Altitude Sickness

This lesson covers Acute Mountain Sickness, High-Altitude Cerebral Edema, and High-Altitude Pulmonary Edema.

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Altitude Sickness occurs when a person goes to a higher altitude faster than his or her body can acclimatize. Most problems at high altitude are preventable. Climbing to higher altitudes without proper acclimatization can lead to life-threatening emergencies.

Altitude sickness normally occurs in people who are “in a rush” to reach the summit of a mountain or to push a little further than their bodies are capable. The golden rule of climbing is to climb high and sleep low. You can climb during the day, but at night your base camp should be no more than 1,000 feet higher than the elevation of your previous night’s sleeping elevation. In other words, if you plan on sleeping on a 12,000-foot mountain and last night you camped at 8,000 feet, tonight you should camp no higher than 9,000.

Up to half of people who ascend to heights above 2500 m may develop acute mountain sickness, pulmonary oedema, or cerebral oedema, with the risk being greater at higher altitudes, and faster rates of ascent.

  • Symptoms of acute mountain sickness include headache, weakness, fatigue, nausea, insomnia, and decreased appetite.
  • It is generally thought that symptoms resolve over a few days if no further ascent is attempted, but little is known about the long-term prognosis.


  • Climb to higher elevations during the day but return to a lower altitude to sleep.
  • Drink plenty of water to prevent dehydration.
  • Avoid drinking caffeine and alcohol, and avoid salty foods while climbing.
  • Gradually ascend to allow for acclimatization. Above 10,000 feet limit your ascent to no more than 2,000 to 3,000 feet in a 24-hour period.
  • Take acetazolamide or ginkgo biloba when you reach high altitudes to reduce the chance of mountain sickness.

Conditions range from mild to severe.  Symptoms range from mild headache to shortness of breath and delirium.

Mild Acute Mountain Sickness normally develops at altitudes over 8,200 feet. Symptoms include loss of appetite, fatigue, insomnia, nausea, and headache.  Treatment: Rest for a day at the current altitude. Maintain hydration and nutrition. Use medication for pain, nausea, and acclimatization.

Moderate Acute Mountain Sickness includes symptoms more prevalent than mild acute mountain sickness. Additional symptoms include vomiting, shortness of breath, and insomnia. Treatment:Mandatory descent immediately. Treat the same as for mild acute mountain sickness. If the person is short of breath when at rest, oxygen may be necessary.

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Severe Acute Mountain Sickness includes all the signs of mild and moderate acute mountain sickness plus difficulty walking, increased heart rate, extreme shortness of breath, persistent dry cough, and delirium or confusion. Treatment: Immediate descent is mandatory. Victim should be taken to a medical facility. Oxygen is necessary. Maintain proper hydration on the way to the medical facility.


High-Altitude Cerebral Edema occurs when high altitude combined with lower air pressure have caused fluid to leak from capillaries and build up in the brain.

Symptoms of High-Altitude Cerebral Edema include changes in mental status (such as confusion and lethargy), loss of consciousness or coma, extreme headache, nausea, and vomiting.

Treatment includes immediate, mandatory descent. If necessary give rescue breaths. An emergency response team is required.


High-Altitude Pulmonary Edema occurs when high altitude combined with lower air pressure have caused fluid to leak from capillaries and build up in the lung.

Symptoms of High-Altitude Pulmonary Edema include coughing, shortness of breath, blue tinge around the lips and mouth (called cyanosis), increased respiratory rate, and increased heart rate.

Treatment includes immediate, mandatory descent. Follow general first aid for general respiratory emergency. If necessary give rescue breaths. An emergency response team is required.


We also offer a free certificate of completion. To receive the certificate you must pass a 50-question test with a score of 70 or higher. Check our Basic First Aid Certificate of Completion page for more information.

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