Heliox

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Heliox is a breathing gas comprising a mixture of helium (He) and oxygen (O ₂ ).

Heliox is a medical treatment for patients with difficulty breathing. The mixture produces less resistance than atmospheric air as it passes through the airways of the lungs, and thus requires little effort by the patient to breathe in and out of the lungs.

Heliox has been used medically since the 1930s, and although the medical community adopted it initially to reduce the symptoms of upper airway obstruction, the range of medical use has grown rapidly, primarily due to low gas density. Heliox is also used in dive saturation and sometimes during the in-depth phase of technical dives.

Video Heliox

Medical use

In the heliox drug it can refer to a mixture of 21% O ₂ (equal to air) and 79% Dia, although other combinations are available (70/30 and 60/40).

Heliox produces fewer airway constraints than air and thus requires less mechanical energy to ventilate the lungs. "Work of Breathing" (WOB) is reduced. This is done with two mechanisms:

1. increased tendency to laminar flow;
2. reduces resistance in turbulent flow.

Heliox has a viscosity similar to air but a significantly lower density (0.5 g/l versus 1.25 g/l in STP). The gas flow through the air passages consists of laminar flow, transition flow and turbulent flow. The tendency for each type of flow is explained by the Reynolds number. The low Heliox heights result in a lower number of Reynolds and therefore higher laminar flow probabilities for each given air channel. Laminar flow tends to produce less resistance than turbulent flow.

In the small airways in which the laminar flow, the resistance is proportional to the viscosity of the gas and not related to density and so the heliox has little effect. The Hagen-Poiseuille equation describes laminar resistance. In large airways where the flow is volatile, the resistance is proportional to the density, so the heliox has a significant effect.

Heliox has been used medically since the early 1930s. It is a mainstay of treatment of acute asthma before the onset of bronchodilators. Currently, heliox is mainly used in conditions of large airway constriction (upper airway obstruction of tumors or foreign objects and vocal cords dysfunction). There is also some use of heliox in medium airway conditions (croup, asthma and chronic obstructive pulmonary disease).

Patients with this condition may suffer from a variety of symptoms including dyspnea, hypoxemia, and eventually weakening of respiratory muscles due to fatigue, which can lead to respiratory failure and require intubation and mechanical ventilation. Heliox can reduce all of these effects, making it easier for patients to breathe. Heliox also found utility in weaning patients from mechanical ventilation, and in nebulisation of inhalable drugs, especially for the elderly. The study also showed advantages in using a mixture of helium-oxygen in the delivery of anesthesia.

Maps Heliox

Diving using

Because of the cost of helium, heliox will most likely be used in deep commercial dives. It's also sometimes used by diving enthusiasts, especially those using rebreathers, which conserve respiratory gas at much better depth than open-circuit scuba.

The proportion of oxygen in the dive mix depends on the maximum depth of the dive plan, but is often hypoxic and usually 10%. Each mix is ​​ordered and made using gas mixing techniques, which often involves the use of a booster pump to reach a typical dive cylinder pressure of 200 bar (2,900 psi) from a low pressure oxygen bank and a helium cylinder.

As the sound moves faster in the heliox than in the air, the sound of the voices is raised, making the diver's speech very high-pitched and difficult to understand by people unfamiliar with it. Surface personnel often use communications equipment called "helium de-scrambler," which electronically lowers the tone of the diver's voice as it flows through communication equipment, making it easier to understand.

Trimix is ​​a slightly cheaper alternative to the heliox for deep dives. Trimix is ​​often used in commercial dive and technical diving.

In 2015, the United States Navy Experimental Diving Unit showed that the decompression of refracting dives using trimix was no more efficient than diving in the heliox.

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See also

• Argox
• Nitrox
• Hydreliox
• Hydrox
• Trimix

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References

Source of the article : Wikipedia