Assessment of lung function is a tool used to both diagnose asthma and to monitor the benefit of treatment.  The test determines how much and how fast air can be passed in and out of the lungs.  Since adequate results require patients to follow directions, the test is not done on patients younger than five years of age.

During the procedure, you will be asked to blow forcefully into a machine (spirometer) which is connected to a computer.  After a few attempts, you will be given a nebulized breathing treatment to dilate you airways, followed by several more attempts.  Large changes in lung function from before and after the breathing treatment can be an indication of asthma.  For patients that have asthma and are started on medications, periodic PFTs are done to monitor response to treatment.  This test is also used to diagnose other lung disease such as emphysema.