Evaluation Model of Microhemodynamics in Finger Skin at Arterial Occlusion and Post-Occlusive Hyperemia

The development of optical noninvasive methods for assessing the functional state of peripheral vessels, including the microcirculatory vascular bed, requires advances in modeling peripheral hemodynamics in order to interpret diagnostic data in terms of vascular tone, wall stiffness, and other related parameters. This study proposes a simple theoretical evaluation model of the dynamics of skin perfusion by blood during a functional test with brachial artery occlusion. As a development of conventional volume-chamber and pressure-volume approaches, this study introduces a problem-oriented three-chamber hemodynamic model of an arm, which allows simulating blood circulation during occlusion of major brachial veins and arteries. The model describes the Poiseuille flow of incompressible viscous blood in vessels with compliant walls, the lumen area of which is regulated by internal blood pressure and vascular tone. The initial diagnostic data for model validation were obtained in clinical trials with the use of the incoherent optical fluctuation flowmetry technique. Comparison of clinical and theoretical results revealed a fundamental qualitative agreement. In this field of medical diagnostics, for the first time, the dynamics of optical signals during the occlusion were successfully interpreted and substantiated as a response to changes in blood pressure and vascular tone in the microcirculatory system.