Heliox is a mixture of oxygen and helium resulting in a gas less dense than air. In asthma, airway resistance causes turbulent airflow which increases the work of breathing. Heliox reduces airway resistance by increasing laminar airflow.
Benefits:
Better lung mechanics
Improved nebulizer delivery
Few known side-effects/complications
Drawbacks:
Expensive
Contraindicated in hypoxemic patients.
Paucity of large prospective randomized trials.
References
McGarvey JM, Pollack CV. Heliox in Airway Management. Emerg Med Clin North Am. 2008 Nov;26(4):905-20, viii.
