Asbestos exposure causes small airway obstruction among asbestosis patients

Background Asbestos exposure has traditionally been considered to cause predominantly restrictive physiologic abnormalities. The role of asbestos as a cause of airway obstruction has been debated. We aimed to evaluate airway function in a cohort of asbestosis patients, whether they had airway obstruction after controlling for smoking factors that impact lung function. Methods: A cohort of 281 asbestosis patients were evaluated. The patients were classified to stage I to III according to International Labor Office classification. Pulmonary function tests were performed by plethysmography and forced oscillation technique. Results: FEV1/FVC ratio was showing mild obstructive defect. Expiratory flow including the predicted values of MEF25 and MEF50 were significantly lower in the different stages of asbestosis. Accordingly the predicted percentage of R5-R20 was significantly higher with increasing stage of asbestosis. Furthermore, FEV1 and FEV1/FVC percentages were lower in smokers than nonsmoker of the asbestosis. In addition, the predicted percentages of MEF25 and MEF50 were decreased in both smokers and nonsmokers. The predicted percentage of R5-R20 was higher in smokers than nonsmokers which showed the significant difference. The predicted values of FEV1, MEF25 or MEF50 significantly correlated with the duration of asbestos exposure in the patients with nonsmoking asbestosis. Conclusions: Asbestos exposure may cause small airway obstructive defect in asbestosis patients although the magnitude of the airway obstruction is relatively small on spirometric parameters (Sponsored by National Science and Technology Major Project of China 2014ZX09J15104 and National Natural Science Foundation of China 81370159).