A mask for delivery of oxygen to a patient, includes a body having a rim to sit comfortablyon a patient's face, a central portion, and webs extending between the centralportion and the peripheral portion and integral therewith. The webs define openareas that make up at least 30% of the mask body. The central portion includes agas diffuser shaped to direct a turbulent gas plume over the patient's noseand mouth. The dimensions of the diffuser permit formation of a suitable gas plumeover a range of oxygen delivery rates.
