The invention relates to a gas mixing device (10) for an air-way management system. The device has an elongated chamber (C) with a first gas inlet port (1P) being arranged for intake of atmospheric air (AA) into the chamber, the first inlet port being positioned at an end section of the internal chamber. Further, a second gas inlet port (2P) is arranged for intake of a gas (G) into the chamber (C), the second gas inlet port having an injector (INJ) from which the gas can exit into the chamber with an injection direction (ID), the injection direction having a projection (ID_proj) being oppositely directed relative to an in-flow direction (F) of the first gas inlet port (1P) so as to provide mixing of the atmospheric air and the gas. Opposite the first gas inlet port (1P) there is a breathing port (3P) for allowing an individual to breathe through the gas mixing device. The device is beneficial in that the breathing resistance is relatively low while the device simultaneously provides a sufficient gas mixing of the gasses to be mixed. Additionally, the invention provides a relatively compact gas mixing device which facilitates easy integration into e.g. a respiration mask for measurements of respiratory parameter of an individual e.g. a patient.
