Mucus clearance from peripheral and central airways of asymptomatic cigarette smokers

Insoluble radioaerosol particles have been used to monitor mucus clearance from peripheral, intermediate and inner lung zones. Nine asymptomatic cigarette smokers and nine healthy non-smokers who closely matched them for age, height and lung function were each tested twice under differing radioaerosol inhalation conditions ('high' and 'low' flow rate inhalation), so that clearance differences between smokers and non-smokers should not be masked by apparent clearance differences merely resulting from differing aerosol deposition patterns. Peripheral zone clearance in the smokers was closely similar to that in the non-smokers and was affected very little by changing from 'low' to 'high' flow rate inhalation. Inner zone clearance (calculated by a method which makes allowance for material cleared into the inner zone from more distal airways) was significantly slower in smokers than in nonsmokers for both inhalation conditions. In fact, inner zone clearance in the smokers after 'high' flow inhalation (favouring central aerosol deposition) was slower (p congruent to 0.05) than in the non-smokers after 'low' inhalation (favouring relatively peripheral deposition).