Effects of surfactant on lung injury induced by hyperoxia and mechanical ventilation in rabbits.

We evaluated the effects of exogenous surfactant on lung injury caused by 100% oxygen and mechanical ventilation in rabbits. Surfactant-treated rabbits (n = 9) were ventilated with 100% oxygen for 36 hours and bovine surfactant was given via the trachea 12 hours after the start of mechanical ventilation. Saline-treated (n = 9) rabbits were treated identically, except that they received saline without surfactant. There were no significant changes in hemodynamics, lung mechanics, or arterial oxygen tension during artificial ventilation. Albumin concentration in the bronchoalveolar lavage fluid (BALF) of saline-treated rabbits was slightly higher than those in surfactant-treated rabbits and significantly higher than in non-treated rabbits. C3a concentration in BALF was significantly higher in saline-treated rabbits than in surfactant-treated and non-treated rabbits. In addition, the wet-to-dry lung weight ratio was significantly lower in surfactant-treated rabbits than in saline-treated rabbits (5.06 +/- 0.10 vs. 5.67 +/- 0.14, P < 0.05). Light microscopy revealed hyaline membrane formation in saline-treated rabbits, but fewer changes were observed in surfactant-treated rabbits. Electron microscopy revealed extensive endothelial cell destruction in saline-treated rabbits, while such changes except endothelial cell swelling were not observed in surfactant-treated rabbits. We conclude that exogenous surfactant attenuated lung injury caused by oxygen exposure and ventilation.