Abstract: An oxygen mask adaptable for upper gastrointestinal (UGI) endoscopy procedures providing enhanced oxygen concentration to maintain patient oxygenation. An oxygen mask in accordance with the present invention provides an aperture of sufficient dimensions to enable substantially unimpeded placement and manipulation of an endoscope during an endoscopic procedure while an overlying closure is in an open position and yet may also be closed to cover the aperture when the procedure is not being performed.