Acute mountain sickness (AMS)

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.

Background

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.

Signs and symptoms

Acute mountain sickness (AMS): Common symptoms of acute mountain sickness (AMS) include fatigue, headache, dizziness, insomnia, shortness of breath, nausea, decreased appetite, swelling of the arms and/or legs, and social withdrawal.
High altitude pulmonary edema (HAPE): AMS may progress to high altitude pulmonary edema (HAPE) after more than one day spent at high altitude. Symptoms may develop gradually or suddenly. Common symptoms include shortness of breath (even when resting), gurgling sounds when breathing, wet cough with frothy sputum, and sometimes fever. If left untreated, this condition may lead to respiratory failure in which the lungs are unable to get enough oxygen. As a result, breathing is no longer possible. Without immediate treatment, the patient will die from respiratory failure.
High altitude cerebral edema (HACE): AMS may also progress to high altitude cerebral edema (HACE). The first symptom of HACE is usually confusion. As the condition worsens, the patient may have a difficult time keeping up with others. Then walking and coordination become impaired. As the brain continues to swell, the patient becomes more lethargic. If left untreated, the patient will go into a coma and eventually die.
High altitude retinal hemorrhage (HARH): The most common symptom of high altitude retinal hemorrhage (HARH) is blurred vision. Bleeding in the eye(s) may or may not be visible to the patient. Left untreated, HARH may lead to permanent eye damage or vision loss.

Diagnosis

General: Mountain sickness is typically diagnosed if the patient was exposed to high altitudes and experiences symptoms that are characteristic of the disorder. If the patient is dizzy, fatigued, has a headache, and decreased appetite, acute mountain sickness (AMS) is diagnosed. If the patient has difficulty breathing, has a wet cough with frothy sputum, and makes gurgling sounds when breathing, high altitude pulmonary edema (HAPE) is diagnosed. If the patient has symptoms of an altered mental state, such as confusion and loss of coordination, high altitude cerebral edema (HACE) is diagnosed. High altitude retinal hemorrhage (HARH) is diagnosed if the patient has blurred vision or bleeding in the eyes. In some cases, tests may need to be performed to confirm a diagnosis or measure the severity of organ damage.
Magnetic resonance imaging (MRI) scan: If a patient has HACE, a magnetic resonance imaging (MRI) scan of the brain may be performed to confirm that the brain is swollen. During the procedure, which is performed at the hospital, a machine takes pictures of the brain.
Ophthalmoscopy: Patients who experience blurred vision should visit their eye doctors. The doctor will use a hand-help instrument, called an ophthalmoscope, to view the eye. If bleeding is present, high altitude retinal hemorrhage (HARH) is diagnosed.
Physical examination: The healthcare provider may hear crackling noises in the patient's lungs when he/she breathes. This indicates that there is fluid in the lungs and the patient has pulmonary edema.
Pulse oximetry: A pulse oximetry test may be performed to determine how much oxygen is in the blood. During this painless procedure, a special clip is placed on the finger, earlobe, or toe. This clip passes two light waves through the skin to measure the amount of oxygen in the blood. Healthy individuals have oxygen saturation between 95% and 99%. Patients with oxygen levels lower than 95% are diagnosed with mountain sickness.
X-ray: A chest X-ray may show fluid filling in the lungs, which is characteristic of HAPE.

Treatment

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.

