Flow Dynamics and Thrombus Formation in Extracorporeal Membrane Oxygenation
A Combined Computational and Experimental Study
Time: Thu 2025-10-30 10.00
Location: F3, Lindstedtsvägen 26
Language: English
Subject area: Engineering Mechanics
Doctoral student: Frida Nilsson , Strömningsmekanik
Opponent: Professor Franck Nicoud, IMAG, University of Montpellier;IUF, Paris
Supervisor: Professor Lisa Prahl Wittberg, Strömningsmekanik, FLOW, Department of Engineering Mechanics, Royal Institute of Technology (KTH), Stockholm, Sweden; Docent Lars Mikael Broman, ECMO Centre Karolinska, Astrid Lindgren’s Children’s Hospital, Karolinska University Hospital, Stockholm, Sweden;Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden; Professor Daniel Söderberg,
QC 251015
Abstract
In cases of severe cardiac and/or respiratory failure, extracorporeal membrane oxygenation (ECMO) can be used as a bridge to organ recovery or transplantation. In ECMO, blood is drained through a venous drainage cannula by a pump, pushed through a membrane lung for gas exchange, and returned to the patient through a return cannula. Along this path blood passes through tubing and several connectors. These components expose blood components to elevated shear rates, highly unsteady flow fields, prolonged residence times, and artificial surfaces, increasing the risk of hemolysis, bleeding, and thrombosis.
This work investigates the flow structures and stresses that arise in ECMO circuit components and connects them to mechanisms for blood damage. It also provides a methodology where the thrombus morphology and composition can be assessed with scanning electron microscopy (SEM) and ultra small angle X-ray scattering (USAXS) to the local flow field. By using large eddy simulations (LES) complemented by Reynolds averaged Navier Stokes (RANS) modeling, flow phenomena were evaluated under clinically relevant operating conditions and compared with experimental observations. Results revealed that the size and intensity of recirculation zones and other flow structures were highly dependent on operating conditions, with inlet recirculation and larger rotating flow cells blocking the main flow at low inlet flow rates in the DP3 pump (Xenios AG,Heilbronn, Germany). The low-weight DP3 impeller exhibited wobbling, that could potentially increase both hemolysis and plastic spallation. Cavities and protrusions were found to promote stagnation, shear layers, with recirculation volumes growing with increased flow rates. Shear rate analysis further identified elongational shear in several locations, including the pump inlet, blade wakes and pump outlet. These regions pose a risk for von Willebrand factor (vWf) unfolding followed by platelet activation and consequently thrombus growth.
Overall, the findings emphasized that both operational settings and circuit design strongly influenced the formation of damaging flow conditions in the ECMO circuit. Linking flow features to thrombus morphology and known mechanisms for blood damage provides a foundation for improved models for thrombosis, refined clinical guidelines, and helps with future device design.