Effect of the compression ratio on properties of lung surfactant (bovine lipid extract surfactant) films

Using axisymmetric drop shape analysis (ADSA) and a captive bubble techniqu e, the properties of lung surfactant (BLES) films under different compressi on ratios (i.e. the ratio of maximum to minimum surface area of the bubble) were investigated. In particular, the effect of the compression ratio of t he films on the shape of the volume-area-surface tension-time (VAST) graphs and on the shape of the surface tension-relative area (gamma-A) graphs was examined at the air-liquid interface. Under relatively low compression rat ios of the films, the VAST and gamma-A graphs indicate that the cycling is reversible (i.e. the gamma-A graphs are identical for expansion and compres sion). When the compression ratio of the films increases, failure tends to occur when the surface him can not support the increasing surface pressure. causing a hysteresis loop in the gamma-A graph. It was also found that low surface tension (i.e, below 5 mJ/m(2)) at the interface could be attained with a 30% compression ratio and collapse of the films always occurs near o r below 1 mJ/m(2). (C) 1999 Elsevier Science B.V. All rights reserved.