What Is Altitude Sickness (acute Mountain Sickness)? What Causes Altitude Sickness?

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Main Category: Sports Medicine / Fitness
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Article Date: 20 Feb 2010 - 0:00 PDT

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Altitude sickness, also called acute mountain sickness (AMS), altitude illness, hypobaropathy, Acosta disease, puna, or soroche is a disorder caused by being at high altitude where air pressure is low without prior acclimatization (the process of gradual exposure). If it does occur, it will do so at altitudes above 8,000 feet (2,500 meters) - 8000 meters is a common height for many ski resorts. More severe symptoms generally occur at above 3,600 meters (about 12,000 feet). Acute mountain sickness can progress to high altitude pulmonary edema (HAPE) or high altitude cerebral edema (HACE).

People with altitude sickness typically have a bad headache, nausea, dizziness and feel exhausted.

At sea level the atmospheric concentration of oxygen is approximated 21% and the barometric pressure averages 760 mmHg. At higher altitudes the 21% remains the same; however the number of oxygen molecules per breath is reduced. At about 5,500 meters (18,000ft) each breath contains approximately half the normal amount of oxygen (compared to sea level). In order to compensate for the oxygen shortfall the person has to breathe faster and their heart has to beat faster too. Even though breathing faster raises blood oxygen levels, they do not reach sea level concentrations.

Rising to higher altitudes can also cause fluid to leak from tiny blood vessels (capillaries), resulting in potentially dangerous fluid accumulation in the lungs and/or the brain. If a human continues rising to higher altitudes without adequate acclimatization, there is a serious risk of life-threatening illnesses.

According to the National Health Service (NHS), UK:

• Mountain sickness is fairly common among skiers, mountaineers and people who spend time at high altitudes.
• At a height of over 3,000 meters (10,000 feet) about three-quarters of people will experience mild symptoms.
• 20% to 25% of Colorado (USA) skiers and 53% of Periche (Nepal) trekkers develop symptoms of altitude sickness.
• About 34% of people in the Swiss Alps who ascend to 3,600 meters (about 12,000 feet) or more experience some degree of altitude sickness.

In the UK altitude sickness does not exist. Ben Nevis, Scotland, UK's highest mountain is 1,344 meters (4,406 feet) high. No matter how fast you went up that mountain, you would not get altitude sickness.

According to Medilexicon's medical dictionary:

Altitude sickness is " a syndrome caused by low inspired oxygen pressure (as at high altitude) and characterized by nausea, headache, dyspnea, malaise, and insomnia; in severe instances, pulmonary edema and adult respiratory distress syndrome can occur."

What is the difference between Chronic Mountain Sickness and Acute Mountain Sickness?

Chronic mountain sickness (CMS), also known as Monge's disease, develops after spending an extended time living at high altitude (over 3,000 meters). Acute mountain sickness is experienced shortly after ascending to rapidly to a high altitude.

What are the signs and symptoms of altitude sickness?

A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor detect. For example, pain may be a symptom while a rash may be a sign.

Severity of symptoms and when they begin depend on several factors, including:

• The person - age, weight, blood pressure, general fitness, etc.
• The speed at which people ascended
• How long was spent at high altitude

The primary symptom to diagnose altitude sickness is a headache. However, one of dehydration's symptoms is also headache. Therefore, for proper diagnosis, experts say the patient needs to be at a height of at least 2,500 meters (8,000 feet), has a headache, as well as at least one of the signs and symptoms listed below:

• Lack of appetite, nausea, or vomiting
• Exhaustion or weakness
• Dizziness (light-headedness)
• Insomnia
• Pins and needles
• Panting (shortness of breath) upon exertion
• Feeling sleepy (drowsiness)
• General malaise
• Swelling of the hands, feet and face (peripheral edema)

The following signs and symptoms may indicate something more serious, perhaps a life-threatening altitude sickness:

• Fluid in the lungs (high altitude pulmonary edema):
  
  
  • Persistent dry cough, often with pinkish sputum
  • Fever
  • Panting (even while resting)
• Swelling of the brain (high altitude cerebral edema)
  
  
  • Persistent headache. Painkillers do not get rid of the pain.
  • Unsteady gait, clumsiness
  • Increased vomiting
  • Gradual loss of consciousness
  • Numbness, and dizziness

What are the causes of altitude sickness?

The main cause of altitude sickness is ascending too rapidly. It may also be caused by going too high and staying there for too long. The human body needs to adapt to the lower air pressure and decreased levels of oxygen - for that it needs a gradual progression (acclimatization).

The average human body needs from 1 to 3 days to get acclimatized to a change in altitude. People who do not spend enough time acclimatizing to a new altitude before going further up have the highest risk of developing altitude sickness.

Altitude sickness - our body's response to a lower oxygen supply to the muscles and brain - can become a serious and fatal condition.

If there is less oxygen in the blood, the heart and lungs have to work harder, raising the pulse and breathing rates. More red blood cells are made to enable the body to carry more oxygen. As our bodies respond to a change in altitude our blood acidity level, lung pressure, electrolyte levels and fluid and salt balance change.

Diagnosing altitude sickness

If a person has climbed to an altitude above 2,500 feet, they have a headache plus at least one of the symptoms listed above, then an accurate diagnosis is fairly straightforward.

The first symptoms of altitude sickness tend to be a headache, light-headedness, exhaustion, insomnia and stomach upset. Anyone who develops these symptoms should immediately stop ascending, or even go down to a lower level and rest until symptoms have completely gone.

What are the treatment options for altitude sickness?

