In vivo quantitation of epithelial lining fluid in dog lung

We used an original saturation bronchoalveolar lavage (SBAL) technique (Eur. Respir. J. 1995;8[Suppl. 19]398S) to quantitate lung epithelial lining fluid volume (V-ELF) In dogs in two separate experiments: control and after oleic-acid-induced injury. We confirmed the hypothesis that (TC)-T-99m-DTPA, infused at constant plasma activity, reaches equilibrium with epithelial lining fluid after 90 min. We performed eight sequential lavages 215 min after beginning the infusion of Tc-99m-DTPA. Tc-99m-DTPA activity (Q(n)) in the lavage fluid increased linearly with time, suggesting transport from the plasma into the alveoli during lavage. We extrapolated Q(n) to time zero (Q(0)), when Tc-99m-DTPA was not affected by lavage. V-ELF was calculated from: V-ELF = Q(0)/C-p, (Cp: Tc-99m-DTPA mean plasma activity). I-125-albumin was used as a nondiffusible alveolar indicator to measure the fluid volume present in the lavaged segment (V-t,V-n). V-t,V-n plateaud for n greater than or equal to 4. V-ELF/(V)over bar>(t,n(n = 5,8)) was 1.7 +/- 0.4 and 25.0 +/- 4.4% (p < 0.05) in control and injury experiments, respectively. SEAL allowed reliable measurements of V,, and detection of alveolar edema fluid in the injured lung.