Betik, Andrew C, Luckham, Vickie B and Hughson, Richard L (2004) Flow-mediated dilation in human brachial artery following different circulatory occlusion conditions. American Journal of Physiology - Heart and Circulatory Physiology, 286. H442-H448. ISSN 0363-6135 (print) 1522-1539 (online)

Abstract

Different magnitudes and durations of post- occlusion reactive hyperemia were achieved by occluding different volumes of tissue with and w ithout ischemic exercise to test the hypotheses that flow-mediated dilation (FMD) of the brachia l artery would depend on the increase in peak flow rate or shear stress and that position of the o cclusion cuff would affect the response. The brachial artery FMD response was observed by hi gh-frequency ultrasound imaging with curve fitting to minimize effects of random measur ement error in eight healthy, young non-smoking men. Reactive hyperemia was graded by 5-minutes oc clusion distal to measurement site at the wrist and the forearm and proximal to the site in the upper arm. Flow was further increased by exercise during occlusion at the wrist and forearm positions. For the two wrist occlusion conditions flow increased 8-fold and FMD wa s only 1-2% (P>0.05). After forearm and upper arm occlusions blood flow was almost identical but FMD after forearm occlusions was 3.4% (P<0.05) while it was significantly greater ( 6.6%, P<0.05) and more prolonged after proximal occlusion. Forearm occlusion plus exercise cau sed a greater and more prolonged increase in blood flow yet FMD (7.0%) was qualitatively and qua ntitatively similar to that after proximal occlusion. Overall the magnitude of FMD was si gnificantly correlated with peak forearm blood flow (r=0.59, P<0.001), peak shear rate (r=0.49, P<0.002) and total 5-min reactive hyperemia (r=0.52, P<0.001). The prolonged FMD after upper ar m occlusion suggests that the mechanism for FMD differs with occlusion cuff position.

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