Facial Remote Photoplethysmography for Continuous Heart Rate Monitoring during Prolonged Cold Liquid Bolus Administration

This study investigates non-contact heart rate (HR) monitoring through camera-based remote PPG during intravenous fluid bolus (FB) therapy. The experiment, at Odense University Hospital, Denmark, involved 4 volunteers and over 350 minutes of filming. We implemented a MATLAB-based HR extraction tool chain. The proposed method includes a two-stage process for dynamically determining regions of interest (ROIs), incorporating deep learning for facial landmarks detection and a subsequential consideration of subjects' facial dimensions. HR estimation uses chrominance-based (CHROM) and plane-orthogonal-to-skin (POS) PPG signal extraction methods, chosen for robustness against motion artifacts. Deviating from usual advice for other methods, omitting preprocessing minimizes signal processing still yielding a low error rate. The system achieved a mean error of fewer than 2 beats per minute (bpm), underscoring iPPG's alignment with ground truth. The results exemplify the feasibility of remote PPG monitoring in critical care and emergency settings.