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Heliox May Be Useful in the Treatment of Acute RSV Bronchiolitis


  • In an otherwise healthy infant with RSV bronchiolitis, does treatment with heliox offer in an improvement in mortality, duration of hospital stay, or need for intubation as compared with conventional therapy?

Clinical Bottom Lines

  1. Compared with conventional management of fluids, oxygen, and nebulized epinephrine, patients in the Heliox group had improvement in a clinical asthma score, heart rate, respiratory rate, and length of Pediatric ICU stay.
  2. Methodical problems with this study, particularly the small sample size, restrict the global applicability of study, although overall positive effects seen, as well as the relatively benign nature of the treatment support both further study, and limited clinical application on the treatment.

Summary of Key Evidence

  1. The initial 19 patients enrolled in the study received conventional therapy. The next consecutive 19 patients were treated with heliox in addition to conventional therapy.
  2. The Modified Wood Clinical Asthma score was used as a surrogate endpoint in this study. The M-WCAS is a clinical scoring system which takes into account oxygen saturation, inspiratory breath sounds, expiratory wheezing, use of accessory muscles, and mental status. A score of 2 represents a mildly ill infant, 5-6 moderately ill, and greater than 6-7 severely ill. Patients in this study had a mean baseline M-WCAS of 6.6.
  3. The M-WCAS, heart rate, respiratory rate, oxygen saturation, and end-tidal CO2 were measured hourly, and are reported below after four hours of treatment.
M - WCAS (4hours)
2.39 +/- 0.69
4.07 +/- 0.96
< 0.01
Heart Rate (4 hours)
Resp Rate (4 hours)
Length of PICU stay (in days)
3.5 +/- 1.1
5.4 +/- 1.6
4. There was no difference in O2 saturation or end-tidal CO2 between the groups.
5. Heliox therapy was stopped when M-WCAS scores were maintained at 2 or below for 6 hours.

Additional Comments

  • The beneficial effects of heliox are felt to be related to the lower density of helium, which preserves laminar flow at higher flow rates, decreasing work of breathing by decreasing resistance to airflow.
  • The study is quite small, and patients were not randomized. The small sample size produced an inability to assess direct outcomes, such as mortality or intubation rates. Instead, the surrogate end point of a clinical asthma score (although a relatively well-validated one) was used. The patients in the treatment group were all enrolled after the control group, leading to the possibility of changing practices in terms of conventional management, and or PICU discharge results skewing the data.
  • Children with chronic cardiac or pulmonary disease were excluded from the study, which likely contributes to the fact that none of the infants in either group progressed to requiring intubation.
  • Heliox administration requires use of a facemask, which may not be well tolerated by all infants.
  • The study was not blinded, due to the use of a facemask with heliox, and changes in voice/cry related to helium.


  1. Martinon-Torres F, Rodriguez-Nunez A, Martinon-Sanchez JM. Heliox therapy in infants with acute bronchiolitis. Pediatrics 2002; 109(1): 68-73.

CAT Author: Tim Cotts, MD

CAT Appraisers: Robert Schumacher, MD

Date appraised: February 8, 2002

Last updated June 16, 2003
Department of Pediatrics and Communicable Diseases
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