PHYSIOLOGICAL VARIATIONS IN LOWER-EXTREMITY VENOUS VALVULAR FUNCTION

We conducted this study to investigate the physiologic variations in venous valvular function and calf muscle pump function that occur in normal limbs after prolonged stationary standing. Twenty-two limbs from 11 healthy volunteers were studied after a brief period of activity and after 4 to 6 hours of stationary standing. Vein diameter, peak reflux flow velocity (PRFV), and valve closure time (VCT) were measured with duplex scanning in the standing position in the common femoral vein (CN), superficial femoral vein (SFV), popliteal vein (POP), proximal greater saphenous vein (GSV), and greater saphenous vein at the knee (kGSV). Pneumatic rapid inflation-deflation cuffs were used to elicit reflux. Vein cross-sectional area (VA) and peak reflux volume (PRVol) were calculated. Venous volume (VV), venous filling index (VFI), ejection fraction (EF), residual volume fraction (RVF), and outflow fraction (OF) were measured with air plethysmography in all limbs. After stationary standing, there was no significant change or trend toward an increase in diameter or VA in any of the deep veins and there was no change in the PRFV or VCT. In the proximal GSV there was a significant increase in diameter (p = 0.0001) and VCT (p = 0.048) without a change in PRFV. No significant changes were noted in the kGSV. In the GSV the PRFV was significantly lower (p < 0.05) and the VCT significantly shorter (p < 0.05) compared with the SFV and POP but values were no different from those in the CFV. The PRFV was significantly higher in the SRV (p < 0.0001) and the POP (p < 0.002) compared with that in the CFV, The VCT was significantly shorter in the CFV (p < 0.004) and the POP (p < 0.01) compared with the SFV. VCTs in the greater saphenous and deep veins remained < 333 msec in 97.5% of all measurements. No significant change in W, VFI, EF, or OF occurred after prolonged standing. Prolonged standing does not produce a significant dilatation or deterioration in valvular function in the large veins of the deep system but does produce a significant dilatation and delayed valve closure in the proximal GSV. VCT in normal lower extremity veins rarely exceeds 1/3 second. Prolonged standing does not produce significant changes in valvular competence or calf muscle pump function in the lower extremities of normal persons as assessed by air plethysmography.