Spirometry (spi-ROM-uh-tree) is a common office test used to diagnose asthma, chronic obstructive pulmonary disease (COPD) and certain other conditions that affect breathing. Spirometry may also be used periodically to check how well your lungs are working once you’re being treated for a chronic lung condition. Spirometry measures how much air you can inhale and exhale. Spirometry also measures how fast you can exhale. Spirometry values below average indicate your lungs aren’t working as well as they should.