The present invention relates to an intraoral flexible mouthpiece comprising: a hollow dome portion comprising a peripheral proximal edge wherein said hollow dome portion extends distally and wherein said hollow dome portion comprises a central orifice located at the distal portion of said hollow dome portion； a peripheral flexible sheet flange attached along said dome portion peripheral proximal edge； a tube attached to said central orifice and extending distally therefrom； wherein said peripheral flexible sheet flange is configured to be placed in the mouth between the teeth and gums on one side and the lips and cheeks on the other side, and wherein the hollow dome portion is configured to protrude distally out of the mouth.
