[Evaluation of lung surfactant function in terms of lipid monolayer micromechanics]

The analysis of compression isotherms of lipid monolayers and thermodynamical estimation of the conditions of the formation of layered systems underlies the explanation of some details of lung surfactant work. When the chemical potential of the monolayer during compression reaches the value of the chemical potential of the liquid bilayer membrane free of the mechanical stress, the conversion of monolayer into bilayer phase commences by means of squeezing out of monolayer in subphase creating bilayer ripples. During inspiration when alveolar surface expands, ripples turn back. Hence, in the course of normal breathing the process is quazi-reversible. During forced breathing definite losses of surfactant in the subphase can occur due to closing of ripples tending to minimize the edge energy. On the other hand, the edge is the place of instability of bilayer where fusing of lipid aggregates with edge takes place enriching thus monolayer by the lipid molecules. It is suggested that the treatment of newborn respiratory distress syndrome necessitates the new ways of the enrichment of a monolayer with lipids from the subphase or the ways for inhalation of lipidic suspension having the morphology of the inverted phases.