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Use of helium-oxygen mixtures in the treatment of acute asthma: a systematic review.

STUDY OBJECTIVE
To determine the effect of the addition of heliox to standard medical care on the course of acute asthma.


DESIGN
Systematic review of randomized and nonrandomized prospective, controlled trials of children and adults that compared heliox to placebo when used in conjunction with other standard acute treatments.


MAIN OUTCOME MEASURES
Pulmonary function tests, hospital admissions, physiologic measures, side effects, and clinical outcomes.


RESULTS
Seven trials were selected for inclusion, with a total of 392 patients with acute asthma. Six studies involved adults, and one study dealt solely with children. The main outcome variable was spirometric measurements (peak expiratory flow or FEV(1)) in six trials. Two studies evaluated the effect of heliox on airways resistance. No significant differences were demonstrated between heliox or oxygen/air groups (standardized mean difference [SMD], - 0.20; 95% confidence interval [CI], - 0.91 to 0.51; p = 0.6). However, the four studies that used heliox to deliver nebulized therapy showed a nonsignificant increase in pulmonary function (SMD, - 0.21; 95% CI, - 0.43 to 0.01; p = 0.06). In two studies of the same subgroup, heliox mixtures produced a significantly greater increase of heart rate than oxygen/air (weighted mean difference, 9.0; 95% CI, 1.27 to 16.8; p = 0.02). However, the four studies that used heliox to deliver nebulized therapy reported a nonsignificant difference in hospital admissions (odds ratio, 1.07; 95% CI, 0.46 to 2.48; p = 0.9). Overall, heliox appears to be safe and well tolerated.


CONCLUSIONS
The existing evidence does not provide support for the administration of helium-oxygen mixtures to emergency department patients with moderate-to-severe acute asthma. However, these conclusions are based on between-group comparisons and small studies, and these results should be interpreted with caution.