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Pulmonary Function Test


A pulmonary function test measures how well your lungs take in and release air, and how well they move gases such as oxygen from the atmosphere into your body’s circulation. Our certified technologist will conduct the test in our Pulmonary Function Testing Lab and will ensure you feel comfortable.

How Do I Prepare for My Pulmonary Function Test?

Do not eat a heavy meal before your test. A full stomach may prevent your lungs from fully expanding. Do not smoke or exercise for six hours before your test.

If your pulmonary function test is done as an outpatient procedure, be sure to wear loose fitting clothing. Do not eat or drink anything that contains caffeine because it can cause your airways to relax and allow more air than usual to pass through, which alters the results of your test.

If you have dentures, wear them during the test to help you form a tight seal around the mouthpiece of the machine.

What Should I Expect?
Please allow 60 to 90 minutes to complete the pulmonary function test, which consists of three parts:

Part One: Spirometer
You will first be asked to breathe as deeply as possible into a mouthpiece that is connected to a machine called a spirometer. The spirometer measures and records the rate and amount of air that enters and leaves your lungs. During the test, you will sit upright and wear a nose clip, ensuring you breathe only through your mouth.

Part Two: Plethysmograph
The second component of the pulmonary function test is lung volume measurement using a large chamber called a plethysmograph. The chamber, which looks something like a clear telephone booth, is sealed, allowing for changes in air pressure and composition to measure how much air your lungs can take in while breathing in and out of a mouthpiece.

Part Three: Diffusion Capacity
In this part of the test, you will breathe a harmless gas, called a tracer gas, for one or two short breaths. The concentration of how much of the gas you breathe out is measured and compared to the concentration you breathed in. The difference tells us how well the gas travels from the lungs into the blood, allowing the technologist to estimate how well your lungs move oxygen from the air into your bloodstream. This test helps measure the amount of damage done to your lungs by disease or injury.

When Will I Receive My Results?
A Mercy Gilbert pulmonologist will evaluate your pulmonary function test and send preliminary results to the ordering doctor immediately after your test. A final written summary will follow in a few days.

We want you to feel comfortable before, during and after your test. If you have any questions, please feel free to ask your respiratory therapist or call Mercy Gilbert's Cardiopulmonary Services at 480.728.7208.