Development and utilization of a wireless and portable photoplethysmograph to study the post-occlusive reactive hyperemic response in a finger

Infrared light, when used in a narrow biological window, can be applied in such a way as to obtain blood flow measurements in vivo in tissues deeper than skin. When using light as a medium for blood flow measurement, the circulatory system´s response to a stimulus such as occlusion may be a useful tool to characterize circulatory health. We developed a wireless, noninvasive device that uses photoplethysmography (PPG) in order to study pulsatile blood volume changes in the finger in both the skin and bone that occur during post-occlusive reactive hyperemia. We used this device at the top of the intermediate phalanx of the middle finger to measure a hyperemic response, which was induced mechanically with the use of a pressure cuff. Our study develops on prior work done by Näslund et al. and J. Mateus which evaluated pulsatile blood volume changes in bone with near-infrared light.