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Altitude sickness

Related terms
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Related Terms
  • Acclimation, altitude, altitude sickness, AMS, cerebral edema, coma, CPAP, edema, Gamow bag, HACE, HAPE, HARH, high altitude sickness, hyperbaric chamber, hyperbaric therapy, mountain climbing, mountain sickness, ophthalmoscopy, oxygen, oxygen saturation, pulmonary edema, pulse oximetry, respiratory failure, retina, supplemental oxygen.

  • Altitude sickness, also called mountain sickness, is an illness that occurs when the body is unable to adjust to high elevations. Symptoms of mountain sickness range from a mild headache and fatigue to a life-threatening build-up of fluid in the lungs or brain.
  • People may be exposed to high altitudes when they go rock climbing, mountain climbing, or skiing. At higher altitudes, there is less oxygen in the air. If a patient does not allow the body sufficient time to adjust to changes in altitude, the body does not receive enough oxygen, and symptoms of mountain sickness develop. Individuals who live at high elevations generally do not experience mountain sickness because their bodies are adjusted to the altitude.
  • Most patients will experience a full recovery if they start to descend to lower elevations shortly after symptoms of mountain sickness develop.
  • There are four forms of mountain sickness: acute mountain sickness, high altitude pulmonary edema, high altitude cerebral edema, and high altitude retinal hemorrhage.
  • Acute mountain sickness (AMS) is the mildest and most common type of mountain sickness. Mountain sickness typically develops when patients travel to elevations higher than 8,000 feet above sea level at a rate that is faster than 1,000 feet per day. Researchers estimate that nearly 50% of people who start at or near sea level and climb to 14,000 feet without scheduling rest time develop this condition.
  • If patients with AMS continue to climb or travel to higher elevations despite their symptoms, their condition may progress to a more severe form, such as high altitude pulmonary edema (HAPE). This condition occurs when fluid builds up in the lungs, making breathing difficult. Additional treatments, such as supplemental oxygen, may help reduce symptoms. If left untreated, the condition can lead to respiratory failure and death. HAPE is the number one cause of death from mountain sickness.
  • AMS may also develop into a severe condition called high altitude cerebral edema (HACE). This condition occurs when fluids builds up inside the brain, causing the brain to swell. As the brain swells, the person begins to feel confused and coordination becomes impaired. Some patients may experience permanent mental impairment and loss of coordination. The severity of these impairments varies among patients. If HACE is not treated, patients will develop a coma and die. More than 50% of HACE patients who develop a coma die.
  • Some patients with AMS may develop high altitude retinal hemorrhage (HARH). This condition occurs when there is bleeding in the eye(s). Bleeding may not be visible to the patient. A common symptom is blurred vision. Left untreated, HARH may lead to permanent eye damage or vision loss.
  • Patients with mountain sickness may develop HAPE, HACE, or HARH separately, or they may develop more than one of these conditions at the same time.

  • General: Patients who have symptoms of acute mountain sickness (AMS) should stop climbing to higher elevations. If possible, they should climb down the mountain. In most cases, symptoms of AMS will go away after two to three days of rest at a lower altitude. If descent is not possible, the patient should stop climbing and rest for several days at the current altitude.
  • Patients who experience symptoms of more serious forms of mountain sickness, including high altitude pulmonary edema (HAPE), high altitude cerebral edema (HACE), or high altitude retinal hemorrhage (HARH), should begin to descend to lower elevations immediately. In most cases, symptoms begin to improve once the patient reaches a healthcare facility. It may take patients several weeks to recover from severe types of mountain sickness.
  • Acetazolamide (Diamox®): Patients with AMS may benefit from treatment with a diuretic drug called acetazolamide (Diamox®). This drug increases the production of urine. As a result, the pH of the blood is decreased, stimulating the patient to breathe more. When patients breathe more, they have higher levels of oxygen in the blood. Therefore, acetazolamide is taken to help prevent or reduce symptoms of AMS. This drug has also been shown to improve symptoms of insomnia in AMS patients.
  • Antihypertensive drugs: A drug called nifedipine (Procardia®), which is used to lower blood pressure, may help treat symptoms of HAPE. This drug decreases the pressure in the pulmonary artery, which is typically elevated in patients with HAPE. The pulmonary arteries become dilated, which improves oxygen transfer.
  • Anti-nausea drugs: An anti-nausea drug called prochlorperazine (Compazine®) has been used to treat patients with AMS. The drug has been shown to decrease nausea, as well as increase breathing rate.
  • Breathing support: If patients with HAPE are not responding to treatment, a breathing tube may be placed in the airway to help the patient breathe. Patients who develop respiratory failure often require a ventilator, which is a machine that helps the patient breathe.
  • Continuous positive airway pressure (CPAP) mask: Severe cases of HAPE may be treated with a continuous positive airway pressure (CPAP) mask. The mask does not breathe for the patient. Instead, it pushes air into the patient's mouth when he/she inhales.
  • Hyperbaric chamber: If the patient cannot descend to a lower elevation, a portable hyperbaric chamber, called a Gamow bag, may be used. The Gamow bag is an inflatable bag. The patient lies inside the bag, and the air pressure inside simulates a lower altitude. The patient is then carried down the mountain while inside the hyperbaric chamber.
  • Oxygen: Oxygen may help treat patients who are experiencing symptoms of mountain sickness. Patients typically inhale two to four liters of oxygen per minute to increase the amount of oxygen in the blood.
  • Steroid: A steroid called dexamethasone (Decadron®) may help treat mountain sickness. This drug increases the amount of alkali (bicarbonate) that is excreted in the urine, making the blood more acidic. Acidifying the blood helps the patient's body acclimate to the altitude change. Some patients may experience a drastic improvement in symptoms with dexamethasone, and they may want to continue climbing. However, patients should continue to climb down.

Author information
  • This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (

  1. American Heart Association. .
  2. Basnyat B. High altitude cerebral and pulmonary edema. Travel Med Infect Dis. 2005 Nov;3(4):199-211. .
  3. Centers for Disease Control and Prevention (CDC). .
  4. Committee to Advise on Tropical Medicine and Travel (CATMAT). Statement on high-altitude illnesses. An Advisory Committee Statement (ACS). Can Commun Dis Rep. 2007 Apr 1;33(ACS-5):1-20. .
  5. Maakestad K. Advice for travelers to high altitude. Mo Med. 2006 Nov-Dec;103(6):623-7. .
  6. Natural Standard: The Authority on Integrative Medicine. .
  7. Serrano-Duenas M. High-altitude headache. Expert Rev Neurother. 2007 Mar;7(3):245-8. .
  8. Vuyk J, Van Den Bos J, Terhell K, et al. Acetazolamide improves cerebral oxygenation during exercise at high altitude. High Alt Med Biol. 2006 Winter;7(4):290-301. .

  • Mountain sickness develops when the body cannot adjust to high elevations. At higher elevations the air pressure decreases, which means there is less oxygen in the air. The body needs time to adjust to lower oxygen levels.
  • Individuals who climb or travel to altitudes higher than 8,000 feet above sea level at a rate that is faster than 1,000 feet per day are at risk of developing mountain sickness.
  • Other factors may also influence a person's risk of developing mountain sickness. If the body is overworked within the first 24 hours of the climb, patients have an increased risk of developing the condition because the body requires more oxygen. Individuals who are dehydrated or hypothermic have an increased risk of developing the condition. Also, consuming alcohol or other sedatives increases the risk of the mountain sickness because these drugs slow breathing.
  • Flying in a plane cannot cause mountain sickness because the oxygen level in the plane does not decrease.

Copyright © 2011 Natural Standard (

The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.

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