DETECTION OF SMALL AIRWAY DYSFUNCTION IN ASYMPTOMATIC SMOKERS USING AEROSOL BOLUS BEHAVIOR

Tests using inhaled particles assess ventilatory nonuniformities and m ay be sensitive to early changes in the small airways of cigarette smo kers. We measured aerosol bolus behavior in 20 asymptomatic smokers an d 20 age- and sex-matched nonsmokers for comparison with pulmonary fun ction parameters including the single-breath nitrogen test. Narrow bol uses containing 1-mu m particles were introduced into 1-l breaths and inhaled to varying lung depths. We examined changes in bolus shape bet ween inhalation and exhalation using plots of aerosol concentration ve rsus respired volume for measurement of bolus dispersion, volumetric c hange in mean location (mean shift), and quantitative particle deposit ion. We found exhaled bolus dispersion to be significantly increased i n smokers compared with nonsmokers. Volumetric mean shift was signific antly different in smokers at shallow lung depths, with the center of bolus mass occurring later in exhalation. FEV(1)/FVC in smokers was si gnificantly inversely correlated with dispersion at deeper lung depths and with mean shift at all lung depths. Smokers with abnormal spirome try (n = 4) or an abnormal single-breath nitrogen test (n = 7) had sig nificantly increased dispersion compared with smokers with normal pulm onary function tests. We conclude that aerosol bolus dispersion is a u seful tool for examination of smalt airway function in asymptomatic sm okers.