• Christiane Vorwerk and Tim Coats.
• Department of Emergency Medicine, Leicester Royal Infirmary, Infirmary Square, Leicester, UK, LE1 5WW.
• Cochrane Db Syst Rev. 2010 Jan 1 (2): CD006822.

BackgroundCroup, a common acute clinical syndrome in children up to the age of six, is thought to be triggered by a viral infection, and is characterised by a varying degree of respiratory distress due to upper airway inflammation and oedema of the subglottic mucosa. Corticosteroids, now part of the standard treatment for croup, improve symptoms but it takes time for their full effect to be achieved. Meanwhile, the child remains at risk of deterioration and developing respiratory failure necessitating emergency intubation and ventilation. Helium-oxygen (heliox) inhalation has been successful in the treatment of upper airway obstruction. Anecdotal evidence suggests that heliox relieves respiratory distress in children, but it remains unclear whether there is robust evidence to support the implementation of heliox for croup into clinical practice.ObjectivesTo examine the effect of heliox on relieving symptoms and distress, determined by a croup score (a tool for measuring the severity of croup) or clinical assessment variables, through comparisons with placebo or active treatment(s) in children with croup.Search StrategyWe searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, issue 2) which contains the Acute Respiratory Infections (ARI) Group's Specialised Register; MEDLINE (1950 to June week 3 2009); EMBASE (1974 to 2009 week 25) and CINAHL (1982 to June 2009).Selection CriteriaRandomised controlled trials (RCTs) and quasi-RCTs comparing the effect of helium-oxygen mixtures with placebo or any active treatment in children with croup.Data Collection And AnalysisBoth authors independently identified and assessed citations for relevance. We assessed included trials for risk of bias using allocation concealment, blinding of intervention, completeness of outcome data, selective outcome reporting and other potential source of bias. We calculated mean differences for continuous data. We presented data not suitable for statistical analysis as descriptive data.Main ResultsTwo eligible RCTs were included (22 intervention, 22 controls). Neither trial compared heliox inhalation with placebo. One study compared heliox with 30% humidified oxygen whilst the other compared it to 100% oxygen with additional racaemic epinephrine nebulisation. There was no significant difference in change of croup score between intervention and control groups.Authors' ConclusionsAt present there is a lack of evidence to establish the effect of heliox inhalation in the treatment of croup in children. A methodologically well-designed and adequately powered RCT is needed to assess whether there is a role for heliox therapy in the management of children with croup.

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