Trial‐to‐Trial and Day‐to‐Day Variability in Forearm Blood Flow During Reactive Hyperemia

Abstract

Reactive hyperemia (RH) following the release of a brief limb occlusion is commonly used to assess resistance vessel function. The purpose of this study was to examine the impact of repeated trials on the within subject day‐to‐day variability of forearm blood flow during RH. Ten young, healthy, non‐smoking subjects (6 female, 4 male) were examined in the fasted state. Brachial artery diameter and blood velocity were assessed with Echo and Doppler ultrasound, respectively. Subjects visited the lab twice and performed four RH trials each visit. The RH protocol was performed on the left arm and included 5 minutes of forearm cuff occlusion at a pressure of 250 mmHg, followed by release. Within subjects trial‐to‐trial and day‐to‐day variability was assessed by the coefficient of variation (CV = (Standard Deviation/Mean) x 100). The Day‐to‐day CV was calculated using 1) Trial 1 from each day and 2) a 4‐Trial average. Peak forearm blood flow did not differ significantly between trials or days (p > 0.05). Within subject trial‐to‐trial variability was consistent between visits (CV, 9.39 ± 7.78% and 10.1 ± 3.19%; p = 0.737). The within subject day‐to‐day CV determined from the first trial on each day was not significantly different from the CV determined from the four trial average (CV, 14.9± 15.1% and 12.0± 9.62%; p = 0.240). In conclusion, averaging over repeated trials on each visit did not significantly reduce the day‐to‐day variability in peak reactive hyperemia blood flow.