The invention relates to a respiratory system comprising a first patient interface for delivery of a first flow of gases to a patient, a second patient interface for delivery of a second flow of gases to the patient, and a device and/or sensing arrangement that is configure to facilitate a switching of the system between a first respiratory mode where the device allowing delivery of the first flow of gases to an outlet of the first patient interface when the second patient interface is absent from the patient, and a second respiratory mode where the device reducing or stopping delivery of the first flow of gases to the outlet of the first patient interface when the second patient interface is located together with the first patient interface upon the patient.