INTERPRETATION OF '24 HOUR LUNG RETENTION' IN STUDIES OF MUCOCILIARY CLEARANCE.

In classic studies of mucociliary clearance, using inhaled aerosols to label the mucous blanket, clearance from ciliated airways is generally accepted to be complete in 24 hrs. This study analyzed the relationship between the initial pattern of deposition, 24 hr retention, and regional retention of aerosol at 24 hrs in a large number of normal and diseased subjects. We found evidence for significant retention of aerosol in central ciliated airways at 24 hrs in both normal and diseased individuals. In addition, an association between chronic retention of aerosol in large airways at 24 hrs and chronic flow limitation was demonstrated.