Dyspnea and exercise testing in workers exposed to silica

In order to provide a better objective assessment of exertional dyspnea and functional impairment due to exposure to silica, 153 workers exposed to silica dust (workers) and 62 patients with silicosis (patients) were performed the medical questionnaires with special reference to exertional dyspnea and exercise testing on bicycle ergometer. Complaints of breathlessness were present in 77 (50%) workers and 53 (85%) patients. The findings of exercise tests indicated that there were definite correlations between index of dyspnea (ID), or breathing reserve (BR) and complaint of breathlessness in both the workers and patients. ID increased and BR decreased with the increasing degree of breathlessness. We defined ID > 70% or BR < 25 I/min as abnormal criteria and checked the ratios of dyspnea quantified objectively. Thus, 30% of the workers and 56% of the patients in this study were verified to have slight or moderate breathlessness, which were considerably lower than that derived from questionnaire on dyspnea. OUr results suggest that objective physiological measures like exercise testing may be of value in evaluating dyspnea in workers exposed to silica.