Acute mountain sickness at intermediate altitude: military mountainous training.

A US Marine Corps Battalion Landing Team (BLT) of 638 men was deployed on a winter training exercise to an altitude of 2,065 to 2,620 m. Nine marines (1.4%) presented to the medical officers with incapacitating symptoms consistent with acute mountains sickness. Seven were treated with acetazolamide and experienced relief of their symptoms within 24 hours. The incidence of nonspecific complaints associated with acute mountain sickness at altitude was found to be significantly greater than the incidence at sea level of those same complaints in the same BLT performing a similar winter training exercise (0.16%). Blacks who had been raised in low-altitude regions were the most commonly afflicted. Prophylaxis with acetazolamide for subsequent altitude exposure can be recommended for those individuals identified as susceptible. Acute mountain sickness is not uncommon at intermediate altitudes.