Altitude is defined on the following scale:
High: 8,000 - 12,000 feet (2,438 - 3,658 meters)
Very High: 12,000 - 18,000 feet (3,658 - 5,487 meters)
Extremely High: 18,000+ feet (5,500+ meters)
There are no specific factors such as age, sex, or physical condition that correlate with susceptibility to altitude sickness.
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What Causes Altitude Illnesses?
The concentration of oxygen at sea level is about 21% and the barometric pressure averages 760 mmHg. As altitude increases, the concentration remains the same but the number of oxygen molecules per breath is reduced. At 12,000 feet (3,658 meters), the barometric pressure is only 483 mmHg, so there are roughly 40% fewer oxygen molecules per breath. In order to properly oxygenate the body, your breathing rate (even at rest) must increase. This extra ventilation increases the oxygen content in the blood, but not to sea level conditions. Since the amount of oxygen required for activity is the same, the body must adjust to having less oxygen. In addition, for reasons not entirely understood, high altitude and lower air pressure causes fluid to leak from the capillaries which can cause fluid build-up in both the lungs and the brain. Continuing to higher altitude without proper acclimatization can lead to potentially serious, even life-threatening illnesses.
Many climbers take Diamox in an attempt to decrease the physical effects of high altitude.
What is High Altitude?
Acute Mountain Sickness
High Altitude Pulmonary Edema (HAPE)
High Altitude Cerebral Edema (HACE)
