Assessment of forearm vasodilator responses to acetylcholine and albuterolby strain gauge plethysmography: reproducibility and influence of strain gauge placement

Aims To determine the within-subject reproducibility of the forearm blood f low response to acetylcholine and the beta (2)-adrenoceptor agonist albuter ol as measured by strain gauge plethysmography. To examine the influence of strain gauge placement on these responses. Methods Vasodilator response to brachial artery infusion of drugs was asses sed by strain gauge plethysmography in six healthy men on each of three occ asions separated by 1 week. Strain gauges were placed on both arms at the p oint of maximum diameter. On the infused arm two further gauges were positi oned approximately 4 cm proximal and distal to the middle gauge. Results Within-subject coefficients of variation (WCV) of absolute blood fl ow responses for each dose of acetylcholine (7.5. 15, 30 mug min(-1)) range d from 24% to 27%, as compared with WCV values of 41% to 62% for the percen tage changes in blood flow ratio (infused: noninfused arm). For albuterol ( 0.3. 1, 3 mug min(-1)) the corresponding WCV values were 16% to 19% and 30% to 55% for absolute blood flow and percentage. change in blood flow ratio, respectively. WCV for the urea under dose-response curve (AUC) for absolut e blood flow was 18% and 13% for acetylcholine and albuterol. respectively. Vasodilator responses were similar whether recorded proximal to or at the point of maximal forearm circumference, Distal strain gauge misplacement un derestimated responses and the difference was greater for acetylcholine tha n for albuterol. Conclusions In healthy men, the WCV for responses expressed as absolute blo od flow, to acetylcholine and albuterol ranges from 16% to 27%.