Analysis of Pulse Wave Morphology Measured by Photoplethysmography During Arm Position Changes

Numerous studies underscore the importance of analyzing pulse wave morphology via photoplethysmography (PPG) as an accessible method for investigating localized vascular responses. Contemporary approaches to modeling pulse wave morphology are based on the assumption that the dicrotic wave arises from reflections at vascular bifurcations and other vascular inhomogeneities. An alternative perspective posits that normal blood circulation is sustained through smooth muscle tone. To validate this hypothesis, we analyzed pulse wave morphology during arm position changes, which are associated with alterations in arterial tone within the vascular system. This study substantiates the feasibility of evaluating vascular resistance changes through dicrotic wave curvature during arm repositioning, measurable via the slope angle of the PPG signal at this segment. Furthermore, it is shown that the venulo-arteriolar reflex triggered by arm position changes leads to ambiguous dynamics in pulse wave amplitude variations. The presence or absence of the venulo-arteriolar reflex impacts pulse wave amplitude but does not affect dicrotic wave curvature, which is exclusively governed by changes in arteriolar smooth muscle tone.