The apparatus 11, wherein {HEAD ~ said gas delivery system} comprises {TAIL ~ a face mask} coupled to a flexible conduit 
comprises
The apparatus 11 , wherein { HEAD ~ said gas delivery system } comprises { TAIL ~ a face mask } coupled to a flexible conduit
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH