Hyperbaric Anaesthesia
Under hyperbaric conditions (pressures above normal atmospheric pressure), other gases such as nitrogen, and noble gases such as argon, krypton, and xenon become anaesthetics. When inhaled at high partial pressures (more than about 4 bar, encountered at depths below about 30 metres in scuba diving), nitrogen begins to act as an anaesthetic agent, causing nitrogen narcosis. However, the minimum alveolar concentration (MAC) for nitrogen is not achieved until pressures of about 20 to 30 atm (bar) are attained. Argon is slightly more than twice as anaesthetic as nitrogen per unit of partial pressure (see argox). Xenon however is a usable anaesthetic at 80% concentration and normal atmospheric pressure.
Read more about this topic: Inhalational Anaesthetic