CFD ANALYSIS OF ANASTOMOSIS RESISTANCE TO ENSURE NORMAL RV FUNCTION

Abstract

High pulmonary system resistance can lead to RV dysfunction during thoracic artificial lung (TAL) attachment. This study analyzes the flow patterns and resistance at pulmonary artery anastomoses during simulated in-series TAL attachment. The hemodynamic changes were investigated with three parameters: the steady, inlet flow rate (Qinlet), anastomotic angle (α), and the percentage of the inlet flow going through the anastomoses, Φ. The Qinlet was given as 2, 4, 8, 12, 16, and 20 L/min. The angles, α, were equal to 90°, 60°, and 45°. The % of inlet flow to the anastomoses are 0%, 25%, 50%, 75%, and 100% of Qinlet. The 90° angle indicates that the graft is attached perpendicular to the PA. It is assumed that the % of flow is created by banding the PA between the anastomoses. Three-dimensional simulations were performed using computational fluid dynamics. Result shows that four possible recirculation zones were observed: near the entrance of the upstream wall of the proximal graft, both upstream and downstream to the PA occlusion, and at the toe near the distal anastomosis. Results indicate that when PA banding is increased, resistance increases linearly in both proximal and distal anastomoses. Resistance also increases linearly with flow rate, and decreases with anastomotic angle. Therefore, a minimal anastomosis angle α is preferable. The 45° proximal anstomosis has a resistance of 0.33 mmHg/(L/min) at 8 L/min, compared to 0.39 and 0.34 mmHg/(L/min) for the 90° and 60° angles. Therefore, the smaller angle should improve RV function due to lower resistance. These results will be confirmed with in-vitro experiment.