Characterization of erythrocyte membrane tension for hemolysis prediction in complex flows

Abstract

Hemolysis is a persistent issue with blood-contacting devices. Many experimental and theoretical contributions over the last few decades have increased insight into the mechanisms of hemolysis in both laminar and turbulent flows, with the ultimate goal of developing a comprehensive, mechanistic hemolysis model. Many models assume that hemolysis scales with a resultant, scalar stress representing all components of the fluid stress tensor. This study critically evaluates this scalar stress hypothesis by calculating the response of the red blood cell membrane to different types of fluid stress (laminar shear and extension, and three turbulent shear and extension cases), each with the same scalar stress. It was found that even though the scalar stress is the same for all cases, membrane tension varied by up to three orders of magnitude. In addition, extensional flow causes constant tension, while tank-treading in shear flow causes periodic tension, with tank-treading frequency varying by three orders of magnitude among the cases. For turbulent flow, tension also depends on eddy size. It is concluded, therefore, that scalar stress alone is inadequate for scaling hemolysis. Fundamental investigations are needed to establish a new index of the fluid stress tensor that provides reliable hemolysis prediction across the wide range of complex flows that occur in cardiovascular devices.

Evaluation of energy dissipation rate as a predictor of mechanical blood damage

“…Experiments to measure membrane tension in flowing cells and to validate that hemolysis is reliably scaled by candidate scalar stresses are lacking. An analytical approach was reported by Faghih and Sharp . They calculated erythrocyte membrane tension in five simplified laminar and turbulent flows.…”

“…RMS values of the membrane tensions calculated with the same energy dissipation rate (Figure ) are compared to those based on the same scalar stress (results for scalar stress of 520 dyn/cm 2 from Faghih and Sharp using the revised Kolmogorov length and frequency scales of Section 2.3.2) in Figure . The tensions for the same scalar stress vary by a factor of 29, while those for the same energy dissipation rate vary by a factor of 46.…”

“…Four turbulence cases were evaluated in this study. Three are similar to those of Faghih and Sharp, corresponding to different locations of the red cell with respect to turbulent eddies (Figure ). These cases include: (i) cell sheared inside an eddy (Figure I); (ii) cell sheared between two co‐rotating eddies (Figure II); and (iii) cell stretched between two counter‐rotating eddies that exert extensional stress on the cell (Figure III).…”

“…An analytical approach was reported by Faghih and Sharp. 21 They calculated erythrocyte membrane tension in five simplified laminar and turbulent flows. The results | 667 FAGHIH And SHARP showed that, even though the scalar stress was equal for all the cases, the membrane tension varied by up to two orders of magnitude.…”

On Eulerian versus Lagrangian models of mechanical blood damage and the linearized damage function

“…For complex flows, it has been proposed that τ be replaced by a scalar stress . However, problems have been recognized with this extension . There is also another class of more mechanistic hemolysis prediction models based on cell membrane strain .…”