Helium^during expiration:VFr/PPres:Pt:Gas delivery system.expiratory limb:Qn
helium^during expiration:vfr/ppres:pt:gas delivery system.expiratory limb:qn
Helium [VFr/PPres] Gas delivery system.expiratory limb --during expiration
helium [vfr/ppres] gas delivery system.expiratory limb --during expiration