Lung Function Tests
How To Prepare continued...
Do not eat a heavy meal just before this test because a
full stomach may prevent your lungs from fully expanding. You should not smoke
or exercise vigorously for 6 hours before the test. On the day of the test,
wear loose clothing that does not restrict your breathing in any way. You
should also avoid food or drinks that have caffeine because it can cause your
airways to relax and allow more air than usual to pass through.
you have dentures, wear them during the test to help you form a tight seal
around the mouthpiece of the spirometer.
How It Is Done
Lung function tests are usually done in
special exam rooms that have all of the lung function measuring devices. The
test is usually done by a specially trained
respiratory therapist or technician. For most of the
lung function tests, you will wear a nose clip to make sure that no air passes
in or out of your nose during the test. You then will be asked to breathe into
a mouthpiece connected to a recording device.
The exact procedure
is different for each type of test. For example, you may be asked to inhale as
deeply as possible and then to exhale as fast and as hard as possible. You also
may be asked to breathe in and out as deeply and rapidly as possible for 15
seconds. Some tests may be repeated after you have inhaled a spray containing
medicine that expands the airways in your lungs (bronchodilator). You may be
asked to breathe a special mixture of gases, such as 100% oxygen, a mixture of
helium and air, or a mixture of carbon monoxide and air. Sometimes a sample of
blood may be taken from an artery in your wrist to measure blood gases.
If you have body plethysmography, you will be asked to sit inside a small
enclosure similar to a telephone booth, with windows that allow you to see out.
The booth measures small changes in pressure that occur as you breathe.
The accuracy of the tests depends on your ability to follow all of the
instructions. The therapist may strongly encourage you to breathe deeply during
some of the tests to get the best results.
The testing may take
from 5 to 30 minutes, depending upon how many tests are done.