The invention relates to an apparatus (2, 4) for tracking a treatment for obstructive sleep apnea, including a gas passage (10) and a Venturi tube (16) having a cylindrical inlet (40) and outlet (42), said Venturi tube (16) being axially arranged in said gas passage (10), a first pressure sensor (101), and a second pressure sensor (102). The diameters (D1) of the inlet (40) and outlet (42) of the Venturi tube (16) are between 10 and 25 mm. The Venturi tube (16) includes, arranged in series between said inlet (40) and outlet (42), a convergent portion (44) having the shape of an arc (46, 48), a cylindrical neck (50), the diameter of which is smaller than the diameter (D1) of the inlet (40), and a divergent portion (52) characterized by an angle of divergence (α) of between 5° and 15°. The invention also relates to equipment for treating sleep apnea, which includes a pressurized-gas source (6) connected to a breathing mask (8) via a gas duct (30), as well as to an apparatus (2, 4) according to the invention, which is arranged between said gas source (6) and said breathing mask (8).
