Potential mechanical blood trauma in vascular access devices: a comparison of case studies.

Since vascular access devices may cause disturbances in blood flow, possibly damaging red blood cells (RBCs), the correlated risk of lysis must be assessed. The monodimensional approach for the evaluation of cannulae hydrodynamic behaviour (in vitro measured flow curves) does not furnish information on the local flow field occurring in specific clinical conditions. Researchers consider the prediction of blood trauma, induced by mechanical loading, to optimize the design phase, and to furnish indications on their optimal clinical use. In this study, a model of cannula inserted in a non compliant wall vessel was used as a test bench in a Computational Fluid Dynamics (CFD) problem. By means of CFD the flow field was 3D analysed to achieve information on velocity and shear stress local values, when cannula is used for inflow and outflow cannulation. A prediction of potential blood corpuscle damage, based on a power law, quantified the potential blood damage. Several numerical simulations, with different cannula/vessel flow rate ratios were provided, to investigate the incidence of local sites in the design on blood damaging potential during cannulation. Several regions appeared to be sensitive to the flow rate not only inside the cannula but also in the space between cannula and vessel, suggesting new indications for the assessment of a quality factor based on the evaluation of induced blood cells injury.