A novel system to record pulses, thrills, and bruit sounds generated by arteriovenous fistulas

Arteriovenous fistulas (AVFs) are the preferred vascular accesses for hemodialysis and are made by anastomosing an artery and a vein. The arterial blood flowing into the anastomosed vein results in abnormal infrasonic and audible vibrations of venous walls, which produce tactile and audible sensations known as thrill and bruit sounds. Physical examination of AVFs is instrumental for early detection of stenoses, but it is operator-dependent. Several measurement systems have been proposed for quantitative analysis of bruit sounds, and only a few focused on thrill. However, none of these has demonstrated that the signals acquired correspond to the thrill and bruit sounds perceived by physicians. This study presents, for the first time in literature, a novel AVF monitoring system that simultaneously records sphygmic pulses, thrills, and bruit sounds signals, also demonstrating that they share the same behaviors of tactile and audible sensations perceived by physicians. The proposed system is based on a small, non-invasive force sensor that captures both infrasonic and audible vibrations, and an ad hoc signal processing that accurately separates sphygmic pulses from thrills and bruit sounds. Experimental tests were carried out on 18 patients to assess two common behaviors observed during medical routine examinations. In particular, recordings were acquired on 3 measurement sites along the anastomosed vein, to verify the progressive amplitude reduction of thrill and bruit sounds from the anastomosis, and also their brisk amplitude reduction during vein occlusion tests. One-tailed Wilcoxon rank sum tests confirmed the expected amplitude reductions in both tests (p < 0.00001). In conclusion, the proposed AVF monitoring system accurately captures all vibrations produced by AVFs, which could be used to quantitatively evaluate the health status of patients and improve their surveillance. • First-ever system that simultaneously records AVF pulse, thrill and bruit sounds • Piezoelectric force sensor for quantitative measurement of tactile sensations • Novel processing algorithm for separation and analysis of AVF vibrations • More comprehensive data could improve early detection of AVF dysfunctions • Potential for implementing telemedicine services for remote patient surveillance