Heliox is the term used to describe mixtures of helium and oxygen. Mixtures containing helium USP are often used for the treatment of fixed partial upper obstruction or increased airway resistance, helping patients breathe easier. When combined with oxygen, helium reduces the density of the breathable mix. A 70/30 helium-oxygen mix is 2.3 times less dense than air and an 80/20 mixture is 3 times less.