Helium-oxygen mixture for nonintubated acute asthma patients.

Abstract

Helium and oxygen mixtures (heliox), have been used sporadically in respiratory medicine for decades. Their use in acute respiratory emergencies such as asthma has been the subject of considerable debate. Despite the lapse of more than 60 years since it was first proposed, the role of heliox in treating patients with acute severe asthma is unclear. To determine the effect of the addition of heliox to standard medical care on the course of acute asthma, as measured by pulmonary function testing and clinical endpoints. Randomized controlled trials were identified from the Cochrane Airways Group Asthma Register which is a compilation of systematic searches of CINAHL, EMBASE, MEDLINE, and CENTRAL and hand searching of the 20 most productive respiratory care journals. In addition, primary authors and experts were contacted to identify eligible studies. References from included studies, known reviews and texts were also searched. Inclusion criteria were: 1) randomized, single or double blind, controlled trials; 2) children or adults with a clinical diagnosis of acute asthma seen in emergency departments or equivalent acute care settings; 3) compared treatment with inhaled heliox compared with a control (oxygen or air). Two reviewers independently assessed the studies for inclusion and quality assessment; disagreement was resolved by a third reviewer and consensus. Data from all included trials were combined using weighted mean differences (WMD), with 95% confidence intervals (95% CI) in a random effects model. Homogeneity of effect sizes were tested with the Dersimonian and Laird method with p<0.1 as the cut point for significance. Sensitivity analyses were performed on age (adults vs. children), different helium-oxygen mixtures and methodological quality. A total of 4 randomized controlled trials were selected for inclusion with a total of 288 acute asthma patients. Three studies involved adults and one study dealt solely with children. Two were of low quality. The main outcome variable was spirometric measurements (PFT % predicted) in all trials. Pooling the four trials showed no significant differences (WMD = -1.61; 95% CI: -6.64 to 3.41). All pulmonary function tests were recorded during heliox administration (15 to 60 min). There was no evidence of heterogeneity between studies. There were no significant differences between groups when adults vs. children, high vs. low quality, and high vs. low heliox dose studies were compared. The findings were the with a fixed effects model. The existing evidence does not provide support for the administration of helium-oxygen mixtures to patients presenting to the emergency department with moderate to severe acute asthma. Heliox treatment does not have a role in the initial treatment of patients with acute asthma. These conclusions are based upon between-group comparisons and small studies. Additional research in this setting may be warranted.