Can lymphatic drainage be measured non-invasively in human limbs, using plethysmography?

There is always rapid volume restitution of the accumulated interstitial fluid after a VCP (venous congestion plethysmography) protocol. It has been suggested that backward extrapolation of the relationship between applied hydrostatic pressure and fluid filtration may give a measure of tissue J_vL (lymph flow); if so, this could be of immense value in pathophysiological investigations. We hypothesized that the congestion pressure decrease following the VCP protocol might be the stimulus for activating the observed rapid interstitial fluid removal mechanism. We investigated this hypothesis by using a cumulative small step VCP protocol to a maximum arterial diastolic pressure, followed by a mirror image of step pressure decreases. The increases and decreases in cuff pressure produced capillary filtration capacities that were not significantly different from one another [(3.8±1.0)×10^-3 and (3.7±1.2)×10^-3 ml·100 ml^-1·min^-1·mmHg^-1 respectively]. However, we did observe a significant 3-fold increase in estimated lymph flow between the up and ‘mirror’ down protocol. Moreover, the calculated supine control value, reflecting interstitial fluid removal (J_vL), of 0.03±0.03 ml·100 ml^-1·min^-1 was within the range of lymph flows in human limbs described by other workers, as was the 3-fold increase to 0.09±0.03 ml·100 ml^-1·min^-1 following the release of the venous congestion. These results support the notion that strain-gauge plethysmography might provide a non-invasive means of assessing peripheral lymph flow in human limbs.