A system for delivering a flow of breathing gas to a patient that includes a main delivery conduit coupled to a gas source, and a rotary coupling device coupled to the main delivery conduit and having a first member and a second member, the first member defining a first channel and a second channel through the first member, the second member defining a third channel and a fourth channel through the second member. The first channel is in communication with the third channel to define a main channel having a main path, and the second channel is in communication with the fourth channel to define a secondary channel separate from the main channel and having a secondary path. The first member and the second member are structured to freely ro tate relative to one another in a manner that separately maintains the main path and the secondary path.
