Abstract
BackgroundPrevious research indicates that venous emptying serves as a stimulus for vasodilation in the human forearm. This suggests the importance of recognizing the potential influence of venous volume on reactive hyperemic blood flow (RHBF) following occlusion. The purpose of this study was to examine the influence of venous emptying on forearm vascular function.MethodsForearm RHBF, venous capacitance and venous outflow were examined in 35 individuals (age = 22 ± 2 years), using mercury in-Silastic strain gauge plethysmography, at rest and following five minutes of upper arm occlusion using standard procedures (Control). In addition, the same measures were obtained following five minutes of upper arm occlusion preceded by two minutes of passive arm elevation (Pre-elevation).ResultsAverage resting arterial inflow was 2.42 ± 1.11 ml·100 ml-1·min-1. RHBF and venous capacitance were significantly greater during Pre-elevation compared to Control (RHBF; Pre-elevation: 23.76 ± 5.95 ml·100 ml-1 ·min-1 vs. Control: 19.33 ± 4.50; p = 0.001), (venous capacitance; Pre-elevation: 2.74 ± 0.89 % vs. Control: 2.19 ± 0.97, p = 0.001). Venous outflow did not differ between the two conditions.ConclusionVenous emptying prior to upper arm occlusion results in a significant greater RHBF response and venous capacitance. Recognition of the influence of venous volume on RHBF is particularly important in studies focusing on arterial inflow, and also provides further evidence for the interplay between the venous and arterial system.
Highlights
Previous research indicates that venous emptying serves as a stimulus for vasodilation in the human forearm
If reactive hyperemia is a dependent measure in interventional trials it may be important to account for the venous volume as these volumes may themselves change throughout an intervention
The present study indicates the maneuver contributes to a 23% greater reactive hyperemic blood flow (RHBF) response compared to five minutes of arterial occlusion without venous emptying
Summary
Previous research indicates that venous emptying serves as a stimulus for vasodilation in the human forearm This suggests the importance of recognizing the potential influence of venous volume on reactive hyperemic blood flow (RHBF) following occlusion. Tschakovsky and Hughson [8] showed that venous emptying served as a powerful stimulus for a transient vasodilation of the brachial artery, which substantially elevated arterial inflow These authors did not examine the influence of the emptying of the veins in the limb under study on the reactive hyperemic response following a period of occlusion. Such information is important, as the venous volume appears to have a direct impact on the rate of arterial inflow. If reactive hyperemia is a dependent measure in interventional trials it may be important to account for the venous volume as these volumes may themselves change throughout an intervention
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