Abstract: The invention relates to a respiratory assistance apparatus equipped with a turbine or compressor making it possible to deliver pressurized gas comprising a casing (1) having a gas inlet orifice (2), a motor (6) having a motor shaft (5) of axis (AA), the said motor shaft (5) being able to move about the axis (AA) when it is driven by the said motor (6), a first propeller (3) and a second propeller (4) mounted securely to the said motor shaft (5), an internal partition (7), arranged in the said casing (1), inserted between the two propellers (3, 4) so as to form a first stage (13) internal to the said casing (1) containing the first propeller (3) and a second stage (14) internal to the said casing (1) containing the second propeller (4), the said first stage (13) and second stage (14) being arranged in series, the said internal partition (7) comprising an opening (8) traversed by part of the motor shaft (5) and through which the first internal stage (13) is in fluid communication with the second internal stage