title: Effect of humidity on lung surfactant films subjected to dynamic compression/expansion cycles.
abstract: The surface activity of bovine lipid extracted surfactant (BLES) preparations used in surfactant replacement therapy is studied in dynamic film compression/expansion cycles as a function of relative humidity, surfactant concentration, compression rate, and compression periodicity. BLES droplets were formed in a constrained sessile droplet configuration (CSD). Images obtained during cycling were analyzed using axisymmetric drop shape analysis (ADSA) to yield surface tension, surface area, and drop volume data. The experiments were conducted in a chamber that allowed both humid (100% RH), and "dry" air (i.e. less than 20% RH) environments. It was observed that in humid environments BLES films are not stable and tend to have poor surface activity compared to BLES films exposed to dry air. Further analysis of the data reveal that if BLES films are compressed fast enough (i.e. at physiological conditions) to avoid film hydration, lower minimum surface tensions are achieved. A film hydration-relaxation mechanism is proposed to explain these observations.
authors.affiliation: Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ont., M5S 3E5 Canada. acosta@chem-eng.utoronto.ca <acosta@chem-eng.utoronto.ca>
authors.forename: Edgar J
authors.initials: EJ
authors.lastname: Acosta
authors.forename: Roya
authors.initials: R
authors.lastname: Gitiafroz
authors.forename: Yi Y
authors.initials: YY
authors.lastname: Zuo
authors.forename: Zdenka
authors.initials: Z
authors.lastname: Policova
authors.forename: Peter N
authors.initials: PN
authors.lastname: Cox
authors.forename: Michael L
authors.initials: ML
authors.lastname: Hair
authors.forename: A Wilhelm
authors.initials: AW
authors.lastname: Neumann
mesh_terms: D000818:Animals; D002417:Cattle; D004548:Elasticity; D006813:Humidity; D008055:Lipids / Q000737:chemistry; D008168:Lung / Q000502:physiology*; D008567:Membranes, Artificial; D011663:Pulmonary Surfactants; D015656:Respiratory Mechanics / Q000502:physiology; D013499:Surface Properties; D013500:Surface Tension
chemical_list: D008055:Lipids; D008567:Membranes, Artificial; D011663:Pulmonary Surfactants