Chest
ReviewsHeliox vs Air-Oxygen Mixtures for the Treatment of Patients With Acute Asthmaa: A Systematic Overview
Section snippets
Physical Principles
Gas flow in the upper respiratory tract is largely laminar and follows the Hagen-Poiseuille law, which states that fluid flow rate (Q˙) through a straight tube is related inversely to gas viscosity (μ) and the length (L) of the tube, and is proportional to the pressure gradient (ΔP) and the fourth power of the radius (r): Q˙ = ΔPπr4/8 μL.1 Helium offers no advantage in laminar flow since gas density (ρ) does not appear in the above-mentioned equation, and gas viscosities are similar among
Search Strategy
MEDLINE (1966 to June 2002), EMBASE (1989 to June 2002), and the Cochrane Controlled Trials Registry were searched for relevant articles. Medical subject headings and text words used in the searches included asthma, helium, and heliox in English. Further articles were identified from the reference lists of relevant articles. Non-English language articles were not included, as they have not been found to add substantially to the body of evidence in reviews.20 During article selection, reviewers
Study Selection
Our search yielded 24 articles, of which 15 articles met the inclusion criteria.456789101112131415161718 There were minor discrepancies between the selections of articles by the authors, and they were resolved easily by consensus. The articles are presented in descending order in Table 1according to the strength of the level of evidence. There were eight RCTs,4567891011 one nonrandomized prospective controlled trial,12 one retrospective case-match controlled trial,13 four before-after case
Discussion
This article reviews the published literature on the use of heliox in patients with acute asthma. The studies included varied widely in design, types of patients recruited, and outcomes collected. Meta-analysis was used only in some of the RCTs,6789 based on the common outcomes of PEFR%, Spo2, and DI. For the majority, significant clinical and statistical heterogeneity (as tested by χ2) prevented pooling of outcomes. These meta-analyses demonstrated an advantage with the use of heliox when
Conclusion
Heliox improves certain respiratory (surrogate) parameters in some asthmatic patients during an attack, but not in others. Heliox may offer benefits in patients with acute asthma within the first hour of use, but its advantages become less apparent beyond 1 h, as most conventionally treated patients improve to similar levels, with or without it. The effect of heliox may be more pronounced in more severe cases. Since there is insufficient data, future studies should focus on whether heliox can
Acknowledgment
We thank LTC E. R. Carter, MD, of the Madigan Army Medical Center, Tacoma, WA, for providing us with the raw data from his trial6 and for his helpful comments, and J. S. Rose, MD, of the University of California Davis Medical Center, Sacramento, CA, for providing us with the preprint of his article.4 We also thank the reviewers and Dr. J. P. Kress of the University of Chicago for their insightful comments.
References (27)
- et al.
Use of heliox in critical upper airway obstruction: physical and physiologic considerations in choosing the proper helium-oxygen mix
Resuscitation
(2002) - et al.
The effect of heliox on nebulizer function using a β-agonist bronchodilator
Chest
(1999) - et al.
Prospective randomized trial of heliox-driven continuous nebulizers in the treatment of asthma in the emergency department
J Emerg Med
(2002) - et al.
Inhaled helium-oxygen revisited: effect of inhaled helium-oxygen during the treatment of status asthmaticus in children
J Pediatr
(1997) - et al.
The effect of heliox in acute severe asthma: a randomized controlled trial
Chest
(1999) - et al.
Inhaled heliox does not benefit ED patients with moderate to severe asthma [letter]
Am J Emerg Med
(2000) - et al.
Use of heliox-driven nebulizer therapy in the treatment of acute asthma
Ann Emerg Med
(1999) - et al.
Heliox does not improve FEV1in acute asthma patients
J Emerg Med
(1998) - et al.
Heliox therapy in acute severe asthma
Chest
(1995) - et al.
Helium-oxygen mixtures in intubated patients with status asthmaticus and respiratory acidosis
Chest
(1990)
Heliox inhalation in status asthmaticus and respiratory acidemia: a brief report
Heart Lung
Heliox for asthma: a trial balloon
Chest
What contributions do languages other than English make on the results of meta-analyses?
J Clin Epidemiol
Cited by (95)
Pediatric Respiratory Emergencies
2016, Emergency Medicine Clinics of North AmericaCitation Excerpt :A single intravenous dose of magnesium sulfate of 25 to 75 mg/kg not exceeding 2 g may be given over 2 hours. Evidence is conflicting regarding the benefits of Heliox, a blend of helium and oxygen, in asthma exacerbations.44–51 Lack of portability may cause a delay in administration thus limiting its use in the ED.
Asthma: Clinical Diagnosis and Management
2015, Murray and Nadel's Textbook of Respiratory Medicine: Volume 1,2, Sixth EditionManagement of Asthma in Infants and Children
2014, Middleton's Allergy: Principles and Practice: Eighth EditionHeliox-driven β<inf>2</inf>-agonists nebulization for children and adults with acute asthma: A systematic review with meta-analysis
2014, Annals of Allergy, Asthma and ImmunologyCitation Excerpt :Slightly more than 1% of patients had episodes of hypoxia that forced them to increase the oxygen concentration, and there was no significant difference between groups. In the past decade, 3 systematic reviews on the use of heliox in patients with acute asthma have been published.8–10 However, they offer incomplete information on this topic.
Airway Management in Intensive Care Medicine
2013, Benumof and Hagberg's Airway ManagementPhysics and Modeling of the Airway
2013, Benumof and Hagberg's Airway Management
Support of this work was entirely from institutional/departmental resources.
This work was presented in part at the 11th European Congress of Anaesthesiology. June 5–7, 2001; Florence, Italy.