Altitude sickness

Altitude sickness is a general term encompassing several disorders that occur at high altitudes. High altitude is greater than 8,000 feet; medium altitude is between 5,000 and 8,000 feet; and extreme altitude is greater than 19,000 feet. About 20% of people ascending above 9,000 feet in one day, for example,  will develop altitude sickness. 

Altitude sickness occurs because the air contains less oxygen at higher altitudes. Therefore, there is a lower amount of oxygen for an individual to breathe. In effect, altitude sickness is a form of hypoxia. 

Whether one gets altitude sickness or not is often a question of how well adapted your body is to those altitudes.  There are groups of people who have lived at high altitudes for generations, and their bodies have become adjusted to living at such altitudes. However, people who are accustomed to much lower altitudes are at risk of developing altitude sickness.  Individuals with pre-existing medical conditions--even a minor respiratory infection--may become sick at even moderate altitudes.

Most healthy individuals, however,  suffer altitude sickness at very high altitudes.

There are various classifications of altitude sickness 

• Acute mountain sickness (AMS) is a mild form of altitude sickness that results from ascent to altitudes higher than 8,000 feet. Some individuals are affected at even lower altitudes. AMS tends to be most severe on the second or third day after reaching the high altitude, and it usually lessens after three to five days if the person remains at the same altitude. Symptoms include dizziness, headache, shortness of breath, nausea, vomiting, loss of appetite, and insomnia. 
• High-altitude pulmonary edema (HAPE) is a life-threatening condition that afflicts a small percentage of those who suffer from AMS. In this condition, fluid leaks from blood vessels into the lung tissue. As this fluid accumulates within the lung tissue (pulmonary edema), the individual begins to become more and more short of breath.
  Typically, the individual with HAPE ascends quickly to a high altitude and almost immediately develops shortness of breath, rapid heart rate, cough productive of a large amount of sometimes bloody sputum, and rapid breathing. Without medical assistance, the patient goes into a coma and dies within hours. 
• High-altitude cerebral edema (HACE), is the rarest and most severe form of altitude sickness. The symptoms often begin with those of AMS, but neurological symptoms such as an altered level of consciousness, speech abnormalities, severe headache, loss of coordination, hallucinations, and even seizures. Without medical intervention, death results. 

“Diagnosing altitude sickness relies on the individual's symptoms during travel to higher altitudes. Mild AMS requires no treatment other than an aspirin or ibuprofen for headache, and avoidance of further ascent. Narcotics should be avoided because they may blunt the respiratory response. Oxygen may also be used to alleviate symptoms of mild AMS. 

As for HAPE and HACE, the most important course of action is to descend to a lower altitude as soon as possible. Even a 1,000-2,000-foot descent can improve symptoms. If descent is not possible, oxygen therapy should be started. ”