Systems analysis of cardiovascular regulation

Abstract

The PhD thesis is focused on systems analysis of cardiovascular regulation. In the first part of the thesis, an averaged model of cardiovascular regulation on short term (i.e. for the cardiovascular system along with its nervous control loop) is derived. A weighted averaging approach is proposed for the cardiovascular system, and the obtained averaged model is coupled with a simplified model for the baroreflex control mechanism. In the second part of the thesis, the averaging approach is generalized for a class of nonlinear systems - pulse-frequency modulated systems with constant duty ratios- whose trajectories exhibit a moving average dependent on the modulation period. The proposed averaging method leads to a period-dependent averaged model, simpler than the original one. The cardiovascular system, regarded as a pulse-frequency modulated system, is considered as a case study. The third part of the thesis addresses the stability analysis problem for the qualitative averaged model of cardiovascular regulation, focusing on deriving new insights on the role of time delays in generating stability or instability, along with assuring some global properties, like trajectory convergence and boundedness. Finally, all results are tested through simulations.