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Heliox in croup

Three Part Question

In [children with croup] is [heliox] effective in [relieving symptoms and reducing croup score]?

Clinical Scenario

A 2 1/2 year old girl is brought to the Emergency Department in respiratory distress. Her father tells you that he noticed a barking cough throughout the night and that her breathing was becoming noisier. On examination the child is alert and tachypnoeic, has got a tracheal tug and recession, an audible inspiratory and expiratory stridor, SpO2 > 92%, Temp 38.3C. You decide that you are going to treat with Dexamethasone and wonder whether heliox might be effective as a 'bridging therapy' in relieving symptoms and improving croup score.

Search Strategy

PubMed 1966-10/05, Medline 1950-wk 3 Feb 2008 using OVID interface, DARE, Cochrane Library Issue 1, 2008
[(croup OR OR larygotracheitis OR OR laryngotracheobronchitis OR AND (heliox OR OR helium OR OR helium-oxygen OR OR helium-oxygen mixture OR helium-oxygen OR HeO2 OR].

Search Outcome

Altogether 50 papers were found. Of which 5 addressed the question, two were considered to be original research of acceptable quality (RCT).

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
Weber et al,
29 patients (6 months – 3 years) with croup score at or more than 5 (modified Taussig) , Heliox 30/70 vs. epinephrineProspective randomised double blind, controlled trial (Class I)Reduction in croup score at 30min (primary)

Change in SpO2, RR, HR (secondary)
Improvement in CS but no significant difference between the groups (p=0.13)Small number of patients Compared Heliox (inert gas) with biologically active epinephrine
Terregino et al,
15 patients (6 months – 4 years) with mild – moderate croup, Heliox 30/70 vs. humidified oxygenProspective randomised double blind, controlled trial (Class I)Reduction in croup score at 20minSignificant improvement in CS but no significant difference (p=0.75) between the groupsSmall study Patients with severe croup excluded
Nelson et al,
14 patients (3-21 months) with croup refractory to epinephrine, referred for possible intubationRetrospective, uncontrolled, non blinded (Class III)Improvement of symptoms (restful state, sleep)Heliox - a valuable adjunct for refractory croup.Small study No control
Duncan et al,
7 patients (newborn – 3 years) with severe airway obstruction due to croupRetrospective , uncontrolled, non blinded (Class III)Reduction in croup score and gas exchangeImprovement in CS (p<0.001) and gas exchange (p equal to or less than 0.10)Very small study Poor patient selection criteria (included patients with congenital heart disease, pneumonia)
Iglesias et al
65 critically ill children (12 days to 8 years) with upper and/or lower airway respiratory insufficiency. All treated with Heliox (facial mask, nasal prongs or non-invasive ventilation).CohortOverall improvement54 patients (83.1%)Article in Spanish, abstract only available. Only 7 of the patients had croup. Overall 29.8% needed non-invasive ventilation after Heliox and 26.5% needed intubation after Heliox.
Clinical scoreImproved from 8.7 to 5.5
Respiratory rateImproved from 51.4 to 38.8
Heart rateImproved from 161.6 to 145.6
Oxygen saturationNo improvement
Blood gas analysisNo improvement


Croup, or laryngotracheobronchitis, is a common cause for attendance at the Emergency Department. There are currently only two studies (Weber et al and Terregino et al) that address the (three-part) question, both of these studies show an improvement in symptoms and a reduction in croup score with Heliox, however insufficient number of patients have been studied to show a clinically significant difference in outcome compared with controls.

Editor Comment

A proposal for a Cochrane Review has been submitted.

Clinical Bottom Line

At present there is insufficient evidence to tell whether or not heliox should be used in the Emergency Department to treat children with croup


  1. Weber JE, Chudnofsky CR, Younger JG, Larkin GL, Boczar M, Wilkerson MD, Zuriekat GY,Nolan B, Eicke DM. A randomized comparison of helium-oxygen mixture (Heliox) and racemic epinephrine for the treatment of moderate to severe croup. Pediatrics. 2001 Jun;107(6):E96.
  2. Terregino CA, Nairn SJ, Chansky ME, Kass JE. The effect of heliox on croup: a pilot study. Acad Emerg Med. 1998 Nov;5(11):1130-3.
  3. Nelson DS, McClellan L. Helium-oxygen mixtures as adjunctive support for refractory viral croup. Ohio State Med J. 1982 Oct;78(10):729-30.
  4. Duncan PG. Efficacy of helium-oxygen mixtures in the management of severe viral and post-intubation croup. Can Anaesth Soc J. 1979 May;26(3):206-12.
  5. Iglesias FC, Lopez-Herce CJ, Mencia BS, Santiago LMJ, Moral TR, Carrillo AA. Efficacy of heliox therapy in respiratory insufficiency in infants and chidren [Spanish] Anales de Pediatria 2007 Mar; 66(3):240-247.