Altitude sickness occurs when a person travels to a high altitude — usually above 8,000 feet — without gradually acclimatizing. Symptoms such as weakness and nausea result from a lack of oxygen. It can lead to life-threatening complications.
Altitude sickness is also known as acute mountain sickness, altitude illness, hypobaropathy, Acosta disease, puna, and soroche.
The condition generally occurs at altitudes higher than 8,000 feet (ft), or 2,500 meters (m), and is usually due to a lack of oxygen. A person who is not used to high altitudes is most at risk of developing altitude sickness. The condition is not to be taken lightly and can lead to serious complications.
The severity of symptoms depends on several factors, including:
- the age, weight, blood pressure, and respiratory capacity of an individual
- how fast a person ascends to a high altitude
- the amount of time spent at that altitude
Symptoms of altitude sickness include:
- lack of appetite, nausea, or vomiting
- exhaustion or weakness
- pins and needles
- shortness of breath upon exertion
- feeling sleepy
- swelling of the hands, feet, and face
A complete diagnosis may require a medical assessment of these symptoms.
A person’s altitude sickness can worsen over time and result in serious complications, including fluid in the lungs and brain swelling.
Fluid in the lungs can cause the following:
Signs of swelling of the brain include:
- a persistent headache that does not respond to painkillers
- unsteady gait or clumsiness
- increased vomiting
- changes in consciousness
Chronic mountain sickness, also known as Monge’s disease, develops after a person spends an extended time living at high altitudes. Chronic mountain sickness is common in many cultures across the globe. A
In contrast, acute altitude sickness occurs in a much shorter time frame. A person may experience acute altitude sickness at any point 1 to 5 days after ascending above 8,000 ft. Acute altitude sickness may develop into more severe conditions, including high-altitude cerebral edema and high-altitude pulmonary edema.
The leading cause of altitude sickness is ascending to a great height too rapidly. Staying at high altitudes for extended periods may also cause forms of altitude sickness.
At sea level, the oxygen concentration in the air is approximately
At higher altitudes, the oxygen concentration remains the same, but air pressure is much lower. For example, at the peak of Mount Everest, air pressure is around 228 mm Hg. Lower pressure means that the air is less dense, and therefore the number of oxygen molecules per breath is reduced.
At around 18,000 ft, each breath contains approximately half of the oxygen found at sea level.
If a person has less oxygen in their blood, their heart and lungs have to work harder. This raises their pulse and their breathing rate. In response, the body creates more red blood cells to carry more oxygen. However, even though breathing faster increases blood oxygen levels, they do not reach sea level concentrations.
The average human body needs from 1 to 3 days to become acclimatized to a change in altitude. People who do not spend enough time acclimatizing to a new altitude before progressing further have the highest risk of developing altitude sickness.
The body may also respond to a change in altitude by altering blood acidity level, lung pressure, electrolyte levels, and fluid and salt balance. Rising to higher altitudes can also cause fluid to leak from tiny blood vessels, resulting in a potentially dangerous fluid buildup in the lungs and the brain.
The primary symptom of altitude sickness is a headache. However, many factors, including dehydration, can cause similar symptoms. As a result, a doctor will assess a range of criteria to reach a diagnosis.
For a doctor to diagnose a person with altitude sickness, the person must have climbed to an altitude higher than 8,000 ft, present with a headache, and be experiencing other associated symptoms. These symptoms may include dizziness, insomnia, and shortness of breath, among others.
A person who develops any of these symptoms should immediately stop ascending and rest until their symptoms have cleared. They may also benefit from descending to a lower altitude.
People with very mild symptoms may continue ascending but should go at a much slower pace. However, if a person experiences even slight symptoms, they should alert others.
Those with more severe symptoms should rest, consume plenty of fluids, and avoid anything that may affect blood oxygen levels, such as smoking.
There are a number of potential treatments that may remedy altitude sickness. These include:
Descending: Moving to a lower altitude is usually the best action to take if a person develops symptoms of altitude sickness. Once acclimatized they may be able to ascend once more.
Pure oxygen: Giving pure oxygen can help a person with severe breathing problems caused by altitude sickness. Physicians at mountain resorts commonly provide this treatment.
A Gamow bag: This portable, plastic hyperbaric chamber can be inflated with a foot pump and is used when a rapid descent is not possible.
Painkillers: Acetaminophens, such as Tylenol, can be taken for headaches. Ibuprofen, an anti-inflammatory medicine, can also help.
Acetazolamide: This medication
Dexamethasone: This is a steroid hormone that can suppress immune activity and inflammation. It can reduce the incidence of acute altitude sickness and other complications. However, the medication has some possible side effects, including stomach pain, depression, and euphoria.
Nifedipine: This is a dihydropyridine calcium channel blocker doctors commonly prescribe to treat high blood pressure. It is effective for treating fluid buildup in the lungs. This medication reduces the narrowing of the pulmonary artery, easing chest tightness and making breathing easier.
High altitude cerebral edema
A lack of oxygen at high altitude combined with the subsequent changes in pressure within the blood vessels causes fluid to leak through tiny blood vessels into the brain, which leads to swelling. Usually, HACE occurs when a person stays at a high altitude for at least 1 week.
If this condition is left untreated, there is a very high risk of death. A person presenting symptoms of HACE should descend immediately.
High altitude pulmonary edema
HAPE causes fluid to build up in the lungs, preventing oxygen from getting into the bloodstream. As HAPE progresses and blood oxygen levels drop, several symptoms may develop, including:
- a blue tinge to the skin
- breathing difficulties
- a tight chest
- a persistent cough with pinkish sputum
- exhaustion and weakness
- confusion and disorientation
This complication can be fatal if it is left untreated. If a person is fully conscious and can reach a health facility, medical professionals can treat HAPE at that altitude with oxygen supplementation. However, in a more remote setting, a person should descend as soon as is practical.
Both of these conditions are uncommon, but may occur if a person ascends to a very high altitude too rapidly and stays there.
Altitude sickness is best prevented by a measured ascension, allowing time for gradual acclimatization. However, a person may be able to take other precautions. These are particularly important should a person climb in a more remote setting where immediate health care will not be available. They include:
- Fluids: A person should
increasetheir fluid intake when ascending to high altitudes.
- Food: When climbing at high altitudes, a person may benefit from consuming a high-calorie diet.
- Sleeping: People should not increase their sleep elevation by more than 985-1,970 ft per night when climbing over several days.
- Resting: Every 3-4 days of climbing, people should rest every for one full day to allow the body to acclimatize.
- Smoking: A person should not smoke before or during a climb.
- Alcohol: Before ascending to high altitudes, a person should avoid alcohol.
- Acetazolamide and dexamethasone: A person can use these medications to prevent altitude sickness. However, their use is not common practice outside of advanced athletes, such as experienced climbers, since these medications have multiple side effects.
Altitude sickness occurs when a person rapidly ascends to high altitudes, normally above 8,000 ft.
Symptoms of altitude sickness can include headaches, dizziness, and shortness of breath. If a person stays at high altitudes for an extended period, they may develop chronic altitude sickness. If they do not get medical help, this can lead to potentially fatal complications.
A person can prevent altitude sickness by ascending gradually and allowing the body to acclimatize to new heights.
A doctor may prescribe several different medications to treat altitude sickness, or in some cases, recommend oxygen supplementation.
However, a person may remedy altitude sickness symptoms most effectively by descending to lower altitudes.