IN-VIVO STUDIES OF AEROSOLIZED EXOGENOUS SURFACTANT

Exogenous surfactant administration is currently being investigated in patients with the adult respiratory distress syndrome (ARDS). Several animal studies and recent clinical experience suggest that this thera py has promise. Currently, the optimal method of delivery is unknown. Both instillation of large doses of exogenous surfactant as well as ae rosolization with small quantities of surfactant deposited in lung tis sue have been evaluated. Both methods of delivery have significantly i mproved lung function in animal models of lung injury and are currentl y being evaluated in multicenter clinical trials. From the animal mode l of lung injury in which injury was induced by repetitive saline lung ravage, it has been shown that aerosolized surfactant was, in some ca ses, superior to instilled surfactant. With improvements in technology resulting in increased aerosolized surfactant deposition within lung tissue, consistent improvements in physiologic parameters have been sh own suggesting a dose-response phenomenon. On the other hand, the effi cacy of aerosolized exogenous surfactant is dependent on the underlyin g pattern of lung injury. In situations where the injury is nonuniform in distribution, aerosolized surfactant has been shown to be ineffect ive in animal models, Finally, different exogenous surfactant preparat ions currently available may have variable efficacy depending on the m ode of delivery, In summary, it is evident that various factors influe nce the efficacy of aerosolized exogenous surfactant and these factors will have to be investigated before optimal surfactant treatment stra tegies are obtained. Whatever the final treatment strategy chosen, it must be easy to use and reliable. With surfactant alterations document ed 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.