Hyperbaric helium

Sturm F, Hurwitz S, Kelly R. Growth of the extreme thermophile Sulfolobus acidocaldarius in a hyperbaric helium bioreactor. Biotechnol Bioeng 1987 29 1066-1074. 

The low breathing resistance of helium—oxygen mixtures is of therapeutic advantage for patients suffering from asthma and other obstmctive respitatory difficulties. The mixtures have also been used for hyperbaric therapy. 

CNS problems are rare, and toxicity occurs only under hyperbaric conditions >200 kPa (2 atm). Symptoms include seizures and visual changes, which resolve when oxygen tension is returned to normal. These problems are a further reason to replace oxygen with helium under hyperbaric conditions see below). 

Helium (He) is an inert gas whose low density, low solubility, and high thermal conductivity provide the basis for its medical and diagnostic uses the gas is supplied in brown cyhnders. Helium can be mixed with oxygen and administered by mask or tracheal tube. Under hyperbaric conditions, it can be substituted for the bulk of other gases, resulting in a mixture of much lower density that is easier to breathe. 

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