A turbine spirometer comprises a breathing tube into which is subject is to breath and a vane to be driven by the subjects breath. The breathing tube has a first axis A-A at its opening in the direction of air flow and the vane rotates about a second axis B-B. The first A-A and second B-B axes are inclined to one another at angle of around 100 degrees such that in use the axis of rotation B-B is substantially vertical.
