A portable easy-to-use triboelectric sensor for arteriovenous fistula monitoring in dialysis patients

Hemodialysis is the primary treatment for patients with total loss of renal function and is performed through a vascular access called an arteriovenous fistula (AVF). AVF can be associated with several complications, such as stenosis, thrombosis, and aneurysms. While digital subtraction angiography (DSA) is the gold standard for AVF monitoring, its limited availability, invasiveness, and harmfulness has enabled Doppler ultrasound (DUS) as alternative technique. Herein, the development of a portable device based on a triboelectric sensor for AVF monitoring that exploits the concept of impedance cardiography (ICG) is presented. The triboelectric sensor consists of a thin polyvinylidene fluoride (PVDF) layer placed close to the AVF to evaluate the triboelectric ICG signal (T-ICG), thus avoiding the need for standard multiple-electrode equipment. Electrocardiographic (ECG) dry electrodes based on a composite of polydimethylsiloxane (PDMS) and multi-walled carbon nanotubes (MWCNTs) were fabricated. Concept validation was performed in a cohort of hemodialysis patients with and without AVF stenosis. The results demonstrated a linear dependence between blood flow and the maximum deviation (dZ/dtmax) of the T-ICG pattern. Patients with stenosis showed a statistically significant change in morphology at the B-point. The extent of stenosis was evaluated by analyzing the temporal slope of the ICG pattern in the B- and C-point regions, evidencing a linear trend for stenosis from 20 % up to 60 %. The proposed device represents an innovative approach compared with the gold clinical standards for the continuous monitoring of AVF in hemodialysis patients.