Superimposed sympathetic activation did not significantly alter calf and forearm venous compliance compared to control (P > 0.05), although unstressed volume appeared to be reduced.
RCT (n=11)
Random order
Does sympathetic activation affect limb venous compliance and unstressed volume in humans?
A rapid, noninvasive method using a venous collecting cuff can reliably measure limb venous compliance, revealing that while compliance is under negligible sympathetic control, unstressed volume is affected by sympathetic activation.
p-value: p=> 0.05
We conducted a series of studies to develop and test a rapid, noninvasive method to measure limb venous compliance in humans. First, we measured forearm volume (mercury-in-Silastic strain gauges) and antecubital intravenous pressure during inflation of a venous collecting cuff around the upper arm. Intravenous pressure fit the regression line, -0.3 +/- 0.7 + 0.95 +/- 0.02. cuff pressure (r = 0.99 +/- 0.00), indicating cuff pressure is a good index of intravenous pressure. In subsequent studies, we measured forearm and calf venous compliance by inflating the venous collecting cuff to 60 mmHg for 4 min, then decreasing cuff pressure at 1 mmHg/s (over 1 min) to 0 mmHg, using cuff pressure as an estimate of venous pressure. This method produced pressure-volume curves fitting the quadratic regression (Deltalimb volume) = beta(0) + beta(1). (cuff pressure) + beta(2). (cuff pressure)(2), where Delta is change. Curves generated with this method were reproducible from day to day (coefficient of variation: 4.9%). In 11 subjects we measured venous compliance via this method under two conditions: with and without (in random order) superimposed sympathetic activation (ischemic handgrip exercise to fatigue followed by postexercise ischemia). Calf and forearm compliance did not differ between control and sympathetic activation (P > 0.05); however, the data suggest that unstressed volume was reduced by the maneuver. These studies demonstrate that venous pressure-volume curves can be generated both rapidly and noninvasively with this technique. Furthermore, the results suggest that although whole-limb venous compliance is under negligible sympathetic control in humans, unstressed volume can be affected by the sympathetic nervous system.
Halliwill et al. (Fri,) conducted a rct in Humans (n=11). Superimposed sympathetic activation (ischemic handgrip exercise) vs. Without sympathetic activation (control) was evaluated on Calf and forearm venous compliance (p=> 0.05). Superimposed sympathetic activation did not significantly alter calf and forearm venous compliance compared to control (P > 0.05), although unstressed volume appeared to be reduced.