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

Summary

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, volumeflow[Q_venous], pulsatility index [PI_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 PI_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 PI_venous increased further from sitting to standing in CFV [10%, 22%, 19%, respectively; p ≤.004], FV [12%, 68%, 2%_[ns]; p <.001)] and popliteal [14%, 50%, 24%; p ≤.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 ≤.003), except for the diameter on horizontal. V_min in popliteal was higher than in CFV (p ≤.003) or FV (p <.025), on horizontal and standing. PI_venous 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, PI_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.

Keywords

Venous stasis - haemodynamics - dependency - flow quantification - coagulation - economy class

• References

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