High Altitude Illness 2022-03-27T22:20:52-04:00

High Altitude Illness can turn a vacation into a nightmare. It can be broken up into three categories:
AMS (Acute Mountain Sickness)
HACE (High Altitude Cerebral Edema)
HAPE (High Altitude Pulmonary Edema)

All types of High Altitude Illness are essentially caused by insufficient oxygen delivery to our body’s cells. This low-oxygen state results in the leakage of fluid from blood vessels into locations where this fluid does not belong, particularly the brain and the lungs.

When exposed to higher altitudes, our bodies can naturally adjust. This is called acclimatization. Steps the body takes to get used to the lower oxygen levels at high altitude include increasing heart output, increasing breathing, and adjusting the amount of sodium bicarbonate that ends up in our urine.

When changes in altitude overpower our ability to acclimatize, we can end up with high altitude illness. This can occur at elevations as low as 4-5,000 feet (the city of Denver, Colorado). More commonly, it develops at an altitude of approximately 8,000 feet or above. See: List of Common High Altitude Destinations.

Who is at-risk for High Altitude Illness?

We are not very good at predicting who will have problems with high altitude illness. Athletes have the same risk as couch potatoes! There are a few situations that predispose someone to having issues at altitude:

  • Past history of high altitude illness. If you had a problem before, you likely will again.
  • Medical conditions that interfere with breathing, such as emphysema and pulmonary hypertension.
  • Conditions that affect oxygen delivery to cells, such as congenital heart defects.

Some medical conditions can worsen with altitude.

For instance, coronary artery disease and sickle cell anemia. Lung issues that already result in low blood oxygen levels, like emphysema, can become more of an issue at higher altitudes. In fact, someone with severe COPD may become more short of breath in an airplane, since the cabin is pressurized to simulate 6-8,000 feet elevation (not sea level, or zero feet elevation). Sugar monitoring equipment can become less accurate at higher elevations.

Pregnant women are not more susceptible to high altitude illness. However, obstetricians often recommend against travel beyond 8,000 feet.

Now let’s look at each type of acute mountain illness:

Acute Mountain Sickness

Cause: AMS is thought to be a mild version of HACE, caused by fluid accumulation outside brain cells.

Symptoms: AMS essentially makes you feel “hung-over.” Symptoms include headache, nausea, vomiting (if nausea is severe) decreased appetite, tiredness. You can also experience difficulty sleeping and mild shortness of breath during exertion.


  • Ascend slowly. Generally, it is recommended that you ascend under 500 meters (aprox 1,600 feet) per day and for every 1000 meters (aprox 3,300 feet), spend one extra day without increasing altitude.
  • Stay hydrated.
  • Avoid alcohol and medication that depresses your breathing.
  • Avoid vigorous activity until you have acclimated to altitude.
  • Acetazolamide 125mg twice a day increases the acidity of your blood. This causes you to breathe faster and increase the oxygen flowing to your tissues.
  • Coca leaves and over-the-counter remedies (ie Ginko, etc.) have NOT been shown to be effective. Chewing coca leaves can cause severe side effects.


    • Treat headache and nausea symptomatically (Tylenol, Ibuprofen, Compazine…).
    • Acetazolamide 125mg twice a day can also help with symptoms, but this is better for prevention.
    • Dexamethasone 2-4mg every 6 hrs is effective for severe AMS.
    • Supplemental oxygen, if available.
    • Descend if symptoms are not improving over a 24-hr period or if symptoms are increasing.

High Altitude Cerebral Edema

Cause: HACE is caused by fluid accumulation outside of brain cells. If accumulation is significant enough, pressure on the brain is increased, forcing it through the opening at the base of the skull and resulting in death.

Symptoms: Symptoms are confusion, severe lethargy and sleepiness, impaired judgement, and difficult or unsteady walking. In other words, the symptoms of HACE are symptoms of encephalopathy. AMS can rapidly progress to HACE.


  • If AMS symptoms are not improving or are worsening, descend! AMS can progress to HACE.
  • See AMS prevention measures above.


    • If signs or symptoms of HACE appear, IMMEDIATE DESCENT may be life-saving.
    • Supplemental Oxygen (if available).
    • Use of a hyperbaric chamber (artificially increases pressure around your body to simulate descent).
    • Dexamethasone 8mg first dose and then 4mg every 6 hours.

High Altitude Pulmonary Edema

Cause: HAPE results when fluid accumulates in lung alveoli. When these air spaces fill up, oxygen can no longer easily enter into the bloodstream, causing shortness of breath. If severe enough, HAPE can also result in death.

Symptoms: HAPE should be considered in anyone who has more than mild shortness of breath on exertion and anyone who is short of breath while resting.


  • See a healthcare professional to assess potential risk for HAPE before climbing to high altitudes.
  • See AMS prevention measures above.
  • Nifedipine ER 30mg twice a day can be given for prevention if it is determined you are at high risk for HAPE.
  • Take note if shortness of breath is becoming more noticeable with less and less exertion while climbing.


    • Supplemental oxygen.
    • Hyperbaric chamber.
    • Descent.
    • Nifedipine may be helpful (debatable).

Some Common High-Altitude Travel Destinations

Please remember that your destination altitude does NOT need to be extremely high to cause you altitude illness. All you need is a medical condition that makes altitude more of a problem or a RAPID ASCENT. For example, flying from Lima (sea level) to Cusco, Peru (11,150 feet). Another problematic itinerary would be attempting to ski in Breckenridge, Colorado (base 9,600 ft and summit 13,000 ft) after arriving from New York City without staying at least a night or two in Denver. And now, a short list:

Santa Fe, New Mexico, USA (7,200 ft)
Mexico City, Mexico (7,349 ft)
Addis Ababa, Ethiopia (7,726 ft)
Machu Picchu, Peru (7,972 ft)
Bogota, Columbia (8,661 ft)
Quito, Ecuador (9,350 ft)
Colorado, USA Ski Resorts base elevations (7,000 ft – 10,500 ft)
Shangri-La, China (10,376 ft)
Cusco, Peru (11,152 ft)
La Paz, Bolivia (11,893 ft)
Lhasa, Tibet (11,995 ft)
Lake Titicaca, Bolivia/Peru (12,507 ft)
Everest Base Camp (17,600 ft)
Kilimanjaro, Tanzania (peak 19,341 ft)*

*Kilimanjaro, in particular, poses a major risk to travelers because it is both extremely high and many hikers who attempt to summit are inexperienced high-altitude hikers/climbers and may not be up to the challenge.

If you are planning a trip to a high altitude destination, please consider visiting your own medical practitioner or our travel medicine clinic to evaluate your risk of having problems and for preventive medication, if needed. Evaluation is especially important if you have any chronic medical conditions, are a smoker, or you have had issues with altitude in the past.

Have a safe trip!

Julian Klapowitz, MD

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