alveolar surfactant systeminsmokers

BackgroundThe permeability ofthe alveolar-capillary barrier totechnetium99m labelled diethylenetriamine pentaacetate(s9mTc DTPA) isknownto be greatly increased insmokers, butthe underlying mechanismispoorly understood.Abnormalpermeability of the alveolar epithelium aswellasimpaired surfactant function hasbeensuggested. Thepurposeofthisstudy wastoexamine transudation ofureaandalbuminintothe alveoli andalveolar surfactant function insmokersandnon-smokers andtorelate thesevariables totherateofalveolarcapillary transfer ofSSmTc DTPA. MethodsStandardised bronchoalveolarlavagewasperformed andtheyield ofureaandalbuminmeasuredinthe lavage fluid. Theintegrity ofthealveolar surfactant system was assessedby measurementofthesurface activity and oftheyieldofphospholipids inalveolar lavage fluid. ResultsThe mean decayconstantfor thepulmonaryclearance ofS9mTc DTPA was 0028/min in the smokersand 0009/minin the non-smokers. The recovery ofalbuminandureainalveolar lavage fluid wasverysimilar inthetwo groups.Thesurface activity ofalveolar lavage fluid waslowerinsmokersthanin non-smokers (minimumsurface tension 37-9versus28-6mN/m)andtheyield of phospholipids was reduced(2-08 versus 3-86mg).Therateconstantforthepulmonary clearanceof "mTc DTPA correlated withtheyield ofphospholipids atbronchoalveolar lavage. Conclusions The studyshows that increased alveolar-capilla ry transfer of 99MTc DTPA insmokersisnotaccompaniedbyincreased transudation ofsmallor large molecules intothealveoli. Thefindings supportthe hypothesis that