Contactless blood oxygen estimation from face videos: A multi-model fusion method based on deep learning

Blood Oxygen (SpO2), a key indicator of respiratory function, has received increasing attention during the COVID-19 pandemic. Clinical results show that patients with COVID-19 likely have distinct lower SpO2 before the onset of significant symptoms. Aiming at the shortcomings of current methods for monitoring SpO2 by face videos, this paper proposes a novel multi-model fusion method based on deep learning for SpO2 estimation. The method includes the feature extraction network named Residuals and Coordinate Attention (RCA) and the multimodel fusion SpO2 estimation module. The RCA network uses the residual block cascade and coordinate attention mechanism to focus on the correlation between feature channels and the location information of feature space. The multi-model fusion module includes the Color Channel Model (CCM) and the Network-Based Model(NBM). To fully use the color feature information in face videos, an image generator is constructed in the CCM to calculate SpO2 by reconstructing the red and blue channel signals. Besides, to reduce the disturbance of other physiological signals, a novel two-part loss function is designed in the NBM. Given the complementarity of the features and models that CCM and NBM focus on, a Multi-Model Fusion Model(MMFM) is constructed. The experimental results on the PURE and VIPL-HR datasets show that three models meet the clinical requirement (the mean absolute error <= 2%) and demonstrate that the multi-model fusion can fully exploit the SpO2 features of face videos and improve the SpO2 estimation performance. Our research achievements will facilitate applications in remote medicine and home health.