Spirometry:
Respiratory Protection. - 1910.134
Definition
Pulmonary function tests are a broad range of tests that are usually done in a
health care provider's office or a specialized facility. They measure how well
the lungs take in and exhale air and how efficiently they transfer oxygen into
the blood.
Spirometry measures how well the lungs exhale. The information
gathered during this test is useful in diagnosing certain types of lung
disorders, but is most useful when assessing for obstructive lung diseases
(especially asthma and chronic obstructive pulmonary disease, COPD).
Lung volume
measurement permits the detection of restrictive lung diseases. In this set of
diseases, a person cannot inhale a normal volume of air. Restrictive lung
diseases may be caused by inflammation or scarring of the lung tissue
(interstitial lung disease) or by abnormalities of the muscles or skeleton of
the chest wall.
Testing the
diffusion capacity (also called the DLCO) permits an estimate of how
efficiently the lungs are able to transfer oxygen from the air into the
bloodstream.
Alternative
names
PFTs; spirometry; spirogram; lung function tests
How the test
is performed
- Spirometry: a person performs the test by breathing into
mouthpiece that is connected to an instrument called a spirometer.
The spirometer records the amount of air and the
rate of air that is breathed in and out over a specified time. Some of the
test measurements are obtained by normal, quiet breathing, and other tests
require forced inhalation or exhalation after a deep breath.
- Lung volume measurement can be performed in two
ways. The most accurate way is for a person to sit in a body plethysmograph, a sealed, transparent box that
resembles a telephone booth, while breathing in and out against into a mouthpiece.
Changes in pressure inside the box allow determination of the lung volume.
Lung volume can also be measured when a person breathes nitrogen or helium
gas through a tube for a specified period of time. The concentration of
the gas in a chamber attached to the tube is measured, allowing estimation
of the lung volume.
- The diffusion capacity is measured when a person
breathes carbon monoxide for a very short time (often one breath). The
concentration of carbon monoxide in exhaled air is then measured. The
difference in the amount of carbon monoxide inhaled and the amount exhaled
allows estimation of how rapidly gas can travel from the lungs into the
blood.
Why is the test done
The test is performed to diagnose certain types of lung disease
(especially asthma,
bronchitis,
and emphysema),
to determine the cause of shortness of
breath, or to measure whether occupational exposure to contaminants affects
lung function. It can also be used after the administration of medications to
assess their effect, and to measure progress in disease treatment.