Study of the blood-flow reactivity in forearm vessels during a cold test by imaging photoplethysmography

Abstract:
Functional tests (such as the cold-stress test) provide valuable information concerning vasomotor regulation of circulation. For quantitative estimation of musculocutaneous blood flow is commonly used venous occlusion plethysmography. However, it is achieved by means of the contact-type sensors. The goal of the research is a demonstration of feasibility to assess the blood-flow reactivity in the forearm vessels during a cold test by using non-contact imaging photoplethys-mography (iPPG) in a state of venous occlusion. Seven healthy volunteers participated in the experiment. We used four mutually synchronized video cameras to record all-around view of the forearm illuminated by the green light (525 nm). Frame-by-frame evolution of the mean pixel value in regions selected for analysis we call as a photoplethysmography (PPG) waveform. The shape of the PPG waveform obtained by our optical system was almost the same as from the classical Dohn occlusion plethysmography. Moreover, the response of both systems on the cold test revealed the same signal change. These findings show good prospects of using the proposed optical system in various functional tests instead of contact occlusal plethysmography.