What is hypoxia
Hypoxia is caused by the progressive reduction of barometric pressure and, consequently, by the reduction of oxygen pressure (oxygen partial pressure always corresponds to 21% of barometric pressure) while low temperatures are due to a progressive decrease (around 1° C every 150 meters) and to wind chill factors.
To have an idea of the severe oxygen reduction which occurs at altitude, it might be useful to consider that the normal values of oxygen pressure in arterial blood (Pa02) at sea level are around >75-88 mmHg, while respiratory failure is referred to at values lower than 60mmHg. Research shows that subjects normally living at sea level who are exposed to high altitude have values of 63mmHg at 2600 m and around 50mmHg at 3400m. It is then obvious that at 3000m a healthy individual finds himself in conditions which would normally be defined "respiratory failure".
To have an idea of the severe oxygen reduction which occurs at altitude, it might be useful to consider that the normal values of oxygen pressure in arterial blood (Pa02) at sea level are around >75-88 mmHg, while respiratory failure is referred to at values lower than 60mmHg. Research shows that subjects normally living at sea level who are exposed to high altitude have values of 63mmHg at 2600 m and around 50mmHg at 3400m. It is then obvious that at 3000m a healthy individual finds himself in conditions which would normally be defined "respiratory failure".