Forearm vascular responsiveness to prolonged venous occlusion in normal subjects.

Fourteen normal subjects (18-42 y) were studied using venous occlusion plethysmography to investigate the characteristics and reproducibility of the forearm vasoconstrictor response following a prolonged venous occlusion stimulus. Upon release of the stimulus, a transient vasodilation is followed by a vasoconstriction. As the stimulus of venous occlusion pressure increased (40, 60, 80, and 100 mmHg for 5 min), there was a significant increase in maximum flow (p = 0.01). Minimum relative flow (minimum divided by control) was unchanged except at the highest occlusion pressure (0.49 +/- 0.05, 0.38 +/- 0.04, 0.47 +/- 0.07, 0.66 +/- 0.12, p = 0.04). As venous occlusion duration increased (3, 4, 5, and 6 min at 80 mmHg), there was no significant change in minimum relative flow (p = 0.73). With increasing ambient temperature (18, 23, and 28 degrees C), there were no significant changes in maximum or minimum relative flows (p = 0.40 and 0.25, respectively). Minimum relative flow was not significantly altered following occlusion with a 2.5-cm cuff vs. a 10-cm cuff (p = 0.77). Thus, the vasoconstriction response was reproducible over a range of venous occlusion stimuli and experimental conditions. We conclude that dynamic vascular responsiveness to prolonged venous occlusion can be measured by venous plethysmography and that calculation of the minimum flow relative to control flow is an appropriate and reproducible index of the vasoconstrictor response. Based on our studies and to conveniently measure these changes, we recommend a 10-cm venous occlusion cuff, with a pressure < or = 80 mmHg, for durations < or = 5 min, in an ambient temperature of 23 degrees C.