Heliox, a mixture of helium and oxygen, was used by Barach in New York for the first time in the treatment of asthma and upper airway obstruction after its introduction to deep sea diving. Since then it has been used not only as a rescue medication in emergency situations for spontaneously breathing patients with airway obstruction but also as the driving gas for mechanical ventilators. The increasing interest in heliox is indicated by the rising number of publications in recent years (Figure 13.1). In this chapter, theoretical considerations, the application of heliox in non-intubated (e.g. with upper and lower airway obstruction) as well as in ventilated patients will be outlined, followed by a brief overview of potential risks, costs and future applications.

Theoretical considerations

In a medical setting, the inhaled gas mixture usually consists of air with a variable oxygen content up to a fractional inspired oxygen concentration (FIO2) of 1.0 and in some cases with the addition of nitric oxide (NO) or other medications in small amounts. Heliox is a commercially prepared mixture of helium and oxygen. Helium is a non-toxic, tasteless and odourless gas with a low solubility in fatty tissue. It can be used up to a fractional inspired helium concentration (FiHe) of 0.79 with an FiO2 of 0.21.