Experimental and Numerical Analysis of the Bulk Flow Parameters Within an Arteriovenous Fistula

Abstract

The creation of an arteriovenous fistula for hemodialysis has been reported to generate unstable to turbulent flow behaviour. On the other hand, the vast majority of computational fluid dynamic studies of an arteriovenous fistula use low spatial and temporal resolutions resolution in conjunction with laminar assumptions to investigate bulk flow and near wall parameters. The objective of the present study is to investigate if adequately resolved CFD can capture instabilities within an arteriovenous fistula. An experimental model of a representative fistula was created and the pressure distribution within the model was analysed for steady inlet conditions. Temporal CFD simulations with steady inflow conditions were computed for comparison. Following this verification a pulsatile simulation was employed to assess the role of pulsatility on bulk flow parameters. High frequency fluctuations beyond 100 Hz were found to occupy the venous segment of the arteriovenous fistula under pulsatile conditions and the flow within the venous segment exhibited unstable behaviour under both steady and pulsatile inlet conditions. The presence of high frequency fluctuations may be overlooked unless adequate spatial and temporal resolutions are employed. These fluctuations may impact endothelial cell function and contribute to the cascade of events leading to aggressive intimal hyperplasia and the loss of functionality of the vascular access.

Keywords: Arteriovenous fistula; Computational fluid dynamics; Instabilities; Pressure drop; Vascular access dysfunction.