Pulmonary Function Testing

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What is pulmonary function testing?

Pulmonary or lung function testing includes various tests that measure how well your lungs are working. Doctors use pulmonary function testing to diagnose and manage many diseases that affect your lungs and breathing. These diseases commonly include asthma, cystic fibrosis, blood clot in the lung (pulmonary embolism), and COPD (chronic obstructive pulmonary disease).

Pulmonary function testing is only one method of diagnosing and managing respiratory diseases. Discuss all the testing and monitoring methods with your doctor to understand which options are right for you.

Types of pulmonary function testing

Common types of pulmonary function testing include:

  • Arterial blood gas test to measure oxygen and carbon dioxide levels and other factors in the blood

  • Body plethysmography to measure how much air is in your lungs when you take a deep breath and how much air remains in your lungs after you exhale as much as you can

  • Bronchoprovocation tests to measure lung function after exposure to factors that commonly trigger asthma. This includes a methacholine challenge test to help diagnose asthma.

  • Lung diffusion capacity to measure how well oxygen moves into your blood from your lungs

  • Peak expiratory flow to measure the speed of exhaling and lung constriction. People with asthma often use this test routinely to monitor their asthma control.

  • Pulse oximetry to measure oxygen levels in the blood

  • Spirometry to measure the amount of air and the rate that you inhale and exhale

Pulmonary function tests are sometimes done at the same time using the same equipment. Body plethysmography, spirometry, bronchoprovocation tests, and lung diffusion capacity are often performed at the same time.

Why is pulmonary function testing used? 

Your doctor may recommend pulmonary function testing to diagnose and determine the severity of diseases that affect breathing and to determine how well treatments are working. These diseases, disorders and conditions include:

Your doctor may also use pulmonary function testing in the following situations: 

  • You are a current or former smoker.

  • You are having surgery including abdominal, heart and lung surgery.

  • You have abnormal test results including abnormal arterial blood gases and chest X-ray.

  • You have symptoms of respiratory disease including chest tightness, cough, phlegm, wheezing, and shortness of breath.

Who performs pulmonary function testing?

A pulmonary function technologist or a specially trained respiratory therapist or nurse usually performs pulmonary function testing. A pulmonary function technologist is a healthcare provider who specializes in performing lung function tests to diagnose and treat lung diseases. Common lung diseases include asthma, chronic obstructive pulmonary disease (COPD), and other breathing problems. 

The following types of doctors are likely to supervise your pulmonary function testing:

  • Allergist-immunologists specialize in caring for people with allergies, asthma, and other diseases of the immune system.

  • Pediatric allergist-immunologists specialize in caring for children from infancy through adolescence with allergies, asthma, and other diseases of the immune system.

  • Pulmonologists specialize in the medical care of people with breathing problems and diseases and conditions of the lungs.

  • Pediatric pulmonologists specialize in the medical care of infants, children and adolescents with diseases and conditions of the lungs.

How is pulmonary function testing performed?

Your pulmonary function testing will be performed in a hospital, office, or pulmonary function test lab. It generally involves blowing into a mouthpiece attached to a device that measures your lung function. Proper technique is important for accurate pulmonary function testing results. Techniques may take a bit of practice to master. 

Specific procedures include:

  • Body plethysmography involves sitting inside a clear, airtight chamber and inhaling and exhaling through a mouthpiece against a closed shutter device. During the test, your chest volume expands, which increases the pressure in the chamber. This pressure reading helps determine your lung function. Other pulmonary function tests may also take place in the chamber.

  • Bronchoprovocation testing involves exposure to common asthma triggers, such as cold air and the drug, methacholine, then measuring your lung function.

  • Lung diffusion capacity involves taking a deep breath of air mixed with a tracer gas, usually carbon monoxide. You then hold your breath for 10 seconds and rapidly exhale into a mouthpiece. The amount of tracer gas in the air you exhale is measured to help determine lung function.

  • Peak expiratory flow involves blowing quickly and forcefully into a small hand-held device, called a peak flow meter, and recording your readings.

  • Spirometry involves blowing into a mouthpiece as hard as you can for several seconds until your lungs are empty. The spirometer takes measurements at different times while you exhale and records them on a graph.

