The DBB-EXA dialysis machine (Nikkiso) consistently underestimates vascular access (VA) flow rates compared with the Transonic technique of measurement—that is the conclusion of a new study in the Journal of Vascular Access which has compared the two methods.
The report, put together by lead author Georgios Kosmadakis (Aura Santé, Clermont-Ferrand, France) and colleagues, begins by setting out that the existing methods of measuring VA flow “are usually based on the indicator dilution theory”, which entails the measurement of recirculation during dialysis sessions. Monitoring VA flow can, according to a study led by Loay Salman (Albany Medical College, Albany, USA) and published in Kidney International Reports in 2020, result in a reduced rate of thrombotic events in patients with fistulas.
Noting the results of Salman et al’s study, Kosmadakis and colleagues set out to compare the accuracy of the DBB-EXA and Transonic technologies for VA flow measurement. They devised an observational study including 65 patients, 38 of whom were male. The patients had a mean age of 72±10 years, and VA flow was measured twice with DBB-EXA and twice with Transonic while they were undergoing dialysis. This was then repeated again seven days later.
With a total of 130 double measurements for each method on the first day, Transonic found a mean flow of 1413±715ml/min while DBB-EXA found one of 1,297 ± 664ml/min. Additionally, a Bland-Altman analysis found that the mean difference between the two methods was 159 ± 211 ml/min (limits of agreement: −274 and 572ml/min). Of the 130 DBB-EXA measurements, 81 were within 25% of those with Transonic, representing an accuracy rate of 62%.
Turning to the reproducibility of the results on different days, the authors add that mean difference in the Bland-Altman analysis was 29±620ml/min (limits of agreement: −1,186 and 1,244ml/min) for the Transonic measurements and 132±625ml/min (limits of agreement: −1,092 and 1,356ml/min) for the DBB-EXA measurements. The authors also note that the measurements on two different days “were within 25% of each other for 52 of the 65 patients (80%) with the Transonic method, and for 35 of the 65 patients (54%) with the DBB-EXA method”.
The authors describe their findings on reproducibility as “poor for both methods” in different-day measurements. They conclude that the DBB-EXA method “underestimates VA flow rates compared to the transonic technique” and describe its 62% accuracy rate as “limited”. Ultimately, they state: “The DBB-EXA method could be used as a simple tool for a rough estimate of VA flow rates but cannot replace the Transonic reference method.”