Review on Contactless Vital Sign Monitoring: Techniques and Applications of Remote Photoplethysmography and Photoplethysmography for Remote Health Monitoring

Abstract

In recent years, companies and governments globally have been investing heavily in the advancement of contactless sensor technologies aimed at reducing the necessity for direct physical interactions betwixt patients and healthcare providers. As a result, healthcare research on cutting-edge contactless technologies has advanced rapidly, especially for infants along with elderly individuals with chronic conditions who need continuous, real-time monitoring and management.  Thus, Contactless Vital Sign Monitoring (CVSM) is a newly introduced technology. CVSM employing techniques like remote photoplethysmography (rPPG) together with traditional photoplethysmography (PPG), has gained major attention because of its ability to measure physiological parameters without the requirement for physical contact. Thus, this paper explores the applications of rPPG and PPG in Remote Health Monitoring (RHM). To detect subtle changes in blood volume, rPPG utilizes ambient or controlled light reflected from a subject's skin, enabling the estimation of Vital Signs (VSs) like Heart Rate (HR), Respiratory Rate (RR), along with oxygen saturation. But, PPG relies on direct optical sensors placed on the skin to capture similar physiological data. Thus, the review's current objective is to analyze PPG and rPPG in RHM.  This study also discusses the key parameters utilized in the analysis of PPG and rPPG for RHM along with the clinical application.