A throwaway device 100 for measuring respiratory flow rates (e.g peak flow, pulmonary function test, spirometer) incorporates a first deflector 104, a blade 108 and a second deflector 106 enclosed inside a housing 102. The first deflector 104 facilitates inflow of air to the cylindrical housing 102 and the second deflector 106 facilitate outflow of air. The deflectors may have helical structures to generate swirl. The blade 108 has two conical ends 110 at two opposite edges. The blade 108 is positioned between the first deflector 104 and the second deflector 106 and rotates about a rotational axis A-A’. A removable mouth piece 112 may be attached to the housing 102. The blade, housing and the two deflectors are made of different medical grade plastic biocompatible materials using multiple sessions of injection moulding process.
