Pulmonary Function Testing

Day to day operations of the Ocean Springs Lung Clinic PFT Lab are carried out by a licensed and board-certified Respiratory Therapist.

Pulmonary Function Tests (PFT) are a group of tests that measure how well the lungs take in and release air and how well the lungs move gases, such as oxygen, from the atmosphere into the body’s circulation.

A complete PFT is comprised of three separate tests. For each test, patients are fitted with a mouthpiece connected to the testing machine. Patients also wear a nose clip to ensure that all airflow is measured through the mouth. The three components of a PFT are:

Flow Volume Loop Test (FV) / Spirometry

This test, also known as spirometry, measures how well the lungs work by measuring how much air is inhaled, how much is exhaled, and how quickly a patient exhales. A spirometer records the rate of air movement and the amount of air the lungs breathe in and out over a period of time.

Spirometry is often performed before and after use a bronchodilator, which is a substance such as albuterol sulfate that widens air passages by relaxing the bronchial smooth muscle. When the test is repeated after use of a bronchodilator, it can determine if albuterol sulfate is effective in opening the bronchioles and relaxing the muscles in the lungs

Diffusion Capacity Test (DLCO)

This test measures how well the lungs allow oxygen and carbon monoxide to pass in and out of the blood, a process called diffusion. Diffusion is most efficient when the surface area for transferring oxygen and carbon dioxide in the lungs is high and blood is readily available to transport these gasses. Certain lung conditions will decrease the surface area or efficiency in which lungs transfer oxygen or carbon dioxide into your bloodstream.

With this test, the patient will breathe a tiny (and safe) amount of carbon dioxide to measure the diffusion capacity. The patient will begin with resting breathing, then the technician will ask the patient to take a deep breath in, a deep breath out, and a final deep breath in that the patient will hold for about 6 seconds. Over the course of this 6 seconds, diffusion takes place. When the patient finally exhales, the air is measured and analyzed.

Total Lung Capacity Test (TLC)

This third test determines Total Lung Capacity (TLC). Even after the patient exhales as much as possible in the FV (spirometry) test there is still a measurable amount of air left in the lungs. The information gathered from this test is combined with data from the FV test. With obstructive diseases, measuring the FV and TLC can reveal air trapping in the lungs and hyperinflation (when air sacs become less elastic). In restrictive diseases, the TLC confirms true restriction and the degree of restriction.

This test is performed with an inert gas such as nitrogen. The patient breathes in nitrogen through the mouthpiece for a specified period of time. The inert gas concentration is then measured in the expired air, from which the residual volume is calculated.

How to Prepare for the Test

  • Do not eat a heavy meal before the test.
  • Do not smoke for 4 to 6 hours before the test.
  • You will receive specific instructions if you need to stop using bronchodilators or inhaler medications.
  • You may have to breathe in medication before the test.

How the Test Will Feel

  • Since the test involves some forced breathing and rapid breathing, you may have some temporary shortness of breath or lightheadedness.
  • You breathe through a tight-fitting mouthpiece
  • You will have a nose clip.


  • Pulmonary Function Test (PFT)
  • Spirometry
  • Spirometry Sitting/Supine
  • Lung Volumes
  • Lung Diffusion Capacity

Six Minute Walk Test

The six-minute walk test (6MWT) is an easy to perform and practical test that has been used in the assessment of patients with a variety of cardiopulmonary diseases. During this test, a patient will walk for six minutes. This test can be used to monitor a patient response to treatments for heart, lung and other health problems. This test is commonly used for people with pulmonary hypertension, interstitial lung disease, pre-lung transplant evaluation or chronic obstructive pulmonary disease (COPD).

What to Expect When Doing the Test

Preparing for your test:

  • Wear clothes and shoes that are comfortable.
  • You may use your usual walking aids such as a cane or walker, if needed.
  • It is okay to eat a light meal prior to your test.
  • Take your usual medications.
  • Do not exercise within two hours of testing.

During the test:

  • The tester will measure your blood pressure, pulse and oxygen level usually with a pulse oximeter before you start to walk.
  • You should be given the following instructions: The object of the test is to walk as far as possible for six minutes. You will walk at your normal pace to a chair or cone, and turn around. And you continue to walk back and forth for six minutes.
  • Let the staff know if you are having chest pain or breathing difficulty.
  • It is acceptable to slow down, rest or stop. After every minute interval, you will be given an update.


  • The tester will watch to see if you have breathing difficulty or chest pain.
  • Oxygen and other supplies will be nearby if you need them.

Understanding the Results

The results of the test are compared to previous tests, repeated tests are useful, for instance six months or a year later. After the test, a physician may change the patient’s medication or exercise program based on test results.

What Are the Risks?

This is a low-risk medical evaluation and medical help is readily available while the test is being done.

Reach Out To Us With Any Questions or Concerns

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Ocean Springs Lung Clinic strives to provide the best and healthiest approaches to lung health care. Live healthier by taking the right steps to lung care. Contact us with any questions or to schedule an appointment.

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