Heliox is a gas mixture consisting of, in this example, 21% oxygen and 79% helium (although other ratios exist). Remember that atmospheric air contains ~21% oxygen and ~78% nitrogen. Although helium and air share a similar viscosity, substituting helium for nitrogen reduces the gas mixture’s overall density.
Our large, conducting airways (trachea, mainstem bronchi, etc.) typically demonstrate turbulent flow and confer most of the airway resistance. Under turbulent conditions, density is a significant determinant of the overall resistance to flow.
Although Heliox is traditionally used more in the pediatric population (smaller airways), as an adult cardiovascular intensivist, I’ve occasionally used it in the CVICU for upper airway obstruction with resulting stridor. With such turbulence, the lower density of Heliox favors delivery of oxygen to the distal airways. Other described situations where Heliox is used in adults include asthma, COPD, and dyspnea following extubation.
Have you seen Heliox used? Drop me a comment below with your experiences and questions!
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