pneumatometer

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An instrument for measuring the force or volume of inspiration or expiration in the lungs.

from The Century Dictionary.

• noun An instrument for measuring the quantity of air inhaled into the lungs at a single inspiration and given out at a single expiration; a pulmometer; a spirometer. Also called pneumometer, pneumonometer.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Physiol.) An instrument for measuring the amount of force exerted by the lungs in respiration.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A device used to measure the force of inspiration or expiration of a person's lungs.