Remote photoplethysmography for heart rate and blood oxygenation measurement: a Review

Usually measured through obtrusive contact-based methods, heart rate (HR) and peripheral oxygen saturation (SpO2) are critical physiological signs used by clinicians during emergency interventions. Remote Photoplethysmography (rPPG) allows for unobtrusive sensing of these vital signs for health monitoring in various settings. We present a review of rPPG-related research conducted including related processes and techniques, such as regions of interest (ROI) selection, extracting the raw signal, pre-processing data, applying noise reduction algorithms, Fast Fourier transforms (FFT), filtering and extracting these vital signs. Further, we present a detailed, critical evaluation of available rPPG systems. Limitations and future directions have also been identified to further advance this field.