Heliox for nonintubated acute asthma patients.

BACKGROUND: 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 severe acute asthma remains unclear. OBJECTIVES: 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. SEARCH STRATEGY: Randomised controlled trials were identified from the Cochrane Airways Group Specialised Register. In addition, we contacted primary authors and experts and searched reference lists of articles. Searches are current to August 2005. SELECTION CRITERIA: 1) randomised, 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; and 3) compared treatment with inhaled heliox to placebo (oxygen or air). DATA COLLECTION AND ANALYSIS: Two review authors independently assessed the studies for inclusion and quality assessment; disagreement was resolved by a third review author and consensus. MAIN RESULTS: This review has been updated in 2006 to include four new trials giving atotal of ten trials involving 544 acute asthma patients. Seven studies involved adults and three studies dealt solely with children. Three were assessed as high quality (Jadad score > 3). Pulmonary function tests were recorded during heliox administration (15 to 60 min). Pooling of the eight trials contributing data to this review showed no significant group differences (standardised mean differences -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. Finally, 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, P = 0.17, I(2) = 0%). AUTHORS' CONCLUSIONS: The existing evidence does not provide support for the administration of helium-oxygen mixtures to all ED patients with acute asthma. At this time, heliox treatment does not have a role to play in the initial treatment of patients with acute asthma. Nevertheless, new evidence suggests certain beneficial effects in patients with more severe obstruction. Since these conclusions are based upon between-group comparisons and small studies, they should be interpreted with caution.

Prospective multicenter study of relapse after treatment for acute asthma among children presenting to the emergency department.

OBJECTIVE: Single-center studies have reported varying relapse rates after treatment of patients with acute asthma. We determined the relapse rate after emergency department (ED) treatment in a cohort of children. DESIGN: This was a prospective inception cohort study performed during 1997-1998. SETTING: The study was performed in 44 EDs including both general and pediatric centers. PATIENTS: Children (n = 1184) aged 2 to 17 years who had been admitted to EDs, with acute asthma restricted to 881 patients discharged from the ED. MAIN RESULTS: Two weeks after discharge, families were telephoned to determine relapse. Follow-up data were available for 762 (86%) of the children with a 10% incidence of relapse. On univariate analysis several factors were associated with relapse including current medications and markers of asthma severity. On multivariate analysis the factors associated with relapse were age (OR 1.4 per 5-year increase), use of second-line asthma medications (OR 3.7), exposure to cigarette smoke (OR 0.5), and ED visits within the past year (OR 1.2 per 5 ED visits). CONCLUSIONS: The incidence of relapse among children is lower than that observed among adults and varies with age. Other risk factors such as frequent ED visits are likely markers of chronic asthma severity. Further research should focus on ways to decrease the relapse rate among patients at high risk.