Pulmonary function responses to ozone in smokers with a limited smoking history

In non-smokers, ozone (O₃) inhalation causes decreases in forced expiratory volume (FEV₁) and dead space (V_D) and increases the slope of the alveolar plateau (S_N). We previously described a population of smokers with a limited smoking history that had enhanced responsiveness to brief O₃ boluses and aimed to determine if responsiveness to continuous exposure was also enhanced. Thirty smokers (19M, 11F, 24±4years, 6±4 total years smoking,4±2packs/week) and 30 non-smokers (17M, 13F, 25±6years) exercised for 1h on a cycle ergometer while breathing 0.30ppm O₃. Smokers and non-smokers were equally responsive in terms of FEV₁ (-9.5±1.8% vs -8.7±1.9%). Smokers alone were responsive in terms of V_D (-6.1±1.2%) and S_N (9.1±3.4%). There was no difference in total delivered dose. Dead space ventilation (V_D/V_T) was not initially different between the two groups, but increased in the non-smokers (16.4±2.8%) during the exposure, suggesting that the inhaled dose may be distributed more peripherally in smokers. We also conclude that these cigarette smokers retain their airway responsiveness to O₃ and, uniquely, experience changes in V_D that lead to heterogeneity in airway morphometry and an increase in S_N.