Physiologic changes in the lungs of rabbits continuously exposed to nitrogen dioxide.

Rabbits exposed to 25 ppM NO/sub 2/ died within 3 days. 50 to 60% of those exposed to 8 to 12 ppM NO/sub 2/ died of extensive pulmonary congestion, edema, and pneumonia within 12 wk. Those surviving 3 to 4 months exposure to 8 to 12 ppM NO/sub 2/ compared with controls; i.e., lower Pa/sub O/sub 2//, no change in Pa/sub CO/sub 2//, marked increase in mean of nonelastic resistance (mainly airway resistance), increase in functional residual capacity, and no significant change in static lung compliance. Changes reversed during the 28-day recovery. Widespread hyperplasia and inflammation in terminal bronchioles of exposed rabbits occurred. Irregular alveolar sacs and destruction of alveolar wall architecture were observed. There were obstructive changes due to bronchiolitis; i.e., persistent destructive changes associated with only minor functional changes and resembling emphysema.