Analysis of Self-excited Oscillation in a Simulated Vascular Access Circuit

Abstract

In hemodialysis, blood is removed from the body through a vascular access (VA) and the filtered blood is returned to the body through the VA. The VA is made by joining an artery and a vein. This connection increases the amount of blood flow into the vein. A dialysis needle, which punctures into the VA, causes endothelial injury. This injury triggers leukocyte adhesion and the proliferation. This phenomenon promotes a thickening of the VA that leads to stenosis. In the clinical field, there are reports that the rapid blood removal vibrates the VA which has the stenosis. There is the possibility that self-excited oscillation has occurred. If the stenosis induces the oscillation, it is possible to estimate the stenosis by detecting the oscillation. In this study, we performed the experiment using a simulated VA circuit made of thin silicon tube (collapsible tube). The stenosis was set the lower end of the collapsible tube in the circuit, and the external pressure of the collapsible tube was controlled to vary the transmural pressure. Experimental results demonstrated that when the stenosis ratio was high, the oscillation of the tube occurred. Also, higher stenosis ratio decreased the frequency of the oscillation and increased the peak power of that. These results suggested that the stenosis could be estimated by analyzing the power spectrum of the oscillation frequency.