Disassociation in the mucociliary function of central and peripheral airways of asymptomatic smokers

Mucociliary function of peripheral airways in asymptomatic smokers may be impaired and contribute to the abnormal airway changes described in these subjects. Techniques using the inhalation and deposition of radioactive particles followed by gamma camera imaging were applied to healthy subjects discordant for smoking habit to determine if mucus transport of peripheral and central airways was altered by smoking. Smokers (n = 8) averaged 26 +/- 2 yr (mean +/- SEM) and less than 7.5 pack-years of smoking, with pulmonary function within normal limits; when compared with the nonsmokers (n = 8) of similar age, their expiratory volumes were similar, i.e., FEV1 as a percent of predicted averaged 94.5 +/- 4% (mean +/- SEM) in the smokers and 98.8 +/- 4% in the nonsmokers. Using 24-h particle retention and planar distribution of particles in the chest as indexes of peripheral and central deposition, the 2 groups had similar deposition patterns. Mucus clearance of particles deposited onto tracheobronchial airways was quantitated as the interval between initial deposition and the time required to attain 75, 50, and 25% retention levels. Six of the 8 smokers had 75% retention times comparable to those of the nonsmokers, but the 50 and 25% retention times differed significantly between the 2 groups (p less than 0.025). Smokers cleared lung mucus at slower rates, i.e., the intervals to attain 25 and 50% retention levels were 60 to 90% greater than the mean values observed for nonsmokers. Velocity of mucus streaming within stem bronchi was comparable for the 2 groups; beta 2-adrenergic stimulation increased mucus transport in the smokers to the baseline control rates of the nonsmokers.(ABSTRACT TRUNCATED AT 250 WORDS)