Analysis and experiments on flow-induced hemolysis

Hemolysis (red cells lysis) caused by fluid stresses in flows within hypodermic needles, blood pumps, artificial hearts and other cardiovascular devices, is one of the major concerns during the design and use of cardiovascular or blood-processing extracorporeal devices. A non-invasive experimental method which does not interfere directly with red blood cells was designed to investigate the red cells' deformations in response to a range of flow conditions. The designed flow chamber and pump system provided a controlled two-dimensional Poiseuille flow with average velocity of up to 4 m/s and a range of fluid stresses up to 5000 dyn/cm2. The dimension of deformed cells and positions was measured to obtain the aspect ratio of red cells under stress from images captured by the microscope-laser-camera system. A strain-based blood damage model from Rand's viscoelastic model was built to predict cell strain. The empirical coefficients in the blood damage model were calibrated by the measurements from the experiments.; Flow-induced hemolysis in the blood flow through hypodermic needles was investigated. The flow-induced hemolysis of the needles may be reduced by a modified design of the entrance geometry of the needle. Three groups of 16 gauge needles were compared: one standard group with sharp entrance, another with beveled entrance and a third with rounded entrance. The CFD analysis combined with the strain-based blood damage model, Heuser et al. model and Giersiepen et al. model respectively was used to analyze the flow-induced hemolysis of the three needles. The predicted results were compared to the experimental results, which showed the rounded entrance reduced hemolysis by 34%, but the beveled entrance increased hemolysis by 38%. The strain-based blood damage model predicted the reduced hemolysis by 7.4% in rounded needle and the increased hemolysis by 13% in beveled needle. Both Heuser et al. model and Giersiepen et al. model predicted increased hemolysis in rounded needle.