In 1934, Dr Alvan Barach first described the medicinal use of helium for resolution and treatment of upper airway obstruction lesions.¹Typically, helium is combined with oxygen (O₂) and referred to by the medical community as heliox. In a heliox gas mixture, helium replaces nitrogen and is generally delivered in concentrations that are three to four times higher than that of oxygen (i.e. 80:20 or 70:30). Since that first description by Barach, heliox gas mixtures have been used and promoted as adjunctive therapy to respiratory diseases and airway lesions for over 70 years. Despite the medical community’s gravitation toward evidence-based medicine in the 21st century, the clinical effectiveness of heliox in pediatric patients with airflow obstruction is relatively sparse and is reported primarily through case presentations, case series, or small, uncontrolled studies. This article is designed to provide a brief evidence review for heliox treatment of children with asthma, airway obstruction, bronchiolitis, and croup.

Asthma
Asthma is a chronic inflammatory disease of the airways that has components of airway hyper-reactivity and airflow obstruction due to smooth airway muscle constriction. While helium has no bronchodilating or anti-inflammatory properties, its lower density and its ability to promote laminar airflow through obstructive airways has several theoretical benefits for patients with asthma. In two frequently cited trials, the use of heliox in pediatric asthma demonstrated different outcomes.^2,3 Kudukis et al. utilized 80:20 heliox in 18 children with asthma in the emergency department (ED) and documented significant improvement in pulsus paradoxus, dyspnea score and peak flow measurements in the heliox group.² Carter et al., in another trial administering 70:30 heliox to 11 children hospitalized with asthma exacerbations, demonstrated no differences in clinical or dyspnea score, forced expiratory volume in one second (FEV₁), and forced vital capacity (FVC).³ There was a slight improvement in peak flow in the heliox group.

A more recent interest in heliox as a gas source for nebulization of asthma medications has been described in the literature. Kim et al. published the first prospective, randomized, single-blind pediatric study of heliox-driven albuterol nebulization with moderately to severely ill pediatric asthmatic patients.⁴ The investigators found that continuous heliox-driven nebulization of albuterol early in the course of ED care substantially improved the Pulmonary Index score and the unblinded discharge rate at the 12-hour treatment point. Rivera et al. studied a similar pediatric asthmatic population; however, this group reported no significant differences in Modified Dyspnea Index scores at 10 minutes or 20 minutes after the initiation of helioxdriven albuterol therapy.⁵ The ability to establish a convincing argument for the use of heliox for asthma from these four studies is largely inconclusive. Many questions regarding heliox treatment strategies and regimens for acute asthma remain unanswered, and there is a need for additional studies to clearly define any potential beneficial role of heliox for acute asthma exacerbations.

Upper Airway Obstruction
The etiology of upper airway obstruction can occur from a multitude of diseases or conditions. The resulting increase in airway resistance and the work of breathing in anatomically smaller airways is a recipe for respiratory failure in children. The ability of heliox to improve gas flow and oxygenation, as well as decrease the work of breathing, makes heliox an ideal approach for airflow obstruction lesions in the upper airways. Grosz and colleagues evaluated heliox effects on 42 children admitted and treated (44 occurrences) for significant upper airway obstruction.⁶ Using largely anecdotal criteria for work of breathing, 32 (73%) of the children had a positive response to heliox—the exception was for children with a history of congenital anomalies or syndromes (67%). Connolly and McGuirt treated 14 consecutive patients with severe subglottic edema or injury and meeting intubation criteria with heliox.⁷ All children without a prior history of subglottic stenosis (71%) were successfully and safely managed on heliox,and avoided intubation.

Rodeberg and colleagues evaluated heliox in eight children with post-extubation stridor from burns.⁸ Helium concentrations (50–70%) demonstrated a decrease in respiratory distress and thus avoided reintubation. In this trial, heliox was able to successfully relieve stridor, reduce respiratory distress and prevent reintubation in children with burns and postextubation stridor. Kemper and colleagues also evaluated heliox’s success in reducing post-extubation stridor in 13 children with burns and trauma.⁹ Respiratory distress scores for heliox were significantly improved. Kemper and colleagues concluded that heliox was successful in decreasing a stridor score for children with post-extubation stridor and was a preferred method of treatment. Although the evidence is largely from uncontrolled trials, heliox therapy for upper airway obstruction has demonstrated the ability to reduce stridor, reduce respiratory distress, and the work of breathing. Furthermore, heliox may lessen the need for post-extubation reintubation in children with upper airway obstructive disorders or diseases.