An apparatus for use in applying mouth to mouth resuscitation, having a tube for insertion into a victim's mouth and a circular, convex shield attached to one end of the tube. A one-way valve, within the tube, allows air to flow through the tube only in a direction away from the shield. A wafer mounted within the tube, is moveable between an open position and a closed position. The wafer has a plurality of notches spaced around the perimeter. The wafer is mounted between first and second annular shoulders within the valve. When the wafer is in the closed position, the first annular shoulder blocks airflow through the notches in the wafer. When the wafer is in the open position, the second annular shoulder allows air to flow through the notches. The apparatus also has a screen for preventing solids of a certain size or larger from entering the valve.