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

How Is Mean Arterial Pressure Calculated in the Iab-Pumped Patient?

Little[2] describes the mean arterial pressure (MAP) as an average pressure or calculated value that does not exist except during an instantaneous measurement during the rise and fall of the patient's pulse. Two methods can be utilized for computation: arithmetic and integration. Arithmetic MAP is computed by the sum of the systolic pressure +2(diastolic pressure)÷[3]. As an example, a systolic pressure of 120 mm Hg and diastolic pressure of 80 mm Hg yields a mean arithmetic MAP of 93 mm Hg. This method is problematic in IAB pumping, when the highest pressure generated is actually "diastolic augmentation." The computer will erroneously interpret that pressure point as the systolic pressure, and thus the MAP calculation will be inaccurate.

A true functional mean divides the "area" of the pressure waveform by the length of the sample, which is described as the integration method (Fig. 5).[3,4] If the area expands secondary to IAB-pumped inflation, it is reflected in the mean pressure calculation. Most balloon pumps employ the integration method. Clinicians need to investigate which method is utlized by the bioinstrumentation used in monitoring the patient.

Integration method of calculating mean arterial pressure (see text for explanation)


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