| 1. |
- Fiusco, Francesco, 1994-, et al.
(författare)
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Effect of low rate ratio and positioning on a lighthouse tip ECMO return cannula
- 2023
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Ingår i: Biomechanics and Modeling in Mechanobiology. - 1617-7959 .- 1617-7940.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Extracorporeal membrane oxygenation is a life-saving support therapy in the case of cardiopulmonary refractory failure. Its use is associated to complications due to the presence of artificial surfaces and supraphysiological stress conditions. Thus, knowledge of the fluid structures associated to each component can give insight into sources of blood damage. In this study, an experimentally validated numerical study of a conventional lighthouse tip cannula in return configuration was carried out to characterize the flow structures using water or a Newtonian blood analog with different flow rate ratios and cannula positioning and their influence on hemolysis. The results showed that strong shear layers developed where the jets from the side holes met the co-flow. Stationary backflow regions at the vessel wall were also present downstream of the cannula. In the tilted case, the recirculation was much more pronounced on the wide side and almost absent on the narrow side. Small vortical backflow structures developed at the side holes which behaved like obstacles to the co-flow, creating pairs of counter-rotating vortices, which induced locally higher risk of hemolysis. However, global hemolysis index did not show significant deviations. Across the examined flow rate ratios, the holes on the narrow side consistently reinfused a larger fraction of fluid. A radial force developed in the tilted case in a direction so as to recenter the cannula in the vessel.
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| 2. |
- Lemetayer, Julien, et al.
(författare)
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Confined jets in co-flow : effect of the flow rate ratio and lateral position of a return cannula on the flow dynamics
- 2020
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Ingår i: SN Applied Sciences. - : SPRINGER INTERNATIONAL PUBLISHING AG. - 2523-3963 .- 2523-3971. ; 2:3
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Tidskriftsartikel (refereegranskat)abstract
- Co-axial tubes have been used to produce a co-flowing confined jet similar to that found in an Extracorporeal Membrane Oxygenation return cannula flow configuration. Particle Image Velocimetry was used to investigate the flow rate ratio between jet and co-flow as well as changes in flow characteristics due to cannula position. The flow was found to be dominated by three main structures: lateral flow entrainment, shear layer induced vortices and backflow along the wall. An increase in cannula flow rate amplified entrainment and recirculation, resulting in a decrease in length required to reach a fully developed flow. Changing cannula position relative the outer cylinder induced a significant reduction in recirculation zone as well as vortex formation on the side to which the cannula was tilted towards, whereas on the other side, the recirculating flow region was enhanced. Proper Orthogonal Decomposition demonstrated that the dominating structure found in the flow is the backflow, composing of several structures having different oscillation frequencies. The significance of the observed and measured flow structures is in enhancing mixing.
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| 3. |
- Lemétayer, Julien, et al.
(författare)
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Flow Dynamics and Mixing in Extracorporeal Support : A Study of the Return Cannula
- 2021
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Ingår i: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media SA. - 2296-4185. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Cannulation strategies in medical treatment such as in extracorporeal life support along with the associated cannula position, orientation and design, affects the mixing and the mechanical shear stress appearing in the flow field. This in turn influences platelet activation state and blood cell destruction. In this study, a co-flowing confined jet similar to a return cannula flow configuration found in extracorporeal membrane oxygenation was investigated experimentally. Cannula diameters, flow rate ratios between the jet and the co-flow and cannula position were studied using Particle Image Velocimetry and Planar Laser Induced Fluorescence. The jet was turbulent for all but two cases, in which a transitional regime was observed. The mixing, governed by flow entrainment, shear layer induced vortices and a backflow along the vessel wall, was found to require 9-12 cannula diameters to reach a fully homogeneous mixture. This can be compared to the 22-30 cannula diameters needed to obtain a fully developed flow. Although not significantly affecting mixing characteristics, cannula position altered the development of the flow structures, and hence the shear stress characteristics.
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