In Vivo Studies of Aerosolized Exogenous Surfactant

Abstract

Exogenous surfactant administration is currently being investigated in patients with the adult respiratory distress syndrome CARDS). Several animal studies and recent clinical experience suggest that this therapy has promise. Currently, the optimal method of delivery is unknown. Both instillation of large doses of exogenous surfactant as well as aerosolization with small quantities of surfactant deposited in lung tissue have been evaluated. Both methods of delivery have significantly improved lung function in animal models of lung injury and are currently being evaluated in multicenter clinical trials. From the animal model of lung injury in which injury was induced by repetitive saline lung lavage, it has been shown that aerosolized surfactant was, in some cases, superior to instilled surfactant. With improvements in technology resulting in increased aerosolized surfactant deposition within lung tissue, consistent improvements in physiologic parameters have been shown suggesting a dose-response phenomenon. On the other hand, the efficacy of aerosolized exogenous surfactant is dependent on the underlying pattern of lung injury. In situations where the injury is nonuniform in distribution, aerosolized surfactant has been shown to be ineffective in animal models. Finally, different exogenous surfactant preparations currently available may have variable efficacy depending on the mode of delivery. In summary, it is evident that various factors influence the efficacy of aerosolized exogenous surfactant and these factors will have to be investigated before optimal surfactant treatment strategies are obtained. Whatever the final treatment strategy chosen, it must be easy to use and reliable. With surfactant alterations documented in other lung diseases including pneumonia and asthma, delivery of aerosolized exogenous surfactant will potentially have a greater role in our therapeutic approach to these diseases.