Figure 2.

General layout of the driving unit of the IABP system. The air pressure waveform in the balloon is in the top right-hand corner. Pd and Pv are the driving and vacuum pressure, respectively. Qi_IABP (Qo_IABP) represents the input (output) flow source. $\dot{Vair}$ (Pair) is the volume (pressure) into the part of the balloon connected to the air tube; $\dot{VIABP}$ is the balloon volume, Vmax is the maximum extension volume of the balloon; $PIABP=\left(\left[\frac{Pair\ast 760}{1000}\right]-760\right)$ is the balloon pressure; AAP is the ascending aorta pressure.