Altitude sickness

acute negative health effects from high altitude

Altitude sickness is the harmful effect of high altitude. The mildest form is known as acute mountain sickness (AMS)

Altitude sickness
Other namesHigh-altitude sickness,[1] altitude illness,[1] hypobaropathy, altitude bends, soroche
Sign displays "Caution! You are at 17586 ft (5360 m)"
Altitude sickness warning – Indian Army
Medical specialtyEmergency medicine
SymptomsHeadache, vomiting, feeling tired, trouble sleeping, dizziness[1]
ComplicationsHigh-altitude pulmonary edema (HAPE),
high-altitude cerebral edema (HACE)[1]
Usual onsetWithin 24 hours[1]
TypesAcute mountain sickness, high-altitude pulmonary edema, high-altitude cerebral edema, chronic mountain sickness[2]
CausesLow amounts of oxygen at high elevation[1][2]
Risk factorsPrior episode, high degree of activity, rapid increase in elevation[2]
Diagnostic methodBased on symptoms[2]
Differential diagnosisExhaustion, viral infection, hangover, dehydration, carbon monoxide poisoning[1]
PreventionGradual ascent[1]
TreatmentDescent to lower altitude, sufficient fluids[1][2]
MedicationIbuprofen, acetazolamide, dexamethasone, oxygen therapy[2]
Frequency20% at 2,500 metres (8,000 ft)
40% at 3,000 metres (10,000 ft)



It is caused by rapid exposure to low amounts of oxygen at high elevation.



The severity of the disorder is related to the speed of ascent and the altitude reached. These symptoms disappear when going to lower altitudes. It occurs from 2,500 meters in altitude, up to the so-called "death zone" at 7,500 meters in altitude.



The main cause is hypoxia (lack of oxygen in the body). Atmospheric pressure decreases with height, which affects the bio-availability of oxygen, since the pulmonary alveoli are not capable of transporting the same amount of oxygen to the blood as in a situation of higher pressure. Although it is known that hypoxia is the cause of this problem, the exact mechanism by which it causes it is still unknown.

The amount of oxygen available to sustain mental and psychological attention decreases as altitude increases. The availability of oxygen and nitrogen, as well as their density, decrease with increasing altitude.



Dehydration due to accelerated loss of water vapor due to altitude can lead to symptoms of altitude sickness. The speed with which one ascends, the initial height, physical activity, as well as individual susceptibility are factors that contribute to this discomfort.



Altitude sickness can be prevented by climbing slowly. In most cases, symptoms are temporary and usually reduce as altitude acclimatization occurs. However, in extreme cases, altitude sickness can be fatal.


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Ferri, Fred F. (2016). Ferri's Clinical Advisor 2017 E-Book: 5 Books in 1. Elsevier Health Sciences. p. 590. ISBN 9780323448383.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 "Altitude Diseases - Injuries; Poisoning". Merck Manuals Professional Edition. May 2018. Retrieved 3 August 2018.

Other websites


  Altitude sickness travel guide from Wikivoyage

External resources