What is the role of heliox (helium-oxygen mixture) therapy in pediatric patients with severe respiratory distress?

Heliox Therapy in Pediatric Respiratory Distress

A therapeutic trial of heliox is reasonable for pediatric patients with mechanical upper airway obstruction (such as croup or postoperative stridor), but there is insufficient evidence to support routine use in lower airway disease like asthma or bronchiolitis. 1

Clinical Context and Mechanism

Heliox (typically 70:30 or 80:20 helium-oxygen mixture) reduces gas density compared to air, which decreases airflow resistance and work of breathing in narrowed airways. 1 A critical care study reported that 73% of heliox use was in pediatric patients, with approximately equal distribution between upper and lower airway disorders. 1

Evidence-Based Indications by Condition

Upper Airway Obstruction (Strongest Evidence)

For croup and mechanical upper airway obstruction, heliox may provide short-term benefit as a bridge to definitive therapy:

• In children with moderate croup receiving dexamethasone, heliox may slightly improve croup scores at 60 minutes (mean difference -1.10) but shows no difference by 120 minutes. 2
• Heliox can provide symptomatic relief while facilitating diagnosis and avoiding aggressive interventions like intubation in severe subglottic obstruction. 3
• The British Thoracic Society recommends a therapeutic trial for mechanical upper airway obstruction or postoperative stridor (Grade D recommendation). 1

Critical limitation: Heliox cannot be used if the patient requires more than 30% oxygen, as the mixture requires at least 70% helium for therapeutic effect. 4

Lower Airway Disease (Weak Evidence)

For asthma exacerbations:

• There is insufficient evidence to support routine use in pediatric asthma. 1, 4
• One small trial (n=30) showed heliox-driven continuous albuterol nebulization improved pulmonary index scores more than oxygen-driven delivery in moderate-to-severe exacerbations, with 73% discharged in <12 hours versus 33% in the oxygen group. 5
• However, systematic reviews conclude that existing evidence does not support routine administration to emergency department patients with moderate-to-severe acute asthma. 1
• The American Academy of Allergy, Asthma, and Immunology states that meta-analyses do not support heliox as initial treatment for asthma. 4

For bronchiolitis and other lower airway conditions:

• Evidence is sparse, consisting primarily of case reports and small uncontrolled studies. 6
• The British Thoracic Society states there is little evidence of benefit over air-oxygen mixtures in lower airway disease. 1

Practical Implementation Considerations

Technical Requirements

• Specialized delivery systems are mandatory to maintain a gas-tight seal and prevent room air dilution, as standard oxygen masks lead to significant dilution. 4
• Heliox affects nebulizer function and airflow measurements (peak flow, FEV1), requiring specialized nebulizer systems. 1, 4
• The 80:20 heliox mixture has similar oxygen content to air (21%), while 70:30 delivers higher FiO2 but is more dense. 4

Oxygen Saturation Targets

• Maintain 94-98% for patients with asthma or upper airway obstruction. 4
• Target 88-92% for patients with severe COPD (though COPD is rare in pediatrics). 4

Monitoring Requirements

• Continuous monitoring is essential to ensure adequate oxygen delivery. 4
• Watch for inadequate oxygenation if heliox concentration is too high. 4

Clinical Decision Algorithm

Step 1: Determine severity and location of obstruction

• Upper airway (croup, stridor, mechanical obstruction) → Consider heliox trial
• Lower airway (asthma, bronchiolitis) → Standard therapy preferred; heliox only in specialist hands for severe cases unresponsive to standard treatment

Step 2: Assess oxygen requirements

• FiO2 requirement ≤30% → Heliox can be used
• FiO2 requirement >30% → Heliox contraindicated (insufficient helium concentration for effect)

Step 3: For upper airway obstruction

• Initiate heliox (70:30 or 80:20) with appropriate delivery system
• Administer standard therapies concurrently (corticosteroids for croup)
• Reassess at 60-90 minutes for clinical improvement
• Use as bridge while definitive therapy takes effect

Step 4: For refractory lower airway disease

• Only consider in specialist/critical care settings after standard therapies fail
• May use heliox to drive nebulized bronchodilators in severe asthma
• Consider enrollment in clinical trials when available

Important Caveats

• Cost consideration: Heliox is more expensive than oxygen-air mixtures without proven mortality or morbidity benefit in most conditions. 1
• No mortality benefit demonstrated: The American College of Chest Physicians notes no reduction in mortality in respiratory conditions. 4
• Limited duration of effect: Benefits in croup appear short-lived (60 minutes), not sustained at 120 minutes. 2
• Adverse events poorly documented: The Cochrane review on croup noted that adverse events were not reported, and it's unclear if these were monitored. 2
• Voice alteration: Temporary voice changes occur but are not clinically significant. 1

When NOT to Use Heliox

• Routine management of mild-to-moderate asthma or bronchiolitis 1, 4
• When oxygen requirements exceed 30% 4
• As initial therapy before standard treatments 4
• Outside of clinical trials or specialist settings for lower airway disease 1, 4