What is Heliox?

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  • Written By: M. Marquardt
  • Edited By: A. Joseph
  • Last Modified Date: 04 November 2019
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Heliox is a gaseous combination of oxygen and helium, a mixture that is less dense than air. In the medical world, it is used to aid those who have illnesses that make it difficult to breathe, such as asthma or chronic obstructive pulmonary disease (COPD). It also has been used for scuba diving during particularly deep dives.

When a person is having difficulty drawing breath, it increases what doctors call the work of breathing. The increase can happen for many reasons, such as from an airway obstruction or a fluid in the lungs, but the most common cause of breathing problems is airway inflammation. When the tissue of the airway and lungs is inflamed, it is swollen and more likely to cause turbulent air flow, meaning that the air does not pass smoothly back and forth from the lungs.

Heliox is less dense than air, meaning it is lighter than what a person typically breathes, so it is physically and mechanically easier to pull into the lungs, and it meets less resistance in the airway. It reduces turbulent air flow, restoring the amount of laminar, or straight, flow of gas to and from the lungs. Heliox also can be used when there is a large obstruction in the airway, such as a tumor or a foreign object, to ease the work of breathing until surgery can alleviate the issue permanently. It also is used to aid breathing in viral diseases such as croup.


A mixture of helium has been used for medical purposes since the 1930s. At that time, there were few options for bronchodilators, the medications found in inhalers, so a form of heliox was one of the only treatments for acute asthma. Typically, the mixture is 20 percent oxygen, which is near to the amount found in air, and 80 percent helium, though mixtures of 30 percent oxygen and 70 percent helium also are used.

Heliox sometimes is used in deep diving excursions, because it does not lead to nitrogen narcosis, a common problem when diving below 50 feet (about 15 m). At deep levels, the added pressure of seawater can increase the work of breathing. Therefore, just like in an asthma attack, divers need access to a way to ease the stress of breathing. Heliox has been shown to be beneficial at depths of more than 200 feet (about 60 m), depths typically reached only by technical and commercial divers. At depths of more than 500 feet (about 150 m), however, heliox might trigger high-pressure nervous syndrome, which causes uncontrollable shaking.


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Post 1

My nephew is a scuba diver and works for a company that does offshore drilling. Through him is the first time I had ever heard of heliox. He had a friend that was his diving partner that almost lost his life two years ago on a dive. They were diving at very deep depths and his partner just couldn’t get enough air. If I remember correctly, they were diving at around 400 feet. He said his partner was struggling because he wasn’t moving air smoothly enough.

When they signaled to bring him up, he had uncontrollable shaking. He was flown out to the nearest hospital and was there for about a month. He’s not diving again but he is okay. It was after that incident that I learned about what heliox was and what its purpose was.

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