Spirometry is a common test for measuring an individual’s lung capacity. It is often used to determine the presence or degree of respiratory illnesses, including COPD, pulmonary fibrosis, asthma, chronic bronchitis, or emphysema. Doctors also use spirometry tests to determine the effectiveness of medications on these conditions.
A spirometry test, which lasts about 15 minutes, involves breathing into a tube attached to a device that measures airflow. Patients are generally seated, with their nostrils clipped shut. The person administering the test will instruct the patient to inhale deeply and then blow out as strongly as possible. In order to obtain reliable results, patients must keep their lips tightly sealed around the tube while exhaling.
The doctor interpreting the test results generally requires three similar results close together in time to ensure accuracy. If there are significant discrepancies, the patient may have to repeat the test. The top reading out of three comparable attempts is considered the final result. Doctors trying to determine whether medication will improve a patient’s breathing may obtain an initial result, administer a bronchodilator, repeat the test a little later, and compare the two outcomes.