Despite the apparently conflicting clinical evidence regarding its utility, heliox has gained widespread support and use in many paediatric emergency departments and intensive care units. Several potential indications have been suggested for heliox therapy, with particularly outstanding beneficial effects for patients with asthma, bronchiolitis and upper respiratory obstructions with various aetiologies. The body of evidence supporting the paediatric indications of heliox therapy is rapidly growing with many interesting ongoing studies. Very importantly, no study to date has detected negative or deleterious effects from heliox administration.
Helium is a biologically inert gas of low molecular weight, which, when blended with oxygen, results in a gas mixture (heliox) with a markedly lower density than air (specifically, heliox with 21% oxygen has one third the density of air). Its application in the setting of obstructive airway disease will decrease airway resistance to flow and thus reduce the work of breathing. Heliox has also been shown to enhance alveolar ventilation due to its high diffusion coefficient, which may improve carbon dioxide removal. Heliox has no inherent therapeutic effect and thus can be used only as a temporising agent; it provides time until definitive therapies act or the subjacent pathological circumstance spontaneously resolves. The inert nature of heliox explains the extreme rarity of secondary effects and the negligible risk of its clinical use. Interestingly, any beneficial effect of heliox should become evident in a relatively short period of time, one hour usually being sufficient.
The logistics of its application constitute a deciding issue in the final effect of heliox. In spontaneously breathing patients, heliox should be administered adequately warmed and humidified through a non-rebreathing reservoir facemask. In addition, its combined use with positive pressure, mainly by non-invasive ventilation but also by invasive ventilation, could have manifold complementary, if not synergistic, effects. The limited availability of paediatric devices designed and approved for the delivery and measurement of respiratory function during heliox therapy has clearly limited research in this setting.
On the basis of the existing data and the experience accumulated, we believe that heliox constitutes an effective, safe and non-invasive respiratory treatment option in the management of paediatric patients with any acute respiratory obstructive disease and particularly in the infant with moderate to severe acute bronchiolitis. The possibility that the same potential benefits apply to other indications or settings (eg, neonates) should be systematically explored, as the existing literature comprises mainly anecdotal data. Moreover, we believe that heliox might have other benefits in “other” non-respiratory clinical conditions not yet explored in humans.