Simulation of shear destruction of red blood cells

A schematic diagram of shear flow. Credit: Fluid Physics (2022). DOI: 10.1063/5.0112967

Many medical devices for the treatment of heart failure generate non-physiological shear flow. This can trigger the destruction of red blood cells after implantation of ventricular assist devices (VADs), artificial heart valves, vascular stents, or interventional thrombectomy devices.

Destruction of red blood cells, or mechanical hemolysis, is an unavoidable complication of interventional devices. Scientists therefore want to better understand the phenomenon.

In Fluid Physics, researchers from Tsinghua University have developed a model of red blood cell destruction based on simulations of the dynamics of dissipative particles in high-shear flow. They used the results to make recommendations for improving VADs.

“After implanting interventional medical devices inside the human body, the nearby flow field generates shear flow with a very high shear rate,” said co-author Xiwen Zhang. “The rate of fluid velocity change will deform the red blood cell membrane. Eventually, the deformation of the membrane exceeds the ultimate stress, and the membrane is disturbed by shear flow.”

The team found that acceleration during shearing is a major factor in red blood cell destruction, beyond exposure time and shear stress. They recommend adding a flow buffer structure to the structural design of VADs to reduce some of the hemolysis caused by shear acceleration.

For research related to hemolysis, many researchers focus on large-scale experiments to obtain a series of empirical fit formulas.

“But our team is exploring the red blood cell-scale shear destruction process in more detail using dissipative particle dynamics,” Zhang said.

A transport dissipation particle dynamics method has been developed to simulate the shear damage of red blood cells in real blood. Credit: Fluid Physics (2022). DOI: 10.1063/5.0112967

“We hope our study can serve as a bridge between macroscopic hemolysis experiments and microscopic simulations of red blood cells (molecular dynamics simulations),” Zhang said. “In future work, we will continue to build shear failure models of multiple red blood cells and perform shear failure simulations based on whole blood for comparison with macroscopic hemolysis experiments.”

Researchers are currently developing a new index to more accurately predict VAD hemolysis and help optimize VAD shape, which should improve hydraulic performance and reduce hemolysis.

They plan to better represent the process of hemoglobin diffusion after shear damage by adding a transport and dissipation particle dynamics model based on this work.