Integrative therapies

Note: Acute mountain sickness (AMS) may develop into life-threatening conditions. Individuals with symptoms of mountain sickness should seek proper medical attention immediately. Individuals who are planning on climbing high altitude mountains should bring proper medical equipment. 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 and seek proper medical attention.
Good scientific evidence:
Yoga: Yoga uses controlled breathing patterns to increase respiratory efficiency. Clinical study has found that at high altitude, subjects practicing yoga had improved oxygen use and ventilation and reduced changes in their blood that resembled Himalayan natives. More research is needed to further clarify the use of yoga in treatment of altitude sickness.
Yoga is generally considered to be safe in healthy individuals when practiced appropriately. Avoid some inverted poses with disc disease of the spine, fragile or atherosclerotic neck arteries, risk for blood clots, extremely high or low blood pressure, glaucoma, detachment of the retina, ear problems, severe osteoporosis, or cervical spondylitis. Certain yoga breathing techniques should be avoided in people with heart or lung disease. Use cautiously with a history of psychotic disorders. Yoga techniques are believed to be safe during pregnancy and breastfeeding when practiced under the guidance of expert instruction (the popular Lamaze techniques are based on yogic breathing). However, poses that put pressure on the uterus, such as abdominal twists, should be avoided in pregnancy.
Unclear or conflicting scientific evidence:
Ginkgo: Ginkgo biloba has been used to treat medical conditions for thousands of years. Today, it is one of the top selling herbs in the United States. A small amount of poorly designed research reports benefits of Ginkgo biloba for the treatment of altitude sickness. Additional study is needed before a recommendation can be made.
Avoid if allergic or hypersensitive to members of the Ginkgoaceaefamily. If allergic to mango rind, sumac, poison ivy or oak, or cashews, then allergy to Ginkgo biloba is possible. Avoid with blood-thinners (such as aspirin or warfarin) due to an increased risk of bleeding. Ginkgo biloba should be stopped two weeks before and immediately after surgical procedures. Ginkgo biloba seeds are dangerous and should be avoided. Skin irritation and itching may also occur due to Ginkgo biloba allergies. Do not use Ginkgo biloba in supplemental doses if pregnant or breastfeeding.
Vitamin E: Vitamin E may offer some benefits in exposure to high altitude. Antioxidant supplementation (vitamin E with beta carotene, vitamin C, selenium, and zinc) may improve ventilatory threshold at high altitudes; however, antioxidants may not reduce inflammation after exercise at high altitudes. More research is needed before conclusions can be drawn on the effectiveness of Vitamin E for altitude sickness.
Avoid if allergic or hypersensitive to vitamin E. Avoid with retinitis pigmentosa (loss of peripheral vision). Use cautiously with bleeding disorders or if taking blood thinners. Avoid above the recommended daily level in pregnant women and breastfeeding women.
Fair negative scientific evidence:
Arginine: Based on early research, L-arginine supplementation has not been shown to be an effective therapy in prevention of altitude sickness.
Avoid if allergic to arginine, or with a history of stroke, or liver or kidney disease. Avoid if pregnant or breastfeeding. Use caution if taking blood-thinning drugs (like warfarin or Coumadin?) or blood pressure drugs or herbs or supplements with similar effects. Blood potassium levels should be monitored. L-arginine may worsen symptoms of sickle cell disease. Caution is advised in patients taking prescription drugs to control blood sugar levels.
Traditional or theoretical uses lacking sufficient evidence:
Reishi mushroom: Reishi mushroom (Ganoderma lucidum), also known as Ling Zhi in China, grows wild on decaying logs and tree stumps. It has been suggested that reishi mushroom may help with treatment and prevention of altitude sickness. However, studies have not been performed to test the safety and effectiveness of this therapy.
Avoid if allergic or hypersensitive to any constituents of Ganoderma lucidum or any member of its family. Use cautiously with diabetes, blood disorders (including hemophilia), low blood pressure, or ulcers. Avoid if pregnant or breastfeeding.
Rhodiola: Rhodiola has been used traditionally in Eastern Europe and Asia for increasing resistance to physical stress, enhancing work performance, reducing fatigue, and preventing altitude sickness. Rhodiola has been suggested to protect against hypoxia (reduction of oxygen supply in the body), however there is a lack of evidence for this use in available human study. Well-designed clinical studies are required in this area.
Avoid if allergic or sensitive to Rhodiola. Use cautiously in people with diabetes, cardiovascular disease, or neurological or psychiatric disorders. Rhodiola is not recommended for use during pregnancy or breastfeeding.
Selenium: Selenium is a mineral found in soil, water, and some foods. Although selenium has been suggested as a possible treatment for altitude sickness, studies are lacking. Research is needed in order to determine if this treatment is safe and effective in humans.
Avoid if allergic or sensitive to products containing selenium. Avoid with a history of non-melanoma skin cancer. Selenium is generally regarded as safe for pregnant or breastfeeding women. However, animal research reports that large doses of selenium may lead to birth defects.

Prevention

Patients who ascend or descend slowly are less likely to develop mountain sickness than patients who ascend or descend quickly. This is because the body has time to adjust to altitude changes.
If patients are traveling to areas, such as ski resorts, that are higher than 8,250 feet above sea level, they should spend one to two days at an intermediate elevation.
Patients should not increase the altitude at which they sleep by more than 1,000 feet every 24 hours.
Patients with a history of mountain sickness may receive the prescription drug acetazolamide (Diamox?). This medication may help reduce the risk of mountain sickness because it helps the body adjust to elevation changes.
Patients with a history of mountain sickness, especially HAPE, may receive the prescription drug nifedipine (Procardia?). This drug is normally used to treat high blood pressure. However, it may also help prevent mountain sickness by stabilizing the blood flow to the lungs.
Patients should avoid physical exertion for the first 24 hours of climbing.
Patients should drink plenty of fluids and avoid alcoholic beverages while they are traveling or climbing to high altitudes.
Patients are encouraged to consume a high-carbohydrate diet during climbs.
Patients who are planning on climbing high mountains that are more than 8,000 feet above sea level should bring proper medical equipment, such as a Gamow bag or supplemental oxygen, with them.

Author information

This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography

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Basnyat B. High altitude cerebral and pulmonary edema. Travel Med Infect Dis. 2005 Nov;3(4):199-211. .
Centers for Disease Control and Prevention (CDC). .
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. .
Maakestad K. Advice for travelers to high altitude. Mo Med. 2006 Nov-Dec;103(6):623-7. .
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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. .

Causes

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.