Helium-oxygen mixture

The low breathing resistance of helium—oxygen mixtures is of therapeutic advantage for patients suffering from asthma and other obstmctive respitatory difficulties. The mixtures have also been used for hyperbaric therapy. 

Another consequence of the effect of pressure on gas solubility is the painful, sometimes fatal, affliction known as the bends. This occurs when a person goes rapidly from deep water (high pressure) to the surface (lower pressure), where gases are less soluble. The rapid decompression causes air, dissolved in blood and other body fluids, to bubble out of solution. These bubbles impair blood circulation and affect nerve impulses. To minimize these effects, deep-sea divers and aquanauts breathe a helium-oxygen mixture rather than compressed air (nitrogen-oxygen). Helium is only about one-third as soluble as nitrogen, and hence much less gas comes out of solution on decompression. 

A helium-oxygen mixture is used in diving gas instead of compressed air (nitrogen-oxygen). If air were used, nitrogen would dissolve in the diver s blood at the high underwater pressures and would be released as painful bubbles when the diver returned to the surface. 

In air,. vSOLmd is approximately 330 m/sec. A common lecture trick involves speaking into a bag filled with a helium/oxygen mixture, which is breathable but raises the speed of sound dramatically compared to air (essentially a nitrogen/oxygen mixture) ... 

Rodrigo GJ, Rodrigo C, Pollack CV, Rowe B. Use of helium-oxygen mixtures in the treatment of acute asthma A systematic review. Chest 2003 123 891-896. 

Although this can use a chilled drum, it is not essential, as the process involves a relatively low heat loading. The process again uses a vacuum chamber provided with a helium—oxygen mixture and a silicon-based monomer such as tetramethyldisiloxane or hexamethyldisiloxane. An applied power creates a plasma which activates the oxidation of the silicon gas, creating reactive chemical molecules which form the SiO coating on the film surface. 

Anderson M, Svartengren M, Philipson K, Camner P. Deposition in man of particles inhaled in air or helium-oxygen mixture at different flow rates. J Aerosol Med 1990 3 209-216. 

Helium-oxygen mixture is used in diving apparatus Why ... 

As we learned in Chapter 14 (page 659), using helium-oxygen mixtures instead of air for deep-sea diving prevents the condition known as the bends because helium is more rapidly and smoothly expelled from the blood than is nitrogen. 

Therapeutic aerosols play a prominent role in the treatment of diseases of the lower airways, such as bronchial asthma and chronic bronchitis. It has been proposed that an increased deposition in the peripheral airways would be of value, in particular for treatment with inhaled corticosteroids. In patients with asthma, tracheobronchial deposition could be increased, practically independent of airway dimensions, by inhaling large aerosol particles extremely slowly (17,114). This could be a potentially useful approach of therapeutic importance, particularly in the treatment of patients with airways obstruction. Still, another possibility to enhance deposition of therapeutic aerosols in asthmatics could be the use of carrier gases such as helium-oxygen mixture (113). 

Svartengren M, Anderson M, Philipson K, Camner P. Human lung deposition of particles suspended in air or in helium/oxygen mixture. Exp Lung Res 1989 15 575-585. 

Schulz H, Schulz A, Eder G, Heyder J. Influence of gas composition on convective and diffusive intrapulmonary gas transport. Exp Lung Res 1995 21 853-876. Svartengren M, Anderson K, Philipson K, Camner P. Human lung deposition of particles suspended in air or in helium/oxygen mixture. Exp Lung Res 1989 15 575-585. 

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