Disclosed is a tubular device for respiratory assistance. The device includes a main channel and at least one auxiliary channel connected to a source of breathable gas. The device includes structure for diverting a volume fraction of the breathable gas intended for the auxiliary channel, and structure for aspirating ambient air that is driven by the diverted fraction of breathable gas. The structure of the device is configured such that the aspirated ambient air is mixed with the diverted fraction of breathable gas and is conveyed into the main channel between the distal orifice of the auxiliary channel and the distal end of the main channel.