Pulmonary Function Tests

What is a Pulmonary Function Test (PFT)?

• A PFT is a relatively simple test. It consists of a clear, airtight box, soft nose clips, a mouthpiece, and a small electronic machine known as a spirometer that measures your airflow.
• The test is safe and doesn’t require a healthcare provider to put any tools or instruments inside your body.
• It is a non-invasive assessment that measures how well your lungs function, evaluating lung volume, capacity, airflow rates, and gas exchange.
• It helps your provider diagnose lung disorders and guide treatment decisions.
• There are many different types of PFTs. Some also measure how well your lungs absorb oxygen into your blood and how exercise affects your lungs.
• A PFT may take between 20 and 60 minutes to complete depending on the type of PFT you are having performed. If you are on oxygen, you can expect it to take up to 20 minutes longer.
• PFTs are performed by specially trained Respiratory Therapists (RT).

Types of lung function test:

• Simple PFT – Spirometry
• Pre & Post PFT – Spirometry test performed without medication, administer medication, wait 10 minutes, and repeat test.
• Complete PFT – Spirometry, Body Plethysmography, and Gas Diffusion study.
• Methacholine Challenge – Performed in outpatient hospital setting with the involvement of pharmacy staff.

Why is a PFT performed?

 Your healthcare provider may order pulmonary function tests if you have lung or airway symptoms like cough or shortness of breath, are undergoing surgery or smoke tobacco products. These symptoms may include:

• Chest tightness, pain or pressure.
• Coughing, especially if you produce mucus or phlegm.
• Difficulty breathing or taking a deep breath.
• Shortness of breath (dyspnea).
• Wheezing.

PFTs help your healthcare provider:

• Detect narrowing in your lungs’ airways.
• Identify early changes in your lungs’ ability to transfer oxygen to your blood.
• Measure the effects of continued smoking on chronic pulmonary diseases.
• Decide if medications may help improve your breathing.
• Understand if exposure to substances in your environment has affected your lungs.
• Determine your ability to tolerate surgery or other medical procedures.
• Help your healthcare provider diagnose Asthma, Chronic Obstructive Pulmonary Disease, Pulmonary Fibrosis, weakness of your breathing muscles, and narrowing of your trachea.

How do I prepare for a pulmonary function test?

• Do not use any breathing medication such as bronchodilators or inhalers for four (4) hours prior to testing.
• No smoking for four (4) hours before the test.
• No heavy meals. Avoid caffeine.
• Do not wear any tight clothing. Wear loose, comfortable clothing that does not squeeze your chest.
• Be prepared to remove any dentures, partials, or flippers for best results.
• Bring a bottle of water as it may cause some dryness of mouth.

What should I expect the day of my PFT?

A specially trained Respiratory Therapists (RT) will bring you into the pulmonary function lab and record the following information to determine a typical value for your demographic:

• Height
• Weight
• Age
• Race
• Sex

After recording your information, the respiratory therapist will escort you to the PFT equipment and give you instructions according to your test. 

During Spirometry –

• The RT will first put soft clips on your nose. The nose clips ensure that you breathe through your mouth, not your nose.
• You’ll put your lips around a mouthpiece, and the mouthpiece connects to a spirometer. The RT will give you directions on breathing in and out.
• You may take deep breaths in and out. You may also take deep breaths in and blow out as hard and as fast as you can.

During Plethysmography –

• The RT will put nose clips and you’ll sit in the clear box. RT will close the door. The door remains closed for about five minutes.
• Tell the RT if you’re uncomfortable in confined spaces. They can help you feel more comfortable during the test.
• You’ll put your lips around the mouthpiece, and the RT will give you directions on breathing in and out.
• As you breathe, the spirometer will detect pressure or volume changes in the box to help measure your lung volume.
   

During Gas Diffusion Story –

• The RT will put on your nose clips.
• You’ll put your lips around the mouthpiece, and a healthcare provider will give you directions on breathing in and out a small, safe amount of carbon monoxide.
• As you breathe, the spirometer measures how much carbon monoxide you exhale. This measurement indicates how much of the gas your lungs absorbed.

Lung function tests include:

• Spirometry – Spirometry measures how much air you can inhale and exhale. It also estimates how much air is in your lungs.
• Lung volumes or body plethysmography – Lung volumes or body plethysmography measure the various amounts of air that are in your lungs after different points of inhalation and exhalation.
• Gas diffusion study – A gas diffusion study measures how much oxygen and other gases transfer from your lungs to your blood.

What happens after my PFT?

After your test, you can resume your breathing medications and your regular activities. Schedule a follow-up appointment with your provider, if you don’t already have one, to discuss your test results.