title: Heliox-driven β2-agonists nebulization for children and adults with acute asthma: a systematic review with meta-analysis.
abstract: BACKGROUND
  The effect of heliox as a nebulizer β2-agonist driving gas in acute asthma remains controversial.
  
  
  OBJECTIVE
  To perform a systematic review with a meta-analysis of randomized trials designed to evaluate the efficacy of heliox versus oxygen in driving β2-agonist nebulization in patients with acute asthma.
  
  
  METHODS
  A search was conducted of all randomized controlled trials published before August 2013. Primary outcomes were change in spirometric measurements and severity composite score (pediatric studies); secondary outcomes were hospitalizations and serious adverse effects.
  
  
  RESULTS
  Eleven trials from 10 studies (697 participants) met the inclusion criteria (7 included adults and 3 included children). The mean duration of heliox therapy was 120 minutes and the most common helium-oxygen mixture used was 70:30. Patients receiving heliox presented a statistically significant difference for mean percentage of change in peak expiratory flow (17.2%; 95% confidence interval 5.2-29.2, P = .005). Post hoc subgroup analysis showed that patients with severe and very severe asthma showed a significant improvement in peak expiratory flow compared with those with mild to moderate acute asthma. Heliox-driven nebulization also produced significant decreases in the risk of hospitalizations (odds ratio 0.49, 95% confidence interval 0.31-0.79, P = .003) and severity of exacerbations (pediatric studies; standard mean difference -0.74, 95%% confidence interval -1.45 to -0.03, P = .04). There were no group differences for serious adverse effects.
  
  
  CONCLUSIONS
  This review suggests that heliox benefits in airflow limitation and hospital admissions could be considered clinically significant. Data support the use of heliox as a nebulizing β2-agonist driving gas in the routine care of patients with acute asthma.
authors: Departamento de Emergencia, Hospital Central de las Fuerzas Armadas, Montevideo, Uruguay. Electronic address: gustavo.javier.rodrigo@gmail.com.
authors: Gustavo J
authors: GJ
authors: Rodrigo
authors: Departments of Pediatrics and Family Medicine, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors: Jose A
authors: JA
authors: Castro-Rodriguez
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D058665:Adrenergic beta-1 Receptor Agonists / Q000008:administration & dosage*; D000328:Adult; D001249:Asthma / Q000188:drug therapy*; D002648:Child; D002675:Child, Preschool; D006371:Helium / Q000008:administration & dosage*; D006801:Humans; D000860:Hypoxia; D009330:Nebulizers and Vaporizers; D010100:Oxygen / Q000008:administration & dosage*; D016896:Treatment Outcome
chemical_list: D058665:Adrenergic beta-1 Receptor Agonists; D006371:Helium; C038949:heliox; D010100:Oxygen