Lung Plethysmography: What It Is And Why It’s Done

If you live with a chronic lung disease, you’ve likely had pulmonary function tests (PFTs). There are several types of PFTs or lung function tests, including spirometry, pulse oximetry and lung plethysmography.

These tests provide your doctor with valuable lung function measurements. Having these important measurements helps your doctor better understand your lungs, how they function and to develop a treatment plan.

We’re here to give you the information you need to know about lung plethysmography, what it is and why it’s done.

What is Lung Plethysmography?

What is Lung Plethysmography?

Lung plethysmography is type of pulmonary function test. It is also called body plethysmography or pulmonary plethysmography.

Doctors order lung plethysmography tests to measure how much air you can hold in your lungs and to assess the progression of chronic lung diseases. In addition, lung plethysmography measures how much air remains in your lungs after you exhale as much as possible.

How is Lung Plethysmography Performed?

How is Lung Plethysmography Performed

You will sit in a windowed, airtight room that resembles a telephone booth. Inside the booth, there will be a chair and a device with a mouthpiece on it. The technologist performing the test will place a clip on your nose and will encourage you to do your best.

The mouthpiece may be open for part of the test and closed for another part of the test. The technician will ask you to breathe or pant into the mouthpiece.

As your chest moves, the amount of air and the pressure inside the booth and against the mouthpiece changes. Based on these changes, your doctor receives an accurate measurement of the amount of air in your lungs.

Measurements Gained During the Test:

  • Total Lung Capacity (TLC) — The total amount of air in the lungs after breathing deeply.
  • Functional Residual Volume (FRC) — The amount of air left in the lungs after breathing normally.
  • Residual Volume (RV) —The amount of air that stays in your lungs after you exhale as much as possible.

How Do You Prepare for the Test?

If your doctor orders a lung plethysmography test, talk with your doctor about the test and what you can expect. Discuss any questions or concerns you have.

If you struggle with small spaces, let your doctor know. Because the lung plethysmography booth is small, it may make some people anxious.

Keep in mind that you will be able to see out of the booth at all time, and the technician performing the test will remain with you. Typically, the test lasts about three minutes.

Tell your doctor about any medications you take, especially medications for breathing. Because your doctor wants the most accurate measurements possible, your doctor may ask you to stop taking certain medications for breathing for a couple days before the test.

In addition, most people wear loose fitting clothing for lung plethysmography.

What To Avoid Before the Test:

  • No heavy meals
  • Don’t drink alcohol
  • Refrain from smoking
  • Avoid strenuous exercise

What Does the Test Feel Like?

Lung plethysmography involves normal and rapid breathing. You may experience shortness of breath or feel slightly lightheaded. Some people find the mouthpiece uncomfortable. However, the test should not be painful.

For people who struggle in tight or small spaces, the booth might cause some anxiety. Remember, the booth is clear, and you will be able to see out at all time. The technician monitors you during the test.

Are There Any Risks?

Are There Any Risks

Generally, lung plethysmography is considered safe. However, there are a few possible risks. While unlikely to happen, these risks include:

  • Dizziness
  • Feeling lightheaded
  • Shortness of breath
  • Anxiety from being inside the closed booth

If you are concerned or have questions about having a lung plethysmography test, it’s important to talk with your doctor.

What Do the Results Mean?

Normal results depend on varying factors, including age, weight, height, gender and ethnic background.

Abnormal results show that there is a problem in the lungs. For example, the problem could be caused because of a breakdown of the lungs’ structures, an issue with the chest wall and its muscles or a condition that makes it difficult for the lungs to expand and contract.

While lung plethysmography will not find the cause of the problem, it helps your doctor narrow down the possibilities. Once your doctor has enough data from various pulmonary function tests and other procedures, your doctor can diagnose and treat your condition more accurately.

What Are the Next Steps?

In addition to keeping track of your pulmonary health, finding the right treatment options for you is essential.

Your treatment plan will depend on factors, such as your lung disease diagnosis, your pulmonary function test results, chest x-rays and CT scans and your lung disease symptoms. Your treatment plan could include medications, inhalers, oxygen therapy, pulmonary and rehabilitation.

Always consult with your doctor to find a treatment plan that will work best for you.