Definition

Pulmonary function tests (PFTs) are a group of tests that measure the function of the lungs, diagnose problems with the lungs, and/or determine how well treatment for a lung condition is working.

Parts of the Body Involved

• Lungs
• Trachea
• Throat

	Respiratory System
	© 2008 Nucleus Medical Art, Inc.

Reasons for Procedure

• To diagnose suspected lung conditions or diseases, such as:
  • Asthma
  • Emphysema
  • Chronic bronchitis
• To measure pulmonary disability
• To evaluate symptoms such cough, wheezing, and dyspnea
• To determine the effectiveness of medication
• To evaluate a condition before surgery

Risk Factors for Complications During the Procedure

These tests should not be done to patients who have:

• An 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

You'll be asked to exhale and inhale in different patterns and speeds into pulmonary testing devices (ie, spirometer, peak flow meter). You will be able to rest between tests.

Anesthesia

None

Description of the Procedure

Immediately before each PFT, the technician will explain how each test is performed and how the PFT device being used works. You may be asked to sit in an atmosphere-controlled booth and/or put on 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). If you have breathing problems, pain, or dizziness during testing, tell the technician right away.

The pulmonary function tests consist of:

• Spirometry—the main measurements include: forced expiratory volume in one second (FEV1) and forced vital capacity (FVC)
• Lung volumes—include 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 (can identify upper airway obstruction) and measurements of maximal respiratory pressures (detects respiratory muscle weakness).

Additional pulmonary function tests that are used in certain situations include:

• Oxygen saturation test—A small probe is painlessly strapped or clipped to one of your fingers or toes to measure 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 experience a mild constriction of the airways when the drug methacholine is inhaled. This test may be done in situations where asthma is suspected but other pulmonary function tests have not shown a clear diagnosis of asthma.

After Procedure

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

How Long Will It Take?

20-45 minutes

Will It Hurt?

The testing is not painful. However, you may experience symptoms of your lung condition or disease (wheezing, coughing, shortness of breath) during or immediately following testing. Symptoms usually can be cleared with the use of a bronchodilator.

Possible Complications

• There may be a slight risk of collapsed lung in some patients 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

None

Postoperative Care

Medications may be adjusted if a new lung condition is diagnosed.

Outcome

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 results of the individual tests may help your doctor diagnose a specific disorder. Your doctor will discuss the results with you, as well as options for further diagnostic testing or treatment.

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

RESOURCES:

American Lung Association
http://www.lungusa.org/

MedlinePlus National Institutes of Health
http://www.nlm.nih.gov/medlineplus/

CANADIAN RESOURCES:

Canadian Lung Association
http://www.lung.ca/

COPD Canada
http://www.copdcanada.ca/

References:

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.

ThirdAge WWW