Investigating stenosis effects on flow dynamics in an intradialytic shunt vessel model using particle image velocimetry.

Arteriovenous shunts created during hemodialysis are common sites of stenosis. While shunt (blood flow) sounds may be potential indicators in developing noninvasive, simple stenosis screening methods, previous studies have not shown sufficient detection accuracy for practical stenosis screening applications. Despite several studies aiming to improve stenosis screening methods, the detailed mechanism of shunt sound generation remains unclear. We aimed to clarify the mechanism of shunt sound generation to aid the development of a stenosis screening method using shunt sounds. We analyzed flow in a shunt blood vessel model using particle image velocimetry. Spectral analysis of vorticity magnitude fluctuations, which are considered candidate sources of shunt sounds, revealed that stenosis increased the high-frequency spectrum above 400-500 Hz by approximately 5-10 dB Hz-1. A similar trend was observed in the vorticity magnitude fluctuations and shunt sound spectra, suggesting that vorticity magnitude fluctuations downstream of the stenosis contribute to shunt sound generation. Moreover, the results suggest that stenosis can be accurately detected by collecting shunt acoustic data at multiple points downstream of the shunt branch and comparing the acoustic spectrum at each point with those upstream and downstream. These findings contribute to the early detection and treatment of intradialytic shunt vascular stenosis.