Mountain climbing and other sports and endeavors that bring people to high elevations increase their risks of altitude sickness, which most often occurs at elevations above 8,000 meters. At this point, the body is no longer taking in the amount of oxygen it needs.
There are three types of altitude sickness. Acute mountain sickness (AMS) is the most common form, with symptoms that feel similar to being intoxicated. High-altitude cerebral edema (HACE) is essentially a more severe form of AMS and occurs when the brain swells to the point that it stops functioning normally. Symptoms include extreme sleepiness, difficulty walking, and confusion and irritability. The third type is high-altitude pulmonary edema (HAPE), which can either be a progression from HACE or occur on its own. HAPE occurs when the lungs fill up with excess fluid and stop functioning normally. Symptoms include intense coughing, weakness, and breathlessness. HACE and HAPE must both be treated immediately or they may result in death.