Control of intraaortic balloon pumping: theory and guidelines for clinical applications.
The effectiveness of intraaortic balloon pumping was investigated by using a lumped parameter model of the cardiovascular/assist device system. The model consists of a time-varying elastance left ventricular simulation, a 2-element windkessel arterial simulation, and an RC venous return and pulmonary simulation. The four major hemodynamic variables, stroke volume (SV), aortic mean diastolic pressure (MDP), tension time index (TTI), and aortic end diastolic pressure (EDP), were divided into two categories related to system energy supply and demand: "external" and "internal" variables. The effects of balloon pumping on these variables can be described by closed-form equations that yield an optimal solution. The model prediction suggests that, in the ideal case, optimization of balloon pumping calls for instantaneous inflation of the balloon to maximum volume at end systole and instantaneous complete deflation at end diastole. For finite inflation/deflation rates, the optimal time for the start of inflation is end systole. Deflation timing, however, involves a tradeoff between maximizing the external variables and minimizing the internal variables. These predictions were tested using a nonlinear digital computer model. The results also suggest that when SV is not being monitored, optimal inflation timing can be controlled from the measurements of TTI or pulmonary venous pressure; optimal deflation timing can be controlled by a weighted combination of MDP and EDP.