Comparison of hemodynamic features and thrombosis risk of membrane oxygenators with different structures: A numerical study

Abstract

Purpose: The geometric structure of the membrane oxygenator can exert an impact on its hemodynamic features, which contribute to the development of thrombosis, thereby affecting the clinical efficacy of ECMO treatment. The purpose of this study is to investigate the impact of varying geometric structures on hemodynamic features and thrombosis risk of membrane oxygenators with different designs.

Methods: Five oxygenator models with different structures, including different number and location of blood inlet and outlet, as well as variations in blood flow path, were established for investigation. These models are referred to as Model 1 (Quadrox-i Adult Oxygenator), Model 2 (HLS Module Advanced 7.0 Oxygenator), Model 3 (Nautilus ECMO Oxygenator), Model 4 (OxiaACF Oxygenator) and Model 5 (New design oxygenator). The hemodynamic features of these models were numerically analyzed using the Euler method combined with computational fluid dynamics (CFD). The accumulated residence time (ART) and coagulation factor concentrations (C[i], where i represents different coagulation factors) were calculated by solving the convection diffusion equation. The resulting relationships between these factors and the development of thrombosis in the oxygenator were then investigated.

Results: Our results show that the geometric structure of the membrane oxygenator, including the location of the blood inlet and outlet as well as the design of the flow path, has a significant impact on the hemodynamic surroundings within the oxygenator. In comparison to Model 4, which had the inlet and outlet located in the center position, Model 1 and Model 3, which had the inlet and outlet at the edge of the blood flow field, exhibited a more uneven distribution of blood flow within the oxygenator, particularly in areas distant from the inlet and outlet, which was accompanied with lower flow velocity and higher values of ART and C[i], leading to the formation of flow dead zones and an elevated risk of thrombosis. The oxygenator of Model 5 is designed with a structure that features multiple inlets and outlets, which greatly improves the hemodynamic environment inside the oxygenator. This results in a more even distribution of blood flow within the oxygenator, reducing areas with high values of ART and C[i], and ultimately lowering the risk of thrombosis. The oxygenator of Model 3 with circular flow path section shows better hemodynamic performance compared to the oxygenator of Model 1 with square circular flow path. The overall ranking of hemodynamic performance for all five oxygenators is as follows: Model 5 > Model 4 > Model 2 > Model 3 > Model 1, indicating that Model 1 has the highest thrombosis risk while Model 5 has the lowest.

Conclusion: The study reveals that the different structures can affect the hemodynamic characteristics inside membrane oxygenators. The design of multiple inlets and outlets can improve the hemodynamic performance and reduce the thrombosis risk in membrane oxygenators. These findings of this study can be used to guide the optimization design of membrane oxygenators for improving hemodynamic surroundings and reducing thrombosis risk.

Keywords: CFD; Coagulation factor; ECMO; Hemodynamic surroundings; Membrane oxygenator; Residence time; Thrombosis.