Flow distribution during cardiopulmonary bypass in dependency on the outflow cannula positioning
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Published on: May 11, 2018
Tim A S Kaufmann1, Marcus Hormes, Marco Laumen
1Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Aachen, Germany. kaufmann@hia.rwth-aachen.de
Insights
Right brain oxygen deficiency during cardiopulmonary bypass (CPB) stems from insufficient cerebral artery perfusion. The Venturi effect from the outflow cannula jet is identified as the primary cause, impacting brain blood flow.
Area of Science:
- Cardiovascular Engineering
- Medical Imaging
- Fluid Dynamics
Background:
- Right brain oxygen deficiency is a frequent complication during cardiopulmonary bypass (CPB).
- This issue is associated with inadequate blood flow to the carotid and vertebral arteries.
- Outflow cannula positioning significantly impacts cerebral perfusion during CPB.
Purpose of the Study:
- To investigate the influence of outflow cannula position on cerebral perfusion during CPB.
- To compare traditional ascending aorta cannulation with right subclavian artery cannulation.
- To identify the primary mechanism responsible for reduced cerebral blood flow.
Main Methods:
- A 3D cardiovascular system model was created using CT and MRI data.
- Computational fluid dynamics (CFD) simulations were performed for various cannula positions.
- Particle image velocimetry (PIV) was used to validate CFD results.
Main Results:
- Analyzed flow distribution across 55 cannula positions in the aorta.
- Identified the Venturi effect from the cannula jet as the main cause of reduced cerebral perfusion.
- Established a PIV-validated CFD methodology for analyzing cardiovascular flow.
Conclusions:
- The Venturi effect significantly impairs cerebral perfusion during CPB.
- Right subclavian artery cannulation offers an alternative approach to consider.
- The developed CFD method is adaptable for other cardiovascular flow analyses.
Abstract:
Oxygen deficiency in the right brain is a common problem during cardiopulmonary bypass (CPB). This is linked to an insufficient perfusion of the carotid and vertebral artery. The flow to these vessels is strongly influenced by the outflow cannula position, which is traditionally located in the ascending aorta. Another approach however is to return blood via the right subclavian artery. A computational fluid dynamics (CFD) study was performed for both methods and validated by particle image velocimetry (PIV). A 3-dimensional computer aided design model of the cardiovascular (CV) system was generated from realtime computed tomography and magnetic resonance imaging data. Mesh generation (CFD) and rapid prototyping (PIV) were used for the further model creation. The simulations were performed assuming usual CPB conditions, and the same boundary conditions were applied for the PIV validation. The flow distribution was analyzed for 55 cannula positions inside the aorta and in relation to the distance between the cannula tip and the vertebral artery branch for subclavian cannulation. The study reveals that the Venturi effect due to the cannula jet appears to be the main reason for the loss in cerebral perfusion seen clinically. It provides a PIV-validated CFD method of analyzing the flow distribution in the CV system and can be transferred to other applications.