Early Response of the Canine Respiratory Tract Following Long-Term Exposure to a Sulfur(IV) Aerosol at Low Concentration. IV. Respiratory Lung Function

Abstract

Respiratory function was studied in eight beagle dogs at the end of a 290-day exposure to a sulfur(IV) aerosol [0.3 mg m−3 S(IV)]and compared to lung function parameters in three dogs exposed to clean air during the same period. The lung mechanics were characterized by lung volumes and quasistatic and dynamic compliances of lungs and thorax. Gas exchange and gas transport were estimated by carbon monoxide rebreathing, single-breath and multiple-breath inert gas washout, and the study of aerosol bolus dispersion. We found a significant decrease in specific lung compliance (728 ± 8 vs. 149 ± 9 ml hPa−1 p<.05) and a tendency toward a fall in membrane diffusing capacity (21.5 ± 2.7 vs. 25.7 ± 4.3 ml min−1 hPa −1) in S(IV)-exposed dogs. The change in membrane diffusing capacity correlated with a decrease in alveolar surface area as demonstrated by postmortem morphometric analysis flakenaka et al., 1992). No differences were observed between exposed dogs and controls in any of the other parameters of lung function. The results show that chronic inhalation of low levels of S(IV) aerosol induces minor changes in respiratory function.