Media Backgrounder: Spirometry
What is spirometry?
Spirometry is a simple, painless test that measures the amount of air a person
can breathe out, and the amount of time taken to do so.
Spirometry is important for diagnosing chronic obstructive pulmonary disease
(COPD) and other lung diseases. Reports from the Global Initiative for Chronic
Obstructive Lung Disease (GOLD), international guidelines, and many national
guidelines for management of COPD all recommend spirometry as the standard
for diagnosing this lung disease.
Who should get spirometry?
The GOLD report recommends that any person at risk for COPD should have a
spirometry test. That means anyone who:
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Is over 40 years old,
Has a history of exposure to COPD risk factors, such as tobacco smoke,
other kinds of smoke, or dusts and fumes encountered on the job, and
Has symptoms of COPD, such as a chronic cough, bringing up phlegm or
mucus most days, and feeling short of breath
How can spirometry help reduce the burden of COPD?
COPD is under-diagnosed, with recent studies indicating that 25% to 50% of
people with clinically significant COPD don’t know they have the disease. In
addition, the early stages of COPD are often unrecognized. This is because the
development of symptoms tends to be slow and people may accept a chronic
cough or mild breathlessness as a “normal” part of getting older or an expected
consequence of smoking.
A spirometry test can identify COPD in its early stages, before symptoms
become troublesome and thus before patients are likely to see their doctor
because of breathing problems. The earlier COPD is detected, the better the
chance to slow or prevent further deterioration of lung function. However,
treatments are available to help patients at all stages of COPD feel better and
live more active lives, so it is never too late to get spirometry and seek treatment
for COPD.
What does spirometry measure?
A number of different measurements of lung function are possible in spirometry.
For the diagnosis of COPD, three measurements are most important:
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Forced Expiratory Volume in One Second (FEV1)
How much air a person can exhale in one second after inhaling as
deeply as possible.
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Forced Vital Capacity (FVC)
The total amount of air a person can exhale after inhaling as deeply as
possible.

Ratio of FEV1 to FVC
How much of the total that is exhaled in the first second (that is, a
measure of how quickly a person can empty his or her lungs).
What do spirometry results mean?
To determine whether a person has COPD, his or her spirometry results are
compared to normal or “predicted” values. The predicted values depend on a
person’s age, height, sex, and ethnicity.
COPD obstructs and slows the flow of air into and out of the lungs. Therefore, in
a person with COPD, both FEV1 and FEV1/FVC are lower than normal.
According to the GOLD report, an FEV1/FVC ratio less than 0.7 means that a
person is likely to have COPD.
When COPD is present, the degree of reduction in FEV1, or degree of airflow
limitation, is one indicator of the severity of the disease. According to the GOLD
classification system, FEV1 at least 80% of the normal value indicates Mild
airflow limitation, FEV1 between 50% and 80% of normal indicates Moderate
airflow limitation, FEV1 between 30% and 50% of normal indicates Severe airflow
limitation, and FEV1 below 30% of normal indicates Very Severe airflow
limitation.
A person’s symptoms, history of exacerbations (periodic worsening of COPD
symptoms), and other health problems also contribute to the overall severity of
COPD.
How is spirometry done?
A spirometry test is done using a machine called a spirometer. Some general
practitioners and family doctors have spirometers available in their offices, but in
other cases a patient may have to visit a pulmonary function laboratory for the
test. Spirometers vary from large, high-tech machines to simple hand-held
devices. But in any case, the test takes only takes a few minutes to do.
A patient should:
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Sit down to perform the test.
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Breathe in fully.
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Seal his or her lips around the mouthpiece of the spirometer.
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Force the air out of the lungs as hard and fast as possible, until the lungs are
completely empty.
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Breathe in again and relax.
Usually this maneuver is repeated three times for best results.