A Study of Machine Learning Regression Techniques for Non-Contact SpO2 Estimation from Infrared Motion-Magnified Facial Video

This work explores the use of infrared low-cost cameras for monitoring peripheral oxygen saturation (SpO₂), a vital sign that is particularly important for individuals with fragile health, such as the elderly. The development of contactless SpO₂ monitoring utilizing RGB cameras has already proven successful. This study utilizes the Eulerian Video Magnification (EVM) technique to enhance minor variations in skin pixel intensity in particular facial regions. More specifically, the emphasis in this study is in the utilization of infrared cameras, in order to explore the possibility of contactless SpO₂ monitoring under low-light or night-time conditions. Many different methods were employed for regression. A study of machine learning regression methods was performed, including a Generalized Additive Model (GAM) and an Extra Trees Regressor, based on 12 novel features extracted from the extracted amplified photoplethysmography (PPG) signal. Deep learning methods were also explored, including a 3D Convolution Neural Network (CNN) and a Video Vision Transformer (ViViT) architecture on the amplified forehead/cheeks video. The estimated SpO₂ values of the best performing method reach a low root mean squared error of 1.331 and an R^₂ score of 0.465 that fall within the acceptable range for these applications.

Thomas Stogiannopoulos, Grigorios-Aris Cheimariotis, Nikolaos Mitianoudis