Lung plethysmography Health Article

Definition

Lung plethysmography is a test used to measure how much air you can hold in your lungs.

See also:

• Limb plethysmography
• Plethysmography

Alternative Names

Pulmonary plethysmography; Static lung volume determination; Whole-body plethysmography

How the test is performed

You will sit in a small, airtight room known as a body box. You will breathe or pant against a mouthpiece. Clips will be put on your nose to shut off your nostrils. Depending on the information your doctor is looking for, the mouthpiece may be open at first, and then closed.

You will be breathing against the mouthpiece in both the open and closed positions - they give different information to the doctors. As your chest moves while you breathe or pant, it changes the pressure and amount of air in the room and against the mouthpiece. From these changes, the doctor can get an accurate measure of the amount of air in your lungs.

Depending on the purpose of the test, you may be given some medication before the test.

How to prepare for the test

Let your doctor know if you are taking any medications, especially ones for breathing problems. You may have to temporarily stop taking certain medications before the test.

Wear loose clothes that allow you to breathe comfortably.

Avoid smoking and heavy exercise for 6 hours before the test.

Avoid heavy meals before the test - they can affect your ability to take deep breaths.

How the test will feel

The test involves rapid and normal breathing, and should not be painful. However, you may feel short of breath or lightheaded. You will be monitored at all times by a technician.

The mouthpiece may feel uncomfortable against your mouth.

Why the test is performed

The test is done to see how well your lungs work. It can help your doctor determine if a lung problem is due to narrowing of the airways or a loss of the lungs' ability to expand (get bigger as air flows in).

The test can also be used to see how well you respond to certain medications that open the airways (such as bronchodilators).

Normal Values

Normal values are based upon the age, height, ethnicity, and sex of the person being tested. Normal results are expressed as a percentage.