Abstract
The optimal driving condition of an assist pump (left ventricle-aorta bypass) applied to the cardiovascular system with a baroreceptor and periperal chemoreceptor loops was studied by computer simulation and animal experiments.
In the cardiovascular model, the peripheral system was represented by the Windkessel model and the heart by an elastance. Baroreceptor control loop regulates heart rate, cardiac contractility, venous compliance and arterial resistance. Peripheral chemoreceptor control loop regulates arterial resistance based on cardiac output. The assist pump was modeled by a variable compliance. Optimal driving condition minimizing tension-time index (TTI), maximizing diastolic pressure-time index/TTI ratio (EVR) or maximizing arterial pressure was analized.
Findings were: (1) Unloading of the left ventricle by an assist pump was augmented by cardiovascular control loops. (2) Optimal driving condition was different depending on with or without cardiovascular control loops. (3) Aortic pressure was not a suitable variable for estimating effectiveness of an assist pump, because it was kept almost constant by the cardiovascular control loops independently of driving conditions. (4) In the left ventricle-aorta bypass, TTI and EVR changed remarkably according to the driving conditions.
It can be concluded that cardiovadcular control loop must be considered when the optimal control system is designed for an assist pump.
