The assessment of sympathetic activity using iPPG based inter-limb coherence measurements

摘要

Photoplethysmography (PPG) is an optical technique that is used to detect blood volume changes and thus to measure assess the physiological parameters. Since PPG is low cost and non-invasive technique, it become a widely used tool for screening purposes and for self-diagnostic. In this regard, the development on remote methods receives the growing attention, such as imaging photoplethysmography (iPPG), which does not require the contact between sensor and the skin. Following the current trends in market, many of public-available iPPG systems are developed for use with smartphone-embedded cameras, and thus have a sample rate about 30-60 frames per second, which is enough for heart rate measurements, but may be too low for some more advanced usages of this technique. In our work, we describe the attempt to use smartphone-based iPPG technique to assess the systemic regulation mechanisms by means of measurement of tiny mismatch in RR interval data series recorded from left and right arms. Specifically, we use the transmission mode iPPG, in which the light transmitted through the finger is recordered by a web-camera placed opposite the LED source. The computational scheme by processing and analysis of the received signal was implemented using MATLAB. We believe that further development of our approach may lead to fast and low-cost method to access the state of the sympathetic nervous system.