Yes disinsection is a word, the spraying I thought was primarily for bugs of the insect kind, not the germ kind.
In a previous company we used the sprays back into Australia, but this was discontinued as we were told they now apply something in the hold which takes care of the needs for manual spraying. No idea what it was though or how it gets into the cabin.
Nasal cannula is correct, most people on long-term oxygen use them as they are more comfortable & more relaxing for the patient... especially if having something covering their face makes them anxious. I think it does depend on the condition though, so I suppose the original poster would know which is best to use in this case.