Pulmonary Function Testing
Pulmonary Function Tests (PFTs) are a broad range of tests that 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 the diagnosis of 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 detects 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 transfer oxygen from
the air into the bloodstream.
PFTs are performed on both inpatients and outpatients for diagnosis and
management of respiratory conditions, pre-operative assessments, disability
How the test is performed?
In a spirometry test, a person breathes into mouthpiece that is connected
to an instrument called a spirometer. The instrument records the amount
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 measurements are performed by having the patient breathe 100 percent oxygen for several
minutes, via a mouthpiece. Completion time for this test varies with different
disease processes or medical conditions.
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.
How to prepare for the test?
Do not eat a heavy meal before the test. Do not smoke for four to six
hours prior to the test. Specific instructions will be given if bronchodilators
or inhaler medications should be withheld. Sometimes, medication may be
inhaled prior to the test.
How the test will feel?
Since the test involves some forced breathing and rapid breathing, some
temporary shortness of breath or lightheadedness may be experienced. There
is a tight fitting mouth piece to breathe through, and nose clips are applied.
Cooperation from the patient performing the test is crucial in providing
accurate results. A poor seal around the mouthpiece of the spirometer
can give poor results that do not permit interpretation.
Pulmonary Function Testing requires a prescription for your primary care
physician. The patient is responsible for all insurance co-payments at
the time of the test.