A question for people who are familiar with IABP. The other day, we had a patient on ECMO with a balloon, and the MAP on the balloon was reading higher than the systolic pressure on the balloon. Something like 67/47, mean was 74, Aug 100. We were talking with perfusion as most of us had never seen that before... and trying to figure out how that could happen. Does the balloon use the augmentation i.e. peak assisted systole for calculation of MAP? That was one of our possible explanations for this, however even after we had switched it to 1:2, unassisted MAP was still higher than unassisted systole.
Naturally, we re-zeroed, changed out console etc, with same results. So I started thinking a little deeper. I wish I could post a pic of the waveform, but this is an explanation of what it looked like. Systole, dicrotic notch, augmentation, then insted of normal drop to diastole, a small increase then decrease, sort of like a chair... was told it was a bicuspid waveform during diastole. So I understand this can be r/t inappropriate sizing or positioning as normally with the iabp, a significant amount of blood has been displaced which is why there is normally a steep decline after augmentation.... however if the balloon is inappropriately sized or position, more blood is left in the aorta during diastole resulting in that bicuspid waveform.
So normally, the monitor & balloon calculate arterial MAP based on it's on hemodynamic curve and everything underneath as opposed to the (SBP+2*DBP)/3, which is why your cuff BP does not equal your art BP even if the MAP is the same. Could that increased diastolic pressure (r/t bicuspid waveform) cause the balloon to calculate out the mean to be higher than the systolic?
Another possible explanation to that waveform other than inappropriate balloon sizing or incorrect position, the patient was on ECMO w/direct aortic art cannulation, so possibly high flows could alter the art waveform on the balloon?
If anyone has any expert opinions or explanations, it would be much appreciated. Trying to expand my knowledge here