Association between increased small airway obstruction and asbestos exposure in patients with asbestosis

Abstract

Background: Asbestos exposure may cause asbestos-related lung diseases including asbestosis, pleural abnormalities and malignancies. The role of asbestos exposure in the development of small airway obstruction remains controversial. Anatomic and physiologic small airway abnormalities may develop as part of the pathophysiologic process of asbestosis. We hypothesized that inhalation of asbestos may induce small airway defects in addition to asbestosis and pleural abnormalities. Methods: In total, 281 patients with newly diagnosed asbestosis were evaluated. Clinical data were collected from the patients' medical charts. The patients were classified into various stages according to their chest X-ray findings using the International Labour Organization classification. Pulmonary function was evaluated by plethysmography and the forced oscillation technique. Results: Expiratory flow, including the predicted values of the maximum expiratory flow between 25% and 50% of the forced vital capacity (MEF25-50), was significantly lower in the different stages of asbestosis. Accordingly, the predicted percentage of R5–R20 was significantly higher with increasing stages of asbestosis. Furthermore, the duration of exposure to asbestos was significantly associated with the forced expiratory volume in the first second (FEV1)/forced vital capacity (FVC) ratio and the predicted percentage of MEF25 or MEF50 according to the regression analysis in non-smoking patients with asbestosis. The predicted percentage of FEV1 or the FEV1/FVC ratio was significantly lower and the predicted percentage of R5–R20 was significantly higher in smokers than non-smokers. Conclusions: The patients with asbestosis have small airway obstructive defects that are significantly associated with asbestos exposure.