The effect of internal profile on cannula outflow

Abstract

One of the medical devices used during the open heart surgery in cardiopulmonary bypass (CPB) is the aortic curve-tip cannula. The aortic curve-tip cannula is also used in the extracorporeal membrane oxygenator (ECMO) to support patient in intensive care unit. There are few complications caused by the non – physiological jet or dispersed flow from the current cannula design. Thus, a novel designs approach to induce spiral flow and reduce the adverse effect on the aortic wall. The objective of this study is to compare the internal helical designs of curved-tip aortic cannula from three groove internal cannula design and three ribs internal cannula design against the standard cannula design; all with variation of straight and tapered body. A comparative study between six cannulae designs were carried out by computational fluid dynamics (CFD) in a steady state condition. Alls proposed internal helical designs have successfully induced spiral flow. The tapered body with 3 rib design was the best curved-tip aortic cannula design, since wall shear stress induced (2310 dyne/cm2) was below the critical value of wall shear stress (4500 dyne/cm2); while the outflow velocity was only slightly more than the standard cannula design. Also, the pressure drop across the cannula (66 mmHg) was significantly below the safe limit (100 mmHg).