Protection of rapidly decompressed rats by pharmacologic and physical means

¹ School of Aerospace Medicine, Brooks Air Force Base, Texas

In a group of rats decompressed from an ambient pressure of 520 mm Hg to 30 mm Hg in 0.075 sec, 72% died. Only 12–37% of animals treated before decompression with drugs acting on the nervous system died. No rats given a local anesthetic agent intraperitoneally prior to decompression died, and no rats whose abdomens were tensely distended with intraperitoneal saline before decompression died. In each experimental group, mortality was significantly correlated with increased lung weight. These observations lead to the speculation that, in rats, the sudden distention of gas-containing abdominal viscera has indirect, perhaps reflex, effects which are related to the development of pulmonary edema and to the survival of the animals.