of death in the United States. Currently, over 40% of the population lives with some form of cardiovascular condition as well as varying degrees of obesity, a significant risk factor for CVD. With the ever-expanding market for health wearable systems, research has exposed some significant shortcomings in accurately capturing health conditions. Many of these systems utilize optical techniques such as photoplethysmography (PPG) to probe for changes in the cardiac output waveform through the skin and surrounding tissues. This signal is impacted by varying skin tones and physiological changes to obesity in our diverse population. To aid in the development of these optical monitoring technologies, we have developed a dynamic phantom incorporating optical and mechanical properties of the tissue surrounding the radial artery at the wrist. The phantoms consist of three main features: a silicone body with optical properties representative of surrounding skin layers ranging from Fitzpatrick skin type I-VI at 660 nm, a vessel chamber with mechanical properties representative of the radial artery, and a pulsatile pump that cycles a blood-mimicking fluid to maintain physiologically accurate pressure fluctuations typically seen at the radial artery. This phantom is developed through the combination of rapid prototyping using both stereolithography (SLA) and fused deposition modeling (FDM) methods to develop mold casting with a silicone-based material to control geometric properties. PPG signal for different properties representing varying skin tone and obesity is collected using a commercial NellCor Pulse Oximeter device.