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

Abstract and Introduction

This paper reviews arterial pressure waveforms and contrasts the differences in waveforms imposed by intra-aortic balloon counterpulsation. It explores questions regarding blood pressure interpretation and offers guidelines for practice.

Intra-aortic balloon (IAB) counterpulsation refers to the process whereby a nonthrombogenic, usually 40-cc, IAB is retrogradely inserted via femoral artery access into the descending thoracic aorta, to a position just below the left subclavian artery (Fig. 1). The IAB is attached to a console that rapidly shuttles helium gas in and out of the balloon chamber. Inflation is timed in response to a biologic signal (usually electrocardiogram [EKG]), and occurs during diastole. Helium inflates the IAB and occupies a space within the aorta that raises the aortic pressure (diastolic augmentation) and displaces blood superiorly and inferiorly. Volume within the aorta expands as the IAB inflates with helium during inflation. An increase in pressure concomitantly occurs. Deflation occurs during isovolumetric contraction or just prior to systole. Blood volume is markedly reduced, which produces a lower end-diastolic pressure.

Schematic illustration of the inta-aortic balloon positioned in the descending thoracic aorta, just below the left subclavian artery, but above the renal arteries. Reprinted with permission from Quaal SJ. Mosby-Yearbook; 1993.[3].

Physiologic pressure changes induced by IAB pumping alter the conventional landmarks on the arterial pressure waveform. Nurses caring for IAB-pumped patients must understand and anticipate these transformational arterial pressure changes and be able to interpret them accurately. Measuring blood pressure during IAB pumping becomes much more complex and poses diagnostic and interpretive questions, such as:

  1. Which pressure should be documented?

  2. How does the bedside monitor digital display measure blood pressure in the balloon-pumped patient?

  3. Which pressures should be used to titrate vasopressor drips?

  4. How is mean arterial pressure computed?

The purpose of this paper is to review the normal arterial pressure waveform, contrast the differences in waveform morphology imposed by IAB pumping, explore challenging questions regarding blood pressure interpretation, and offer guidelines for practice. Troubleshooting causes of poor diastolic augmentation are also presented.

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