Numerical Analysis of Blood Flow Dynamics in Pediatric ECMO Circuits

Extracorporeal membrane oxygenation (ECMO) offers lifesaving support for severe cardiac or respiratory failure patients, yet thrombotic complications within the circuit remain a major challenge. Although design improvements to individual ECMO components have provided some benefits, the overall influence of full-circuit design on hemodynamics and thrombotic risk remains poorly understood. We investigated whole-circuit ECMO hemodynamics and their implications for hemolysis and thrombus formation using computational fluid dynamics (CFD). We developed a full ECMO-CFD model of our center's pediatric support circuit and validated it against in vitro measurements using blood-analog fluid circulated under clinically relevant operating conditions. The model was then used to assess the cumulative impact of circuit components and junctions on hemodynamics, and we further extended the analysis to evaluate the effect of non-Newtonian blood behavior on local flow dynamics. Flow analysis revealed largely uniform flow in the ECMO tubing, with localized disturbances near connectors and internal loops that could propagate downstream and increase thrombosis risk. While tubing and connectors experienced shear stresses below 10 Pa, ~ 0.18% of pump volume experienced 50-100 Pa, and 0.0035% exceeded 100 Pa at 1500 RPM. At 4000 RPM, these values increased ~ 23-fold, resulting in a ~ 52-fold rise in the hemolysis index, demonstrating substantial pump-driven blood trauma. Incorporating non-Newtonian effects further revealed shear and hemolysis hotspots near the pump that were overlooked under Newtonian assumptions. Our findings underscore the importance of the whole ECMO circuit in optimizing flow dynamics and reducing blood trauma, highlighting the need to consider the entire system to better predict and mitigate thrombotic complications.