Assessment of the Stiffness of Small Arterial Vessels of Superficial Biotissues by their Spectral-Temporal Profiles of Diffuse Reflection of Light Radiation

Abstract

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