CO-diffusion capacity in asbestos-exposed workers with or without abnormal chest X-ray findings

Background: Exposure to asbestos can cause a restrictive lung disorder with impaired pulmonary gas exchange. It is controversial, whether lung function impairments occur in the absence of radiological abnormalities. Aim: To assess CO-diffusion capacity in asbestos-exposed workers according to radiological findings. Methods: Medical surveillance of 63 male workers formerly asbestos-exposed included a comprehensive medical and occupational history. All subjects underwent spirometry and bodyplethysmography according to ATS/ERS quality standards. CO-diffusion capacity (DLco) was measured according to MacIntyre et al. 2005. Results are reported as% predicted. Subjects were classified according to chest X-ray findings. Results: Exposure varied widely across workers (2-420 fiber-years). Asbestosis (ILO≥1/1, ±pleural fibrosis) was found in 4 workers, 18 had pleural fibrosis and 41 had normal chest X-ray findings. Pulmonary gas exchange was reduced in all three groups: DLco 51% (95%-CI 24%, 78%), 73% (95%-CI 65%, 81%) and 84% (95%-CI 79%, 89%), respectively. DLco was below the lower limit of normal in 37 cases. Mean DLco of never smokers (n=12), ex smokers (n=24), and smokers (n=5), all with normal chest X-ray, was 85% (95%-CI 77%, 93%), 84% (95%-CI 76%, 91%), and 84% (95%-CI 70%, 99%), respectively. We found no statistical association between DLco and fiber-years. Conclusions: We detected significantly impaired gas exchange in all three groups of workers formerly exposed to asbestos in the order asbestosis > pleural fibrosis > none. There was no relation to smoking habits. DLco was shown to be a sensitive method to detect early impairment of lung function in asbestos workers.