Flow mediated dilation of the brachial artery: an investigation of methods requiring further standardization.
BACKGROUND
In order to establish a consistent method for brachial artery reactivity assessment, we analyzed commonly used approaches to the test and their effects on the magnitude and time-course of flow mediated dilation (FMD), and on test variability and repeatability. As a popular and noninvasive assessment of endothelial function, several different approaches have been employed to measure brachial artery reactivity with B-mode ultrasound. Despite some efforts, there remains a lack of defined normal values and large variability in measurement technique.


METHODS
Twenty-six healthy volunteers underwent repeated brachial artery diameter measurements by B-mode ultrasound. Following baseline diameter recordings we assessed endothelium-dependent flow mediated dilation by inflating a blood pressure cuff either on the upper arm (proximal) or on the forearm (distal).


RESULTS
Thirty-seven measures were performed using proximal occlusion and 25 with distal occlusion. Following proximal occlusion relative to distal occlusion, FMD was larger (16.2 +/- 1.2% vs. 7.3 +/- 0.9%, p < 0.0001) and elongated (107.2 s vs. 67.8 s, p = 0.0001). Measurement of the test repeatability showed that differences between the repeated measures were greater on average when the measurements were done using the proximal method as compared to the distal method (2.4%; 95% CI 0.5-4.3; p = 0.013).


CONCLUSIONS
These findings suggest that forearm compression holds statistical advantages over upper arm compression. Added to documented physiological and practical reasons, we propose that future studies should use forearm compression in the assessment of endothelial function.
Peretz
Alon
A
Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington, USA. alonpe@u.washington.edu <alonpe@u.washington.edu>
Leotta
Daniel F
DF
Sullivan
Jeffrey H
JH
Trenga
Carol A
CA
Sands
Fiona N
FN
Aulet
Mary R
MR
Paun
Marla
M
Gill
Edward A
EA
Kaufman
Joel D
JD
D000328:Adult; D001132:Arm / Q000098:blood supply; D001794:Blood Pressure / Q000502:physiology*; D001795:Blood Pressure Determination / Q000379:methods; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000502:physiology*; D004730:Endothelium, Vascular / Q000502:physiology; D005260:Female; D005542:Forearm / Q000098:blood supply; D006801:Humans; D008297:Male; D012039:Regional Blood Flow / Q000502:physiology; D015203:Reproducibility of Results; D013997:Time Factors; D014463:Ultrasonography; D014664:Vasodilation / Q000502:physiology*