Theoretical Considerations Regarding the Optimization of Cardiac Assistance by lntraaortic Balloon Pumping

A lumped parameter model representing the effects of cardiac assistance by intraaortic balloon pumping was developed. The model permits closed-form calculations of important hemodynamic events in the system. The equations derived from the model were used to determine pumping parameters for optimum assistance. The model indicates that, in the ideal case, optimization of assistance requires instantaneous inflation of the balloon to maximum volume at end systole and instantaneous complete deflation at end diastole. Since an impulse flow rate is not realizable in practice, the model was used to investigate the effects of finite inflation/deflation periods. In general, it was found that fast inflation/deflation rates give higher benefits than slow rates. The optimal time to begin inflation is end systole. Timing of deflation was shown to involve a tradeoff between lower end diastolic pressure (achieved with early deflation) and increase of mean diastolic pressure and cardiac output (achieved with late deflation). The model's predictions were validated using a nonlinear distributed parameter digital computer model previously described. The lumped model results should make possible a quantitative as well as a simple approach to automatic control of in-series cardiac assistance.