A base unit for use as part of a breathing circuit which delivers heated, humidified gases to a patient (13) for medical purposes. Said breathing circuit is of the type that includes a humidifier chamber (5) adapted to hold a quantity of water (6) and having an inlet (16) and an outlet (4) to allow gases to flow through said humidifier chamber, a source of pressurised gases (15) which in use are delivered to the inlet of said humidifier chamber, and a gases transportation pathway (3) connected to said outlet of said humidifier chamber to convey said gases flow to said patient. Said gases transportation pathway includes a patient interface (12) adapted to supply said patient with said gases flow. Said base unit includesa heater plate (7) adapted to allow said humidifier chamber to be located in use on said heater plate so that said heater plate heats said quantity of water in said humidifier chamber and gases flowing through said humidifier chamber become heated and humidified, and a control system (9) configured to adjust one or more output parameters of said breathing circuit, said control system including an RFID interrogator adapted to interrogate and receive data from at least one RFID tag (2) in real time. In use, said RFID interrogator receives data relating to at least one sensed parameter and said control system adjusts one or more of the output parameters of said breathing circuit according to said received data.
