Altitude sickness

Altitude sickness
Other names	High-altitude sickness, altitude illness, hypobaropathy, altitude bends, soroche
Altitude sickness warning – Indian Army
Specialty	Emergency medicine
Symptoms	Headache, vomiting, feeling tired, trouble sleeping, dizziness
Complications	High-altitude pulmonary edema (HAPE), high-altitude cerebral edema (HACE)
Usual onset	Within 24 hours
Types	Acute mountain sickness, high-altitude pulmonary edema, high-altitude cerebral edema, chronic mountain sickness
Causes	Low amounts of oxygen at high elevation
Risk factors	Prior episode, high degree of activity, rapid increase in elevation
Diagnostic method	Based on symptoms
Differential diagnosis	Exhaustion, viral infection, hangover, dehydration, carbon monoxide poisoning
Prevention	Gradual ascent
Treatment	Descent to lower altitude, sufficient fluids
Medication	Ibuprofen, acetazolamide, dexamethasone, oxygen therapy
Frequency	20% at 2,500 metres (8,000 ft) 40% at 3,000 metres (10,000 ft)

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

Causes

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

Altitude

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.

Hypoxia

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

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.

Prevention

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.

Other websites

Altitude sickness travel guide from Wikivoyage

Classification	D ICD-10: T70.2 ICD-9-CM: E902.0 MeSH: D000532 DiseasesDB: 8375
External resources	MedlinePlus: 000133 eMedicine: med/3225

• "Travel at High Altitude: a free booklet about how to keep healthy at altitude. Available in many languages". Archived from the original on 2012-07-11.
• Merck Manual entry on altitude sickness
• Altitude Illness Clinical Guide for Physicians Archived 2006-10-18 at the Wayback Machine