Surfactant inactivation and surfactant replacement in experimental models of ARDS.

Lung structure and function, and the effect of surfactant replacement, were studied in three animal models of adult respiratory distress syndrome (ARDS): surfactant depletion by repeated lung lavage, proteinaceous pulmonary edema induced by prolonged exposure to hyperoxia, and inoculation with hybridoma making an antibody to the hydrophobic surfactant-associated protein, SP-B. Surfactant replacement therapy restored normal gas exchange in respiratory failure induced by repeated lung lavage but was ineffective in animals with severe lung parenchymal lesions induced by hyperoxia or antibody to SP-B. Lung edema fluid from animals exposed to hyperoxia inhibited surfactant function in a concentration-dependent manner. These observations indicate that, in experimental ARDS, the effect of surfactant replacement depends on the type of animal model and, especially, on the degree of lung injury present at the time of therapy.