This invention relates to a patient interface, a system and/or method for providing a dedicated or sole inspiratory line or conduit for provision of inspiratory gases to a patient, and a dedicated sole expiratory line or conduit for provision of expiratory gases to a downstream device, where the inspiratory line or conduit is sealing engageable with first of a user's nares and the expiratory line or conduit is sealing engageable with the second of a user's nares.