Assessment of the Stiffness of Small Arterial Vessels of Superficial Biotissues and Their Spectral-Temporal Diffuse Light Reflection Profiles

The development of an operational noninvasive technique for assessing the state of the microcirculatory blood vessels in the cardiovascular system is a promising direction for the creation of equipment for the differential diagnosis of the causes of vascular dystonia and arterial hypertension. The feasibility of using diffuse reflection spectroscopy to determine the major parameters of the microvasculature is analyzed. A computational model for the formation of the spectral-temporal profile of local light diffuse reflection by pulsating blood-filled tissue is proposed based on the diffusion approximation of radiation transfer in scattering media and simplified analytical expressions describing the relationship between the shape of the photoplethysmogram and blood pressure. The structural features of the microcirculatory bed and the relationship of the parameters of the arterial vessels of the pulsating section of this bed to the systolic and diastolic blood pressure have been analyzed. It has been shown that taking account of the relative resistance to blood flow of different sections of the bloodstream and using a normalized photoplethysmogram to calculate intraluminal blood pressure in arterioles allow us to obtain an expression for the annular distensibility of arteriole walls. A technique for recording spectral-temporal diffuse reflection profiles and their modeling as well as forming the corresponding residual function and searching for its minimum are considered. The results obtained using a model for determining the parameters of the microvasculature taking into account equipment noise are presented. These results confirm the feasibility of creating a complex unit based on a miniature spectrophotometer, pulse oximeter, and pulse wave velocity sensors designed for the rapid noninvasive assessment of both the stiffness of the major arterial vessels and small arterial vessels of the microvasculature.