Altitude Sickness

Altitude sickness (aka, altitude illness and acute mountain sickness, or AMS) is an “umbrella” term for several conditions usually brought on by traveling too quickly to significantly higher altitude.

It appears to be caused by both the high-altitude drop in barometric pressure itself and the resulting deconcentration of air molecules and therefore oxygen.

The ailments covered as AMS include mild altitude illness, high altitude pulmonary edema (HAPE), high altitude cerebral edema (HACE), and Monge’s disease.

Any altitude sickness can progress to serious problems, including death. So it’s important to know and recognize its symptoms, and to watch for them when traveling at altitude.

It’s rare at elevations below 6,000 feet, but is common above 7,000 feet. 1% of travelers will experience an acute case above 9,000 feet—3% when above 10,000 feet. Symptoms usually show up within a few hours of arriving and staying at altitude, and if the case doesn’t become acute, will subside in one to two days.

Altitude sickness is also unpredictable. A person who has never had it before can experience it on any given trip, while someone who has always had it may not. Also, it can also recur even after acclimatization.

BTW, You won’t see altitude illness in an airliner: the pressurized cabin prevents it.

Prevention

• “Test the waters” at high elevation, preferrably for a couple of nights. Be ready to descend immediately from any elevation if stronger than mild symptoms develop. This is especially true above 9,000 feet
• Even after acclimatization at altitude, try not to camp more than 1,000 feet above your previous night’s camp. It’s ok to ascend higher, but come back down for the night
• Rest a lot when today’s camp is 1,000 feet or more above your last camp. Activity makes AMS worse
• Eating high-carbohydrate, low-fat foods can help
• Stay hydrated! This can be challenging, and is a rule always. Your urine is the best test; it should be clear or light in color, unless you’re taking medications that have urine-coloring results
• Deep breathing can help, as it increases oxygen in the lungs and bloodstream
• Acetazolamide (aka Diamox) is a prescription drug that can help prevent altitude sickness, but ruins the taste of carbonated drinks and beer (No! Not the beer!), and can have other rather unpleasant side effects, including allergic reactions
• Never ignore symptoms that may indicate altitude sickness, even after acclimatization. It can recur (known as Monge’s disease)

Symptoms of Altitude Sickness

The primary symptom is a headache. Try hydrating, as headache is also a symptom of dehydration (dehydration is common at altitude, because of heavier breathing due to thinner air). Either way, a headache plus any of the following should be considered altitude-related:

• Vomiting, nausea, or lack of appetite
• Weakness or fatigue
• Dizziness or light-headedness
• Difficulty sleeping
• Also possible: shortness of breath upon exertion, persistent rapid pulse, drowsiness, general malaise, and swelling of hands, feet, and face

These symptoms are considered mild altitude illness.

Severe altitude illness is when either or both of the following develop. If they do, take immediate action, as there is considerable danger:

• High altitude pulmonary edema
• Persistent dry cough, eventually producing pink froth
• Fever
• Shortness of breath even when resting
• Bluish color of lips and fingernails
• High altitude cerebral edema
• Headache that does not respond to analgesics
• Poor coordination, unsteady walking, stumbling
• Increasing vomiting
• Confusion, inappropriate behavior, hallucinations, stupor or coma

Treatment

The Golden Rules of altitude sickness (The link has a wonderfully comprehensive discussion of AMS):

1. If you feel sick at altitude, it is altitude illness until proven otherwise
2. Never ascend if you have symptoms of altitude illness
3. Descend immediately if you are getting worse or have HACE or HAPE

And that pretty well sums it all up: if it’s mild AMS, slow down, relax, eat carbohydrates and keep fats down for now, don’t ascend any higher.

If it progresses toward or into HAPE or HACE, descend. Now. Probably at least 2,000 feet, but in any event to the point where symptoms clear up.

My favorite reference book for first aid matters is A Comprehensive Guide to Wilderness & Travel Medicine, by Eric A. Weiss. Handy, small, easy to pack around, but solid in its coverage.

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