A nasal interface device (20) comprising: first and second nasal prongs (22,24) and a base (26) connected to each of first and second nasal prongs (22, 24) by means of a first passage (72) and a second passage (74) respectively, each defining a passage axis (P), the first and second nasal prongs (22,24) each including: a bellows segment (42), a tip (40) having a tip body (48) extending from the bellows segment (42) and terminating in a tip end (46) opposite the bellows segment, a foot (44) extending from the base (26) to the bellows segment (42) and a lumen (28, 30) extending through the prong and open at the tip end, wherein in an undeflected state, a central axis (Abellows) of the lumen as defined by the bellows segment (42) is transversely offset from a central axis (Atip) of the lumen as defined by the tip end (46), and, relative to the passage axis (P), a central axis (Afoot) of the foot (44) projects laterally outwardly with proximal extension of the foot (44) from the base (26).
