A nasal interface device (20) comprising:first and second nasal prongs (22,24) anda 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) anda 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).
