Altitude sickness is a condition that can occur when you ascent to high altitudes too quickly. It is also known as acute altitude sickness or altitude illness. Symptoms usually start to kick in within 6 to 12 hours after arriving at an altitude above 8,000 feet. They peak at 24 to 48 hours, and then they generally go away. The severity of symptoms depends on the rate of ascent and the altitude reached.

 

The reason people get altitude sickness is because there is less oxygen in the air at high altitudes. This condition is also called hypoxia. When people have altitude sickness, their bodies are not able to get enough oxygen from the air they're breathing. The lack of oxygen causes fluid to leak from the capillaries into the brain and lungs. This can lead to cerebral edema (HACE-High Altitude Cerebral Edema) or pulmonary edema (HAPE-High Altitude Pulmonary Edema). Both conditions are potentially fatal if not treated promptly.

 

The most common symptom of altitude sickness is headache. Other symptoms include nausea, vomiting, fatigue, lightheadedness, and difficulty sleeping. If you have any of these symptoms, immediate decent in altitude is imperative.

 

Treatment for mild to moderate altitude sickness involves taking medications to help with headaches and nausea. More severe symptoms as HAPE or HACE may require emergency life-saving dexamethasone injection. Immediate supplemental oxygen and decent from altitude is critical at all phases.

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Tips to Avoid Altitude Illness

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• Ascend gradually. Avoid traveling from a low elevation to an elevation higher than 9,000 feet (2,750 m) above sea level in one day. If possible, spend a few days at 8,000–9,000 feet before traveling to a higher elevation. This gives your body time to adjust to the lower oxygen levels.

• Once you are above an elevation of 9,000 feet, increase where you will sleep by no more than 1,600 feet per day. For every 3,300 feet you ascend, try to spend an extra day at that elevation without ascending further.

• Do not drink alcohol or do heavy exercise for at least the first 48 hours after you arrive at an elevation above 8,000 feet.

• Traveling to elevations greater than 9,000 ft for 2 nights or more, within 30 days before your trip, can help avoid altitude illness on a longer trip at a high elevation.

• Consider taking day trips to a higher elevation and then returning to a lower elevation to sleep.

• Medicines are available to prevent acute mountain sickness and shorten the time it takes to get used to high elevations. Talk to your doctor about which is best for you given your medical history and trip plans.

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If your itinerary does not allow for gradual travel to a higher elevation, talk to your doctor about medicine you can use to prevent or treat altitude illness. Many high-elevation destinations are remote and access to medical care may be difficult. Learn the symptoms of altitude illness so that you can take steps to prevent it.

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Altitude Illness

Acute mountain sickness (AMS) is the mildest form of altitude illness. Symptoms include:

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• Headache

• Tiredness

• Lack of appetite

• Nausea

• Vomiting

• Children who cannot yet talk may just seem fussy

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Mild cases can be treated by easing symptoms, for example using pain relievers for a headache. Symptoms should go away on their own within a couple days.

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People with altitude illness should not travel to higher elevations until they no longer have symptoms. A person whose symptoms get worse while resting should travel to a lower elevation to avoid becoming seriously ill or dying.

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High-altitude cerebral edema (HACE) is a more serious form of AMS. Symptoms include:

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• Extreme fatigue

• Drowsiness

• Confusion

• Loss of coordination

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High-altitude cerebral edema is rare, but it can cause death. If it develops, the person must immediately move, or be moved, to a lower elevation.

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A third type of altitude illness, is called high-altitude pulmonary edema (HAPE). It can quickly become life-threatening. Symptoms of high-altitude pulmonary edema include:

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• Shortness of breath

• Weakness

• Cough

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A person with these symptoms must immediately move, or be moved, to a lower elevation and will likely need treatment with oxygen.

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Preexisting Medical Conditions

People with pre-existing medical conditions should talk with a doctor before traveling to high elevation.

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• People with heart or lung disease should talk to a doctor who is familiar with high-altitude medicine before their trip.

• People with diabetes need to be aware that their illness may be difficult to manage at high elevation.

• Pregnant women can make brief trips to high elevations but they should talk with their doctor because they may be advised not to sleep at elevations above 10,000 feet.

• People with some illnesses (e.g., sickle cell anemia, severe pulmonary hypertension) should not travel to high elevations under any circumstances.