combination

Heliox

Route: inhaled (continuous)
Onset: Minutes (immediate reduction in airway resistance)
Duration: Only effective while being administered (no residual effect)

Mechanism of action

Mixture of helium (60–80%) and oxygen (20–40%). Helium is less dense than nitrogen. Lower gas density reduces turbulent flow (decreases Reynolds number) and resistance to flow in large airways. Enhances laminar flow through narrowed airways → reduces work of breathing.

Dosing

Adult: 70:30 or 80:20 (He:O2) mixture. Delivered via non-rebreather mask, Venturi mask, or ventilator with heliox-compatible circuit
Pediatric: Same ratios; ensure adequate SpO2

Minimum 60% helium for meaningful clinical effect

Indications

Upper airway obstruction (croup, tracheal stenosis, post-extubation stridor)
Severe asthma exacerbation (refractory to bronchodilators)
Foreign body aspiration (bridge to bronchoscopy)
Tracheal/subglottic stenosis
Facilitation of bronchodilator delivery via nebulizer (enhanced deposition)

Contraindications

FiO2 requirement >40% (limits helium concentration — minimum 60% He needed for effect)
Clinically not useful if high oxygen requirement is present

Side effects

Voice change (high-pitched — Donald Duck effect)
Dizziness if FiO2 too low
No direct pharmacological toxicity

Monitoring parameters

SpO2 (ensure adequate oxygenation at reduced FiO2)
Work of breathing / respiratory rate
Ability to speak / stridor severity

Drug interactions

None significant

NBRC high-yield

Helium-oxygen mixture — reduces gas density → decreases work of breathing
Best for large airway obstruction (croup, tracheal stenosis)
Minimum 60% helium required for clinical effect
Not effective if FiO2 requirement >40%
Bridge therapy only — not definitive treatment
Enhances nebulized bronchodilator delivery

Clinical pearls

Effect is immediate but temporary — bridge therapy, not definitive treatment
Most beneficial in large airway obstruction (turbulent flow zone)
Less effective in small airway disease (COPD, bronchiolitis) — flow is already laminar
70:30 mixture: FiO2 = 0.30 (helium 70%) — acceptable for most patients without severe hypoxemia
Voice change (high-pitched) is expected and harmless
Can enhance nebulized bronchodilator deposition in severe asthma

Mnemonic

HELIOX: HElium Lowers airway resistance In Obstructed eXpiration (and inspiration)

All Drugs

NBRC high-yield

Helium-oxygen mixture — reduces gas density → decreases work of breathing

Best for large airway obstruction (croup, tracheal stenosis)

Minimum 60% helium required for clinical effect

Not effective if FiO2 requirement >40%

Bridge therapy only — not definitive treatment

Enhances nebulized bronchodilator delivery

Clinical pearls

Effect is immediate but temporary — bridge therapy, not definitive treatment

Most beneficial in large airway obstruction (turbulent flow zone)

Less effective in small airway disease (COPD, bronchiolitis) — flow is already laminar

70:30 mixture: FiO2 = 0.30 (helium 70%) — acceptable for most patients without severe hypoxemia

Voice change (high-pitched) is expected and harmless

Can enhance nebulized bronchodilator deposition in severe asthma