THE EFFECTS OF EXTENSIONAL STRESS ON RED BLOOD CELL HEMOLYSIS

Artificial prostheses create non-physiologic flow conditions with stress forces that may induce blood cell damage, particularly hemolysis. Earlier computational fluid dynamics (CFD) prediction models based on a quantified power model showed significant discrepancies with actual hemolysis experiments. These models used the premise that shear stresses act as the primary force behind hemolysis. However, additional studies have suggested that extensional stresses play a more substantial role than previously thought and should be taken into account in hemolysis models. We compared extensional and shear stress flowfields within the contraction of a short capillary with sharp versus tapered entrances. The flow field was calculated with CFD to determine stress values, and hemolysis experiments with porcine red blood cells were performed to correlate the effects of extensional and shear stress on hemolysis. Our results support extensional stress as the primary mechanical force involved in hemolysis, with a threshold value of 1000 Pa under exposure time less than 0.060 ms.