Interpreting the Arterial Pressure Waveform in the Intra-aortic Balloon-Pumped Patient

Susan J. Quaal, PhD, APRN, CVS, CCRN, University of Utah Health Sciences Center and Department of Cardiology, VA Salt LakeHealthcare System

Prog Cardiovasc Nurs. 2001;16(3) 

In This Article

What Factors Cause a Decrease in Diastolic Augmentation?

The magnitude of augmented diastolic pressure is frequently, but erroneously, used as an assessment parameter to evaluate whether IAB pumping is successful. Many variables can impact the amount of pressure generated by balloon inflation. Weber and Janicki[4] proposed a framework of physical and biologic variables that influence diastolic augmentation. These factors include: IAB position, volume, systemic vascular resistance, and timing.

The proximal tip of the IAB should be positioned just below the bifurcation of the left subclavian artery (Fig.1). If the IAB is positioned too low, diastolic augmentation will be reduced as inflation momemtum is decreased.

Diastolic augmentation is maximized when stroke volume is equal to balloon volume. If stroke volume is less than 25 ml, little diastolic augmentation can be expected. On the contrary, a stroke volume greater than 50 ml is beyond the displacement capabilities of the inflating IAB. Augmentation will, therefore, also be decreased.

As systemic vascular resistance increases, diastolic augmentation may decrease because of the associated decrease in compliance. Conversely, an extremely low systemic vascular resistance also will produce poor augmentation.

Early inflation or late deflation can decrease the amount of time that helium gas inflates the IAB. Thus, a shortened deflation imposed by erroneous balloon timing will understandably decrease the magnitude of inflation.

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