01
Heliox
Helium's low density converts turbulent flow to laminar flow, lowering the work of breathing through a narrowed large airway.
- Indications: severe asthma exacerbation, upper airway obstruction, post-extubation stridor, and large-airway tumors. It does not treat inflammation — it buys time.
- Common mixtures are 80/20, 70/30, and 60/40 helium to oxygen. The higher the oxygen fraction, the less benefit, and above 40% oxygen the density advantage is largely lost.
- An oxygen flowmeter under-reads heliox: multiply by 1.8 for 80/20 and 1.6 for 70/30.
- Deliver by tight nonrebreather with a reservoir; a loose mask entrains room air and defeats the therapy. Ventilator delivery requires a heliox-validated machine.
At the bedside
A patient whose stridor and accessory muscle use ease within minutes of heliox is telling you the obstruction is proximal and mechanical.