What is body plethysmography?
Body plethysmography is a medical test that measures lung volume and breathing mechanics very precisely. You sit inside an airtight cabin, similar to a small telephone box, and breathe through a mouthpiece as instructed, while various measurements are recorded.
How does the test work?
For body plethysmography, you take a seat inside a glass chamber. This chamber is completely sealed. You breathe through a mouthpiece, and a small clip is placed on your nose so that no air can escape. During the test, you are given clear instructions: sometimes you breathe in and out gently, and sometimes you breathe in or out more forcefully. At certain points, you briefly breathe against a closed valve. The cabin measures very precisely how pressure and volume change inside your lungs and in the surrounding space.
This might sound a little unusual at first, but it is neither painful nor dangerous. The test usually takes only a few minutes. Throughout, the amount of air in your lungs and how open your airways are is continuously monitored.
What does body plethysmography measure?
Body plethysmography can measure your total lung volume, including the air that stays in your lungs after you breathe out. This is not possible with simpler lung function tests such as spirometry. Doctors can also use this method to see how narrowed or blocked the airways are. This is especially important in conditions such as asthma, COPD, or other chronic lung diseases.
The test also gives information about whether the breathing muscles are working well enough, or whether changes in the chest are affecting breathing. The results help to tell apart different causes of breathlessness or coughing.
When is body plethysmography used?
Body plethysmography is mainly used when a detailed assessment of lung function is needed. This is often the case when a chronic airways condition is suspected or already known. It can also provide important information before chest surgery or when breathlessness has no clear cause.
In children, the method is used less often because it requires good cooperation. For adults and older teenagers, however, it is a standard procedure in respiratory medicine.
What do the results mean?
The measurements from body plethysmography show how much air the lungs can hold, how flexible the lungs are, and whether the airways are clear. Typical values include the residual volume (the air that remains in the lungs after breathing out as fully as possible) and the total lung capacity (the maximum amount of air the lungs can hold).
Results that differ from normal values can point to various conditions. Narrowed airways may suggest asthma or chronic obstructive bronchitis. A raised residual volume suggests that the lungs can no longer empty fully, which is seen in advanced COPD.
Is the test uncomfortable or risky?
Body plethysmography is generally well tolerated. The cabin can feel a little confined, especially for people who feel uneasy in small spaces. If you feel uncomfortable at any point, you can let the team know straight away, and the test can be paused or adjusted. Dizziness, the urge to cough, or mild breathlessness can occur, but these are rare and usually harmless.
There is no radiation involved. The test is also safe for pregnant women.
What happens after the test?
After the measurements are taken, the results are assessed by a specialist. They help to narrow down the causes of breathing difficulties and to tailor treatment more precisely. Sometimes body plethysmography is repeated over time to check how well a treatment is working or to monitor how a condition is progressing.
The test provides valuable information without placing any strain on the body, and it is an important part of modern respiratory medicine.
