Aerosolized surfactant therapy for endotoxin-induced experimental acute respiratory distress syndrome in rats

We have compared the effects of inhalation of aerosolized surfactant on exp erimental acute respiratory distress syndrome. Escherichia coli endotoxin ( 55 (SD 20) mg kg(-1)) was injected into the tracheas of 36 adult rats anaes thetized and mechanically ventilated with pure oxygen. When the Pa-O2 decre ased to 11.3 (3.3) kPa, the animals were randomly subjected to inhalation o f aerosolized modified natural surfactant (MNS) for 0 min (control group), 30, 60, and 120 min. In the control group, Pa-O2 remained below 12 kPa for 180 min. In the groups receiving inhalation of surfactant for 30 and 60 min , Pa-O2 increased but decreased soon after termination of the inhalation. I n contrast, Pa-O2 of the group receiving inhalation of surfactant for 120 m in continued to increase, reaching 52.1 (12.5) kPa at 180 min (P<0.05 vs co ntrol). Thus, we conclude. that improvement in gas exchange as a result of inhalation of MNS depends on the duration of inhalation.