The red blood cell damage after long-term exposure to shear stresses

Artificial cardiovascular devices, such as vascular stents, artificial valves, and artificial hearts, can rebuild human cardiovascular functionalities via rebuilding the blood flow passing through these devices. To evaluate the red blood cells (RBCs) damage induced by a non-physiological blood flow in these devices, many hemolysis models have been proposed, of which the most popular one is a power function model. However, it was found that the newly obtained experimental data often did not match the existing power function model. In addition, the experimental period was usually short and the summarized power function model cannot reflect the RBCs damage after long-term exposure to shear stress. To address this issue, in this study a shear device was established on a torque rheometer; the changes of plasma free hemoglobin (FHB) of sheep blood under the shear stress from 10 to 70 Pa and exposure time from 5 to 30 min were recorded and compared. The results showed that as the shear stress and exposure time increased, FHB also increased, but the increase rate gradually decreased. As a result, after undergoing high shear stress or a long period of exposure time, FHB eventually became stable. Obviously, the existing power function model cannot describe this FHB change. In the current study, we used a sigmoidal logistic function model to describe the FHB increment upon the increase of shear stress and long exposure time. The results showed that the proposed model can provide better predictions of hemolysis, particularly in these cases under long exposure time.