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Physiological Effects of High Altitude

by Katie Hart
Edited by Anna Mracek

What changes with altitude?

The density of the air decreases as altitude increases since gravity keeps most of the air molecules close to the Earth’s surface. This decrease in density means fewer gas molecules, such as oxygen, are found at higher altitudes. This corresponds to lower air pressure at high altitudes. Temperature also decreases with altitude in the first several kilometers above the earth.

How does high altitude affect humans?

The lower temperatures, oxygen levels, and air pressures associated with high altitude can cause altitude sickness, even in physically fit people. The reduced pressure and oxygen levels cause the body to have a shortage of oxygen in the blood. To deal with this, the body produces more red blood cells in the hopes of capturing more oxygen. This condition can cause nausea, headache, weakness, hyperventilation, insomnia, and diminished alertness. Not everyone experiences all of these symptoms, and there is no way to determine if high altitudes will adversely affect someone. If taken to extremes, this lack of oxygen could lead to blacking out. Lower temperatures can lead to hypothermia, the condition associated with sudden, drastic lowering of body temperature due to prolonged exposure to cold conditions.

What are the cures for Altitude Sickness and Hypothermia?

The simplest cure for both altitude sickness and hypothermia is to return the patient to sea-level conditions. This may involve lowering altitude, entering a pressurized chamber, or wrapping the patient in blankets with a source of heat to relieve hypothermia. A person suffering from altitude sickness should drink large amounts of water to re-hydrate their blood and reduce the concentration of red blood cells. It is a myth that alcohol warms the body, as it actually causes heat loss. It should not be given to a person suffering from diminished body temperature.

How can Altitude Sickness and Hypothermia be avoided?

Acclimation and insulation are the keys to preventing altitude sickness and hypothermia. The human body is remarkably adaptable. If given the chance, it can adapt to lower atmospheric pressure and reduced oxygen levels. To do this, time must be spent at gradually increasing high altitudes. Performing moderate physical exercise quickens the acclimation process. Limiting exposure to cold, staying dry if prolonged exposure is necessary and dressing warmly and in layers can prevent hypothermia. While at high altitudes, one should drink plenty of water to prevent over-saturation of red blood cells. Calorie intake also needs to be high because of the additional energy required to maintain body temperature in a cold environment. Good sources of calories are carbohydrates such as grains and fruit.

How is Steve Fossett preparing for the affects of high altitude?

Although Fossett will never go above an altitude of 10,000 m (33,000 feet), he will be high enough to feel the diminished oxygen supply. To prepare for the flight, Fossett has been acclimating himself to high altitudes by spending time in the Rocky Mountains of Colorado and by sleeping in a chamber that is depressurized to the levels he will experience while in the balloon. This will adapt his body to the conditions that he will experience during his flight. During the flight he will have an additional oxygen supply to breathe inside the capsule. To deal with the cold temperature associated with high altitude, the capsule will also have a heating system that will keep the cabin at comfortable temperatures. He will have an insulated sleeping bag and other warm clothing to help him be comfortable and to survive in the event of a heater failure.

Sources:

Curtis, Rick. "Outdoor Action Guide to High Altitude: Acclimatization and Illness." Outdoor Action
Program. Princeton University, 1995. http://www.princeton.edu/~oa/altitude.html

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