Airway resistance is dictated by the diameter of the airways and by the density of the inspired gas. Therefore, when nitrogen (or air) is replaced by helium, airway resistance is reduced due to the lower density of the inspired gas.

Medical helium/oxygen mixtures may assist the flow of oxygen in the airway for patients with severely obstructed airways in conditions such as upper airway obstruction, asthma, chronic obstructive pulmonary disease (COPD), bronchiolitis and croup. Patients with these conditions may suffer a range of symptoms including breathlessness, below-normal oxygen content in the arterial blood and eventually a weakening of the respiratory muscles due to exhaustion. Medical helium/oxygen mixtures may reduce these effects, making it easier for the patient to breathe, and as it will reduce work of breathing, help to prevent respiratory failure.

HELIOX can be used for nebulisation therapy as the driving gas for generation of aerosol and as the carrier gas for inhalation of aerosol.