PT - JOURNAL ARTICLE AU - Dean R Hess AU - James B Fink AU - Shekhar T Venkataraman AU - IN K Kim AU - Timothy R Myers AU - Benoit D Tano TI - The History and Physics of Heliox DP - 2006 Jun 01 TA - Respiratory Care PG - 608--612 VI - 51 IP - 6 4099 - http://rc.rcjournal.com/content/51/6/608.short 4100 - http://rc.rcjournal.com/content/51/6/608.full AB - Since the discovery of helium in 1868, it has found numerous applications in industry and medicine. Its low density makes helium potentially valuable in respiratory care applications, to reduce work of breathing, improve distribution of ventilation, reduce minute volume requirement, and improve aerosol delivery. This review includes a brief history of the use of heliox (a mixture of helium and oxygen) and addresses issues related to the physics of gas flow when heliox is used. Specifically covered are the Hagen-Poiseuille equation, laminar versus turbulent flow, the Reynolds number, orifice flow, Bernoulli's principle, Graham's law, wave speed, and thermal conductivity.