Design and development of a novel multi-channel photoplethysmographic research system

Photoplethysmography (PPG) is a non-invasive optical technique used in detecting blood volume changes in vascular tissue. In recent years, photoplethysmography has generated renewed interest among researchers, particularly due to its potential for widespread clinical applications beyond estimating heart rate and arterial oxygen saturation. Progress in these areas of research is dependent on PPG systems with the ability to record raw photoplethysmographic signals with high signal-to-noise ratio, ideally from more than one channel and one wavelength, for real-time or retrospective analysis. In this work we present the design, development and validation of such a modular PPG system. “Zen PPG” - a portable (16.0 × 10.3 × 5.4 cm) battery operated dual channel, dual wavelength system with the capability to operate with commercial sensors was developed and calibrated using a FLUKE Index 2 SpO
₂
simulator. A brief study has been conducted on a small group of healthy volunteers to demonstrate the functionality of the system. Red and Infrared PPG signals obtained from volunteers were used to estimate SpO
₂
and heart rate. These results were compared with simultaneously acquired data from a commercial pulse oximeter (Masimo Radical 7). The SpO
₂
values showed close correlation between commercial and custom made system (Channel 1: r
²
= 0.978; channel 2: r
²
= 0.708).