Brief overview
- Description: Altitude sickness refers to a group of symptoms that result from oxygen deprivation at high altitudes (e.g., mountains).
- Symptoms: Usually symptoms are nonspecific (e.g., headache, nausea, dizziness), but life-threatening high-altitude pulmonary edema or high-altitude cerebral edema may develop.
- Causes: Difficulty of the body to adapt due to reduced oxygen content and air pressure at higher altitudes.
- Diagnosis: conversation with the doctor, physical examination (e.g. blood test, blood gas analysis, X-ray, CT, MRI).
- Treatment: Rest, physical rest, medication (e.g. painkillers, antiemetics, dexamethasone, acetazolamide), administration of oxygen. In severe cases, it is also necessary to descend quickly to lower altitudes.
- Course: With proper treatment, symptoms usually disappear within one to two days. In severe cases (e.g., high-altitude pulmonary edema or high-altitude cerebral edema) and/or inadequate treatment, there is a risk that affected persons will fall into a coma and die.
- Prevention: Slowly ascending and getting the body used to the altitude is the best preventive measure. In exceptional cases and only on a doctor’s orders, drugs such as acetazolamide or dexamethasone help.
What is altitude sickness?
Altitude sickness (also known as High Altitude Illness, or HAI; or D’Acosta disease) is a set of symptoms that occur due to a lack of oxygen in the body at high altitudes. In this case, the body is unable to process the lower oxygen content in the air and the falling air pressure at high altitudes, and develops various symptoms.
Altitude sickness is most noticeable in the form of headaches. It can usually be avoided through proper prevention, especially by slowly adapting to altitude. If the affected person does not react appropriately and ascends to further altitudes despite symptoms, the complaints can turn into life-threatening high-altitude cerebral edema or high-altitude pulmonary edema.
Depending on the symptoms that occur, altitude sickness is divided into:
- Acute Mountain Sickness (AMS for short)
- High Altitude Cerebral Edema (HACE for short).
- High Altitude Pulmonary Edema (HAPE)
These forms of altitude sickness occur both alone and in combination with each other. The transition from one to the other form is often fluid.
At what altitude does altitude sickness occur?
It is possible for symptoms of altitude sickness to occur at altitudes as low as about 2,500 meters. Acute altitude sickness or mountain sickness occurs most frequently. It occurs in around 30 percent of mountain hikers who are above 3,000 meters. In rare cases, altitude sickness occurs at altitudes as low as 2,000 meters.
At extreme altitudes above about 5,300 meters, severe forms of altitude sickness (high-altitude cerebral edema and high-altitude pulmonary edema) usually develop and are life-threatening. They are among the most frequent causes of death among mountaineers.
Residents on the mountain (e.g., in the Andes) usually do not show symptoms of altitude sickness because their bodies have adapted to the environmental conditions.
Who is affected?
Altitude sickness can basically affect anyone who goes to higher altitudes (e.g., mountaineering or traveling to higher places) or lives there (e.g., residents of mountain villages). Up to one in four people who live at a low altitude or in the lowlands and spend time at an altitude above 2,500 meters without slowly acclimatizing the body to it show (usually mild) symptoms of altitude sickness.
Old people are affected just as often as younger people, men just as often as women, and athletes no less often than the untrained. Not even whether someone smokes plays a role in whether or not they develop altitude sickness. Only children seem to be more susceptible to altitude sickness than adults.
What are the symptoms of altitude sickness?
Symptoms of altitude sickness usually begin with headache, dizziness, nausea, and a general feeling of malaise. The pulse accelerates (tachycardia). These early warning signs of incipient or acute altitude sickness should be taken seriously. At the very least, it is important for those affected to rest immediately.
Symptoms usually appear six to ten (four to six at the earliest) hours after exposure to altitude (above 2,000 to 2,500 meters).
Only when the symptoms have completely disappeared is it advisable to continue ascending. If sufferers continue to ascend despite symptoms, their condition usually worsens within twelve to 24 hours. There are clear warning signs such as:
- The affected person feels nauseous and has to vomit.
