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Acute Mountain Sickness

This is about Acute Mountain Sickness (AMS), an illness that affects climbers ascending a mountain too fast. I am not a doctor, this is based on what I read and observed over the years. Use this information at your won risk.

What is AMS?
When we climb to high elevations, the atmospheric pressure and partial pressure of Oxygen decreases at rates that may surprise you. We have all noticed that bags of potato chips inflate and our eardrums pop out when we go up the mountains for a ski trip. But it is hard to imagine that at 14,000ft (summit of Shasta), the air pressure is only 50% compared to sealevel. At the summit of Everest, it drops to about 33%.

Altitude Mountain Sickness (AMS) is an illnes caused by lack of Oxygen in our bodies. This is cause by inneficient transfer of gases to the bloodstream in the lungs. It can affect the nervous system, lungs, muscles, and heart.

AMS can start anywhere above 8,000ft, but most people develop initial sympthoms between 11,000 and 12,000ft when ascending from sea level in a day or two. Sympthoms may include severe headache, nausea, exhaustion, loss of apetite, accelerated heart rate, difficult breathing and general feeling of illness. AMS affects your humor, your strenght and the ability to make sane decisions.

In extreme conditions (above 14,000ft) and if kept untreated for long periods of time (days), AMS can cause more serious problems that are potentially fatal. Fluid collecting in the lungs can cause pulmonary edema (causing extreme shortness of breath and further decreasing oxygenation). Swelling in the brain (cerebral edema), can cause confusion, coma and, if untreated, death.

Preventing AMS
Acclimatizing by spending time at moderately high altitude prior to the climb and ascending gradually gives time to your body to react to the scarcity of O2 and (e.g. by increasing production of red cells to transport oxigen more efficiently in your bloodstream). This process occurs over several days and requires a relatively slow climb (say, 2,000ft per day).

Planning for proper acclimatization may be challenging on a weekend climb, but even a good selection of the place to sleep the night before or avoiding a sudden elevation gain by car can help.

Being rested, fit and prepared for the climb helps to avoid AMS (the higher the level of exertion, the higher the chance of getting it). Dehydration is also a common factor to amplify AMS symptoms, so climbers should drink lots of water before and during a climb.

I've seen people successfully using Acetazolamide (e.g. Diamox) to prevent and minimize the symptoms of AMS and allow them to climb to altitudes where they had problems before. Those drugs (usually used to treat glaucoma) causes the kidneys to excrete bicarbonate and re-acidifies the blood, balancing the effects of the hyperventilation that occurs at altitude in an attempt to get oxygen. It stimulates breathing, accelerate acclimatization and minimize the mild sympthoms of AMS. They can also cause side-effects (such as drowsiness) that makes you less able to climb.

Taking drugs is your choice, but I personally think that AMS is integral part of mountaneering and if you don't want to deal with AMS, you would better pick another sport. If you want to climb a big mountain, you need to make time for it.

How to detect and deal with AMS?
If you are climbing up to 15,000ft in a one to three day climb, the most common consequences of AMS is headache, nausea/vomiting, and consequent dehydration. Sympthoms go away quickly without consequence as soon as you descend to lower altitudes.

Detecting AMS is not necessarily easy, but if you are above 8,000ft, any discomfort should be taken as an indication (a headache is not "normal", it is the most common sympthom). Once you develop AMS, rest or painkillers will not make you better. AMS is your brain complaining about lack of oxigen and oxigen is what you need to give to your brain. You need to descend at least to the point where it started and the earlier you descend the earlier you will get better.

If sympthoms beyond mild dehydration persists after you descended the mountain, look for medical assistance.

There is no way to know in advance how one will react to high altitude. Some people can get very sick at 9,000ft, while others can climb to 14,000ft without feeling any effect. Not having AMS in one trip is no sure indication that one will not get AMS in the next trip.

How can I help someone suffering from AMS?