Heliox

CLASS

Heliox is a mixture of helium and oxygen
Helium is an inert gas with a significantly lower density (and specific gravity) than room air (1.42g/L for O2 vs 0.17g/L for He)

MECHANISM OF ACTION

by substituting helium for nitrogen -> reduction in density of the gas -> reduction in Reynolds number -> more laminar flow
-> reduces airflow resistance, work of breathing and dynamic hyperinflation

PHARMACEUTICS

gas administered via a mask with a reservoir bag or via endotracheal tube
supplied at 137 bar as either Heliox (79% He, 21% O₂) in white cylinders with white/brown shoulders or as 100% helium in brown cylinders (size C, D, E and G cylinders (410, 1400, 3500 and 7300L nominal capacity respectively)
can be used as the driving gas for nebulisation

DOSE

helium:oxygen mix of 80:20 or 70:30, which are 1.8 and 1.6 times less dense than pure oxygen, respectively.

INDICATIONS

lower airways disorders – e.g. severe asthma, severe COPD, bronchiolitis, bronchiectasis, lung cancer
extrathoracic or tracheal obstruction – e.g. croup, epiglottitis, foreign body, tumour, tracheal stenosis, tracheomalacia
FRC assessment (helium dilution technique)
decompression sickness

ADVERSE EFFECTS

expensive (10x the cost of oxygen)
lack of availability
can’t use on those with a high FiO2 (>0.4)
ventilators require recalibration for FiO2 and TV – interferes with valve function
requires heated humidified circuits as helium conducts heat 6x faster than nitrogen
alteration of vocal pitch
may reduce the efficiency of coughing

PHARMACOKINETICS

EVIDENCE

anecdotal evidence of avoiding need for intubation in upper airway obstruction
little evidence of benefit in lower airways obstructive lung disease – the common theme is that heliox is a temporising measure but is not a treatment

Journal articles and textbooks

Fink JB. Opportunities and risks of using heliox in your clinical practice. Respir Care. 2006 Jun;51(6):651-60. PMID: 16723042.
Gentile MA. Inhaled medical gases: more to breathe than oxygen. Respir Care. 2011 Sep;56(9):1341-57; discussion 1357-9. PMID: 21944684.
Hess DR, Fink JB, Venkataraman ST, Kim IK, Myers TR, Tano BD. The history and physics of heliox. Respir Care. 2006 Jun;51(6):608-12. PMID: 16723037
Kim IK, Saville AL, Sikes KL, Corcoran TE. Heliox-driven albuterol nebulization for asthma exacerbations: an overview. Respir Care. 2006 Jun;51(6):613-8. PMID: 16723038.
McGarvey JM, Pollack CV. Heliox in airway management. Emerg Med Clin North Am. 2008 Nov;26(4):905-20, viii. Review. PMID: 19059090.
Reuben AD, Harris AR. Heliox for asthma in the emergency department: a review of the literature. Emerg Med J. 2004 Mar;21(2):131-5. PMC1726290.
Vorwerk C, Coats T. Heliox for croup in children. Cochrane Database Syst Rev. 2010 Feb 17;(2):CD006822. PMID: 20166089.
Wigmore T, Stachowski E. A review of the use of heliox in the critically ill. Crit Care Resusc. 2006 Mar;8(1):64-72. PMID: 16536724.