Lung surfactant (LS) is a complex mixture of lipids and proteins that occupies the air-liquid interface of the alveoli. LS is responsible for modulating the surface tension at the interface which both greatly reduces the work of breathing and prevents the collapse of the alveolar air sacs. Inhibition of LS, and the ensuing loss of surface tension modulation, is seen during acute respiratory distress syndrome (ARDS) which afflicts 150,000 patients annually and has a 40% mortality rate. LS inactivation similar to that seen in ARDS cases occurs in vitro when surface-active serum proteins prevent the adsorption of LS bilayer aggregates. However, the addition of select hydrophilic polymers has been shown to reverse the inhibition of replacement LS and such polymers may help increase the effectiveness of replacement LS therapy.

A newly-designed Langmuir trough coupled with confocal microscopy was used to characterize the competitive adsorption between serum proteins and LS. Confocal microscopy proved advantageous because it allowed characterization both laterally and axially, which was an improvement over traditional interfacial fluorescence microscopy. Additionally, multiple dyes were imaged simultaneously, and their relative positions determined both laterally and axially yielding insight into LS and serum protein competitive adsorption. Finally, the continuous steel-ribbon barrier of the new Langmuir trough system maintained very low surface tensions allowing for in situ imaging of LS monolayer collapse.