Small airway function improvement after smoking cessation in smokers without airway obstruction.

OBJECTIVE: Studying smokers with normal spirometry requires monitoring tools of the peripheral lung. A validated multiple breath washout technique was used to assess possible recovery of smoking-induced small airway malfunction in acinar and conductive lung zones.
METHODS: Eighty-seven smokers with a smoking history of at least 10 pack-years but absence of spirometric airflow obstruction were invited for assessment of lung function and small airway function at baseline and after 1 wk, 3 mo, 6 mo, and 12 mo of smoking cessation. A control group of 16 persistent smokers was studied at the same time intervals.
MEASUREMENTS AND MAIN RESULTS: Of the 87 smokers, 66, 32, 28, and 21% successfully ceased smoking for 1 wk, 3 mo, 6 mo, and 12 mo, respectively. Lung function parameters remained essentially unaffected by smoking cessation. Ventilation heterogeneity showed transient improvements after 1 wk in the acinar lung compartment with a return to baseline afterwards. By contrast, there were persistent improvements in the conductive airway compartment; for example, smokers who successfully quit smoking for 12 mo (n=18) showed a 30 and 42% reduction of conductive airways abnormality after 1 wk and 1 yr, respectively.
CONCLUSIONS: Smokers with early signs of small airway malfunction who successfully quit smoking show sustained improvements of conductive airway malfunction. In contrast, acinar airway malfunction quickly returns to baseline after a transient improvement.