Monroe Carell Jr. Children's Hospital at Vanderbilt
Monroe Carell Jr. Children's Hospital at Vanderbilt
Monroe Carell Jr. Children's Hospital at Vanderbilt
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Lung Function Testing


A pulmonary function test (PFT) provides information about how well a child's lungs are working. Children over age five are usually capable of performing the test. The most common PFT is called spirometry. It is a painless test to measure how much and how fast you can move air into and out of your lungs.

What happens during the spirometry test?

While standing up, you will be asked to take in a deep breath and blow hard and fast into a filtered mouthpiece attached to a data-recording device called a spirometer. You will be encouraged to continue to blow out until your lungs feel completely empty. To make sure that no air is escaping from your nose, you may have to wear a nose clip. You will be asked to repeat this test several times until there are two or three good efforts.

How does it work?

A computerized sensor, which is part of the spirometer, will calculate and graph your blowing results. The results demonstrate your rate of air flow, and the volume of air flow (the amount that you were able to blow out within the first second). This is referred to as the Forced Expiratory Volume in the first second (FEV1). This machine also records the total volume of all the air you were able to blow out of your lungs, called the Forced Vital Capacity (FVC).

What does it mean?

Abnormal findings suggest an airflow obstruction (narrowing) that may be a result of asthma. If an obstruction is discovered, your health care provider may have you inhale a medication called a bronchodilator. This medicine should cause your airways to open up. A repeat or post spirometry will be obtained. An improved post measurement will show the obstruction may be reversible. Spirometry is an effective measure in diagnosing asthma, along with medical and symptom history.

Last Edited: June 23, 2016
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