Abstract: An apparatus is provided for oxygenating a patient, comprising an oxygen supply means with an oxygen applicator for supplying oxygen via the nose, the oxygen applicator being a closed system, with the applicator affixable about the nose in a tightly-sealable manner so that it supplies pure oxygen solely via the nose in a directed flow, and additionally comprising a one-way valve which can be inserted in substantially sealing-tight manner into the mouth of the patient, the one-way valve opening only upon gas outflow out of the mouth, the closed system at all times having a pressure which is greater than the pressure necessary to open the one-way valve, such that respired air from the patient can escape only through the mouth and no air can escape through the nose.