Remote Blood Oxygen Estimation From Videos Using Neural Networks
<div>Blood oxygen saturation (SpO<sub>2</sub>) is an essential indicator of respiratory functionality and is receiving increasing attention during the COVID-19 pandemic. Clinical findings show that it is possible for COVID-19 patients to have significantly low SpO<sub>2</sub> before any obvious symptoms. The prevalence of cameras has motivated researchers to investigate methods for monitoring SpO<sub>2 </sub>using videos. Most prior schemes involving smartphones are contact-based: They require a fingertip to cover the phone's camera and the nearby light source to capture re-emitted light from the illuminated tissue. In this paper, we propose the first convolutional neural network based noncontact SpO<sub>2</sub> estimation scheme using smartphone cameras. The scheme analyzes the videos of a participant's hand for physiological sensing, which is convenient and comfortable, and can protect their privacy and allow for keeping face masks on.</div><div>We design our neural network architectures inspired by the optophysiological models for SpO<sub>2</sub> measurement and demonstrate the explainability by visualizing the weights for channel combination. Our proposed models outperform the state-of-the-art model that is designed for contact-based SpO<sub>2</sub> measurement, showing the potential of our proposed method to contribute to public health. We also analyze the impact of skin type and the side of a hand on SpO<sub>2</sub> estimation performance.</div>