Pulmonary Function Test

• 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.
• Cardiopulmonary exercise test (CPET). A CPET measures how well your heart, lungs and muscles work while you’re exercising.

Spirometry is the most common type of pulmonary function test.

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 use tobacco products (smoke). 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.

Even if you don’t have symptoms, your healthcare provider may order a pulmonary function test as part of a routine physical examination.

PFTs also 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.

PFTs help your healthcare provider diagnose:

• Asthma.
• Chronic obstructive pulmonary disease (COPD).
• Pulmonary fibrosis.
• Weakness of your breathing muscles.
• Narrowing of your trachea.

Who performs pulmonary function testing?

A specially trained respiratory therapist usually performs pulmonary function testing.

A pulmonary function test is relatively simple.

A PFT consists of a clear, airtight box, soft nose clips, a mouthpiece and a small electronic machine that measures your airflow (spirometer).

Before your pulmonary function testing, your healthcare provider may ask you to:

• Stop taking your breathing medicines for a short period.
• Wear loose, comfortable clothing that doesn’t squeeze your chest.
• Avoid any heavy exercise before your test.
• Avoid using tobacco products before your test.

These precautions will help ensure that you get accurate results from your PFT.

You shouldn’t eat a heavy meal before your PFT.

You should also avoid any caffeine.

You’ll take a PFT at a pulmonary function lab at an outpatient office or a hospital.

Before the test, your healthcare provider will record some personal information, including your:

• Height.
• Weight.
• Age.
• Race.
• Sex.

Your healthcare provider will use this information to determine a typical value for your demographic.

After recording your information, your healthcare provider will take you to a room with PFT equipment and give you instructions according to your test.

Spirometry

A healthcare provider 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 provider will then 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.

A healthcare provider will put on your nose clips, and you’ll sit in the clear box. Your provider will close the door. The door remains closed for about five minutes.

Tell the healthcare provider if you’re uncomfortable in confined spaces (claustrophobic). They can help you feel more comfortable during the test.

You’ll put your lips around the mouthpiece, and the provider 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.

Your healthcare provider 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.

A healthcare provider will attach you to machines that measure your heartbeat, blood pressure and blood oxygen. You’ll then walk on a treadmill or ride a stationary bicycle.
The machines will measure various aspects of your heart, lungs and muscles during the test.

Pulmonary function testing is safe. But you may feel dizzy, lightheaded or tired from breathing so deeply. You may also cough from blowing into the mouthpiece or feel tired from exercising. These symptoms should go away shortly after you complete the PFT. Let the healthcare provider know if you need a break during testing.

In very rare cases, pulmonary function testing may cause a collapsed lung (pneumothorax).

A PFT can also increase your heart rate. Tell the healthcare provider if you’ve had a heart attack recently or any other heart condition.

The healthcare provider will compare your score against the typical scores for your demographic. There’s a normal range expected for your age, height and sex.

There’s no such thing as failing a PFT. If it’s abnormal, your provider will discuss additional work you may need to obtain a diagnosis and a treatment plan.

You should receive the results of your pulmonary function test within a few days.

Your healthcare provider will contact you a few days after your pulmonary function test with your results. Reach out to your provider if you don’t hear from them with your results after a few days.

Based on your diagnosis, you may need regular testing to follow your condition at future visits.