What is heliox?

Heliox is the common name for a helium and oxygen mixture.

Is heliox a new gas?

No. Heliox has been used for more than 70 years in medical applications and is widely used in diving applications.

How is helium used in heliox?

Helium is one of the lightest chemical elements --- this allows a heliox mix of 80% helium/20% oxygen to be three times lighter than air for the same amount of oxygen. This lighter gas is easier to breathe. Helium is an inert gas and not subject to chemical reaction with other substances.

Which heliox mix is the best?

There is currently no clinical evidence favoring one mix over another. The choice of a proper mix of helium and oxygen depends on several criteria. A compromise between a high percentage of helium to achieve a lighter mix over a high percentage of oxygen for proper oxygenation should be evaluated on a case by case basis.

Praxair, however, does not recommend the use of 100% helium (even when blended with oxygen to obtain proper oxygenation level) due to the inherent risks involved with a hypoxic mixture. Praxair can supply heliox in two standard mixes: 80% helium or 70% helium with the balance being oxygen.

How do I administer heliox?

You can administer heliox in a similar fashion as you would administer any breathing gas. For instance, heliox can be given by high flow nasal cannula, hood or facemask. Proper attention should be taken to ensure proper oxygenation of the patient and an avoidance of room air entrainment that will dilute the gas and increase its density.

How do I know the flow rate with heliox?

The flow rate of heliox is underestimated by an air or oxygen flow meter unless a conversion is performed. Ball float meters are usually calibrated for a specific gas at 50 psig. The actual flow rate is obtained by multiplying the flow rate on the meter by the square root of the density ratios. For instance, if using heliox 70/30, multiply the reading from the ball meter by 1.6 if using an oxygen-calibrated meter and 1.5 for an air-calibrated one. 10 liters/minute on the oxygen meter actually corresponds to a true flow of 16 liters/minute of heliox.

For heliox 80/20, the multiplying factors are 1.8 and 1.7 for oxygen and air-calibrated devices respectively.

Can I use heliox to power a jet nebulizer?

Yes, heliox can be used to power a jet nebulizer. Special attention should be taken, however, since the lower density of the gas will affect the aerosol generation. 

Why would I want to use a reservoir?

Heliox has a lower density than air. The flow rate provided by a standard respiratory apparatus often does not provide enough breathing gas during inspiration. The excess gas comes then from room air via open valves or loose fittings. This gas can dilute heliox significantly, thereby increasing its density. The addition of a reservoir in the respiratory system provides that extra volume of breathing gas during inspiration without diluting heliox with room air