Spirometry (meaning the measuring of breath) is the most common of the Pulmonary Function Tests (PFTs), used to measure lung function. It specifically is used for the measurement of the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled. Spirometry is an important tool used for assessing conditions such as asthma and is used in combination with symptoms to assess asthma control.

The actual procedure is relatively straightforward. If the doctor determines that a breathing test is necessary, you will be taken to the testing area and introduced to the machine. A tight seal around the mouthpiece is required to assure the accuracy of the test. You will be asked to take the deepest breath you can, and then exhale into the sensor as hard as possible, for as long as possible. It is sometimes directly followed by a rapid inhalation (inspiration), in particular when assessing possible upper airway obstruction. Filter mouthpieces may be used to prevent the spread of microorganisms, particularly for inspiratory maneuvers. Frequently a short-acting bronchodilator (such as albuterol) will be given to you and then spirometry repeated approximately 10 minutes later to further assess possible inflammation.

On occasion further breathing tests may be ordered including exercise testing to assess symptoms with exertion or a methacholine challenge to assess airway reactivity when the diagnosis of asthma is uncertain.