Nasal patient interface arrangement, breathing apparatus, and method for operating a breathing apparatus

A nasal patient interface arrangement for transporting breathing gas from a pressurised gas supply to a patient, the arrangement being adapted to provide a first bidirectional gas passage in contact with ambient air and adapted to receive nasally expired air, the arrangement comprising:

• an inspiratory air conduit connecting to a pneumatic unit;
• a nose adapter configured for a bidirectional gas transport, wherein the nose adapter is arranged to be connected to a nose of the patient;
• a valve arrangement controlling the passage of gas through the first bidirectional gas passage;
• wherein the arrangement is adapted to provide a second bidirectional gas passage which is connected to the inspiratory air conduct (150), the nose adapter, and the first gas passage and
• wherein the valve arrangement is substantially enclosed in the first bidirectional gas passage.

A method for operating a breathing apparatus, comprising the steps of:

• inflating a valve which is substantially enclosed in a first bidirectional gas passage so that the first bidirectional gas passage is at least partly blocked;
• providing breathing gas through a second bidirectional gas passage from a pressure gas supply to a nose adapter of a patient so that the patient can inhale the breathing gas, wherein the breathing gas is provided at least during a substantial fraction of an inhalation period of the patient;
• and
• deflating the valve so that a gas passage through the first bidirectional gas passage is allowed and so that the majority of exhaled gas from the patient can pass through the first gas passage to ambient air during an exhalation period of the patient.