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.
Highlights
Extracorporeal Membrane Oxygenation (ECMO) is a life-saving treatment used for patient suffering from acute refractory respiratory or cardio-respiratory failure, offering both circulatory and respiratory support
In ECMO, cannulae are available in sizes from 6 to 29 French (Fr, 1 Fr = 1/3× the outer cannula diameter do in millimeters)
To ensure the symmetry of the flow, measurements of the flow velocity and its fluctuations were performed for two symmetric positions of the cannula relative to the outer tube centreline
Summary
Extracorporeal Membrane Oxygenation (ECMO) is a life-saving treatment used for patient suffering from acute refractory respiratory or cardio-respiratory failure, offering both circulatory and respiratory support. Cerebral bleedings and thromboembolism are the most common severe complications leading to death in 80–85% of the cases (Dalton et al, 2015; Fletcher-Sandersjöö et al, 2017). These complications are associated with blood component damage/activation with subsequent increased risks of hemolysis, thrombosis, and emboli (Chen et al, 2019b). If the return cannula is placed on the venous side of the patient’s circulation veno-venous ECMO (lung support) is offered. If the return is into the arterial side of the circulation veno-arterial ECMO for cardio-pulmonary support is provided
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