A Wearable Device For Continuous, Non-invasive Remote Monitoring Of Vascular Access In Hemodialysis Patients
Richard Neville, MD, Forrest Miller, David Kuraguntla, MD.
Inova Health System, Falls Church, VA, USA.
Objectives - Over 2.5 million hemodialysis patients worldwide are dependent on a functional arteriovenous fistula (AVF). This study investigates a wearable device that enables remote monitoring of AVF function as well as physiologic parameters. The aim of the study was to evaluate the ability of the device to assess AVF function as well as measure hemoglobin (Hgb) and hematocrit (Hct), markers that can impact dialysis fluid management.
Methods - 128 patients undergoing hemodialysis by an AVF were studied from three dialysis sites. Each patient had an external monitoring device placed over the fistula for a one week period. Some patients (57) had Hgb and Hct tested with a HemoCue Hb 201 device and others (21) had volumetric flow measured with a Transonic flowmeter. The remaining patients (71) received a fistulogram due to suspicion of stenosis by physical exam or hemodialysis parameters to correlate percent stenosis by the device and fistulography. Multi-sensor data was recorded and analyzed using the remote data hub and software backend. A subset (116 reads) was used to develop machine-training algorithms for quantitation of Hgb and Hct. These algorithms were tested on the remaining reads (157). An algorithm was also developed to identify volumetric flow rates below 1000 mL/min.
Results - The system accurately measured Hgb and Hct with a root-mean-square error (RMSE) of 1.20 g/dL and 3.60, respectively, compared to reference values obtained from the HemoCue device. Standard deviations were computed, averaged, and weighted by group size as a measure of precision. These precision metrics were computed to be 0.410 g/dL and 1.230 for Hgb and Hct, respectively. Flow rates were compared to Transonic flowmeter values taken during a dialysis session within 1-5 days from the remote monitor readings. The system was able to reliably identify volumetric flow rate values less than 1000 mL/min with a sensitivity of 100% and specificity of 75%. Of the patients who received a fistulogram, 100% of stenoses >50% were accurately detected.
Conclusion – This study demonstrates the ability of a wearable, remote monitoring system to measure Hgb/Hct and volumetric flow in hemodialysis patients with a AVF. The external monitoring system was also able to detect a hemodynamically significant degree of stenosis in an AVF. Remote monitoring shows promise in the care of the hemodialysis patient.
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