During a spirometry test, patients are instructed to breathe several times into a tube attached to a machine called a spirometer, according to Mayo Clinic. Spirometry tests are used by clinicians to diagnose chronic lung conditions such as asthma, chronic bronchitis and pulmonary fibrosis.
Before a spirometry test, clinicians instruct patients to take a deep breath and blow out as hard a possible into a tube for several seconds, explains Mayo Clinic. Health care providers also instruct patients to make sure that their lips form a seal around the tube so that no air leaks out. Spirometry tests are usually repeated at least three times to ensure that results are accurate and consistent.