Influence of Venous Emptying on Reactive Hyperemic Blood Flow and Exercise Performance

Abstract

0179 Recent work by Tschakovsky & Hughson (Am J Physiol Heart Circ Physiol 279: H1007, 2000) indicates that venous emptying serves as a stimulus for vasodilation. This suggests the importance of recognizing the potential Influence of venous function on reactive hyperemic blood flow (RHBF) following occlusion. PURPOSE: To examine the Influence of venous emptying on RHBF. METHODS: Participants underwent an upright incremental cycle ergometer exercise test with gas exchange analysis. Non-dominant forearm in-flow, venous capacitance and outflow were examined in 22 individuals [age = 22±2.34y]. Forearm arterial inflow, venous capacitance, and outflow were obtained two times using strain gauge plethysmography. Forearm blood in flow was estimated at rest and following 5 min of upper arm occlusion. Forearm venous capacitance and outflow were obtained following 5 min of upper arm venous occlusion pressure at 7 mmHg below diastolic blood pressure. Prior to the second measure the arm was passively elevated for 2 minutes. Immediately before returning the arm to its original position the upper arm cuff was again inflated to 240mmHg. Subsequently, RHBF and venous measures were obtained. RESULTS: Average resting in-flow was 2.76±1.15 ml/100ml/min. RHBF was significantly greater following venous emptying (Before: 18.01±4.03; After: 23.6±6.06 ml/100ml/min, p = 0.001). Venous capacitance was also greater (Before: 2.04±0.81; After: 2.90±0.81%, p = 0.001), whereas venous outflow (Before: 36.61±10.86; After: 37.83±12.44 ml/100ml/min, p = 0.18) remained unaffected after venous emptying. Interestingly, venous outflow after emptying was significantly associated with VO2peak (r = 0.78, p = 0.01) as measured on a cycle ergometer. Finally, venous outflow was strongly related to RHBF (r = 0.71, p = 0.01). CONCLUSION: Venous emptying prior to upper arm occlusion results in a significant greater RHBF response and venous capacitance. Moreover, venous outflow was strongly associated with the RHBF response. This suggests the importance of recognizing the Influence of venous outflow on blood inflow. Finally, the strong association between venous outflow and exercise performance warrants further attention.