Pulmonary Function Tests
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Pulmonary Function Tests


En Español (Spanish Version)


Pulmonary function tests (PFTs) are a group of tests that:

  • Measure lung function
  • Diagnose lung problems
  • Determine how well treatment for a lung condition is working

Parts of the Body Involved

  • Lungs
  • Trachea
  • Throat

Respiratory System

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Reasons for Procedure

  • Diagnose suspected lung conditions or diseases, such as:
  • Measure pulmonary disability
  • Evaluate symptoms such cough, wheezing, and dyspnea
  • Determine the effectiveness of medication
  • Evaluate a condition before surgery

Risk Factors for Complications During the Procedure

These tests should not be done if you have:

  • Unstable heart or lung disease
  • Recently suffered a heart attack
  • Active tuberculosis
  • An acute asthma attack
  • Respiratory distress
  • Active bleeding from the lower respiratory tract

What to Expect

Prior to Procedure

  • Review your medications with your doctor. There may be some that you should stop taking before testing.
  • Don't eat, smoke, or exercise 4-8 hours before testing.
  • Wear loose-fitting clothing.

During Procedure

A technician will ask you to exhale and inhale in different patterns and speeds into pulmonary testing devices (ie, spirometer, peak flow meter). You will rest between tests.

Peak Flow Meter

Lung test peak flow meter

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Description of the Procedure

The technician will explain how each test is done and how the PFT device being used works. You might sit in an atmosphere-controlled booth. You may have to wear a nose clip. In some cases, one or more of these tests may be done during or immediately following exercise (on a treadmill or stationary bike). Tell the technician right away if you have breathing problems, pain, or dizziness during testing.

Some pulmonary function tests:

  • Spirometry—the main measurements include: forced expiratory volume in one second (FEV1) and forced vital capacity (FVC)
  • Lung volumes—includes total lung capacity (TLC), functional residual capacity (FRC), and residual volume (RV)
  • Quantification of diffusing capacity—measures gas exchange

Other tests may include flow-volume loops. This test can identify upper airway obstruction. There are also tests to measure maximal respiratory pressures. These tests detect respiratory muscle weakness.

Additional pulmonary function tests that are used in certain situations:

  • Oxygen saturation test—A small probe is painlessly strapped or clipped to one of your fingers or toes. This measures the amount of oxygen being carried in the blood.
  • Allergen challenge tests—You are exposed to specific allergens during pulmonary function testing. This is only done in limited situations, under close and careful supervision.
  • Bronchoprovocation testing:
    • Methacholine provocation test—People with asthma will feel a mild constriction of the airways when they inhale the drug methacholine. This test may be done if your doctor thinks you have asthma, but other PFTs have not shown a clear asthma diagnosis.

After Procedure

Rest until you feel able to leave. You'll be given a bronchodilator or other medication if testing causes symptoms of a lung condition or disease.

How Long Will It Take?

20-45 minutes

Will It Hurt?

The test does not hurt. But you may experience symptoms of your lung condition or disease (wheezing, coughing, shortness of breath) during or immediately following testing. Symptoms usually are cleared using a bronchodilator.

Possible Complications

  • There may be a slight risk of collapsed lung in some people with lung disease.
  • Allergen challenge tests can pose dangers, since side effects may occur hours after testing. Such tests should only be done in limited, specific circumstances, and under close and careful supervision by a doctor or specially trained technician.

Average Hospital Stay


Postoperative Care

Your doctor may adjust your medications if she diagnoses a new lung condition.


Your doctor will compare the results of your tests with charts of normal values based on your age, sex, and height. If your values are less than 80% of the normal values, then you are more likely to have some type of lung disease. The individual test results may help your doctor diagnose a specific disorder. Your doctor will discuss the results with you. She will also discuss options for further diagnostic testing or treatment.

Call Your Doctor If Any of the Following Occurs

After you leave the hospital, call your doctor if any of the following occurs:

  • Headaches, nausea, muscle aches, dizziness, or general ill feeling
  • Shortness of breath or difficulty breathing
  • Chest pains after testing


American Lung Association

National Institutes of Health


Canadian Lung Association

COPD Canada


Birnbaum S, Barreiro TJ. Methacholine challenge testing: identifying its diagnostic role, testing, coding, and reimbursement (review). Chest. 2007 Jun;131(6):1932-1935.

Chang J, Mosenifar Z. Differentiating COPD from asthma in clinical practice. J Intensive Care Med. 2007 Sep-Oct;22(5):300-309.

Crapo RO, Casaburi R, Coates AL, et al. Guidelines for methacholine and exercise challenge testing (1999). Am J Respir Crit Care Med. 2000;161:309.

Pulmonary function tests. MedlinePlus, National Library of Medicine website. Available at: http://www.nlm.nih.gov/medlineplus/ency/article/003853.htm. Accessed October 16, 2007.

Walsh JM. Interpreting pulmonary function test. Loyola University Medical Education Network website. Available at: http://www.meddean.luc.edu/lumen/MedEd/medicine/pulmonar/fellow/exam2.htm. Accessed October 30, 2006.

Last reviewed October 2007 by Marcin Chwistek, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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