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

Objective: Measurement of capillary-alveolar permeability to fluorescein is othiocyanate-dextran (FITC-D) (molecular mass, 71,300 daltons) by a sequent ial bronchoalveolar lavage (BAL) technique. Design: Animal research. Setting: The Department of Physiology at a scientific and medical universit y. Subjects: Nine anesthetized and mechanically ventilated dogs. Interventions: Two separate experiments were performed in each subject-an i nitial control experiment followed by an oleic acid-induced lung injury. Th e 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-alveo lar clearance at saturation, mL/min) was calculated and normalized to lavag e fluid volume (measured by I-125 serum albumin dilution) to obtain a trans port 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-alveola r 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 corr elation was found between cardiac output and TR in injured lung. Conclusions: Saturation BAL allowed us to estimate capillary-alveolar macro molecule permeability in vivo in dogs. Further study may allow bedside eval uation of lung injury by BAL in patients.