Analysis and evaluation of vascular sounds in hemodialysis

A vascular access is required for hemodialysis. Because the vascular access is an important lifeline for patients with renal failure, its monitoring and management are essential. The vascular access is typically monitored through auscultation of vascular sounds because these sounds provide some indication of access patency; however, this is not a quantitative assessment. The objective of this study is to develop a quantitative assessment of vascular sounds in hemodialysis. We propose several parameters to evaluate discontinuities in sound power and to specify the shape of the power spectrum, using signal processing techniques such as the theory of spectral distance with autoregressive model and the nonlinear closing operation from the field of mathematical morphology, which is essential for robust segmentation of waveform. In our demonstrations, abnormal vascular sounds are seen to exhibit different parameters compared to normal sounds. This shows that these parameters may be useful for assessing conditions of vascular sounds.