Altitude sickness, the mildest form being acute mountain sickness (AMS), is the negative health effect of high altitude, caused by rapid exposure to low amounts of oxygen at high elevation. People can respond to high altitude in different ways. Symptoms may include headaches, vomiting, tiredness, confusion, trouble sleeping, and dizziness. Acute mountain sickness can progress to high altitude pulmonary edema (HAPE) with associated shortness of breath or high altitude cerebral edema (HACE) with associated confusion. Chronic mountain sickness may occur after long term exposure to high altitude.
Headaches are the primary symptom used to diagnose altitude sickness, although a headache is also a symptom of dehydration. A headache occurring at an altitude above 2,400 meters (7,900 ft) – a pressure of 76 kilopascals (0.75 atm) – combined with any one or more of the following symptoms, may indicate altitude sickness:
|Gastrointestinal||Loss of appetite, nausea, or vomiting, excessive flatulation|
|Nervous||Fatigue or weakness, headache with or without dizziness or lightheadedness, insomnia, “pins and needles” sensation|
|Locomotory||Peripheral edema (swelling of hands, feet, and face)|
|Respiratory||Nose bleeding, shortness of breath upon exertion|
|Cardiovascular||Persistent rapid pulse|