title: Surface tension in situ in flooded alveolus unaltered by albumin.
abstract: In the acute respiratory distress syndrome, plasma proteins in alveolar edema liquid are thought to inactivate lung surfactant and raise surface tension, T. However, plasma protein-surfactant interaction has been assessed only in vitro, during unphysiologically large surface area compression (%ΔA). Here, we investigate whether plasma proteins raise T in situ in the isolated rat lung under physiologic conditions. We flood alveoli with liquid that omits/includes plasma proteins. We ventilate the lung between transpulmonary pressures of 5 and 15 cmH2O to apply a near-maximal physiologic %ΔA, comparable to that of severe mechanical ventilation, or between 1 and 30 cmH2O, to apply a supraphysiologic %ΔA. We pause ventilation for 20 min and determine T at the meniscus that is present at the flooded alveolar mouth. We determine alveolar air pressure at the trachea, alveolar liquid phase pressure by servo-nulling pressure measurement, and meniscus radius by confocal microscopy, and we calculate T according to the Laplace relation. Over 60 ventilation cycles, application of maximal physiologic %ΔA to alveoli flooded with 4.6% albumin solution does not alter T; supraphysiologic %ΔA raise T, transiently, by 51 ± 4%. In separate experiments, we find that addition of exogenous surfactant to the alveolar liquid can, with two cycles of maximal physiologic %ΔA, reduce T by 29 ± 11% despite the presence of albumin. We interpret that supraphysiologic %ΔA likely collapses the interfacial surfactant monolayer, allowing albumin to raise T. With maximal physiologic %ΔA, the monolayer likely remains intact such that albumin, blocked from the interface, cannot interfere with native or exogenous surfactant activity.
authors: Department of Chemistry, Chemical Biology & Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey.
authors: Angana Banerjee
authors: AB
authors: Kharge
authors: Department of Chemistry, Chemical Biology & Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey.
authors: You
authors: Y
authors: Wu
authors: Department of Chemistry, Chemical Biology & Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey cperlman@stevens.edu.
authors: Carrie E
authors: CE
authors: Perlman
mesh_terms: D000418:Albumins / Q000494:pharmacology*; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid; D066298:In Vitro Techniques; D008297:Male; D011650:Pulmonary Alveoli / Q000503:physiopathology*; D011663:Pulmonary Surfactants / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015656:Respiratory Mechanics / Q000502:physiology; D013500:Surface Tension / Q000187:drug effects*
chemical_list: D000418:Albumins; D011663:Pulmonary Surfactants
keywords: albumin; alveolar edema; plasma proteins; surface tension; surfactant