Studies of the potential role of a semisynthetic surfactant preparation in an experimental aspiration trauma in rabbits.

The intratracheal administration of 2 mL of betaine hydrochloride-pepsin mixture (pH 1.78) per kilogram body weight in healthy rabbits leads to severe impairment of lung mechanics. This deterioration becomes significant after 6, 24, and 48 h for the parameters of static compliance and the difference in volume between 0 and 20 mmHg airway pressure. This model was used to investigate the efficacy of a surfactant preparation consisting of a combination of synthetic phospholipids and natural surface-active rabbit material containing the protein fraction. This mixture has been shown be superior to the single components alone with regard to their behavior in vitro in a Wilhelmy balance after extensive cycling. This preparation was able to reverse the deterioration of lung mechanics when applied 24 h after an aspiration injury. Instillation of Ringer's solution alone did not show any therapeutic effect. This aspiration injury model may be helpful in further studies of therapeutic effects of surfactant preparations designed on the basis of the preparations' properties in vitro as preselective criteria.