A nasal interface uses asymmetrical nasal delivery elements to deliver an asymmetrical flow through the interface to both nares or to either nare, and a mouthpiece may be inserted to maintain a leak, to improve dead space clearance in the upper airways, decrease peak expiratory pressure, reduce noise, increase safety of the therapy for smaller patients and reduce resistance in the interface allowing desired flow rates to be achieved at reduced motor speeds of associated flow generating devices. Different forms of fittings, such as sleeves or inserts can be attached to nasal delivery elements to improve or optimise the therapeutic effects of nasal high flow. It may allow high pressures to be achieved at lower flow rates, reduce noise, improve patient comfort and efficiently clear anatomical dead space.
