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