Tobacco smoking and the pulmonary surfactant system.

To explain enhanced retention of water insoluble gases and water insoluble particulate matter (tar)when smoke is inhaled we propose that these compounds interact physically with phospholipids forming the mono-molecular layer of surfactant lining the alveolar epithelium. This would account for the alteration in surface tension lowering properties of surfactant when exposed to whole smoke but not gas phase. Also it explains the observed reversible reduction in 'free' surfactant as opposed to cellular contained surfactant in smokers. Surfactant levels improve rapidly on abstinence from smoking and the time course of this improvement follows closely the reduction in alveolar epithelial permeability to a small hydrophilic molecule of diethylene triamine penta acetate (DTPA) and the improvement in homogeneity of ventilation as measured by the slope of alveolar washout (a measure of elusta properties of the peripheral airspaces of the lungs).