The nonlinear closed loop mechanism underlying the LF oscillation in blood pressure

The Low Frequency (LF) generation mechanism based on linear feedback theory has not been successful in describing the presence of a sustained LF oscillation (≈0.1 Hz) in blood pressure and heart rate. The purpose of this paper is to show that nonlinearity in the blood pressure regulatory mechanism is indeed responsible for the generation of the LF component. This is accomplished through identification of the sympathetic control loop of the blood pressure and replacing the bang-bang element in the brainstem, presented in earlier models, by a more realistic nonlinearity. It is demonstrated that, together with showing a close resemblance with the practical data, the new model provides convincing explanations for some of the fundamental features of the LF oscillation which are observed experimentally