Altitude Illness

Definition

Altitude sickness: Altitude sickness (or altitude illness) is a disorder caused by being at high altitude. It more commonly occurs above 8,000 feet (2,440 meters) (Medical Dictionary, 1999[3]).

Theoretical frame

Although the causes of altitude illnesses are not properly known, they occur due to exposure to low atmospheric pressure usually above 2,400 meter or 8000 feet. Different people are affected at different altitudes, because of differences in acclimatisation. Acclimatisation refers to the body adjusting to the decreased oxygen levels at high altitudes. This process is very slow and takes few days or weeks. That is, different people can survive without being affected by altitude illnesses at different heights. There are three major types of altitude illnesses: acute mountain sickness (altitude sickness), high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE). (FamilyDoctor, 2006 [2] & Dietz, 2006 [1]).

Acclimatisation

Barometric pressure decreases as the altitude increases. Thus, when one ascends through the atmosphere, the number of oxygen molecules during inhalation process decrease making breathing process more difficult. One practical example is difficulty in breathing while walking uphill. To supply enough oxygen, breathing rate increases, however, when reached to a certain level even an increased rate of breathing cannot supply enough oxygen. Acclimatisation occurs at the level where increased breathing rate can supply enough oxygen necessary for body activities.

1. Acute mountain sickness (Altitude sickness)

Acute Mountain Sickness (AMS) is a type of altitude illness which occurs when you reach above the altitude, usually above 2500 meters, where your body cannot get proper acclimatisation. At this level your body cannot tolerate the decreased oxygen levels, and cannot function properly. You start feeling sickness.

Symptoms

Although the reasons for AMS are not very clear, it is thought that hypoxic stress caused by lower oxygen level results in mild swelling of brain tissue. This swelling causes number of symptoms that may vary from mild to worse:

  • headache
  • loss of appetite
  • nausea
  • vomiting
  • fatigue
  • dizziness
  • ldifficulty sleeping
  • light headedness
  • dizziness

2. High Altitude Cerebral Edema (HACE)

While AMS is generally considered as mild, HACE is effect of altitude at the worse end of the spectrum. When swellings in brain become worse, brain stops functioning properly. Hence, AHCE can be life threatening. Specific sign of HACE is reduction in cognitive ability and ataxia (loss of or poor coordination). People with HACE may walk similar to an intoxicated person. In other words, they will not pass the “tandem gait test”(Dietz, 2006 [1]).

3. High Altitude Pulmonary Edema (HAPE)

This is another form of severe altitude illness which affects lungs. HAPE occurs after MAS but not necessary after HACE. Usually this illness is a result of accumulation of fluids in lungs.

Symptoms

  • Breathlessness at rest
  • Cough and pink sputum
  • Chest tightness
  • Drowsiness
  • Extreme fatigue
  • Fast breathing
  • Blue fingernails

Treatment for HACE and HAPE

The best treatment for HACE and HAPE is immediate descent to altitudes where oxygen level is adequate. However, during mountaineering HACE often attack in the night making this treatment almost impossible. Descent should be made to a safe level which may be the highest level patient woke up feeling well (500-1000 meter descent). Alternatively, dexamethasone, oxygen or hyperbaric bags can be used.

Prevention of Altitude Illnesses (MedicineNet, 1999 [4])

  • Do not drive or fly to heights above 3,048 meters or 10,000 feet. Instead, walk up where necessary.
  • Increase 305 meters (1000 feet) per day
  • Do not over-exert during first 24 hours
  • Sleep at a low level
  • If any mild sign is apparent, do not climb further
  • Descent if symptoms increase
  • Note that different people acclimatise at different levels, so your health may be affected before any one else
  • Hydration at all times is important
  • No alcohol or tobacco – no drugs which reduces respiratory drive during sleep
  • Carbohydrate diets are important for high level of energy.

Supporting evidence

Treatment for AMS

Tissont, Leadbetter, Keyes, Maakestad, Olsen, and Hackett (2008 [6]) carried two sets of research to see whether acetazolamide helps in preventing/reducing altitude sickness. The first piece of research has found that low-dose acetazolamide is effective in preventing Acute Mountain Sickness in poeple already at high altitude and then moving further higher (low-risk condition). The second piece of research was carried out to see if the same drug can help in high-risk settings (quick ascent from 1600 to 4300 meters). Same drug given in low-doze helps reduce the severity of AMS at high-risck situation.

AMS in children and their parents

Families often involve in mountain climbing and ask physicians about the effects of altitudes on their health. Moragam, Pedreros and Rodriguez (2008 [5]) carried out a research to see the differences (if any) of AMS effects on children and their parents. It was found that children are more sensitive to AMS. Thus, the authors concluded that young age might be an additional risk for development of AMS.

References
1. Dietz, T. E. (2006). An altitude tutorial. Retrieved from http://www.ismmed.org/np_altitude_tutorial.htm#AMS on 24 January, 2009.
2. FamilyDoctor. (2006). High-altitude illness: How to avoid it and how to treat it. Retrieved from http://familydoctor.org/online/famdocen/home/healthy/physical/injuries/247.html on 24 January, 2009.
3. Medical Dictionary (1999). Altitude sickness. Retrieved from http://www.medterms.com/script/main/art.asp?articlekey=8584 on 24 January, 2009.
4. MedicineNet (1999). Defintion of altitude sickness. Retrieved from http://www.medterms.com/script/main/art.asp?articlekey=8584 on 24 January, 2009.
5. Moragam F. A., Pedreros, C. P., & Rodriguez, C. E. (2008). Acute Mountain Sickness in Children and Their Parents After Rapid Ascent to 3500 m (Putre, Chile). Wilderness & Environmental Medicine,19, 4, 287-292.
6. Tissot, v. P. M. C., Leadbetter III, G., Keyes, L. E., Maakestad, K. M., Olsen, S., & Hackett, P. H. (2008). Prophylactic low-dose acetazolamide reduces the incidence and severity of acute mountain sickness. High Altitude Medice & Biology, 9, 4, 289-293.
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