Mucus clearance from peripheral airways.

Mucociliary clearance data obtained with 5 microns radioaerosol particles have been analyzed for asymptomatic young cigarette smokes and non-smokers. The rate and the amount of peripheral zone clearance were both considered in relationship to the overall depth of radioaerosol lung penetration. In the smokers, but not in the non-smokers, the forms of relationship found appeared compatible with prediction based on simple mathematical modelling of aerosol deposition sites within the lung. We suggest that the results found in the non-smokers are attributable to poor mucociliary defence (which is rarely required) of their more distal peripheral airways--due presumably to low levels of cross-linked glycoprotein mucus in these airways--whilst those in the smokers functionally reflect the presence of an increased supply of mucus appropriate for mucociliary transport.