What is "heliox"

n. A gas, a mixture of helium and oxygen used in medicine and in diving.

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

Heliox is a medical treatment for patients with difficulty breathing. The mixture generates less resistance than atmospheric air when passing through the airways of the lungs, and thus requires less effort by a 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 alleviate symptoms of upper airway obstruction, its range of medical uses has since expanded greatly, mostly because of the low density of the gas. Heliox is also used in saturation diving and sometimes during the deep phase of technical dives.

Heliox is a cryogenically cooled system produced by Oxford Instruments.

Presently available in 2 varieties, the VL and TL, vertically loaded and top-loaded respectively. They are both pumped He cryostats, the TL capable of magnetic fields of up to 14 T, and the VL capable of achieving magnetic fields of up to 2 T. The base temperature for both systems is ~250 mK. Whilst the basis of operation of system is pumping of liquid Helium 3 below 2.2 K, this low temperature is achieved by first cooling the system to 2.2 K by pumping of Helium 4. A constant supply of liquid He is necessary, constituting a typical overhead of ~£1 / liter, whilst He is efficiently conserved as it is valued at ~£300 / liter.