Dog lymph flow in increased capillary permeability states

The lung lymph flow rate ($\text{Q}\text{?}{}_{\mathrm{<mtext>L</mtext>}}$) is increased in edema caused by an increase in lung microvascular permeability. This increase in $\text{Q}\text{?}{}_{\mathrm{<mtext>L</mtext>}}$ could be caused by either a decrease in the effective resistance of the lymph vessels (R_L), or by an increase in the effective lymph driving pressure (P_L), or by a change in both R_L and P_L. We estimated P_L and R_L from the linear relationship between $\text{Q}\text{?}{}_{\mathrm{<mtext>L</mtext>}}$ and the pressure at the outflow end (P_O) of five cannulated dog lung lymph vessels ($\text{R}{}_{\mathrm{<mtext>L</mtext>}}\text{=}\text{?ΔP}{}_{\mathrm{<mtext>O</mtext>}}\text{Δ}\text{Q}\text{?}{}_{\mathrm{<mtext>L</mtext>}}$ and P_L = the P_O at which $\text{Q}\text{?}{}_{\mathrm{<mtext>L</mtext>}}\text{= 0}$). We increased lung microvascular permeability by giving the dogs 100 mg/kg of alloxan and found that $\text{Q}\text{?}{}_{\mathrm{<mtext>L</mtext>}}$ increased from 24.5 ± 8.9 μl/min to 112 ± 41 μl/min (mean ± SD). R_L decreased from 0.35 ± 0.12 to 0.11 ± 0.04 cm H₂O min/μl and P_L 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 $\text{Q}\text{?}{}_{\mathrm{<mtext>L</mtext>}}$ increased to 169.9 ± 47.8 μl/min. P_L increased by an additional 6.3 cm H₂O but R_L decreased by only an additional 0.02 cm H₂O min/μl. These results show that the $\text{Q}\text{?}{}_{\mathrm{<mtext>L</mtext>}}$ vs P_O relationship is changed in edema secondary to an increase in microvascular permeability, and that this change can be represented as changes in R_L and P_L. In terms of these parameters, $\text{Q}\text{?}{}_{\mathrm{<mtext>L</mtext>}}$ increased in edema as a result of a decrease in R_L and an increase in P_L.