When people ascend to altitudes over 5000 feet, some will experience adverse symptoms. Where very few people will have symptoms at this altitude, at 8000 feet or above, as many as 30% or more people will experience the effects of altitude. Altitude illness covers a spectrum from mild headaches and tiredness (acute mountain sickness) to more severe conditions involving fluid in the lungs (high altitude pulmonary edema) and swelling of the brain (high altitude cerebral edema.) Most symptoms of high altitude will begin within a few hours of ascending however the more severe cases often do not become apparent until 2-3 days of experiencing the higher altitude.
*Please be aware of the seriousness of High Altitude when traveling:
Treatment
Prevention is the best cure! Slow ascent when climbing and taking sleeping breaks at lower altitudes is the common prevention in alpine climbers. For those arriving to a high altitude destination by jet airplane—that may be impossible. Oxygen given from a pure high flow source (not a ‘can” from a store) is the best way to prevent symptoms.
Although not completely understood, the illness from altitude is definitely due to a lack of oxygen. All of the changes in the lungs, brain, and the rest of the body all stem from a lack of oxygen and then the body’s response to that condition. By periodically using supplemental oxygen, one can often entirely prevent the symptoms from ever developing.
Over the counter, ibuprofen at 600 mg 3 times a day for the first day can also help prevent the symptoms of high altitude, although that is unlikely to prevent symptoms at altitudes that are higher (over 9000-10000 feet.) Also, sedatives (including alcohol), should be avoided the first 2 days as slowing the breathing or increasing snoring at night can greatly exacerbate altitude illness.