Definition
Heliox (70% helium, 30% oxygen) therefore affects gas flow in two ways – first, the Reynold’s number is lower (because density is lower), and thus flow is more likely to be laminar, and second, if flow IS turbulent, resistance to flow will be lower, becuase Heliox is less dense (~ 0.5 g/L versus 1.2 5g/L).
Note that in laminar flow, Heliox offers no advantages, as it has approximately the same viscosity as air. Also note that Heliox is ~ 70% helium, thus the potential benefit of improved gas flow must be balanced by the knowledge that a lower FiO2 may be delivered
Heliox: Summary
- ~ 70% helium, ~ 30% oxygen
- Significantly less dense than air (0.5 vs 1.2 5g/L), but viscosity is about the same
- Improves gas flow by lowering Reynold’s number (converting to laminar flow) or decreasing resistance when flow is turbulent (lower density)
Subspecialty
Related Media
Keyword history
90%/2011
See Also:
ABA:Helium advantages – Small-bore tube
Sources
-
Miller’s Anesthesia, 7th Edition. Pages 1218, 2360