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Acute Mountain Sickness (AMS)

Published online: Dec 06, 2007 Feature
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Anybody who has snowmobiled in the West has most likely heard of altitude sickness. Those who live at lower elevations and don't normally ride in the West but maybe only visit once or twice a winter are especially susceptible to the effects of altitude sickness.

Thanks to the Grand Lake (CO) Fire Department, here is a list of things to watch out for and how to treat altitude sickness-or Acute Mountain Sickness as the fire department labels it.

One of the first points the fire department makes is to drink lots of water, go easy on the alcohol, get plenty of rest and pace yourself.


Acute mountain sickness is an illness that can affect snowmobilers, mountain climbers, hikers, skiers or travelers who climb too fast. It usually occurs when people rapidly reach a high altitude (typically above 8,000 feet). Grand Lake is at 8,300 and goes up from there.

Causes, incidence and risk factors:

Acute mountain sickness occurs from the combination of reduced air pressure and a lower concentration of oxygen at high altitude. Symptoms can range from mild to life threatening and can affect the nervous system, lungs, muscles and heart.

In most cases the symptoms are mild. In severe cases, fluid collects in the lungs (pulmonary edema) causing extreme shortness of breath, which further reduces how much oxygen a person gets. Brain swelling may also occur (cerebral edema). This can cause confusion, coma and, if untreated, death.

The chance of getting acute mountain sickness increases the faster a person climbs into a high altitude. The severity of the symptoms also depends on this factor, as well as how much the person pushed (exerted) him or herself. Persons who normally live at or near sea level are more prone to acute mountain sickness.

Approximately 20 percent of people will develop mild symptoms at altitudes between 6,300 to 9,700 feet, but pulmonary and cerebral edema are extremely rare at these heights. However, above 14,000 feet, a majority of people will experience at least mild symptoms. Some people who stay at this height can develop pulmonary or cerebral edema.


Symptoms generally associated with mild to moderate altitude illness include: headache, difficulty sleeping, loss of appetite, nausea or vomiting, fatigue, dizziness or light-headedness, rapid pulse (heart rate) and/or shortness of breath with exertion.

Symptoms generally associated with more severe altitude illness include: cough, shortness of breath at rest, chest tightness or congestion, bluish discoloration of the skin, coughing up blood, inability to walk in a straight line, or to walk at all, decreased consciousness or withdrawl from social interaction, confusion and/or gray or pale complexion (cerebral edema).


The main form of treatment for all forms of mountain sickness is to climb down (descend) to lower altitude as rapidly and safely as possible. Supplemental oxygen should also be given, if available.

People with severe mountain sickness may be admitted to a hospital.

Acetazolamide (Diamox) is a drug used to stimulate breathing and reduce mild symptoms of mountain sickness. This drug can cause increased urination. Make sure you drink plenty of fluids. Do not drink alcohol while taking this drug.


Education of mountain travelers before ascent is the key to prevention. Basic principles include: gradual ascent, stopping for a day or two of rest for each 2,000 feet (600 meters) above 8,000 feet (2,400 meters); sleeping at a lower altitude when possible and learning how to recognize early symptoms so you can return to lower altitude before worsening symptoms occur.

Acetazolamide (Diamox) helps to speed acclimatization and reduce minor symptoms. Therapy should start one day before the ascent and continue one to two days into the excursion. This measure is recommended for those making a rapid ascent to high altitudes.

Those susceptible to anemia (particularly women) should consult a doctor regarding an iron supplement to correct the condition before traveling in high altitudes. Anemic persons have a reduced red blood cell count, and therefore, a lower amount of oxygen carried in the blood.

Drink sufficient fluids, avoid alcohol and eat regularly. Foods should be relatively high in carbohydrates.

People with underlying cardiac or pulmonary (lung) diseases should avoid high altitudes.

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