As a curious consequence of advances in aviation, b it is now the soldier rather than the aviator or astronaut who is confronted with hypoxia as a serious environmental stress. The aviator is protected by a variety of oxygen systems, but advances in mass air transportation now subject the soldier to exposure. Further, large numbers of troops may be transported rapidly only to encounter hypoxia on the ground, albeit unique ground, such as that of the Ladakh region of northwest India which rises to more than 20,000 feet above sea level.
Two medical problems are peculiar to such an environment: acute mountain sickness and acute high-altitude pulmonary edema. The high-altitude pulmonary edema occurs only in certain individuals; the cause of the susceptibility is not known. Although the incidence is low, mortality is relatively high. Conversely, in acute mountain sickness the incidence is high, but mortality is low. Mountain sickness is