Airway Size and the Rate of Pulmonary Function Decline in Grain Handlers

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Abstract
Tracheal diameter and chest dimensions were measured from postero-anterior chest radiographs in grain handlers to prospectively identify airway size and chest size-related predictors of the rate of pulmonary function decline. A total of 634 grain workers were studied at the initial survey, of whom 239 satisfied the following inclusion criteria: (1) had a satisfactory chest radiograph taken at the initial survey in 1975, (2) performed spirometery at the 1975, 1978, and 1981 surveys, and (3) had no change in smoking status from 1975 to 1981. Radiographic measurements consisted of height of the right lung, transverse diameter of the chest at the level of the right diaphragm and at a level two-thirds up the right lung, and tracheal diameter (Tr). Areas of both lungs were measured by planimetery. Tr was only weakly related to height (r = 0.24). Increasing age was strongly associated with faster rates of FEV1 decline. After adjusting for the effects of age and cigarette smoking, Tr was the only radiographic measurement associated with FEV1 decline. Workers with Tr of 16 mm or less lost an average of 0.2% of their FEV1 per year compared to 0.9% per year for those with larger tracheas. This association was not modified by dust exposures estimates based on measurements of total dust. However, the strength of the association did depend upon smoking status, being strongest in current smokers (Tr .ltoreq. 16 mm lost 0.2% annually and Tr .gtoreq. 21 mm lost 1.4% annually). It is concluded that a larger airway diameter may be a risk factor for more rapid lung function decline in grain handlers, especially in cigarette smokers.