Will I feel pain with pulmonary function testing?

Your comfort and relaxation is important to both you and your care team and will help obtain the most accurate test results. Pulmonary function testing is not painful, but you may feel short of breath or lightheaded briefly after some tests. Tell your care team if this does not pass quickly or if you have any other symptoms.

What are the risks and potential complications of pulmonary function testing?  

Pulmonary function testing is generally safe, without serious risks or complications for most people. Some people should not have certain pulmonary function tests. Before having a pulmonary function test, discuss your risks with your doctor. Make sure your doctor is aware of your complete medical history including the following conditions:

How do I prepare for my pulmonary function testing?

You are an important member of your own healthcare team. The steps you take before your test can improve your comfort and help obtain the most accurate test results.You can prepare for pulmonary function testing by:

  • Not eating a large meal before the test

  • Not smoking. Even stopping for a few days before the test is beneficial.

  • Stopping your medications before the test as directed by your doctor

  • Wearing loose, comfortable clothing

Questions to ask your doctor

Have pulmonary function testing can be stressful. It is common for patients to forget some of their questions during a doctor’s visit. You may also think of other questions after your appointment or after you leave the hospital. Contact your doctor with concerns and questions before your procedure and between appointments.

It is also a good idea to bring a list of questions to your appointments. Questions can include:

  • Why do I need pulmonary function testing? What are the other options for diagnosing and monitoring my condition?

  • Who will perform my pulmonary function testing? It this person a nurse, respiratory therapist or pulmonary function technologist? Is this person certified to perform pulmonary function testing or has he or she had other special training?

  • How often will I need pulmonary function testing?

  • How should I take my medications before and after pulmonary function testing?

  • When and how will get my results?

  • When should I follow up with you?

  • How should I contact you? Ask for numbers to call during and after regular hours.

What can I expect after my pulmonary function testing?

Knowing what to expect after pulmonary function testing can help you get back to your everyday life as soon as possible.

How will I feel after my pulmonary function testing?

You should be breathing normally after your pulmonary function testing and should not feel any ill effects of the test. Tell your care team if you are dizzy, short of breath, or have any other symptoms or concerns. 

When should I call my doctor?

You should keep your follow-up appointments after pulmonary function testing. Contact your doctor if you have any concerns between appointments. Seek emergency medical care or call 911 if shortness of breath or other breathing problems are getting worse quickly.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2018 Oct 24
  1. An Approach to Interpreting Spirometry. American Academy of Family Physicians. http://www.aafp.org/afp/2004/0301/p1107.html.
  2. Body Plethysmography. Johns Hopkins School of Medicine. http://oac.med.jhmi.edu/res_phys/Encyclopedia/BodyPleth/BodyPleth.HTML.
  3. Body Plethysmography. Morgan Scientific, Inc. http://www.morgansci.com/pft-pulmonary-testing-products/pft-products-and-pulminary-testing/body-plet....
  4. Bronchoprovocation testing. Wolters Kluwer Health. http://www.uptodate.com/contents/bronchoprovocation-testing.
  5. Diffusing capacity for carbon monoxide. Wolters Kluwer Health. http://www.uptodate.com/contents/diffusing-capacity-for-carbon-monoxide.
  6. Lung Diffusion Capacity Testing (DLCO). National Jewish Health. http://www.nationaljewish.org/programs/tests/pulmonary-physiology/pulmonary-function/lung-diffusion-....
  7. Methacholine Challenge Testing: Identifying Its Diagnostic Role, Testing, Coding, and Reimbursement. American College of Chest Physicians. http://journal.publications.chestnet.org/article.aspx?articleid=1085169#Contraindications
  8. Peak Flow Meter. Wexner Medical Center. http://medicalcenter.osu.edu/patientcare/healthcare_services/allergy_asthma/about_asthma/asthma_peak....
  9. Peak Flow Meter. Tips to Remember. https://www.aaaai.org/conditions-and-treatments/library/at-a-glance/peak-flow-meter.aspx.
  10. Spirometry: how to take a lung function test. European Lung Foundation YouTube video. http://www.youtube.com/watch?v=6kbgZWS5wH0.
  11. Spirometry to measure breathing. University of Washington. http://www.spirometrytraining.org/.
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