EFFECTS OF SURFACE-ROUGHNESS ON MECHANICAL HEMOLYSIS

Previous in vitro hemolysis test results showed that an inlet taper or a round corner in the leading edge of a stenotic connector played an important role in the reduction of hemolysis. However, computational f luid dynamics (CFD) analysis of these results indicated that the shear rate and hemolysis level were not always related to each other. Then, further research was performed, focusing on the effects of surface ro ughness on hemolysis. The results thus far can be summarized as threef old. First, the rate of hemolysis occurring at an abrupt change in the stenotic section was different if the longitudinal length of the sten osis was changed. The level of plasma-free hemoglobin after 6 h of cir culation was decreased from 280 mg/dl to 70 mg/dl when the longitudina l length was shortened from 15 mm to 1 mm. Second, a comparison of hem olysis rates in identical stenotic connectors with differing surface r oughness (Ra = 0.45 and 1.35 mu m) revealed that a smooth surface achi eved as much as an 80% reduction in the rate of hemolysis. Third, the in vitro hemolysis results obtained were further defined through CFD a nalysis.