Computational Fluid Dynamics of Blood Flow in an Extracorporeal Blood Circuit for the Analysis of Thrombogenic Hemodynamic Factors

Blood flow in a filter for an extracorporeal blood circuit was analyzed numerically to assess fluid mechanical quantities related to thrombogenesis. Results showed stagnant flow regions, in particular at the downstream side of the ceiling of a filter. A particle tracking along with an evaluation of a shear stress exerted on a particle demonstrated that a particle experiences a large shear stress when passing through a pore of the filter. These results suggest that a platelet would be activated when it goes though the pore and could then aggregate with other activated platelets to develop into a thrombus beneath the ceiling of a filter. Based on this hypothesis, the filter design was modified by making a protrusion on the downstream side of the filter. The protrusion design was varied in two ways in shape (sharp, blunt) and three ways in height (1/4, 1/3, 1/2 of the height of the original filter). The simulation results showed a positive contribution of the protrusion to a decrease in the stagnant flow region on the downstream side of the filter ceiling. A comparison of the stagnant volume for models between a model with blunt protrusion and the one with sharp protrusion revealed that the blunt protrusion decreased the stagnant region more than that for models with a shape one. The protrusion also contributed to decreasing the shear stress at pores of the filter. This effect was more pronounced with an increase in the height of the protrusion. These results address benefits of the protrusion in the anti-thrombogenic design of a filter for an extracorporeal blood circuit.