Airways Obstruction From Asbestos Exposure: History
One medical team gave questionnaires to these workers and did chest physical examinations, chest radiographs, spirometry, and measured alveolar carbon monoxide to validate smoking histories. The questionnaire was completed by trained interviewers. Occupational history included proximity to and duration of exposure to asbestos, medical, pulmonary, and cardiovascular histories, including criteria to define chronic bronchitis and asthma based on the Epidemiology Standardization Project, DLD-78.
Spirometry was done on rolling seal spirometers (Ohio 820, Sensor Medics, Anaheim, Calif) with the subjects standing using a nose clip and otherwise followed the American Thoracic Society (ATS) Snowbird recommendations. Spirometer calibrations were checked for volume and clock speed repeatedly at each site. Care was taken to ensure complete expiration, that is a plateau or a duration of at least 10 s. Alveolar carbon monoxide was measured after a 20-s breath hold with a fuel cell analyzer. buy ventolin inhaler
The outlines of the posteroanterior and lateral images of the lungs on the radiographs were planimetered for area by an experienced technician. Total lung capacities were calculated from the sum of the areas using a regression equation. Residual volume was obtained by subtracting the FVC from TLC. Recent comparisons of TLC measured from radiographs in 46 men with prolonged asbestos exposure and pulmonary asbestosis showed identical mean values to those measured using body plethysmography. Because the radiographic method is much faster and simpler for field use, we made all TLC measurements using it. Chest radiographs were obtained on standard 35X42.5-cm films using a portable x-ray machine (Picker) (KVp 120-130 and suitable grid) and a processor (Kodak). Unsatisfactory or borderline radiographs were repeated until film technical quality was ILO 1. Radiographs were interpreted in the workers’ presence for asbestosis, pleural and other abnormalities by a pulmonologist (K.H.K.) experienced in application of the ILO criteria for pneumoconiosis 1980. Workers were questioned about past pulmonary trauma and disease. In accord with ILO guidelines, a profusion of irregular opacities of 1/0 and greater placed the worker in the category of pulmonary asbestosis while those with 0/0 and 0/1 profusions were considered asbestos exposed.