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Airway Function and Respiratory Resistance in Taiwanese Coal Workers with Simple Pneumoconiosis

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Author(s): Shieh-Ching Yang | Yu-Fan Lin

Journal: Chang Gung Medical Journal
ISSN 2072-0939

Volume: 32;
Issue: 04;
Start page: 438;
Date: 2009;
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Keywords: airway obstruction | coal workers’ pneumoconiosis | respiratory resistance | forced oscillation technique

ABSTRACT
Background: Occupational exposure to coalmine dust consisting of coal particles and freesilica eventually results in massive lung fibrosis. However, clinical observations of patients with coal workers’ pneumoconiosis (CWP) suggest that airway dysfunction may be a predominant feature in the initial development ofthe disease.Methods: Forced expirogram, plethysmographic determination of lung volumes, andmeasurement of respiratory resistance (Rrs) by the forced oscillation technique at 3, 9, and 18 Hz were conducted in a sample of 71 coal miners withsimple pneumoconiosis and 36 healthy subjects.Results: The forced vital capacity (FVC) was well-preserved even in miners with category 2 and 3 CWP. There were no differences in the mean forced expiratoryvolume in 1 second (FEV1) values between healthy subjects and miners withcategory 1 disease. However, the level of airflow limitation in these minersincreased with the transition from category 1 to category 2 and 3. TheFEV1/FVC ratio fell below 70% in miners with category 2 and 3 disease, inboth smokers and non-smokers. A consistent increase in the ratio of theresidual volume to total lung capacity (RV/TLC) in the miners comparedwith that of the control workers was found. An abnormally high Rrs at 3 Hz(Rrs3) and frequency dependence in the flow resistance were also demonstrated in these subjects. There was an upward trend in the values of Rrs3 inthe higher radiological categories. The correlation between respiratory conductance at this frequency (Grs3) and the RV/TLC ratio was good (r =– 0.763, p < 0.001).Conclusion: Simple CWP is not associated with a clinically apparent reduction in lungvolume. The Rrs3 appears to be a sensitive parameter for detecting airwayobstruction in patients with simple CWP associated or not with a reducedFEV1.

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