Browne Leonard D, Walsh Michael T, Griffin Philip
Department of Mechanical, Aeronautical and Biomedical Engineering, Materials and Surface Science Institute, Centre for Applied Biomedical Engineering Research (CABER), University of Limerick, Limerick, Ireland.
Cardiovasc Eng Technol. 2015 Dec;6(4):450-62. doi: 10.1007/s13239-015-0246-6. Epub 2015 Sep 23.
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.
据报道，用于血液透析的动静脉内瘘会产生不稳定至湍流的流动行为。另一方面，绝大多数关于动静脉内瘘的计算流体动力学研究在层流假设的基础上，使用低空间和时间分辨率来研究总体流动和近壁参数。本研究的目的是调查充分解析的计算流体动力学（CFD）是否能够捕捉动静脉内瘘中的不稳定性。创建了一个具有代表性内瘘的实验模型，并分析了该模型在稳定入口条件下的压力分布。计算了具有稳定流入条件的时间CFD模拟以作比较。在此验证之后，采用脉动模拟来评估脉动对总体流动参数的作用。发现在脉动条件下，超过100Hz的高频波动占据了动静脉内瘘的静脉段，并且在稳定和脉动入口条件下，静脉段内的流动均表现出不稳定行为。除非采用足够的空间和时间分辨率，否则高频波动的存在可能会被忽略。这些波动可能会影响内皮细胞功能，并导致一系列事件，进而引发侵袭性内膜增生和血管通路功能丧失。
