Hemodynamic Assessment of Hollow-Fiber Membrane Oxygenators Using Computational Fluid Dynamics in Heterogeneous Membrane Models

Abstract

Extracorporeal membrane oxygenation (ECMO) has been used clinically for more than 40 years as a bridge to transplantation, with hollow-fiber membrane (HFM) oxygenators gaining in popularity due to their high gas transfer and low flow resistance. In spite of the technological advances in ECMO devices, the inevitable contact of the perfused blood with the polymer hollow-fiber gas-exchange membrane, and the subsequent thrombus formation, limits their clinical usage to only 2-4 weeks. In addition, the inhomogeneous flow in the device can further enhance thrombus formation and limit gas-transport efficiency. Endothelialisation of the blood contacting surfaces of ECMO devices offers a potential solution to their inherent thrombogenicity. However, abnormal shear stresses and inhomogeneous blood flow might affect the function and activation status of the seeded endothelial cells (ECs). In this study, the blood flow through two HFM oxygenators, including the commercially-available iLA® MiniLung Petite Novalung (Xenios AG, Germany) and an experimental one for the rat animal model, was modelled using computational fluid dynamics (CFD), with a view to assessing the magnitude and distribution of the shear stress on the wall of the hollow fibers and flow fields in the oxygenators. This work demonstrated significant inhomogeneity in the flow dynamics of both oxygenators, with regions of high hollow-fiber wall shear stress and regions of stagnant flow, implying both regions of increased flow-induced blood damage and a variable flow-induced stimulation on seeded ECs in a biohybrid setting.

Extended Cellular Deposits on Gas Exchange Capillaries Are Not an Indicator of Clot Formation: Analysis of Different Membrane Oxygenators

“…18 The calculation of shear stress within oxygenators is critical due to a tortuous blood path through the fibers. 12 While De Somer 12 calculated comparable shear stresses of different hollow-fiber oxygenators, 26 Dipresa et al 30 demonstrated a significant inhomogeneity in the flow dynamics of different oxygenators with regions of high hollow-fiber wall shear stress and regions of stagnant flow. However, correlations to blood cell activation and increased leukocyte adhesion failed so far.…”