A spirometry test measures lung function. A patient takes a deep breath and blows into a tube as hard as possible, explains Mayo Clinic. The test is repeated at least three times for consistency, and the highest result of the three consistent trials is used as the final result.
Spirometry is the first and most common test medical professionals use to determine lung function, says WebMD. Spirometry results in a spirogram, which reports the amount of air a patient can exhale with force after one breath, the total lung capacity, the amount of air in the lung after exhaling, and the amount of air a patient can exhale slowly after a single breath.