Single-Cycle Bronchoalveolar Lavage to Determine Solute Concentrations in Epithelial Lining Fluid

An accurate and reproducible measure of solute concentration of lung epithelial lining fluid (ELF) by bronchoalveolar lavage would be valuable in lung research and in patient care. Measurements of the albumin/total protein ratio in a previously proposed rewash lavage procedure showed that albumin enters the lavage fluid. Therefore, the rewash lavage may measure ELF volume accurately, but it overestimates ELF protein concentration (PELF). To avoid problems of solute exchange, we examined five sequential fractions of lavage fluid obtained from sheep after a single 60-ml lavage containing a 99mTcO2− tracer. Assays of albumin, 99mTcO4−, total protein, and endogenous urea concentrations allowed calculation of PELF from each fraction. PELF was 8 ± 4 mg/ml when calculated from dilution of either endogenous urea or 99mTc04− in fractions collected after the first 15 to 20 ml. Paired lavages provided a reproducible measure of PELF (SD, 1.2 mg/ml) that was unaffected by any solute exchange that occurred during the 4...