Patent ID: 7207335

Claim:
A CPAP mask assembly for use with a system for supplying breathable gas pressurized above atmospheric pressure to a human or animal, the CPAP mask assembly comprising: a mask adapted to be in fluid communication with a gas supply conduit; and a vent assembly provided to the mask, the vent assembly including at least one gas washout orifice extending from an inner side of the vent assembly placed, in use, adjacent the human or animal's face to an outer side placed, in use, adjacent the atmosphere, the gas washout orifice being open in use, wherein a cross-sectional area of the orifice at the inner side of the vent assembly is larger than a cross-sectional area of the orifice at the outer side of the vent assembly, the inner side of the vent assembly extends inside the mask and the outer side of the vent assembly extends outside the mask, and the orifice does not substantially change shape upon application of pressurized gas at a level suitable for CPAP treatment for obstructive sleep apnea.