Shear stress evaluation on blood cells using computational fluid dynamics.

BACKGROUND: Thrombus formation and hemolysis are important factors in developing blood pumps and mechanical heart valve prostheses. These phenomena are induced by flow properties. High shear stress induces platelet and red cell damage. Computational fluid dynamics (CFD) analysis calculates shear stress of fluid and particle pathlines of blood cells. OBJECTIVE: We studied blood cell damage in a blood pump by using CFD analysis and proposed a method for estimating blood damage. METHODS: We analyzed a pulsatile blood pump that was developed as a totally implantable left ventricular assist system at Tokai University. Shear stress on blood cells throughout pulsatile blood pumps were analyzed using CFD software. RESULTS: Based on the assumption that the effect of shear stress on platelets is accumulated along the trace, we proposed a method for estimating blood damage using the damage parameter D. Platelet damage parameter is calculated regardless of the division time 𝛥t which is dependent on the calculation time step. The results of the simulations are in good agreement with Giersiepen's equation obtained from the experiments. CONCLUSION: The history of shear stress on a particle was calculated using CFD analysis. The new damage parameter D yields a value close to that of Giersiepen's equation with small errors.

An estimation method of hemolysis within an axial flow blood pump by computational fluid dynamics analysis.

Evaluation of hemolysis within a blood pump on a computer is useful for developing rotary blood pumps. The flow fields in the axial flow blood pump were analyzed using computational fluid dynamics (CFD). A blood damage index was calculated based on the changes in shear stress with time along 937 streamlines. Hemolysis of the pumps was measured using bovine blood. A good correlation between the computed and measured hemolysis results was observed. CFD analysis is useful for estimating hemolysis of rotary blood pumps on a computer.

Computational fluid dynamics analysis of an intra-cardiac axial flow pump.

A low rate of hemolysis is an important factor for the development of a rotary blood pump. It is, however, difficult to identify the areas where hemolysis occurs. Computational fluid dynamics (CFD) analysis enables the engineer to predict hemolysis on a computer. In this study, fluid dynamics throughout intracardiac axial flow pumps with different designs were analyzed three-dimensionally using CFD software. The computed pressure-flow characteristics of the pump were in good agreement with the measurements. The Reynolds shear stress was computed along particle trace lines. Hemolysis was estimated on the basis of shear stress (tau) and its exposure time (Deltat): dHb/Hb = 3.62 x 10(-7)(tau)(i)(2.416) x Delta(t)(i)(0.785). Particle damage increased with time along the particle trace lines. Hemolysis of each of the pumps was measured in vitro. The computed hemolysis values were in good agreement with the experimental results. CFD is a useful tool for developing a rotary blood pump.