Introduction of dimensionless parameters for in-silico washout evaluation within membrane oxygenators

• In-silico method for the investigation of blood washout within oxygenators • Effect of pulsatility on the washout behavior for oxygenators • Invention of dimensionless parameters to evaluate the washout behavior throughout different oxygenator models Extracorporeal membrane oxygenators are a key component within extracorporeal life support systems. A major complication is thrombus formation which has life-threatening consequences for the patients. The flow path within the oxygenators is a driver of thrombotic events and its optimization is a central engineering requirement, however there is a lack of a quantitative metrics to assess the thrombus risk in those devices. In this study, we present an in-silico method for evaluating oxygenators' flow path and introduce quantitative metrics for the optimization of such through three dimensionless parameters defining stagnation areas, flow homogeneity, and washout capabilities. Based on these parameters, we compare four commercially available oxygenators with respect to their thrombus risk at flows between 0.5-1.5 l/min and flow pulsatilities between 25-75%. The results outline how overall oxygenator design - wound vs. stacked fiber bundles – impacts washout metrics. Further on, we uncover that while low flow pulsatility of 25% does improve washout, further increase does not yield any additional benefit. This work shows the suitability of the presented parameters for a computational evaluation and optimization of existing or newly developed oxygenators.