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 reproducibilit y of the forearm vasoconstrictor response following a prolonged venous occlusion stimulus. Upon release of the stimulus, a transient vasodil ation is followed by a vasoconstriction. As the stimulus of venous occ lusion pressure increased (40, 60, 80, and 100 mmHg for 5 min), there was a significant increase in maximum flow (p = 0.01). Minimum relativ e flow (minimum divided by control) was unchanged except at the highes t occlusion pressure (0.49 +/- 0.05, 0.38 +/- 0.04, 0.47 +/- 0.07, 0.6 6 +/- 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 re lative flow (p = 0.73). With increasing ambient temperature (18, 23, a nd 28 degrees C), there were no significant changes in maximum or mini mum 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 experime ntal conditions. We conclude that dynamic vascular responsiveness to p rolonged venous occlusion can be measured by venous plethysmography an d that calculation of the minimum flow relative to control flow is an appropriate and reproducible index of the vasoconstrictor response. Ba sed on our studies and to conveniently measure these changes, we recom mend a 10-cm venous occlusion cuff, with a pressure less than or equal to 80 mmHg, for durations less than or equal to 5 min, in an ambient temperature of 23 degrees C.