Can Camera-PPG Imaging be Used to Measure Perfusion Index?

The perfusion index (PI) is widely used in the medical field to assess the peripheral perfusion of skin tissues. Recent advancements in camera photoplethysmography (camera-PPG) permits robust measurement of heart-rate remotely, but its feasibility on PI measurement was not thoroughly investigated. In this study, we investigated the feasibility of using AC/DC of camera-PPG signals to calibrate PI based on a generalized or personalized regression model, through an ice water stimulation experiment. The results indicate that the coefficient of determination (R²) for personalized modeling is as high as 83%. But for the generalized modeling, the R² is negative even though the camera-PPG waveforms are of high-quality. This suggests that there is a strong subject-dependency on PI calibration which may due to skin properties of camera-PPG measurement, and such issue must be considered for designing methods for contactless PI measurement.