Spirometry is a type of pulmonary function test that measures how well the lungs are functioning. It involves breathing into a machine called a spirometer, which measures the amount of air that is breathed in and out, as well as the speed of the air flow. Spirometry can be used to diagnose and monitor a variety of lung conditions, including asthma, chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis. It can also be used to assess the effectiveness of certain treatments for these conditions. During a spirometry test, the person is asked to take a deep breath and then blow out as hard and fast as possible into the spirometer. The results of the test can help doctors determine how well the lungs are functioning and if there are any abnormalities in the respiratory system.