A pulmonary function test (PFT) is a group of tests that measure how well the lungs are working. These tests assess lung volume, capacity, and the flow of air in and out of the lungs. They help doctors diagnose conditions like asthma, chronic obstructive pulmonary disease (COPD), and other respiratory issues. During a PFT, patients may be asked to breathe into a device called a spirometer. This device records the amount of air inhaled and exhaled, as well as how quickly air can be expelled. The results help healthcare providers determine lung function and guide treatment options.