Drager respirometer

Drä·ger res·pi·rom·e·ter

(drā'gĕr),
an inferential meter to measure tidal and minute volume from the number of revolutions of a vane rotated by the gas stream as the latter passes through two lightweight lozenge-shaped meshing rotors.

Dräger,

Heinrich, German manufacturer of industrial and diving respiratory apparatus, 1898–.
Dräger respirometer - an inferential meter to measure tidal and minute volume.