Non-contact reflection photoplethysmography towards effective human physiological monitoring

A non-contact reflection photoplethysmography (NRPPG) with its engineering model was created to access human physiological information. The NRPPG engineering setup with a vertical cavity surface emitting laser (VCSEL) as a light source and a high-speed PiN photodiode as a photodetector was configured based upon the principles of light-tissue interaction and Beer-Lambert’s law. In this paper, we present three aspects of the NRPPG performance: (1) photonics engineering work to capture photoplethysmographic signals with a non-contact manner in an optimal setup of the NRPPG; (2) a 5-minute protocol with 22 participants to determine a good agreement between NRPPG and contact photoplethysmography (CPPG) by means of Bland-Altman statistical analysis and Pearson’s correlation coefficient; and (3) a physiological experiment designed for cardiac-physiological monitoring utilizing NRPPG. The experimental results suggest that clean PPG signal can be obtained between 30-110 mm. The outcome from agreement study indicates that the performance of NRPPG is compatible with CPPG. The NRPPG technique has great potential in cardiac-physiological assessment in a required clinical circumstance

Insight into the dicrotic notch in photoplethysmographic pulses from the finger tip of young adults

This study aims to investigate arterial stiffness in selected young adults by non-invasively determining the characteristics of the photoplethysmographic dicrotic notch. A total of 15 volunteers participated in this study, divided into four groups by age and gender. Contour analysis was applied to analyse the photoplethysmographic dicrotic notch, including time-related and height-related parameters. The height of reflected wave, mirrored by the notch relative amplitude (NRA), was found to be significantly larger in the older group compared to the younger group (p = 0.016). The timing of the reflected wave, measured by three parameters, i.e. notch index (NI), notch latency (NL) and peak-to-notch latency (PTNL), significantly increased in the female group compared to the male group (all p < 0.02). The results confirm that arterial stiffness occurs in young adults, and demonstrate that a difference of arterial stiffness exists between young male and female. This study indicates that examining the characteristic notch of the PPG pulse could help in identifying differences of vascular activities

Poincare plot analysis for pulse interval extracted from non-contact photoplethysmography

An analysis of pulse-to-pulse interval (PPI) derived from non-contact photoplethysmography (PPG) is performed using the Poincare plot technique. Eleven healthy volunteers participated in a protocol utilising both spontaneous and paced breathing methodologies with a customised non-contact PPG system to obtain adequate quality signals for a distance of 80 mm between source and detector. An adaptive trough-searching algorithm (ATSA) is developed to extract the PPI which is effective in the presence of artefact during non-contact PPG measurement. A Poincare plot for each 5 minute period of the protocol shows significant pattern differences between spontaneous and paced breathing measurements. Geometric parameters extracted from the Poincare plot are shown to be sensitive to breathing interval changes and are a useful indicator for the variation of pulse rate variability measured using non-contact PP