Equipment

Historically, the adult IABP consisted of an 8.5F to 12F catheter, the distal 30 cm of which was covered with a polyurethane balloon. For adult patients, 7F catheters also with 25-mL to 50-mL balloons are currently most commonly used, with the size of the balloon dependent upon the patient’s height. The pediatric catheter is 4.5F to 7F with a 2.5-mL to 12-mL balloon.

The catheter is inserted into the common femoral artery percutaneously by the Seldinger technique or by an open surgical procedure. It is then threaded proximally so that the balloon lies high in the descending thoracic aorta, just distal to the origin of the left subclavian artery.

The catheter is connected to a drive console that has a pneumatic pump that uses helium to rapidly inflate the balloon and, just as quickly, deflate the balloon after a brief period of time. Balloon cycling is triggered either from the electrocardiogram R wave, inflating with diastole and deflating with onset of systole (Figure 153-1), or from the aortic pressure waveform. It should be adjusted to inflate when the dicrotic notch occurs in the pressure cycle (Figure 153-2). The balloon can be set to trigger with every beat, every other beat, or some other pattern.

Hemodynamic effects

With balloon deflation at onset of systole, the peak aortic systolic pressure falls 10% to 15% (systolic unloading) and inflates immediately with appearance of the dicrotic notch. Balloon inflation can increase intraaortic diastolic pressure by approximately 70%. The cardiac index increases 10% to 15%, whereas the pulmonary artery occlusion pressure falls by a similar amount. Coronary blood flow increases as a result of increased diastolic pressure.