What causes altitude sickness and how can you prevent it?

Try a longer vacation. Altitude sickness is not linked to a person’s general condition but to specific adaptations to high altitudes; even puny permanent residents are usually immune.

Medical experts say the body usually adjusts within a few days to the complex changes in blood chemistry that come about because of the relative shortage of oxygen on high slopes. It produces more oxygen-carrying red blood corpuscles and more capillaries to carry them. The experts also recommend a gradual ascent, if possible. Some recommend medications, including diuretics, to ease the adjustments.

If you get symptoms of what is also called acute mountain sickness (including some that are often mistaken for flu), you should seek oxygen, move to a lower elevation, avoid exertion, and drink plenty of fluids.

In 1992, researchers working with astronomers on 13,796-foot Mauna Kea in Hawaii found that floods of water helped ease splitting headaches in many healthy workers. Dehydration occurs because the body tries to thicken its blood to improve absorption of the scanty oxygen.

The Mauna Kea researchers also recommended a breathing technique in case of faintness, disorientation, or nausea: Take a deep breath and hold the nose and mouth tightly closed while pushing to expel the air from the lungs.

The increased pressure of the air in the lungs is enough to drive more oxygen into the bloodstream.