Measurement of the time course of peripheral vasoactivity: results in cigarette smokers

The brachial artery response to flow was assessed non-invasively by ultrasonic measurement of arterial diameter before and 1 min after 5 min of cuff-induced ischemia. It was hypothesized that continuous measurement of arterial diameter and flow velocity would provide a more complete and accurate evaluation of the response to change in blood flow. Therefore, a system to provide this data was developed and its utility in exploring the acute and chronic effects of smoking on arterial function was demonstrated. Brachial artery diameter and flow velocity were measured before, during and for at least 3 min after 5-min of forearm cuff occlusion. Measurements were acquired from 12 habitual smokers (mean 18.3 pack years), after at least 2 h (mean 6.5 h) without smoking ('pre-cigarette') and immediately after smoking one cigarette ('post-cigarette'), as well as from 12 age- and sex-matched lifelong non-smokers. The slope of brachial artery diameter versus time during the occlusion period and the maximum dilation after cuff release relative to the pre-occlusion diameter were significantly decreased in pre-cigarette smokers compared with non-smokers (P < 0.0001 for both comparisons). Importantly, the absolute arterial dilation during the period of increased flow (i.e. reactive hyperemia) was equal for the pre-cigarette smokers and non-smokers (0.31 +/- 0.03 vs. 0.32 +/- 0.04 mm, respectively). Immediately after smoking, the flow response parameters in chronic smokers changed toward non-smoker values (P < 0.001 for post-cigarette vs. pre-cigarette comparisons of the diameter slope during occlusion and the maximum dilation after cuff release relative to pre-occlusion diameter). Thus, continuous diameter measurements in smokers who refrained from smoking demonstrated abnormal constriction of the brachial artery during the low flow period of cuff occlusion, but normal absolute dilation during the period of increased flow. Immediately after smoking, the artery no longer constricted during occlusion. These findings demonstrate the potential value of continuous monitoring of arterial diameter and flow velocity before, during and after application of a vasoactive stimulus.