Lung plethysmography
Definition
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Lung plethysmography is a test used to measure how much air you can hold in your lungs.
See also:
Alternative Names
Pulmonary plethysmography; Static lung volume determination; Whole-body plethysmography
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 damage to the lung structure, or a loss of the lungs' ability to expand (get bigger as air flows in).
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 light-headed. You will be monitored at all times by a technician.
The mouthpiece may feel uncomfortable against your mouth.
Risks
- Dizziness
- Light-headedness
- Shortness of breath
Normal Results
Normal values depend on your age, height, ethnic background, and gender. Normal results are given as a percentage.
What Abnormal Results Mean
Abnormal results point to a problem in the lungs. This problem can be due to a breakdown of the lung structure, or an inability of the lungs to expand.
Lung plethysmography will not find the cause of the problem. However, it will help the doctor narrow down the list of possible problems.
Reviewed By: Benjamin Medoff, MD, Assistant Professor of Medicine, Harvard Medical School, Pulmonary and Critical Care Unit, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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