High Altitude Sickness

June 21, 2013

By Medical Discovery News

For those visiting Denver or other mile-high cities, the incredible panoramic views may be overshadowed by headaches that worsen with higher altitudes. Such headaches are a common symptom of altitude sickness, but it is impossible to predict who will react to high altitudes and the severity of those symptoms. And now, research shows that serious altitude sickness may result in long-term brain damage.

Contrary to popular belief, the concentration of oxygen at higher altitudes is the same as sea level, about 21 percent. But the atmospheric pressure changes significantly, from 760 millimeters of mercury at sea level to only 410 millimeters of mercury at the top of Longs Peak in the Rocky Mountains. That 46 percent drop in pressure allows oxygen molecules to be spaced farther apart in the air. As a result, a person breathes in fewer oxygen molecules in each breath.

To compensate, the body breathes faster to take in more oxygen molecules and maintain blood oxygen levels. But this adjustment generally takes one to three days, which explains why the No. 1 cause of altitude sickness is going too high too fast. Then the body can’t keep healthy oxygen levels and the amount of oxygen in the body lowers, called hypoxia. This can cause fluid to leak from small blood vessels called capillaries and accumulate in the lungs and the brain. While some cases of altitude sickness end with headaches, the added stress on the lungs, heart, and arteries can lead to serious consequences, including death.

When fluid continues to leak into the brain, an incredibly dangerous condition known as high altitude cerebral edema (HACE) can develop. Symptoms include inhibited mental function, hallucinations, loss of coordination, impaired speech, personality changes, nausea, and coma. The only treatment options are to move the person to lower altitude (10,000 feet or less) or put them in a high-oxygen hyperbaric chamber. Doctors used to believe that once treated, patients fully recovered.

However, a new study looked at brain scans of 36 mountain climbers and found several small blood vessels leaking into brain tissue in eight of the 10 climbers with earlier cases of HACE. Only two of the other 26 climbers without previous case of HACE had similar leaks, called microhemorrhages. This shows that a person’s chance of developing mircohemorrages probably increases with HACE. The severity of the hemorrhages correlated to the severity of the climber’s HACE. It’s unclear if more time in high altitudes affects the lesions or what their long-term consequences may be.

Earlier studies showed that almost every MRI of a Mt. Everest climber showed evidence of brain damage. Even amateur climbers, climbers of lesser altitudes, and climbers with no symptoms of altitude sickness showed some sign of brain damage. The damage was still evident years later, even if the climber no longer went to high altitudes.

This recent finding has raised many questions; for example, do HACE victims have an increased incidence of developing dementia or other neurological disorders?  More studies are necessary to verify the results of long-term changes to the brain as a result of high altitudes and HACE. Mountain climbers need to be aware of these risks before they pursue that next peak.

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