[Model fluids of blood for in vitro testing of artificial heart valves]

The increasing development and implantation of artificial organs subject to perfusion with human blood once implanted (grafts, heart-valve prostheses and assist systems) require extensive testing of hydrodynamic performance in mock circulation models. As human blood ist not always available in the necessary quantities, different fluids (water, saline or glycerine solutions) are employed for measurements of flow characteristics. However, these model fluids do not possess the non-Newtonian rheological properties of blood. In addition, they do not allow estimation of possible blood damage. Aqueous solutions of high molecular weight polyacrylamides (PAA) have rheological properties similar to blood, displaying also molecular degradation due to shear stress in the flow. Therefore, they were used as model fluid for blood. Different model solutions were compared to blood with regard to their influence on characteristic flow parameters of mechanical heart valves. Likewise, the shear damage of erythrocytes could be compared to flow-induced polymer degradation. It was shown that PAA solutions in definite concentrations are suitable models for blood, not only in terms of non-Newtonian rheology, but also in terms of estimation of hemolytic potential of artificial heart valves.