The following article requires a subscription:



(Format: HTML, PDF)

: It has been shown that structural changes in small airways of smokers with average smoking histories greater than 35 pack-years could be reflected in the single-breath washout test. The more sophisticated multiple breath washout test (MBW) has the potential to anatomically locate the affected small airways in acinar and conductive lung zones through increased phase III slope indices Sacin and Scond, respectively. Pulmonary function, Sacin, and Scond were obtained in 63 normal never-smokers and in 169 smokers classified according to smoking history (< 10 pack-years; 10-20 pack-years; 20-30 pack-years; > 30 pack-years). Compared with never-smokers, significant changes in Sacin (p = 0.02), Scond (p < 0.001), and diffusing capacity (DLCO; p < 0.001) were detected from greater than 10 pack-years onwards. Spirometric abnormality was significant only from greater than 20 pack-years onwards. In smokers with greater than 30 pack-years and DLCO less than 60% predicted, the presence of emphysema resulted in disproportionally larger Sacin than Scond increases. We conclude that Scond and Sacin can noninvasively detect airway changes from as early as 10 pack-years onwards, locating the earliest manifestations of smoking-induced small airways alterations around the acinar entrance. In these early stages, the associated DLCO decrease may be a reflection of ventilation heterogeneity rather than true parenchymal destruction. In more advanced stages of smoking-induced lung disease, differential patterns of Sacin and Scond are characteristic of the presence of parenchymal destruction in addition to peripheral airways alterations.

(C) 2004 American Thoracic Society