Equilibrium multiplicity in a cardiovascular system model

The aim of this paper is to show that, for some parameters, a two-dimensional cardiovascular system model can exhibit intrinsic equilibrium multiplicity generated by a backward bifurcation, regardless of the baroreflex effect. The model considers the dynamics of arterial and venous compartments and a feedback effect in the stroke volume induced by venous pressure changes. The results of the mathematical analysis indicate that multiple non-trivial equilibrium points exist when the stroke volume function is convex around the origin. Interestingly, this equilibrium point structure would imply that under certain stroke volume functions, the baroreflex system would have to stabilize and regulate an unstable operating condition produced by certain values of the stroke volume. The paper ends with the discussion of some implications for the reliability and robustness of the baxoreflex-feedback mechanism.