The signs and symptoms of altitude sickness should not be ignored, because the potential complications of the condition could be fatal. Death from altitude sickness used to be much more common in the past; mainly because people did not spot the signs or symptoms (or decided to ignore them).

People with very mild symptoms may continue ascending, but at a much slower pace. It is important to let others know the symptoms are there, no matter how mild they might be.

People with slightly more severe symptoms should:

• Rest completely
• Consume plenty of (non-alcoholic) fluids
• Not smoke

Descending - descending to a lower altitude is probably the best thing to do if symptoms develop. Attempts to treat or stabilize the patient in situ at altitude is dangerous, unless highly controlled and with good medical facilities. People with moderate symptoms usually respond well if they descent just 1,000 feet (300 meters) and stay there for 24 hours. If the individual with moderate symptoms remains at this lower altitude for a couple of days their body will have become acclimatized and they can then start ascending again.

People with severe symptoms should descend at least 2,000 feet (600 meters) as soon as possible. If this is not done quickly there is a risk of serious of life-threatening complications. People whose symptoms do not improve after descending 600 meters should go down further until they start feeling better.

Pure oxygen - giving pure oxygen to a person with severe breathing problems caused by altitude sickness can help. Oxygen is commonly provided by physicians at mountain resorts.

Gamow bag - this is used when a rapid descent is not possible. It is a portable plastic hyperbaric chamber inflated with a foot pump. It can be used to reduce the effective altitude by up to 1,500 meters (5,000 feet). It is usually used as an aid to evacuate patients with severe symptoms, not to treat them at high altitude.

Coca plant - this is a folk remedy for altitude sickness in Ecuador, Peru and Bolivia. A tea is made from the coca plant.

Painkillers - Tylenol (paracetamol) or ibuprofen can be taken for headaches.

Acetazolamide - this medication corrects the chemical imbalance in the blood caused by altitude sickness, as well as accelerating the patient's breathing rate. If the person can breathe more quickly their body will have more oxygen, resulting in an alleviation of some symptoms, such as nausea, dizziness and headache. This medication has some possible side effects, including pins-and-needles on the face, fingers and toes, excessive urination, and blurred vision (rare).

Dexamethasone - a potent synthetic member of the glucocorticoid class of steroid hormones. It acts as an anti-inflammatory and immunosuppressant. Its potency is about 20-30 times that of hydrocortisone and 4-5 times of prednisone. It is an effective medication for the treatment of cerebral edema, one of the complications of altitude sickness - it reduces swelling (inflammation) of the brain. Patients usually experience an improvement within approximately six hours. This medication has some possible side effects, including stomach upset, depression and euphoria.

Nifedipine - a dihydropyridine calcium channel blocker, commonly used for the treatment of hypertension (high blood pressure). It is effective in the treatment of pulmonary edema (fluid accumulation in the lungs). This medication reduces the narrowing of the pulmonary artery, resulting in less chest tightness and easier breathing. As blood pressure can suddenly drop after taking this medication, patients are advised not to get up too quickly.

What are the possible complications of altitude sickness?

The two main altitude sickness complications are:

• High altitude cerebral edema (HACE) - in UK English edema is spelled oedema, hence the name in the UK is HACO. A lack of oxygen causes fluid to leak through tiny blood vessels (capillaries) and into the brain, which swells. Usually, HACE occurs when somebody stays at high altitude for at least one week. If left untreated death is likely. The patient should be descended by at least 600 meters (2,000 feet) immediately.
• High altitude pulmonary Edema (HAPE) - in UK abbreviation it is HAPO. Fluid builds up in the lungs, preventing oxygen from getting into the bloodstream. As HAPE progresses and blood oxygen levels drop the patient will develop a blue tinge to the skin (cyanosis), breathing will become more difficult, the chest will tighten, there will be a persistent cough with pinkish sputum, the patient will feel very exhausted and weak, and there will be confusion and disorientation. If left untreated death is a likely outcome.
  
  Also, in cases of HAPE, the patient should be descended by at least 600 meters (2,000 feet) immediately.

Both these conditions are uncommon, but may occur if somebody ascends to a very high altitude too rapidly, and stays there.

Prevention of altitude sickness

Climbers should be informed of the risks, symptoms and treatments for altitude sickness. If the ascent is to take place in a remote mountain it is important to be prepared and to take precautions.

• Acclimatization - the best way to prevent altitude sickness is to ascend gradually, so that your body can become acclimatized to the changing altitude. Plan the acclimatization and make sure your trip includes enough time for this. Make sure everyone in the group is fully acclimatized before ascending.
• Vacation packages - beware of vacation packages that promise to ascend a mountain in just a few days.
• Fluids - consume between 4 to 6 liters of water per day.
• Food - eat a high calorie diet while at high altitude.
• Worsening symptoms - if moderate altitude symptoms worsen you should descend immediately.
• Sleeping - when your altitude is over 3,000 meters, ascend no more than 300 meters each night. In other words, do not sleep at more than 300 meters higher than you slept the previous night. Even if you ascend more than 300 meters during the day, before going to sleep come back down so that you are no more than 300 meters higher than the night before when you go to sleep.
• Smoking - do not smoke.
• Alcohol - do not consume alcoholic drinks.
• Acetazolamide/Dexamethasone - these medications can also be used to prevent altitude sickness.
• Moderate symptoms - people with moderate symptoms should stay at their current altitude until their symptoms have gone completely.
• Other medications - some medications may make symptoms worse while at high altitude, or ascending, including tranquilizers and sleeping pills.

Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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