Hypobaric chamber

One or more subjects (usually, pilots or crew members, though anyone interested in the effects of high altitude can usually arrange a visit) are placed in the chamber.

With masks in place, the atmospheric pressure inside the chamber is then reduced to simulate altitudes of up to tens of thousands of feet.

Subjects may also ensure that they are able to do tasks such as clear their nose and sinuses easily, as pain from such problems can be a major distraction in an emergency such as rapid decompression.

Usually new aircrew will undergo a familiarization profile, where the chamber ascends to an altitude of 10,000 ft. During the ascent they are instructed on the proper procedure to clear the ears.

Since the human body adapts to extended mild hypoxia by increasing the quantity of red cells in the blood and this raises aerobic performance, athletes sleep in them as part of their training regimen.

This has roughly the same effect as training in high altitudes, but the use of hypobaric chambers plays into the controversial issue of enhanced athletic performance.

Mika LaVaque-Manty asks in his book, "Are hypobaric chambers, which simulate high-altitude conditions, a natural way to improve your body?