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IABP Review
http://www.nurse411.com/Review_Sheets/IABP_Review.html
Increase O2 Supply
NTG (coronary artery vasodilation)
More oxygen delivery
PTCA
CABG
IABP Inflation
Decrease O2 Demand
NTG (peripheral vasodilation)
Beta-blockers
ACE inhibitors
IABP Deflation
Table 1 – Ways to effect the myocardial O2 supply and demand balance
Mechanics of IABP:
Inflation occurs just before the dicrotic notch (when the aortic valve closes). This is
when the coronary arteries fill. If we increase the pressure in the aorta at this time, then
the pressure of blood going into the coronary arteries will also increase, and in turn
increase coronary artery perfusion. Since balloon inflation does not force blood only to
the coronary arteries, additional benefits of balloon inflation are increased perfusion to
the carotid arteries above the balloon (cerebral perfusion), and increased perfusion to the
renal arteries below (maintaining renal blood flow and function). Thus we have increased
O2 supply to the heart, brains and kidneys.
Deflation of the balloon occurs just prior to or just after the aortic valve opens (during
systole when the ventricles are contracting). This is when blood is ejected from the
ventricles into the aorta. By deflating the balloon at this time, we create a “vacuum
effect” which lowers the pressure in the aorta. More blood is then ejected from the left
ventricle to fill the void in the aorta created by the balloon deflation. Therefore, with the
same effort, the ventricle has become more efficient. The heart pumps more blood per
contraction, without needing more oxygen. Thus, we have decreased the O2 demand of
the heart muscle.
So, by the inflation and deflation we have decreased the O2 demand at the same time
increasing the O2 supply. Frequently this will correct the O2 imbalance and stabilize the
patient’s hemodynamics.
Balloon inflation should occur about 40 milliseconds before the dicrotic notch forming a
sharp “V” shape on waveform. If inflation is timed correctly Rule #4 (below) will be
true. If inflation is timed late then Rule #4 will be violated
Balloon deflation should occur just before systole. If timed right Rule #3 (below) will
be true, if timed incorrectly Rule #3 will be violated.
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Figure 1 - Intra-Aortic Balloon pump arterial waveform (1:2 augmentation)
Letter
Represents
A
Unassisted Systolic Pressure
B1,B2
C
D
E
F
Dicrotic Notch
Augmented Diastolic Pressure
Assisted End Diastolic Pressure
Assisted Systolic Pressure
Unassisted End Diastolic Pressure
Rule
Must be less than (C) and more than
(E)
(B1) should be higher than (B2).
Should be higher than (A)and (E)
Should be lower than (F)
Should be lower than (A) and (C)
Should be higher than (D)
Table 2 – Identifying important points on the Intra-Aortic Balloon pump waveform
IABP Rules of the waveform:
1. Unassisted Systolic BP (A) > Assisted (balloon deflation) Systolic BP (E)
2. Augmented (balloon inflation) Diastolic BP (C) > Unassisted Systolic BP (A)
3. Unassisted End Diastolic BP (F) > Assisted (balloon deflation) End Diastolic BP (D)
4. Dicrotic notch on balloon inflation (B1) > Dicrotic notch without balloon inflation (B2)
Rule #
Violation
1 A=E
2 A => C
3
4
F<D
B1 = B2
Timing Error
Early deflation
Early inflation (Check slope of balloon
inflation) or
Late inflation (Look for “W” at balloon
inflation)
Late deflation
Late inflation (Look for “W” at balloon
inflation) or
Early deflation
Table 3 – Rules violations and the timing errors they can cause