Surface chemistry of the lung surfactant system: techniques for in vitro evaluation

Our lungs. are lined by a surface-active material which is responsible for lowering surface tension to near zero values on expiration, and preventing lung collapse. The presence of a functional lung surfactant reduces the work of breathing. Respiratory Distress Syndrome (RDS) is a disease due to lack of lung surfactant in pre-term babies (born before nine months). Surfactant dysfunction also occurs in many adult respiratory diseases like adult respiratory distress syndrome, asthma and chronic bronchitis. The surface properties of surfactants are important factors, which determine their suitability for exogenous therapy in conditions of surfactant dysfunction. Various in vitro techniques, commonly used in surface science, are modified to suit them for application to the lung surfactant system - for study of the surface properties of surfactants under dynamic conditions, which simulate those present in vivo in the pulmonary system. This paper outlines some of these techniques as applied to the lung surfactant system and discusses the relevance of surface properties to pulmonary physiology.