Effects of surfactant distribution and ventilation strategies on efficacy of exogenous surfactant.

The effects of both surfactant distribution patterns and ventilation strategies utilized after surfactant administration were assessed in lung-injured adult rabbits. Animals received 50 mg/kg surfactant via intratracheal instillation in volumes of either 4 or 2 ml/kg. A subset of animals from each treatment group was euthanized for evaluation of the exogenous surfactant distribution. The remaining animals were randomized into one of three ventilatory groups: group 1 [tidal volume (VT) of 10 ml/kg with 5 cmH2O positive end-expiratory pressure (PEEP)]; group 2 (VT of 5 ml/kg with 5 cmH2O PEEP); or group 3 (VT of 5 ml/kg with 9 cmH2O PEEP). Animals were ventilated and monitored for 3 h. Distribution of the surfactant was more uniform when it was delivered in the 4 ml/kg volume. When the distribution of surfactant was less uniform, arterial PO2 values were greater in groups 2 and 3 compared with group 1. Oxygenation differences among the different ventilation strategies were less marked in animals with the more uniform distribution pattern of surfactant (4 ml/kg). In both surfactant treatment groups, a high mortality was observed with the ventilation strategy used for group 3. We conclude that the distribution of exogenous surfactant affects the response to different ventilatory strategies in this model of acute lung injury.