- He has a severe continuous headache; usually in the forehead and temples, rarely unilateral or in the back of the head; the headache intensifies with physical exertion.
- His performance drops rapidly. He can only keep up with difficulty.
- The affected person gets palpitations.
- Even without stress, he finds it difficult to breathe.
- He feels mentally battered, listless and confused.
- The affected person develops a dry cough.
- He feels dizzy and light-headed.
- He has an unsteady gait (“staggers”).
- He excretes much less urine than usual (less than half a liter of dark urine per day).
- The affected person cannot fall asleep or sleep through the night (sleep disorders).
- The hands and feet sometimes swell.
If the affected person continues to ignore the symptoms, there is an acute danger to life! In this case, it is necessary to take immediate emergency measures (administration of oxygen and medication) and descend to lower altitudes.
In the final stage of altitude sickness (risk of high-altitude cerebral and pulmonary edema), the symptoms worsen further: headaches are unbearably severe, and heart palpitations and nausea increase. In some cases, those affected are physically no longer able to descend. At this stage, they are often no longer able to pass urine.
High altitude pulmonary edema
If altitude sickness is already far advanced, fluid accumulates in the lungs and brain (edema). In high-altitude pulmonary edema, sufferers begin to cough heavily, which makes breathing even more difficult. Some cough up rusty brown mucus in the process. High-altitude pulmonary edema is seen in about 0.7 percent of climbers who are above 3,000 meters in altitude.
High Altitude Cerebral Edema
If high-altitude cerebral edema develops, people with altitude sickness experience hallucinations and are very sensitive to light (photophobia). Some behave strangely (“crazy”) at this stage, putting themselves and others in danger. The initial drowsiness sometimes culminates in the individual becoming unconscious. High-altitude cerebral edema affects about 0.3 percent of climbers above an altitude of 3,000 meters.
If nothing is then done, those affected usually die due to the severe complications.
How does altitude sickness develop?
Altitude sickness occurs when the body has difficulty adapting to environmental conditions at high altitudes. As altitude increases – for example, when climbing a high mountain – the air pressure and oxygen content in the air decrease. This reduces the partial pressure of oxygen (shows the amount of oxygen in the blood), which causes the blood vessels in the lungs to constrict. The lungs thus absorb less oxygen, as a result of which the body is no longer supplied with sufficient oxygen via the blood (hypoxia).
At an altitude of 5,000 meters, the oxygen content is only half that at sea level. At over 8,000 meters, only 32 percent of the oxygen content at sea level is available to the climber.
The lack of oxygen in the blood causes the body to try to adapt to the new conditions. Breathing speeds up and the heart beats faster to transport more oxygen into the body via the lungs. If the organs are still not sufficiently supplied with oxygen as a result, altitude sickness occurs.
The lack of oxygen reduces the pressure in the pulmonary alveoli, causing increased water to be deposited from the blood vessels into the surrounding tissue. Under certain circumstances, this leads to an accumulation of fluid in the lungs and brain (edema) – high-altitude pulmonary edema or high-altitude cerebral edema develops.
How does the doctor make the diagnosis?
Since the symptoms of altitude sickness are often nonspecific at the beginning, it is important for the doctor to examine the affected person closely. In most cases, the fact that the affected person shows the symptoms at high altitude already indicates altitude sickness.
For diagnosis, the doctor first conducts a detailed interview (anamnesis). He then performs a physical examination. If, for example, the doctor notices gait difficulties and a noticeable drop in performance in addition to severe headaches and nausea, these are already clear signs of altitude sickness.
In addition, the doctor rules out other causes for the symptoms. For example, headaches also occur with sunstroke, migraine, a lack of fluids or high blood pressure (hypertension). For this purpose, the doctor asks, for example, where the headache occurs (e.g., on the forehead, at the back of the head, at the temples) and since when it has existed (already before the ascent or only afterwards?).
