A parametric model of cannula to investigate hemolysis by using CFD

Extracorporeal circulation and more recently ventricular assistance are used in cardiovascular surgery helping the success of complex intervention; however hemolytic problems are provided by the use of a great amount of external surfaces and the scheme of both cannulation and device application. In this view a parametric model of cannulae (usable for dialysis needle as well as for cardiopulmonary bypass) inserted in a pipe (representing at present a venous region) is presented to study the hemolysis related variables. By means of CFD (computational fluid dynamics) the flow field is 3D analysed to achieve correct information on the velocity and shear stress fields as a first step in evaluating the incidence of geometry on the hemolytic potential. Further methodological aspects on the application of hemolysis indices are discussed in order to suggest a way to introduce a quality factor based on the quantitative evaluation of local or global induced red cell injury. The need to use a 3D model is emphasized with respect to the partial results that can be obtained from a 2D model.