Forearm blood flow measurements using computerized R-wave triggered strain-gauge venous occlusion plethysmography: unilateral vs. bilateral measurements

The human forearm is a well established model to study local vascular react ivity in humans in vivo, using strain-gauge venous occlusion plethysmograph y to measure blood flow and changes in blood flow in the forearm. To reduce the intra-individual variability of the forearm blood flow (FBF), it has b een advocated that simultaneous measurements of contralateral forearm blood flow is obligatory. Therefore, the use of the calculated forearm ratio (FR ) is recommended instead of using the actual FBF. In the present study we c ompared the intra-individual variability of forearm blood flow measurements and the forearm ratio, by using computerized R-wave triggered strain-gauge venous occlusion plethysmography, to test if bilateral expression of measu rements is better than unilateral. Results were obtained in eight volunteer s. Intra-arterial infused sodium nitroprusside induced a dose dependent inc rease in forearm blood flow and a dose dependent increase in the calculated forearm ratio. Intra-arterial infused norepinephrine induced a dose depend ent decrease in forearm blood flow and a dose dependent decrease in the cal culated forearm ratio. The differences between the variation coefficients o f the forearm blood flow measurements and the calculated forearm ratio were different. These results support our hypothesis that by using a computeriz ed, R-wave triggered system for unilateral forearm blood flow measurement i s a more reliable outcome than the calculated forearm ratio derived from bi lateral measurements.