In vivo measurement of lung capillary-alveolar macromolecule permeability by saturation bronchoalveolar lavage.

Objective: Measurement of capillary-alveolar permeability to fluorescein isothiocyanate-dextran (FITC-D) (molecular mass, 71,300 daltons) by a sequential bronchoalveolar lavage (BAL) technique. Design: Animal research. Setting: The Department of Physiology at a scientific and medical university. Subjects: Nine anesthetized and mechanically ventilated dogs. Interventions: Two separate experiments were performed in each subject-an initial control experiment followed by an oleic acid-induced lung injury. The indicator was administered at constant blood concentration before serial BAL including eight fluid instillation-recovery cycles. Measurements: Plasma to BAL solute clearance at saturation (capillary-alveolar clearance at saturation, mUmin) was calculated and normalized to lavage fluid volume (measured by 125 I serum albumin dilution) to obtain a transport rate (TR) constant. Main Results: TR for FITC-D70 was 4.0 ± 0.8 and 46.1 ± 18.1 x 10 -5 .min -1 in control and injured lung, respectively (p < .02). Capillary-alveolar clearance of FITC-D70 was not affected by the lavage procedure itself. TR reflected essentially epithelial permeability in normal lung and combined epithelial and endothelial permeability in injured lung. A significant correlation was found between cardiac output and TR in injured lung. Conclusions: Saturation BAL allowed us to estimate capillary-alveolar macromolecule permeability In vivo in dogs. Further study may allow bedside evaluation of lung injury by BAL in patients.