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

• near instantaneous onset an offset
• eliminated within a few breaths

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

References and Links

Journal articles and textbooks

• Fink JB. Opportunities and risks of using heliox in your clinical practice. Respir Care. 2006 Jun;51(6):651-60. Review. PubMed PMID: 16723042. [Free fulltext]
• Gentile MA. Inhaled medical gases: more to breathe than oxygen. Respir Care. 2011 Sep;56(9):1341-57; discussion 1357-9. Review. PubMed PMID: 21944684. [free fulltext]
• 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. Review. PubMed PMID: 16723037. [free fulltext]
• 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. Review. PubMed PMID: 16723038. [free fulltext]
• 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. Review. PubMed PMID: 14988333; PubMed Central PMCID: PMC1726290.
• Vorwerk C, Coats T. Heliox for croup in children. Cochrane Database Syst Rev. 2010 Feb 17;(2):CD006822. doi: 10.1002/14651858.CD006822.pub2. Review. Update in: Cochrane Database Syst Rev. 2012;10:CD006822. PubMed 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. Review. PubMed PMID: 16536724. [free fulltext]