Hemodynamic Measurements
and
Dynamics
of
Assisted Circulation
23
5
aortic arch and is operated in a counterpulsation mode (Fig.
8.2.1).
In this
type of operation the balloon is inflated during diastole and deflated
during systole. Timing
of
inflation and deflation is considered the most
important determinant of efficacy.
Fig.
8.2.1
:
illustration
of
the placement
of
intra-aortic balloon pump in the descending
aorta.
Inflation in diastole
and
deflation in systole constitutes the basis
of
counterpulsation in-series cardiac assistance.
Some
of
the bypass devices have been utilized as temporary assist
devices and in-series devices have been utilized as permanent assist
devices. In all of the applications, the control of the device timing
relative to the natural heart is quite critical. While for temporary devices
manual controls are, in many cases, acceptable, it
is
clear that for
permanent implanted devices, automatic, and preferably implantable,
controls are essential. Many of the attempts at automatic control of heart
assist devices were studied in conjunction with
IABP
since the balloon
pumps are widely used in the clinical setting.
