Lung function and morphology of dogs after sublethal exposure to nitrogen dioxide

The relationship between respiratory function and morphological changes in 10 dogs exposed for 6 h to 69 ppm nitrogen dioxide was studied. Two additional dogs served as controls. Functional assessments included breathing pattern, breathing mechanics, forced expiration, gas exchange, and acid-base status. Gross, microscopic, and ultrastructural evaluations were made of lung tissues from dogs killed at 0.1, 1.0, 2.0, 3.0, 7.0 and 14.0 d after exposure. Functional changes were similar to those reported for man. The principal dysfunction was gas-exchange impairment, apparently resulting from foam in the airways. Breathing-pattern alterations appeared to result from stimulation of neural receptors. Gas-exchange measurements provided the most useful indicators of the pulmonary damage observed in this study.