The doctor also examines the blood. A blood gas analysis and the blood values help to rule out other diseases (e.g. pneumonia) in which similar symptoms occur.
If edema is suspected in the lungs or brain, the physician performs further examinations. These include, for example, an X-ray examination of the chest, a computer tomography of the head and lungs, or an electroencephalography (EEG, measurement of brain waves).
Although altitude sickness is not immediately behind every symptom at high altitude, suspicion is valid until a clear diagnosis is made.
What can be done against altitude sickness?
At the first signs of acute altitude sickness, it is important that sufferers give their bodies time to adjust. For mild to moderate symptoms, it is recommended to take a day off and rest. It is also important to drink plenty of fluids, but not alcohol.
To treat mild symptoms such as headache, an analgesic (e.g., ibuprofen) can be taken. Antiemetics, which suppress nausea, help against nausea. However, it is important to take the symptoms seriously and not to mask them by taking medication: rest and do not continue to rise as long as you have symptoms!
If these measures do not improve symptoms after one day, it is important to descend 500 to 1,000 meters in altitude. In case of severe symptoms or if symptoms continue to worsen, it is necessary for people with altitude sickness to descend immediately and as far as possible, as well as to seek medical help.
If the symptoms are severe, doctors give the affected person oxygen via an oxygen mask. To prevent or reduce water retention in the body (edema), they administer a diuretic (dehydrating drug), for example acetazolamide.
In the case of high-altitude cerebral edema, the physician also administers cortisone (dexamethasone); in the case of high-altitude pulmonary edema, the physician administers an antihypertensive drug (e.g., nifedipine or tadalafil).
These drugs are not suitable for self-treatment or prevention of altitude sickness! In case of severe symptoms, medical treatment is always necessary.
In some cases, it makes sense to treat the affected person in a hyperbaric chamber or in a mobile hyperbaric bag. There he is again exposed to higher air pressure, which corresponds to a descent to a lower altitude.
What is the forecast?
Mild symptoms of altitude sickness usually disappear within one to two days. Provided:
Those affected do not continue to rise.
- You will take a rest day.
- They take it easy on themselves physically.
- You drink enough (at least 1.5 liters per day).
In contrast, severe symptoms such as high-altitude cerebral edema or high-altitude pulmonary edema pose an acute danger to life. If those affected are not treated quickly and consistently, there is a risk that they will fall into a coma and subsequently die. High-altitude cerebral edema occurs in about 0.3 percent of climbers above 3,000 meters, high-altitude pulmonary edema in about 0.7 percent, of which about 40 percent of those affected die in each case.
How to prevent altitude sickness?
To prevent altitude sickness, it is important that you give your body time to adapt to the changed environmental conditions (acclimatization). This is because the faster you ascend, the greater the risk of developing altitude sickness. The speed at which you ascend is much more important than the altitude you reach.
The only effective protection here is the right “tactics” during the ascent: from an altitude of between approx. 2,500 to 3,000 meters, cover no more than 300 to 500 meters of altitude per day. Take a day’s break every three to four days. If you have an increased risk of high-altitude cerebral or pulmonary edema (e.g., heart disease), it is advisable that you cover no more than 300 to 350 meters of altitude per day.
If you have a cardiovascular or pulmonary disease, you should ask a doctor for advice before going to an altitude of more than 2,000 meters!
If you want to climb to a total of 4,000 to 5,000 meters in altitude, it is advisable to spend a few days to a week beforehand between 2,000 and 3,000 meters in altitude to acclimate the body. Only when this acclimatization phase is over should you continue to climb slowly.
In exceptional cases, it is possible to prevent altitude sickness with medication. These are generally intended for people who have to ascend unexpectedly to high altitudes, such as emergency personnel rescuing an injured person. In some cases, preventive medication is also useful for people who have already been affected by altitude sickness.
Preventive medications should only be considered in individual cases! They do not replace the measure of acclimatizing the body to altitude and should only be taken after consulting a doctor!
For acute emergencies, it is also useful to carry a mobile hyperbaric chamber or a hyperbaric bag.
