OPTIMISTISATION OF BLOOD PUMPING SYSTEMS

Abstract The necessity of blood pumping systems is present in open-heart surgery and in many assistdevices. Roller pumps are used practically in all cases of blood pumping for historical reasons and for their undoubted simplicity of use. But even if these pumps are widely used, many serious mistakes are made in their use. As the red cells must not be damaged, a complete squashing of the tube must be avoided, which means keeping a meatus between tube wall at the passage of the rolls. Under these conditions the characteristic diagram becomes similar to that of a centrifugal pump. Therefore the flow evaluated by rev/min, independently of the head, can cause very serious mistakes. Diagrams illustrating the correct relations among flows, meatus and numbers of revolutions are presented. Moreover, a flow dynamics investigation has been carried out on the behaviour of blood in the interior of the pump to evaluate the shear stress (and therefore the haemolysis) due to back flow caused by the meatus. Results show the importance of pump calibration in comparison with haemolytic damage. Finally, new pumping systems are proposed as a desirable development for extracorporeal circulation.