Modelling development of ECMO return flow in bifurcating arteries

Sammanfattning: Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is a life saving therapy for critically ill patients experiencing a heart and lung failure. During this therapy, a common complication is limb ischemia in the leg where the return cannula reintroduces the oxygenated blood to the patient. The hemodynamics leading to limb ischemia during V-A ECMO therapy is not yet understood. This work uses computational fluid dynamics to model the interacting blood flows from the V-A ECMO return cannula and the native cardiac output in the abdominal aorta and iliac bifurcation. A two-element Windkessel (WK) model is used to model the downstream vasculature. In total, five simulations of four cardiac cycles are conducted, where either one WK model parameter or the aorta inflow boundary condition (BC) is altered. Results suggest that the outflow distribution between the iliac arteries is dependent on the WK model parameters, but it is independent of the inflow BC imposed at the aorta inlet. Increasing the resistance value of the WK model leads to an increase of pressure in the domain relative to the 0.8 L/min baseline case and increases the outflow through the non-cannulated iliac artery. The opposite effect is reached when decreasing the resistive value or increasing the compliance value. The velocity field close to the aortic bifurcation, where the return cannula flow is redirected, shows large variations and complex, three-dimensional flow structures. At the aorta inlet, the velocity field is sensitive to the aorta inflow BC. In the XY -plane, areas of high sensitivity are located in areas with high unsteady flow motion. The sensitivity analysis of the velocity field in the XY -plane seems to be independent of the BCs. The pressure field is sensitive to the BC since the pressure in the domain is dependent on the WK model parameters. This work can be a starting point to further investigate the influence of a change in BCs on the flow structures and the outflow distribution between the iliac arteries. Those results can develop a framework stating the factors with an increased patient’s risk for developing limb ischemia.