Spirometry refers to tests that use a special machine to measure a person's lung function. It determines how much air a person can exhale, how fast a person can exhale, and how much air a person can inhale.

Who is a candidate for the test?

Spirometry is done in a healthcare setting using special equipment. It may be done when a person has shortness of breath, or difficulty breathing. The test can be used to diagnose respiratory conditions, including the following:

Once a respiratory problem has been diagnosed, spirometry can be used to monitor response to treatment.

How is the test performed?

Spirometry is performed using a simple instrument called a spirometer. The person taking the test puts the instrument in his or her mouth. The individual inhales as much air as the lungs will hold, then blows out the air as fast and for as long as possible. The spirometer records the volume that the lungs can exhale. It also measures the speed of exhalation.

The maximum volume ventilation, or MVV, test measures the volume exhaled in 15 seconds. This result is multiplied by four to give the value for one minute.

Both the forced vital capacity, or FVC, test and the forced expiratory volume, or FEV1, test measure the rate and amount of air exhaled in one second. The individual inhales and blows into the spirometer as hard and fast and long as possible. The procedure is repeated three times and the highest numbers are recorded.