Mathematical model of vascular tone autoregulation

Background and Objectives: The conventional approach to study the blood circulat ion in the cardiovascular system of humans and animals is based on representation of the vascular system as a hierarchical structure of branching elastic tubes. 212 While considerable progress has been achieved in the framework of this p aradigm, the other fails when one needs to analyze the dynamical patterns in networks of small arterial vessels. It mainly caused by the dominant contribution of cellular regulatory pathways that adjust a vascular tone in response to systemic signals and local metabolic demands. Since its complexity, these cellular mechanisms are typically studied (and modeled) separately from the blood flow modeling studies. We believe that the progress in the field essentially depends on the availability of simple enough, but still problem-relevant mathematical models that would provide the better understanding of the behavior of the vascular system as a complex network of nonlinear elements. Results: In this paper, we propose a minimized mathematical model of the process of autoregulation of the blood flow in the blood vessel segment. Being considerably simplified our model still takes into account both the typical nonlinearities and the basic mechanisms of active regulation of a vascular tone. We verifiy our model in order to check whether the observed b ehavior is consistent with the known basic properties of real vessels. We show that the model successfully reproduces the effect of changes in the vessel radius and the corresponding stabilization of the flow with considerable (up to several times) pressure changes at the entrance to the segment. The oscillatory response of the radius of the segment on the pressure jump at the inlet has been revealed. This behavior possibly can underlie the complex types of reaction in small and medium microcirculatory networks. Next, we have studied the propagation of the pulse wave in the 100-segment model of the blood vessel. The nonlinear dependence of its pulse wave velocity on the pressure pulse amplitude applied to the first (input) segment of the model has been revealed. Conclusion: We suggest that the simultaneous control of both the speed of the pulse wave and its pressure derivative is promising from the point of solving the practically important inverse problem being the pressure recovery from the measured pulse wave velocity.