Helium is an inert gas with a density that is one-seventh that of air. In addition, carbon dioxide (CO 2 ) diffuses more easily through helium than through air [9] . With helium, a more laminar flow is preserved in narrowed airways, resulting in lower resistance to gas flow allowing for increased bulk flow [10] . Based on these properties, MV with heliox could be considered in mechanically ventilated infants with RSV LRTD. Its use in these patients has been studied once but with inconclusive results [11] .