Body plethysmography is a type of lung function test. You enter a see-through plastic box, where machines measure how much air goes into and out of your lungs when you breathe. Body plethysmography is safe, but deep breathing may make you feel lightheaded or dizzy. Your healthcare provider will contact you after a few days with your test results.
Body plethysmography (pronounced “pleh-thiz-mah-graf-ee”) is a noninvasive type of lung function testing known as a pulmonary function test. It can help determine how much air is in your lungs after you take a deep breath in (inhale). It also helps determine how much air remains in your lungs after you take a deep breath out (exhale).
Body plethysmography is safe and comfortable. It gives your healthcare providers critical information about how well your lungs function. This information helps them work with you to create the best treatment plan.
Other names for body plethysmography include lung plethysmography and pulmonary plethysmography.
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Body plethysmography helps diagnose lung and airway diseases, such as:
Body plethysmography can also:
Your healthcare provider may order a body plethysmography test if you have lung or airway condition symptoms. Some symptoms for which your healthcare provider may order body plethysmography include:
An abnormal body plethysmography test result can help your healthcare provider confirm that a condition is preventing your lungs from holding as much air as they should.
Body plethysmography is an accurate and relatively quick test — it typically takes fewer than 20 minutes to complete. Your healthcare provider can also get many measurements within just a few minutes.
The different types of body plethysmography include:
A healthcare provider who helps treat conditions that affect your lungs or breathing (respiratory therapist) usually performs body plethysmography in a lung function lab. A pulmonologist reviews and confirms the findings.
Body plethysmography takes place in an enclosed, airtight, see-through plastic box. As you breathe into a mouthpiece, a sensor inside the box measures any changes to the air pressure. The mouthpiece also has a sensor that measures your airflow and pressure in your mouth.
As your chest expands and contracts while you breathe, the sensor inside the box registers changes in the amount of air and air pressure in the box. The sensor in the mouthpiece also registers changes in pressure.
Body plethysmography measures the following:
Body plethysmography uses the relation Boyle’s law to determine the relationship between gas volume and pressure at a constant pressure. You can use gas volume measurements to determine the gas pressure. Conversely, you can use gas pressure measurements to determine the gas volume.
Other names for Boyle’s law include Boyle-Mariotte law and Mariotte’s law.
Tell your healthcare provider about any medications you’re taking. They may tell you to stop taking certain medications on the day of the test.
Your healthcare provider will give you directions on how to prepare for your body plethysmography. These include:
These directions will help ensure that your body plethysmography results are accurate.
During body plethysmography, you’ll sit in an enclosed, air-tight, see-through plastic box. Talk to your healthcare provider if you’re uncomfortable in confined spaces (claustrophobic). They may prescribe a medication for you to take before the body plethysmography to help calm your nerves. They’ll also talk to you throughout the test, and you can see them and everything else around you in the room while in the box. Let your healthcare provider know if you need a break during testing.
Your healthcare provider will place soft clips on your nose. The nose clips help you breathe out only through your mouth. Your healthcare provider will also give you instructions on how to breathe through the mouthpiece.
Once you’re ready, your healthcare provider will seal the door, and the test will begin.
If you usually get additional oxygen through a storage tank or machine (supplemental oxygen), you won’t be on it during the procedure.
No, body plethysmography isn’t painful.
However, you may feel dizzy, lightheaded or tired from breathing in and out deeply. Blowing into the mouthpiece may also cause you to cough. These symptoms should go away shortly after you complete the test. Let your healthcare provider know if you need a break during testing.
In rare cases, you may get too much carbon dioxide in your blood (hypercapnia) or too little oxygen in your blood (hypoxia). These conditions may occur if you spend a long time in the body plethysmography box.
Body plethysmography can also increase your heart rate. Tell your healthcare provider if you’ve had a heart attack in the past or any other conditions that affect your heart.
Body plethysmography takes about 15 minutes to complete.
After your body plethysmography, you may return to your normal daily activities.
If you felt dizzy or lightheaded during the test, your healthcare provider will monitor your health until your symptoms go away and you can go home.
A “normal” body plethysmograph depends on a few factors, including your:
Your healthcare provider will use these factors to determine a typical reading for your demographic. As a result, a normal body plethysmograph result for you may be different from the result of another person.
You should expect your body plethysmography results within a few days after taking the test.
Your healthcare provider will contact you a few days after your body plethysmography to discuss your results. Reach out to your healthcare provider if you don’t hear from them with your results after a few days.
If your body plethysmography helps your healthcare provider diagnose a chronic lung disease, you may have to schedule lung function tests yearly.
Spirometry is another type of pulmonary function test. It’s the most common test healthcare providers use to determine lung function.
However, it’s not as accurate as body plethysmography. Spirometry doesn’t measure residual lung volume or total lung capacity.
Body plethysmography also measures other characteristics, such as the pressure difference between your mouth and lungs (airway resistance) and the volume of gases in your thorax (intrathoracic gas volume, or ITGV).
A note from Cleveland Clinic
If you notice any changes in your breathing, it’s a good idea to reach out to your healthcare provider. The changes might not be serious or they might be a symptom of a lung condition. Your healthcare provider can use body plethysmography to help diagnose any possible lung conditions. The test is quick and accurate, it isn’t painful and you should get your results within a few days. A proper diagnosis can help you and your healthcare provider determine a healthcare plan that enables you to improve or maintain your quality of life.
Last reviewed by a Cleveland Clinic medical professional on 12/18/2022.
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