Prediction of reactive hyperaemia in vascular pathologies using elastic porous tube model.

A mathematical model of reactive hyperaemia has been developed, in which the limb vascular system is represented by an elastic porous tube, with flow in the tube equivalent to blood flow in the arteries and large arterioles. Flow through the porous walls represents flow into the small arterioles, which respond actively by contracting as pressure throughout the system rises following occlusion release. A variety of vascular pathologies have been simulated; the effect of venous packing of the limb is to reduce the transient peak flow from normal, owing to a reduction in the pressure gradient. Occlusive disease of the femoral artery and lower arterial vessels reduces the magnitude and extends the duration of hyperaemic flow, due to a reduced pressure gradient and increased resistance. Small vessel disease reduces the hyperaemic flow, principally due to a reduction in the initial dilation of the vessels. Venous disease does not affect the initial arterial flow following occlusion release but reduces the equilibrium flow. The venous outflow increases in response to an increase in the arterio-venous pressure gradient.