Spirometry is a common breathing test that assesses how well your lungs work. The test measures how quickly and how much air you can breathe in and out. It is part of the testing done with full pulmonary function testing which may include other assessments. During normal breathing, air flows in and out of your lungs freely. However, people with chronic obstructive pulmonary disease (COPD) have a hard time breathing out, and therefore too much air stays in their lungs. This is known as “air trapping” and is one of the causes of feeling short of breath. Spirometry is an important test that should be done in addition to asking about your symptoms and medical history when COPD is diagnosed. Spirometry can help decide what medicines you will take and it can be used to follow your lung health over time.