On the Accuracy of Hemolysis Models in Couette‐Type Blood Shearing Devices

Abstract

Hemolysis is one of the most challenging issues faced by blood contacting devices. Empirical hemolysis models often relate hemolysis to shear stress and exposure time. These models were generally derived from the experimental results of Couette‐type blood shearing devices, with assumption of uniform exposure time and shear stress. This assumption is not strictly valid since neither exposure time nor shear stress is uniform. Hence, this study evaluated the influence of the nonuniform exposure time and rotor eccentricity or run‐out on the accuracy of power‐law hemolysis models, using both theoretical and CFD analysis. This work first provided a systematic analysis of the flow regime in a typical Couette shearing device, and showed the axial flow component can be regarded as fully developed laminar plane Poiseuille flow. It was found that the influence of nonuniform exposure time is within 4% for several widely used power‐law models, which were validated by steady CFD simulations. A theoretical relationship was then built between the rotor run‐out and hemolysis. We noticed that the influence of rotor run‐out on hemolysis is within 5% for a moderate rotor run‐out ratio of 0.2. Next, transient CFD simulations were performed to investigate the influence of rotor run‐out on hemolysis with run‐out ratios of 0.1 and 0.2. The results showed negligible effects for a moderate run‐out ratio of 0.1. However, a run‐out ratio of 0.2 led to a significant increase of hemolysis, resulting from back flows induced by the run‐out of the rotor. These findings will be of great importance for the improvement of the hemolysis estimation and blood compatibility design.

Haemolysis induced by mechanical circulatory support devices: unsolved problems

“…Goldsmith and Turitto 6 have determined these deviations in extensive comparative tests. Wu et al 26 were able to show that the critical limit of shear stresses determined with a frequently used Couette viscometer is only of limited significance for the occurrence of haemolysis. Beissinger and Laugel 27 were also able to demonstrate that the haemolysis level increases when the erythrocytes get into contact with foreign materials, regardless of the shear rate present.…”

Artificial Organs 2018: A Year in Review

“…Peng Wu et al of Soochow University, Suzhou, Jiangsu, China, investigated the accuracy of hemolysis models in Couette‐type blood shearing devices. The study evaluated the influence of the nonuniform exposure time and rotor eccentricity or run‐out on the accuracy of power‐law hemolysis models, using both theoretical and CFD analysis.…”

Hemolysis and von Willebrand factor degradation in mechanical shuttle shear flow tester

“…Large multimers with high-molecular-weight VWF are extended by the fluid forces in a shear flow and are cleaved by ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) under high shear stress flow conditions in the cardiovascular system [4][5][6][7][8]. Previously, empirically estimated hemolysis or VWF degradation models were developed to predict the concentration and accumulation of shear flows in MCSs through their development processes [9][10][11][12].…”

“…The present study provides an experimental analysis of hemolysis and the VWF degradation degree for goat blood using a newly designed shuttle shear flow tester. The maximal velocity in the tester was designed according to the threshold Reynolds stress that would cause hemolysis, i.e., 400–800 Pa, as described in previous studies [ 10 , 15 ]. The present study aimed to examine the lysis of red blood cells and VWF degradation in the shear stress flow range of approximately 10–600 Pa under the assumption of the threshold of either the VWF degradation or the hemolysis with time-dependent variations in blood flow velocity.…”