A Cochrane review [Abstract] 1 included 10 studies with a total of 529 subjects with acute asthma (6 studies with adults only, n=408; 1 study with both adults and children, n=39; 3 studies with children only, n=82). Three were assessed as high quality. Pulmonary function tests were recorded during heliox administration (15 to 60 min). Pooling of the eight trials contributing data to the review showed no significant group differences (standardised mean differences [SMD] -0.28; 95% confidence interval [CI] -0.56 to 0.01). There was significant heterogeneity among the studies. Heliox use did improve pulmonary function only in the subgroup of patients with the most severe baseline pulmonary function impairment; however, this conclusion is based on a small number of studies. There were no significant differences between groups when adults versus children, and high versus low heliox dose studies were compared. At the end of treatment, participants treated with heliox showed no significant different risk of admission to hospital (RR 0.83, 95%CI 0.66 to 1.08).
Comment: The quality of evidence is downgraded by imprecise results (limited study size for each comparison), by inconsistency (variability in results across studies) and by potential reporting bias.
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