What causes altitude sickness?

Altitude sickness is not just for mountain climbers. It can strike anyone, suddenly and unpredictably.

Most of our knowledge about the sickness is geared toward climbing, but symptoms of the illness can be caused by flying or even driving to higher altitudes. Flying into the airport in Cusco, in Peru, which has an altitude of 11,000 feet above sea level can cause some to feel the common effects of altitude sickness.

Normally, however, you would naturally acclimate by remaining at that elevation.

The physical symptoms of altitude sickness are the result of low oxygen levels in the body. As one ascends through the atmosphere, barometric pressure decreases and thus every breath contains fewer molecules of oxygen. One must work harder to obtain oxygen by breathing faster and deeper. This is particularly noticeable with exertion, such as walking uphill. (This answer provided for NATA by the Marist College Athletic Training Education Program)

Mountain sickness develops when the body cannot adjust to high elevations. At higher elevations the air pressure decreases, which means there is less oxygen in the air. The body needs time to adjust to lower oxygen levels.

Individuals who climb or travel to altitudes higher than 8,000 feet above sea level at a rate that is faster than 1,000 feet per day are at risk of developing mountain sickness.

Other factors may also influence a person's risk of developing mountain sickness. If the body is overworked within the first 24 hours of the climb, patients have an increased risk of developing the condition because the body requires more oxygen. Individuals who are dehydrated or hypothermic have an increased risk of developing the condition. Also, consuming alcohol or other sedatives increases the risk of the mountain sickness because these drugs slow breathing.

Flying in a plane cannot cause mountain sickness because the oxygen level in the plane does not decrease.

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