A description is given of a gas separation device for a physiological fluid, comprising a containing body (6) having at least a first inlet aperture (7) for a physiological fluid, positioned with a tangential direction of access, at least one outlet aperture (9) for the said fluid, spaced apart from the said inlet aperture, and a guide element (17) housed within the said body. The guide element (17) has a continuous active surface (15) designed to contact and guide the said fluid and delimits, together with the containing body (6), a first annular chamber (20) into which the first inlet aperture (7) opens directly.