Preflight studies on tolerance of pocket mice to oxygen and heat. II - Effects on lungs

An electron microscope examination was carried out on the lungs of 11 pocket mice (Perognathus longimembris) that breathed oxygen at 10 psi or 12 psi partial pressure over a period of 7 d, at the end of which time they were decompressed to sea-level O2 pressure, either suddenly or in 30, 60, or 90 min. Vesiculation was noted in the endothelium of the alveolar-capillary wall in most of the animals and, occasionally, blebbing. Some mitochrondria were swollen in a few of the animals. Alveolar exudate was, in general, sparse. Compared with the lungs of other rodents, the lungs of pocket mice appeared relatively resistant to the toxic effects of oxygen. This conclusion needs, however, to be tempered by the fact that 5% N2 was used in the tests reported here. Nonetheless, the results suggest that the oxygen pressures anticipated on the flight of Apollo XVII should be well tolerated by the pocket mice.