An exchanger conduit permits temperature and/or humidity conditioning of a gas for a patient respiratory interface. In an example embodiment, a conduit has a first channel and a second channel where the first channel is configured to conduct an inspiratory gas and the second channel configured to conduct an expiratory gas. An exchanger is positioned along the first channel and the second channel to separate the first channel and the second channel. The exchanger is configured to transfer a component (e.g., temperature or humidity) of the gas of the second channel to the gas of the first channel. In some embodiments, an optional flow resistor may be implemented to permit venting at pressures above atmospheric pressure so as to allow pressure stenting of a patient respiratory system withouta substantial direct flow from a flow generator of respiratory treatment apparatus to the patient during patient expiration.