PHYSIOLOGICAL VARIATIONS IN LOWER-EXTREMITY VENOUS VALVULAR FUNCTION

We conducted this study to investigate the physiologic variations in v enous valvular function and calf muscle pump function that occur in no rmal limbs after prolonged stationary standing. Twenty-two limbs from 11 healthy volunteers were studied after a brief period of activity an d after 4 to 6 hours of stationary standing. Vein diameter, peak reflu x flow velocity (PRFV), and valve closure time (VCT) were measured wit h duplex scanning in the standing position in the common femoral vein (CN), superficial femoral vein (SFV), popliteal vein (POP), proximal g reater saphenous vein (GSV), and greater saphenous vein at the knee (k GSV). Pneumatic rapid inflation-deflation cuffs were used to elicit re flux. Vein cross-sectional area (VA) and peak reflux volume (PRVol) we re calculated. Venous volume (VV), venous filling index (VFI), ejectio n fraction (EF), residual volume fraction (RVF), and outflow fraction (OF) were measured with air plethysmography in all limbs. After statio nary standing, there was no significant change or trend toward an incr ease in diameter or VA in any of the deep veins and there was no chang e in the PRFV or VCT. In the proximal GSV there was a significant incr ease 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 PR FV was significantly lower (p < 0.05) and the VCT significantly shorte r (p < 0.05) compared with the SFV and POP but values were no differen t 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, Th e 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. Prolon ged standing does not produce a significant dilatation or deterioratio n in valvular function in the large veins of the deep system but does produce a significant dilatation and delayed valve closure in the prox imal GSV. VCT in normal lower extremity veins rarely exceeds 1/3 secon d. Prolonged standing does not produce significant changes in valvular competence or calf muscle pump function in the lower extremities of n ormal persons as assessed by air plethysmography.