What Are Pulmonary Function Tests?


What Are Pulmonary Function Tests?

If you struggle with catching your breath, smoke, have symptoms of lung disease such as asthma, or are about to undergo a major surgery, your physician may order pulmonary function tests (PFTs). These non-invasive tests reveal how well your lungs are working, by measuring your ability to take in oxygen. They can help your physician understand why you may have trouble breathing, diagnose lung disorders, if any, and design the best treatment plan for you.

PFTs can help diagnose conditions that affect the lungs, such as:

  • Asthma/allergies
  • Bronchitis/ respiratory infections
  • Lung fibrosis
  • COPD
  • Asbestosis (due to exposure to asbestos)
  • Sarcoidosis (inflammation of lungs and other tissues)
  • Scleroderma (disease that affects connective tissue)
  • Pulmonary tumors
  • Lung cancer

What To Expect At A Pulmonary Function Test

Before scheduling PFTs, your physician may request a preliminary consultation with you. Tell your doctor’s office about any and all prescription and over-the-counter medications you are taking. If you are actively using medications that may affect the test results, your physician may ask you to stop taking them before the test.

You can also help to ensure accurate test results by following important guidelines as you prepare for your PFTs. First, avoid food and drinks that contain caffeine. Caffeine can open your airways and alter test results. Second, avoid any activities that may stress your lungs, such as heavy exercise or smoking. Third, avoid wearing constrictive clothes or eating a big meal before the tests. Tight clothes and/or a full stomach can restrict breathing and limit lung capacity.

The following are the components of PFTs, although your provider may not order them all:


For this test, you will be asked to stand in a booth and breathe through a mouthpiece. The test accurately measures your lung volume by recording the changes in pressure in the booth as you breathe.


This is a good test for the diagnosis of asthma or COPD, because it measures how well you can move air in and out of your lungs.

Diffusing Capacity (DLCO)

DLCO measures your lungs’ ability to uptake oxygen and deliver it into your blood.

Other tests may include short, simple exercises, such as a 6-minute walk, to evaluate your baseline breathing function. This way, your provider can measure improvement during and after your treatment.

Risks Of PFTs

PFTs are only available in healthcare facilities, and our staff carefully evaluates potential risks before scheduling any of these tests. For this reason, they are generally safe.

Pulmonary Function Testing At WWMG

At WWMG, all PFTs are performed in our Pulmonary Department’s specialized lab, which is designed specifically to diagnose and treat pulmonary respiratory function. All PFTs at WWMG are directed by our team of board-certified pulmonary and sleep physicians. Before taking PFTs, you will receive specific instructions on how to prepare, and a technician will walk you through each test. You will see your provider immediately after the PFTs are done, and go over your results at that time.

The physicians and staff of WWMG’s Department of Pulmonary and Sleep Disorders are dedicated to giving you high-quality, comprehensive care and customer service. You can reach the Pulmonary Department in Everett at 425-252-1116 and in Edmonds at 425-791-3084.