heliox

Heliox is a medical breathing gas composed of helium and oxygen. The most common mixtures are 70% helium with 30% oxygen or 80% helium with 20% oxygen, with the exact oxygen fraction tailored to the patient’s needs. Heliox is used as a temporary measure to aid ventilation in cases of airway obstruction or severe bronchospasm.

The therapeutic effect of heliox arises from its physical properties. Helium is far less dense than nitrogen, so when helium is used in a narrowed or obstructed airway, the gas flow tends to be less turbulent. This reduces airway resistance and the work of breathing, and can improve the delivery of inhaled medications. The benefit is typically greatest in dynamic obstructions such as acute bronchospasm or upper airway edema; it is less impactful for fixed, complete obstructions or extensive alveolar disease.

Administration and practical considerations vary. Heliox is delivered through specialized equipment or ventilators that are compatible with gas mixtures. It is generally used for short periods, from minutes to hours, and is intended as an adjunct to standard therapies such as bronchodilators, steroids, and supportive care. Because the oxygen fraction is limited by the mixture, heliox may not be suitable when a high FiO2 is required.

Limitations include its temporary nature, potential for delayed recognition of worsening hypoxemia, equipment compatibility issues, and cost. It is not a substitute for definitive treatment of the underlying condition. Heliox has been used since the mid-20th century, with particular prominence in pediatric croup and other acute airway obstructions.