Lung lymph and free interstitial fluid protein composition in sheep with edema

In 10 anesthetized sheep with mild or moderate pulmonary edema we determined whether the protein composition of lung lymph is representative of free interstitial fluid. We measured protein concentration and albumin fraction in 1-mul samples of plasma, lung lymph, and free interstitial fluid. We also measured lung lymph flow. In five sheep with edema caused by increased pulmonary microvascular pressure, the average (+/- 1 SE) plasma protein concentration was 6.0 +/- 0.4 g/100 ml, lung lymph 3.4 +/- 0.2, and interstitial fluid 3.1 +/- 0.3. Lymph flow increased from an average base-line value of 9.4 ml/h to 43.4 ml/h during edema. Average albumin fractions in lymph and interstitial fluid were 0.56 +/- 0.02 and 0.50 +/- 0.01, respectively, compared with 0.44 +/- 0.01 for plasma. In five sheep with increased-permeability edema, average plasma protein concentration was 5.7 +/- 0.3 g/100 ml, lung lymph 4.1 +/- 0.4, and interstitial fluid 4.6 +/- 0.4. Base-line lymph flow was 11.0 ml/h and increased to 27.8 ml/h during edema. Average albumin fractions in lymph and interstitial fluid were 0.53 +/- 0.01 and 0.50 +/- 0.02, respectively, compared with 0.43 +/- 0.01 for plasma. We conclude in both high-pressure and altered-permeability edema, the protein composition of lung lymph collected from the major lung efferent lymphatic is representative of the free interstitial edema fluid.