Spirometry is the most basic test of pulmonary (lung) function. Spirometry is most often used to diagnose and monitor lung problems, such as chronic bronchitis, emphysema, pulmonary fibrosis, chronic obstructive pulmonary disease (COPD), or asthma.

Spirometry is also used to monitor how well medicines for respiratory problems are working.

In a spirometry test, a device called a spirometer is used to measure how much air the lungs can hold and how well the lungs are able to move air in and out.

The accuracy of a spirometry test depends on the patient's understanding and cooperation.

Spirometry is different from a peak flow reading and must be performed in a doctor's office.

A spirometer consists of a mouthpiece and disposable tubing connected to a machine that records the results and displays them on a graph.

To perform spirometry, a person inhales deeply, closes the mouth tightly around the tube and then exhales through the tubing while measurements are taken. Some test measurements are obtained by normal breathing, and other tests require rapid and forceful inhalation and/or exhalation.

Nose clips are usually used to make sure air is only coming out of the mouth. Sometimes a test will be repeated to get the best effort. Often, the tests are repeated after a person takes a medicine that opens the airways of the lungs (a bronchodilator). A spirometry test can take anywhere from five minutes to a half an hour, depending on the different types of breathing tests being measured.

Normal spirometry results are based on the age, height, and gender of the person being tested and most are experienced as a percentage of a predicted value.

Because a spirometry test involves forced and rapid breathing, some people may experience temporary shortness of breath. Spirometry should not be done if a person suffers from chest pains, has had a recent heart attack, or has serious heart disease.

To prepare for a spirometry test:

• Do not eat a heavy meal before spirometry testing
• Refrain from smoking for four to six hours before the test
• Empty your bladder right before testing
• Specific instructions are given if medicines such as bronchodilators or inhalers need to be withheld before the test.
• Sometimes, medicine can be inhaled before the test, to see how well a patient responds to the medicine