To develop cardiopulmonary devices, it is important to investigate the causes of hemolysis occurred by the blood flow speed and the behavior inside these devices. The flow speed in these devices is higher than the speed of under physiological conditions. Moreover, the flow behavior is different from physiological flow behaviors. Therefore, it is obvious that the hemolysis rate is heavily depended on the flow rate and the flow behavior. In previously, the other studies shown, high shear stress in cardiopulmonary devices was one of the main cuases of hemolysis (1). Thus, many experimental studies have been conducted to measure thresholds of shear stress that responsible for blood trauma. Constant stress exmperiments have revealed that there is threshold fo stress level above which damage to blood cells occur depending on the time of exposure (2). However, during extra corporeal circulation, blood cells are subjected to several physical forces simultaneously. Therefore, inorder to investigate the causes of hemolysis, it is necessary to examine the relation between hemolysis and the physical forces with in-vitro tests. The purpose of this study is to present the effect of physical forces, for example pressure and shear rate, on hemolysis. In this study, the experiments wre performed by using a rotational viscometer and a pressure chamber. These devices were prepared to apply physical forces to red blood cells. As result, we found that the combination of pressure and shear trate have a great influence on hemolysis.
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