A group of tests that measures the function of the lungs, diagnoses problems with the lungs, and/or determines how well treatment for a lung condition is working. 


Lungs, mouth, windpipe


  • To help diagnose suspected lung conditions or diseases, such as:
    • Asthma
    • Emphysema
    • Chronic bronchitis
  • To quantify pulmonary disability
  • To determine the effectiveness of medication given for a known lung condition
  • To evaluate a patient's condition before surgery


  • These tests should not be administered 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


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 for 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, and you'll be able to rest between tests.

Anesthesia – None

Description of the Procedure - Immediately before each pulmonary function test, the doctor or technician will explain how each test is performed and how the PFT device being used (i.e., spirometer, peak flow meter) 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 conducted during or immediately following exercise (on a treadmill or stationary bike). If you have trouble breathing, pain, or dizziness during testing, tell the doctor or technician immediately.

The pulmonary function tests usually administered are:

Peak expiratory flow – Take as deep a breath as possible, then exhale as forcefully as possible into the mouthpiece of a peak flow meter. Repeat three times.

Forced expiratory time – Take as deep a breath as possible, then, with your mouth wide open, blow out as hard as possible until your lungs feel completely empty, while your exhalation time is measured with a watch.

Maximum ventilatory volume – Blow as hard and as fast as possible into the mouthpiece of a spirometer with rapid in and out breaths for a period of 15 seconds. Repeat three times.

Forced vital capacity – Take as deep a breath as possible, then blow out into the mouthpiece of a spirometer as hard and as fast and long as possible. Repeat three times.

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.

After Procedure – Rest until you feel able to leave. If testing causes symptoms of 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:

  • Slight risk of collapsed lung in some patients with lung disease.
  • Allergen challenge tests can pose dangers, since adverse effects of the test may occur hours after testing.

Accordingly, such tests should only be done in limited, specific circumstances, and then only 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


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 probably 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, and, if necessary, recommend medication and/or other treatment options best suited for you.


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

University of Iowa

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