Helium is an inert gas which is used to reduce the specific gravity of inhaled gas mixtures. It is typically provided as a 0.79/0.21 Helium-Oxygen (Heliox) mixture (though other dilutions exist).
|Specific Gravity (as compared to air)||0.18||0.34||1.09|
Reduced specific gravity results in a proportional reduction in Reynolds Number, improving laminar flow within the airways.
|Uses||Obstructive lung disease, deep water diving|
|Presentation||Clear, colourless solution|
|Route of Administration||Inhaled|
|Dosing||Typically as Heliox: 79% He/21% O2|
|Absorption||Diffusion across the alveolar capillary membrane in proportion to membrane area and partial pressure gradient, and inversely proportional to membrane thickness|
|Distribution||Distributes proportionally to solubility and tissue partial pressures|
|Elimination||Respiratory exhalation along a pressure gradient|
|Resp||Significantly decreases the specific gravity of inhaled gas mixtures|
|Toxic Effects||High Pressure Neurologic Syndrome at >16 atm|
- RAH Advanced Diving Medicine Course Notes: Chapter 6 Oxygen and Carbon Dioxide Toxicity