DYNAMICS OF BALLOONS IN INTRAAORTIC COUNTERPULSATION

To optimize intraaortic balloon pulsation, the inflation and deflation mechanisms of different intraaortic balloons were studied in a model aorta with pressure volume characteristics approximating those of a natural aorta and in anesthetized dogs by cineangiography. It could be demonstrated that inflation of straight balloons begins at the tip and proceeds from there to the end of the balloon. The distention of the aortic arch balloons is first observed in the aortic arch; inflation than proceeds to the end of the balloon. Deflation of both balloon types has the same direction as inflation, beginning at the tip.

From the model investigations it can be concluded that the balloon dynamics are definitely pressure dependent: inflation begins in that balloon part, where the pressure is lowest; deflation where the highest pressure is exerted. These results explain the behavior of balloons in vivo.

In the aorta of living dogs in the early diastole, the pressure nearest to the heart is less than in lower parts of the aorta. Therefore, gas filling is first accomplished at the balloon tip. However, following diastolic increase in late diastole, the pressure difference between the proximal and distal aorta is reversed: deflation begins at the tip of the balloon.

When hypotension decreases the diameter of the aorta to that of the balloon, occlusion is produced at the balloon tip and only a minor or no pulse wave is allowed to run towards the heart. This is the reason for failure of intraaortic balloon pulsation in very hypotensive states and in those with a small diameter of the aorta.

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