Does plasma protein depletion increase lung liquid conductance?
RL Conhaim, AM McGrath and BA Harms Department of Surgery, University of Wisconsin-Madison, USA. Lung liquid conductance (Kf) is calculated as the quotient of lung lymph flow divided by net filtration pressure (Pnf), where Pnf is the balance of osmotic and hydrostatic pressures in the lung microcirculation. In protein depletion, lymph flow rises with little change in Pnf, suggesting that calculated Kf also rises. However, several previous reports have concluded that protein depletion causes little change in Kf, leaving open the question of how lung lymph flow can rise in protein depletion with little change in Pnf. To address this, we measured Kf in sheep following two kinds of protein depletion: batch plasmapheresis (BP; n = 5) and thoracic duct drainage (TD; n = 5). Both methods lowered plasma protein concentrations by 30%, and raised lung lymph flows by 55%. Lung microvascular hydrostatic pressures and plasma-to-lymph osmotic pressure gradients both changed by 1 to 2 mm Hg. With BP,
