Pulmonary Function Testing
Why are Pulmonary tests done?
Pulmonary testing not only detects the presence of lung and breathing problems,
it also identifies the specific type of problem and evaluates its severity.
These tests can also help your physician determine the proper course of therapy.
How long do these tests take?
Depending on which tests are conducted, pulmonary testing can take from
20 minutes to two hours.
What tests are most commonly performed, and what do they involve? (Note: A complete pulmonary function test includes all of the above tests, and
usually takes anywhere from one to two hours.)
Simple Spirometry: In this test you are asked to breathe normally, and then to take in a
deep breath. When you have inhaled all the air your lungs can hold, you
are then asked to blow it into a machine as fast as possible. As you exhale,
we record the size of your breath and how fast you expelled it.
You may also be asked to perform a Maximal Voluntary Ventilation (MVV): This test requires you to breathe as deeply and rapidly as you can for
about 12 seconds in order to measure your maximal breathing capacity.
These two tests are commonly performed as a screening procedure to evaluate
your lungs. If you are having such a pulmonary screen done, you can expect
to spend about 20 minutes taking the two tests.
Sometimes your physician wants more detailed pulmonary function testing
performed. In this case, you will be asked to participate in one or more of the following
Bronchodilator Study: After completing the Simple Spirometry and the MVV, you are given an
aerosol medication to breathe. The medication is a bronchodilator that
relaxes your airways. After waiting 15 minutes for the medication to have
maximal effect, the above two tests are repeated. This bronchodilator
study allows us to evaluate the effect of the medication on your airways.
Lung Volumes: In this test, you are asked to breathe oxygen through a mouthpiece for
about eight minutes. We measure the total amount of air in your lungs
by watching how the oxygen exchanges with the air already in your lungs.
Diffusing Capacity: In this test, you are asked to breathe normally, then to take in as deep
a breath as you possible can, hold it in for 10 seconds, then exhale rapidly
until you get all the air out. Some of the special air mixture you inhale
travels from your air sacs (alveoli) into your bloodstream during the
10-second interval. Measuring the amount that gets into your bloodstream
allows your physician to assess how your lungs can absorb oxygen.
Arterial Blood Gases: Oxygen and carbon dioxide gases are carried by blood. Some lung problems
can cause either insufficient oxygen to be delivered to the blood or excess
carbon dioxide to be retained. This can be determined by testing a small
sample of blood, taken from a wrist artery using a small needle.
Are there things I can do to get ready for the test?
If you are an inpatient here at Hoag Hospital, the hospital staff will
be sure you are ready for the tests. If you are coming in for testing
as an outpatient, there are a few things you can do to achieve your best results:
- Avoid eating a heavy meal prior to your test.
- Wear loose-fitting clothing that will allow you to breathe deeply and comfortable.
- No smoking, alcohol or caffeine for 12 hours prior to your test.
What about medications?
Some inhaled medications and pills may need to be discontinued prior to
your testing. Please call the Respiratory Care Department to confirm which
medications you should stop taking. Also, remember to check with your doctor.
Is there anything else I should know?
These tests have great value in evaluating the health of your lungs and
airways. It is important that you give your best effort so that your test
results will be as revealing as possible. Always feel free to ask questions.
The respiratory therapist and your physician will be happy to explain
these tests in more detail.
High Altitude Simulation Test
This test is designed to examine the patient’s physiologic response
to low concentrations of oxygen. This simulates travel to a high altitude
environment, including commercial air travel during which cabin pressures
drop to levels as high as 8000 feet. The test is especially useful for
patients with a moderate decrease in oxygen at sea level who may have
further decreases of oxygen at higher altitudes. Patients inhale decreased
concentrations of oxygen selected to simulate the desired altitude. When
stable, the patient is walked briefly on a slow-moving treadmill to assess
his response to mild exercise at that “altitude.” Measurements
include single-lead electrocardiogram, oxygen saturation by oximetry,
and ventilation, as well as the monitoring of clinical signs and symptoms.
Supplemental oxygen therapy is provided as needed to estimate what liter
flow may be required