The present disclosure relates to a nasal patient interface arrangement (100) for transporting breathing gas from a pressurised gas supply (111) to a patient (190). The arrangement (100) is adapted to provide a first bidirectional gas passage (130) in contact with ambient air (170) and adapted to receive nasally expired air. The arrangement (100) comprises an inspiratory air conduit (150) for connection to a pneumatic unit (110). The arrangement (100) further comprises a nose adapter (120) for bidirectional gas transport. The nose adapter (120) is arranged to be connected to a patient's (190) nose (199). The arrangement further comprises a valve arrangement (140) for controlling the passage of gas through the first bidirectional gas passage (130). The arrangement (100) is adapted to provide a second bidirectional gas passage (160) which is connected to the inspiratory air conduct (150), to the nose adapter (120), and to the first gas passage (130). The valve arrangement (140) is substantially enclosed in the first bidirectional gas passage (130).The present disclosure also relates to a breathing apparatus (200) and to a method for operating a breathing apparatus.
