Protruding Objects in the Membrane Lung Outlet May Increase Thrombogenicity: Fluid Dynamical Insights.

Thrombosis in extracorporeal membrane oxygenation (ECMO) circuit components remains a challenge. Besides blood state and surface properties, flow plays a critical role in hemostasis. In this work, we aimed to study the fluid dynamics of a membrane lung (ML) outlet due to its complex design with pins protruding into the blood flow stream (temperature sensor and cap of purge line), with respect to the potential risk of flow-induced coagulation activation. Large eddy simulations were carried out for blood flow of 1 and 4 L/min. Recirculation bubbles and strong vortical structures developed in this geometry. These flow structures were similar to characteristics of flow past bluff bodies, which facilitate entrapment of platelets that may be activated by the elongational shear rates (> 2,000 s-1), observed near the surface of the temperature sensor for the 4 L/min case. Moreover, a thrombus, extracted from an ECMO circuit, was analyzed by scanning electron microscopy. It is concluded that a review of devices used for ECMO with auxiliary objects protruding into the bloodstream is warranted for improvement of design to reduce the risk of blood trauma and coagulation activation.