The primary function of local blood flow control in the circulation is to maintain the equilibrium between oxygen supply and consumption. Several mechanisms regthe rate of regional blood flow to meet local oxygen needs. A major role in local regulation of tissue perfusion is attributed to arterioles. Changes in the tone of smooth muscles surrounding the arterioles control the vessel’s hemodynamic resistance, thereby affecting the rate of blood flow.
Changes in smooth muscle tone are controlled by a mechanism not yet fully understood. Three hypotheses have been suggested to explain this mechanism; metabolic, myogenic and tissue pressure. In coronary circulation, the metabolic hypothesis is the preferred explanation. This hypothesis suggests that the level of myocardial metabolism provides a local feedback for maintaining tissue oxygenation following changes in oxygen supply or consumption. Although various mediators have been proposed for the feedback loop, we believe that oxygen is the best studied mediator since myocardial function is highly dependent on the presence of oxygen and is sensitive to the lack of it.
In this research, we are studying the relationship between locally regulated erythrocyte velocity and optimal oxygen delivery using both mathematical models and experimental techniques. Our model forms the basis of a closed-loop control system that simulates coronary autoregulation based on oxygen supply and consumption. The experimental part of our work focuses on the response of the arteriolar smooth muscle to oxygen concentration and the level of PO2 in the myocardium in response to changes in coronary flow generated by vasodilatation techniques.
Our research is expected to elucidate coronary feedback mechanisms and to provide explanations based on a systems approach. This will contribute valuable data and missing parameters regarding optimal blood flow velocity in respect to myocardial oxygen delivery and consumption, subjects of prime importance to optimization of cardiac assist devices and of pharmaceutical treatment of patients.
