Simulation of human circulation at cardiopulmonary bypass.

This article describes a simulation model of the human circulatory system under extracorporeal circulation. The model is supposed to enable the design of a controller for heart-lung-machines, and to perform simulations of the controllers' behaviour. The controller should be able to control extracorporeal circulation based on the oxygen supply to individual organs. The model contains all important control mechanisms in the human circulation that maintain hemodynamics, and the influences of extracorporeal circulation to them. We considered the renin-angiotensin-system, the arterial local autoregulation and the autonomic nervous system. The behaviour of the most important hormone levels is reproduced. Furthermore, hemodynamics in the arterial tree is modeled with locally distributed pressure and flow parameters in 128 vessel segments to gain knowledge about the oxygen supply position of single internal organs. The influences of the special circumstances of an operation under extracorporeal circulation such as anesthesia or hypothermia are implemented in the model. Simulation results show that our model describes the behaviour of human circulation detailed enough to validate the designed controllers.