Deformability of red blood cells and its relation to blood trauma in rotary blood pumps

In this study, mechanical trauma to red blood cells was evaluated by conventional hemolysis test and a newly developed cyclically reversing shear flow generator. The fresh porcine blood obtained from a local slaughterhouse was subjected to the conventional hemolysis test using a commercial centrifugal blood pump for the duration of 8 h. The measurements consisted of (i) plasma-free hemoglobin based on the standard optical measurement and (ii) the deformability of red blood cells (RBCs) using a cyclically reversing shear flow generator and microscope image acquisition system. The deformability of RBCs was expressed by the L/W value where L and W were the longer and shorter axes of the elongated RBCs' images. Although the plasma-free hemoglobin level increased with the pumping duration, the L/W remained unchanged for the duration of 8 h of pumping to indicate no alteration in the deformability. It was speculated that (i) although RBCs might have been circulated for so many times through the test pump, after each exposure to mechanical stress, RBCs might have recovered, and net effect due to shear stress-exposure time might have been small; and (ii) RBCs' deformability might be maintained near normal until sudden burst or membrane rupture, or the hemoglobin might have continuously leaked through the pores of the thinned membrane created by the mechanical stress. The deformability testing under a fluctuating shear flow could be a new method to quantify subhemolytic mechanical damage that has been accumulated in the RBCs' membrane and that may not be assessed by the conventional hemolysis test.