A conduit assembly, for delivery of a breathable gas flow generated by a respiratory treatment apparatus to a patient interface to provide a patient with a respiratory treatment, the conduit assembly comprising a tubular conduit having: a first side and a second side, the second side opposing the first side along the length of the tubular conduit; a venting portion; and a flexible channel divider having a first side and an opposing second side, wherein the flexible channel divider is configured to dynamically create, in use: an inspiratory channel in the tubular conduit in response to an inspiratory flow in the tubular conduit, the inspiratory channel configured to conduct an inspiratory gas in use; and an expiratory channel in the tubular conduit, the expiratory channel configured to conduct an expiratory gas, wherein the conduit assembly is structured such that the flexible channel divider is disposed along said inspiratory channel and said expiratory channel, respectively, when dynamically created in use, wherein the flexible channel divider is configured to: traverse from the first side of the tubular conduit to the second side of the tubular conduit in use to create the inspiratory channel between the first side of the tubular conduit and the first side of the flexible channel divider and thereby block the venting portion of the tubular conduit, and traverse from the second side of the tubular conduit to the first side of the tubular conduit in use to create the expiratory channel between the second side of the tubular conduit and the second side of the flexible channel divider and thereby open the venting portion of the tubular conduit, characterised in that: the flexible channel divider is configured to dynamically create, in use, the expiratory channel in the tubular conduit in response to an expiratory flow in the tubular conduit. a first side and a second side, the second side opposing the first side along the length of the tubular conduit; a venting portion; and a flexible channel divider having a first side and an opposing second side, wherein the flexible channel divider is configured to dynamically create, in use: an inspiratory channel in the tubular conduit in response to an inspiratory flow in the tubular conduit, the inspiratory channel configured to conduct an inspiratory gas in use; and an expiratory channel in the tubular conduit, the expiratory channel configured to conduct an expiratory gas, wherein the conduit assembly is structured such that the flexible channel divider is disposed along said inspiratory channel and said expiratory channel, respectively, when dynamically created in use, wherein the flexible channel divider is configured to: traverse from the first side of the tubular conduit to the second side of the tubular conduit in use to create the inspiratory channel between the first side of the tubular conduit and the first side of the flexible channel divider and thereby block the venting portion of the tubular conduit, and traverse from the second side of the tubular conduit to the first side of the tubular conduit in use to create the expiratory channel between the second side of the tubular conduit and the second side of the flexible channel divider and thereby open the venting portion of the tubular conduit, characterised in that: the flexible channel divider is configured to dynamically create, in use, the expiratory channel in the tubular conduit in response to an expiratory flow in the tubular conduit. an inspiratory channel in the tubular conduit in response to an inspiratory flow in the tubular conduit, the inspiratory channel configured to conduct an inspiratory gas in use; and an expiratory channel in the tubular conduit, the expiratory channel configured to conduct an expiratory gas, wherein the conduit assembly is structured such that the flexible channel divider is disposed along said inspiratory channel and said expiratory channel, respectively, when dynamically created in use, wherein the flexible channel divider is configured to: traverse from the first side of the tubular conduit to the second side of the tubular conduit in use to create the inspiratory channel between the first side of the tubular conduit and the first side of the flexible channel divider and thereby block the venting portion of the tubular conduit, and traverse from the second side of the tubular conduit to the first side of the tubular conduit in use to create the expiratory channel between the second side of the tubular conduit and the second side of the flexible channel divider and thereby open the venting portion of the tubular conduit, characterised in that: the flexible channel divider is configured to dynamically create, in use, the expiratory channel in the tubular conduit in response to an expiratory flow in the tubular conduit. traverse from the first side of the tubular conduit to the second side of the tubular conduit in use to create the inspiratory channel between the first side of the tubular conduit and the first side of the flexible channel divider and thereby block the venting portion of the tubular conduit, and traverse from the second side of the tubular conduit to the first side of the tubular conduit in use to create the expiratory channel between the second side of the tubular conduit and the second side of the flexible channel divider and thereby open the venting portion of the tubular conduit, characterised in that: the flexible channel divider is configured to dynamically create, in use, the expiratory channel in the tubular conduit in response to an expiratory flow in the tubular conduit.