Lymph pump mechanics in the rabbit hind leg.

Abstract

The mechanisms that govern fluid uptake by the initial lymphatics and adjustment of lymph flow rates remain to a large degree uncertain. The aim of this study was to examine how passive tissue movement contributes to lymph flow rates. Lymph fluid was collected via a cannula inserted into one of the popliteal prenodal lymphatics in the rabbit hind leg. Lymph flow rates were measured during periodic whole leg rotation and controlled oscillatory massage of the dorsal skin of the foot. Without whole leg rotation, lymph flow remained at low values (< 0.01 ml/h). Introduction of whole leg passive rotation caused a frequency-dependent increase in lymph flow rates, which were increased linearly with the log of frequency between 0.03 and 1.0 Hz. Local skin massage in the region of the initial lymphatics also led to a similar increase of lymph flow rates dependent on frequency as well as amplitude of skin displacement. Lymph flow rates during local skin massage reached a comparable order of magnitude regardless of whether the animal was alive or the heart had been arrested, suggesting that local lymph flow rates can be adjusted by periodic tissue motion independently of capillary fluid filtration pressures. The results indicate that periodic expansion and compression of initial lymphatics provide a mechanism for lymph pumping.