A hypo barometric environment is an area of terrestrial elevation in the lands topography such as a hill or a mountain. An area of land in considered high altitude when it is over 2438 metres or above sea level. There are currently over 40 million people who live, work and recreate' (McArdle, 2001) in areas such as the European Alps, Rocky Mountains and the Himalayas (Priory, 2001).
An un-acclimatised person in these areas can get hypoxia, which is the subnormal oxygen pressure. Hypoxia happens when there is an "Insufficient levels of oxygen in blood or tissue" (American Heritage Dictionary, 2002). This happens because the higher up an individual goes above sea level, the less pressure there is, which decreases the amount of Oxygen available. The time requirements of ascent depends on the individuals current elevation but a broad guideline requires 2 weeks for up to 2300 metres and each additional 610 metres requires an extra week.

If an individual gets hypoxia then the body has an inadequate supply of energy for the body's needs. This can be compensated by using the anaerobic glycolysis, but this has its disadvantages. "There is less ATP per gram of fuel than aerobic metabolism, it varies on the carbohydrate stores in the body and it also produces more lactic acid which may disturb the acid balance of the cells" (Armstrong, 2000).
As well as hypoxia, there are risks of other disorders that can affect an individual. These are acute mountain sickness (AMS), High- Altitude Pulmonary Edema (HAPE), High -altitude Cerebral Edema (HACE), High- altitude retinal haemorrhages' (HARH) and high- altitude flatulent expulsion (HAFE).
AMS occurs above 6500 metres and is more noticeable above 8000 metres. The symptoms of AMS are nausea, headache, insomnia, and fatigue, loss of appetite and shortness of breath. AMS is not very serious to begin with but can become severe altitude sickness. AMS can be prevented by a slow ascent, so the body can acclimatise gradually to the altitude level. It can also be prevented by being well hydrated, by eating a high carbohydrate diet, a low fat diet and by doing physical activity at a moderate intensity. If AMS occurs then the individual must descend at least 750 metres to about 2000 metres. If the individual stays at a high altitude the more dangerous, the AMS can become to their health and may need assisting in travelling. There is also a portable hyperbaric bag known as a Gamow bag, which simulates lower altitudes, which can provide

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