Effect of Lung Collapse on Alveolar Surfactant in Rabbits Subjected to Unilateral Pneumothorax

To determine whether atelectasis might modify lung surfactant, we injected N2 into the right pleural space of adult rabbits. Daily, under sedation, pleural gas volume and pressure were measured and adjusted to 20 ml/kg and 0 to +2 cm H2O with N2. On the sixth day, pHa, PaCO2 PaO2, and FRC were measured. Pressure-volume diagrams or bronchoalveolar lavages (BAL) were performed separately on right and left lungs. Surfactant subfractions were obtained from BAL fluid, and total protein, LDH, and cell counts were determined. Phospholipid (PL) was assayed in lung homogenate, BAL fluid, and subfractions, and PL composition was determined on the largest BAL subfraction (P4). On the sixth day the pleural gas volume was 19.7 ± 2.7 (SD) ml/kg, and PaO2 and FRC were significantly decreased. Air volume in excised right lungs at 30 cm H2O was 13.1 ±2.8 (SE) ml/kg with pneumothorax (PN) and 22.8 ±1.9 (SE) ml/kg in controls. Total PL was decreased 43% in BAL and 59% in P4 of collapsed lungs. Phosphatidylglycerol to phosph...