A patient interface comprising: a first nasal interfacing component to be provided in fluid communication with a user's first nare, the first nasal interface component is configured for substantially sealingly engaging or interfacing with the user's first nare, and an associated first conduit provided for an independent and/or dedicated fluid connection with the first nasal interfacing component ; a second nasal interfacing component to be provided in fluid communication with a user's second nare, the second nasal interface component is configured for substantially sealingly engaging or interfacing with the user's second nare, and an associated second conduit provided for an independent and/or dedicated fluid connection with the second nasal interfacing component ; wherein one of either: the first nasal interfacing component with said associated first conduit , or the second nasal interfacing component with said associated second conduit , is configured as a sole inspiratory line or conduit for delivery of a source of gases to one of the user's nares, and wherein the other of the one of the first nasal interfacing component with said associated first conduit or the second nasal interfacing component with said associated second conduit, is configured as a sole expiratory line or conduit for receiving gases from the other one of the user's nares, said sole expiratory line or conduit being fluidly coupled to a downstream device configured to provide for a pre-determined or an adjustable back-pressure or a positive end expiratory pressure. a first nasal interfacing component to be provided in fluid communication with a user's first nare, the first nasal interface component is configured for substantially sealingly engaging or interfacing with the user's first nare, and an associated first conduit provided for an independent and/or dedicated fluid connection with the first nasal interfacing component ; a second nasal interfacing component to be provided in fluid communication with a user's second nare, the second nasal interface component is configured for substantially sealingly engaging or interfacing with the user's second nare, and an associated second conduit provided for an independent and/or dedicated fluid connection with the second nasal interfacing component ; wherein one of either: the first nasal interfacing component with said associated first conduit , or the second nasal interfacing component with said associated second conduit , the first nasal interfacing component with said associated first conduit , or the second nasal interfacing component with said associated second conduit , is configured as a sole inspiratory line or conduit for delivery of a source of gases to one of the user's nares, and wherein the other of the one of the first nasal interfacing component with said associated first conduit or the second nasal interfacing component with said associated second conduit, is configured as a sole expiratory line or conduit for receiving gases from the other one of the user's nares, said sole expiratory line or conduit being fluidly coupled to a downstream device configured to provide for a pre-determined or an adjustable back-pressure or a positive end expiratory pressure. <EOS>