HELIOX is a mixture of Helium and Oxygen. It is a therapeutic modality that can improve upper and lower airway obstruction. The lower density of Helium can help to relieve airway obstruction and is known to lower the work of breathing. The fraction of Helium (FHe) in HELIOX should be maximized (e.g. up to a fraction of 79% with 21% of oxygen added) in order to achieve optimal anti-obstructive outcome and according to the literature a FHe below 60% renders HELIOX ineffective.