Dog lymph flow in increased capillary permeability states

The lung lymph flow rate (QL) is increased in edema caused by an increase in lung microvascular permeability. This increase in QL could be caused by either a decrease in the effective resistance of the lymph vessels (RL), or by an increase in the effective lymph driving pressure (PL), or by a change in both RL and PL. We estimated PL and RL from the linear relationship between QL and the pressure at the outflow end (PO) of five cannulated dog lung lymph vessels (RL = - delta Po/delta QL and PL = the PO at which QL = 0). We increased lung microvascular permeability by giving the dogs 100 mg/kg of alloxan and found that QL increased from 24.5 +/- 8.9 microliters/min to 112 +/- 41 microliters/min (mean +/- SD). RL decreased from 0.35 +/- 0.12 to 0.11 +/- 0.04 cm H2O min/microliters and PL increased from 8.5 +/- 1.5 to 15.9 +/- 2.7 cm H2O. We then increased the capillary pressures from 18.3 +/- 3.8 to 41.3 +/- 7.3 cm H2O and QL increased to 169.9 +/- 47.8 microliters/min. PL increased by an additional 6.3 cm H2O but RL decreased by only an additional 0.02 cm H2O min/microliters. These results show that the QL vs PO relationship is changed in edema secondary to an increase in microvascular permeability, and that this change can be represented as changes in RL and PL. In terms of these parameters, QL increased in edema as a result of a decrease in RL and an increase in PL.