To be honest, I don’t have any idea what a spirometer is until I saw the picture of it at Wikipedia. When I saw photo, I already got an idea what it is but just don’t know how it was called back then.
Anyway, a spirometer is a deviced used to measure the volume of air inspired and expired by the lungs. This is a medical gadget usually used by patients with pulmonary problems.
If you don’t have an idea what a spirometer is, here is a photo I took from Wikipedia:
