Hemodynamics of artificial devices used in extracorporeal life support
Time: Tue 2021-09-28 14.00
Subject area: Engineering Mechanics
Doctoral student: Francesco Fiusco , Teknisk mekanik
Opponent: Dr., Lecturer Katharine Fraser, University of Bath, Department of Mechanical Engineering
Supervisor: Docent Lisa Prahl Wittberg, Teknisk mekanik
Extracorporeal Membrane Oxygenation (ECMO) is a life-saving therapy usedfor support in critical heart and/or lung failure. Patient’s blood is pumped viaan artiﬁcial lung for oxygenation outside of the body. The circuit is composedof a blood pump, cannulae for drainage and reinfusion, a membrane lung,tubing and connectors. Its use is associated with thromboembolic complicationsand hemolytic damage. Detailed numerical studies of two blood pumps anda lighthouse tip drainage cannula were undertaken to characterize the ﬂowstructures in diﬀerent scenarios and their link to platelet activation. The pumpsimulations were modelled according to manufacturer’s proclaimed use but alsoin oﬀ-design conditions with ﬂow rates used in adult and neonatal patients.Lagrangian Particle Tracking (LPT) was used to simulate the injection ofparticles similar in size to platelets to compute platelet activation state (PAS).The results indicated that low ﬂow rates impacted PAS similarly to high ﬂowrates due to increased residence time leading to prolonged exposure to shearstress despite the fact that shear per se was lower at low ﬂow rate. Regardingthe cannula, the results showed that a ﬂow pattern similar to a jet in crossﬂowdeveloped at the side holes. A parameter study was conducted to quantifydrainage characteristics in terms of ﬂow rate distribution across the holes wheninput variables of ﬂow rate, modelled ﬂuid, and hematocrit were altered. Theﬁndings showed, across all the cases, that the most proximal hole row drainedthe largest fraction of ﬂuid. The eﬀects due to the non-Newtonian nature ofblood were conﬁned to regions far from the cannula holes and the ﬂow structuresshowed very limited dependence on the hematocrit. A scaling law was found tobridge the global drainage performance of ﬂuid between water and blood.