On the day of the test, you will sit or stand upright, take a deep breath and blow hard and fast into a plastic mouthpiece connected to a machine called a spirometer. Since you will be blowing hard and fast, you may develop dizziness, lightheadedness, or cough. You should let the technician know if you notice any discomfort. The test will be repeated at least three times to make sure the results are consistent. The machine will calculate and graph your results, including measurements known as Forced Expiratory Volume (FEV1) and Forced Vital Capacity (FVC).
After the test, you may be given a medication to open your lungs (bronchodilator) and a repeat test will be performed to find out if the medication improved your breathing measurements. Your doctor will explain what your results mean after interpreting them.