This test measures the amount of air that can be taken in with
a deep breath and how quickly it can be expelled from the lungs
by a forceful exhalation. The tests can be used to diagnose &
monitor lung conditions.
There are different tests in the series:
The match test - this is a simple test that checks
the force of exhalations. It involves holding a lighted match six
inches away from the mouth, then exhaling as hard as possible to
blow out the flame. If the flame is blown out easily, the result
The forced expiratory time (FET) test - Involves
taking a deep breath in, then exhaling as fast as possible with
the mouth open wide. The exhalation time is measured in seconds.
Normal values for test: all the air in the lungs is expelled in
two to five seconds.
The peak expiratory flow (PEF) test - Involves inhaling
deeply, then blowing as hard as possible into a peak flow meter.
The highest of three values is recorded. Normal values for test:
the value should be 80 percent of the predicted normal value.
The maximum ventilatory volume (MVV) test - Uses an
instrument called a spirometer. Involves putting a mouthpiece in
the mouth & blowing into into as hard as possible for 15 seconds.
The result is recorded on a graph, and multiplied by four to give
the value for 1 minute. Normal values for test should be 15 to 20
times the FVC.
The forced vital capacity (FVC) test and forced expiratory
volume (FEV1) - Also uses the spirometer. Again, it involves blowing
into the mouthpiece as hard & long as possible. It is repeated
three times & the highest value recorded.
A test to measure your lung volume (size) will be
done in one of two ways. One way to measure lung volume is to have
you inhale a small carefully measured amount of a specific gas (such
as helium) that is not ever absorbed into your bloodstream. This
gas can mix with all of the air in your lungs before you breathe
it out again. The air and helium that you breathe out will be tested
to see how much the helium got diluted by the air in your lungs
and a calculation using this information can decide how much air
your lungs must have been holding in the first place.
The other way to measure lung volume is with a test
called "plethysmography." In this test, you will sit inside an airtight
cubicle that looks like a phone booth, and you will breath in and
out through a pipe in the wall. The air pressure inside the box
will change with your breathing because your chest expands and contracts
while you breathe. This pressure change can be measured and used
to calculate the amount of air you must be breathing.
Your lungs' efficiency at delivering oxygen and other
gases to your bloodstream can be tested and is known as your "diffusion
capacity." For this test, you will breathe in a small quantity of
carbon monoxide (too small a quantity to do you any harm) and the
amount you breathe out will be measured and compared. Your ability
to absorb carbon monoxide into the blood is representative of your
ability to absorb other gases such as oxygen.