Breathlessness at rest is the sign of life-threatening high-altitude pulmonary edema.
Travelers to high elevations might require acetazolamide, dexamethasone, or other medications to prevent or treat altitude illness. Mental status changes and ataxia are warning signs for high-altitude cerebral edema. Breathlessness at rest is the sign of life-threatening high-altitude pulmonary edema. See Sec. 4, Ch. 5, High Elevation Travel & Altitude Illness.