Voluntary hyperventilation into a simple mixing chamber relieves high altitude hypoxia.

Involuntary hyperventilation is a critical factor in acclimatization to a high altitude. Unacclimatized subjects do poorly when acutely exposed to high altitude. This may not be due to hypocapnia itself, but rather an associated symptom which inhibits hypoxic respiratory stimulation. In an unacclimatized individual, voluntary hyperventilation may greatly relieve hypoxia and may be an alternative to involuntary hyperventilation. However, subjects voluntarily hyperventilating may overventilate and become disabled from severe hypocapnia. A simple mixing chamber is described which makes voluntary hyperventilation easier, safer, and possibly more effective. A subject breathing into a mixing chamber was able to maintain an SaO2 of 90% at 20,000 ft.