Mechanical properties of rabbit lung with edema caused by exposure to ozone

Rabbits were intermittently exposed to ozone (O3) and the mechanical properties of their lungs were studied in order to know details of ventilatory functions in lung injuries caused by this gas. The lungs of rabbits exposed to 2 ppm O3 for 6 hours daily for 3 days showed the earlier stage of edema, and tended to trap air as distending pressure was lowered at the measurement of volume-pressure relationship. In this group of animals, dynamic compliance decreased, pulmonary flow resistance increased, and flow-volume curve obtained by forced deflation showed a definitely altered slope with reduced flows at the latter part of descending limb. On the other hand, the significant change observed in rabbits exposed to 1 ppm O3 for 6 hours daily for 7 days was only the increase in pulmonary flow resistance: the extent was similar to that observed in the former group of rabbits. Light-microscopical study for the airways of O3-exposed rabbits revealed varying degrees of epithelial damages and submucosal edema in the large airways and in terminal and respiratory bronchioles, and thickening of alveolar walls in the proximal alveolar ducts, being much more evident in the former group.