Lower limb venous haemodynamic impairment on dependency: quantification and implications for the "economy class" position

The role of stasis in venous disease is undisputed, yet surprisingly, its haemodynamic quantitation remains largely undefined. We investigated the phenomenon of venous stasis in the lower limb upon sitting and standing and project its implications to economy class aircraft passengers. 26 normal limbs, 13 subjects, age 29-54, selected after duplex, plethysmography and ABPI, had peak[V-peak], mean[V-mean] and minimum[V-min] velocities, volume-flow[Q(venous)], pulsatility index [Pl(venous)] and diameter obtained on horizontal, sitting (as in economy aircraft seats) and standing with duplex, at popliteal, femoral[FV] and common femoral[CFV]veins [differences in median %]. V-peak,V-mean and Q(venous) decreased from horizontal to sitting in the CFV [57%, 71%, 31% , respectively], FV [51%, 70%, 34%] and popliteal [31%, 58%, 42%] (all, p < .001). V-peak,V-mean and Q(venous) decreased further from sitting to standing in the CFV [26%, 44%, 25%, respectively], FV [21%,42%,27%] and popliteal [14%, 42%, 20%] (all, p < .001). Diameter, V-min and Pl(venous) increased from horizontal to sitting in the CFV [50%, 63%, 38%, respectively], FV [39%, 23%, 66%] and popliteal [21%, 14%, 84%] (all, p < .001)]. Diameter, V-min and Pl(venous) increased further from sitting to standing in CFV [10%, 22%, 19%, respectively; p less than or equal to .004], FV [12%, 68%, 2 %([ns]); p < .001)] and popliteal [14%, 50%, 24%; p less than or equal to .017]. In all postures: V-peak, V-mean Q(venous) and diameter at CFV exceeded FV (p < .025) and popliteal (p < .001) ones; also those at FV exceeded the popliteal ones (p less than or equal to .003), except for the diameter on horizontal. V-min in popliteal was higher than in CFV (p less than or equal to .003) or FV (p < .025), on horizontal and standing. Plvenous in CFV was lower than in FV or popliteal (p < .025) on sitting. Right to left differences nonsignificant. [Wilcoxon(+Bonferroni) test: significance at p < .025] A shift from horizontal to sitting generates a most significant attenuation in Q(venous),V-peak and V-mean linked to a reciprocal increase in V-min Pl(venous) and vein diameter, with further exacerbation on standing. V-peak, V-mean and Q(venous) decline with distance from groin enhancing venous stasis in the periphery. By restricting activation of the natural venous pumps, sitting cramped during long flights may protract the status of haemodynamic stagnation sustained on dependency which paired with marked venous dilatation generates a milieu that may promote thrombogenesis.