A special thanks to Thersea Frey, a Pediatric Emergency Medicine Attending at Cincinnati Children’s who amassed much of this data for today’s quick review.
At some point most of us have probably had a patient on, or at least discussed heliox therapy. I wanted to use this post as a way to quickly highlight some of the background information and the current state of the literature as we jump headlong into respiratory season.
It’s a blend
Heliox is actually a blend of various combinations of oxygen and helium. Generally the mix is either 80%:20%, 70%:30% or 60%:40%. Helium has a lower density than oxygen or room air, and it is felt that it may flow more efficiently through small or perhaps partially obstructed airways. From a physics standpoint the hope is that turbulent airflow becomes more laminar, leading to decreased resistance to flow. This in turn, is hypothesized to reduce work of breathing by improving ventilation. It is important to note that heliox has a capped blend/percentage of oxygen. Thus, for hypoxic patients it is not useful if you need higher FiO2s.
In the Pediatric Emergency Department we see many respiratory illnesses. Let’s take a brief look at some of the evidence in asthma, bronchiolitis and croup – the ABCs of respiratory disease!
Asthma
Overall it is important to note that studying heliox in children has proven difficulty – generally due to logistic reasons. There have been five notable randomized placebo controlled trials over the last two plus decades. The results have been mixed, with only mild improvement in respiratory scores shown. In the interest of brevity I’ll present only the high points of each, but I’ve also included links to the articles so you can read more.
This study investigated admitted patients with asthma and noted that there were no significant short term benefits when brief periods of 70%:30% were administered.
The authors concluded, based on a small number of patients that inhaled 80%:20% heliox lowered the pulsus paradoxus, increased peak flow, and improved dyspnea. They also concluded that it may have staved off at least three intubations.
This small trial of 30 children with asthma in an urban Pediatric Emergency Department showed that respiratory score improved more for children with moderate to severe asthma exacerbations that had heliox used as the carrier for continuous albuterol.
Children with asthma exacerbations in a Pediatric Emergency Department were randomized to get heliox. It did not seem to lower the risk of admission.
This was a study of 42 admitted children with asthma. Per the authors heliox did not “shorten hospital length of stay or hasten rates of clinical improvement when compared with air/oxygen-powered nebulized albuterol.”
The bottom line: Heliox may improve respiratory score, but it probably won’t reduce the risk of admission. Nor should you use it in routine asthma to stave off intubation.
Bronchiolitis
Ah bronchiolitis! Everyone’s favorite. Fortunately we have a Cochrane Review to look at when it comes to heliox and bronchiolitis.
This review focused on seven trials with a total of 447 patients. All were under two years of age and diagnosed with viral bronchiolitis. Most were in the PICU 378/447, the remaining 69 were in the ED. Each of the seven studies employed a slightly different protocol, limited the homogeneity of the results. Some high points:
In the PICU the risk of intubation was NOT decreased
In the ED there was NO effect on the rate of admisison
Only in infants started on CPAP immediately on presentation were decreased length of treatment seen
There were lower respiratory scores in the first hour for heliox vs oxygen/room air.
No adverse events were noted for heliox
Though there are some newer trials, like one from Egypt this year, the evidence suggests that there is need for more study. Right now I would not use heliox in an attempt to stave off intubation or change disposition location within my hospital.
Croup
Just like in bronchiolitis we have a Cochrane Systematic Review. Unfortunately the three trials included, with 91 children total included different interventions and outcomes, so the results could not be pooled. This obviously suggests the need for further RCTs. Furthermore the review was actually withdrawn by Cochrane, but is available in an archived version.
In a trial of 70%:30% heliox version humidified 30% FiO2 in mild croup there were no differences in croup scores.
In the second trial children with moderate to severe got either IM decadron + 70%:30% heliox + saline neb or IM decadron + 100% oxygen + 1-2 racemic epi treatments. The heliox group had better score at the 90 minute mark, but no difference was seen at 4 hours. By the way, what an interesting protocol.
The third trial was PO dexamethasone and 70%:30% heliox versus no treatment in moderate croup. The heliox group had better respiratory scores at 60 but not 120 minutes.
There probably is some benefit for respiratory scores in croup, but it won’t prevent admission. The use seems to be more useful in inpatient, especially ICU settings.
Final thoughts
Clearly there isn’t a preponderance of evidence to suggest that heliox is a game changing treatment for asthma, bronchiolitis or croup. I think there are situations where it makes a lot of sense, but the evidence just isn’t there.
- A child with a structurally abnormal airway with respiratory distress
- A child with post intubation stridor
- A child with significant airway edema
- A child transferred to your Emergency Department already on heliox (this kid will be admitted)
