Pulmonary Function Test

Pulmonary function studies allow your doctor to assess various aspects of the functioning of your lungs in order to help determine a diagnosis and a suitable treatment.

There can be an improvement in lung function with proper medication, abstinence from smoking, adequate diet, sufficient rest and participation in an exercise program.

What is a pulmonary function test?

Pulmonary function tests consist of a series of breathing maneuvers to determine various measurements about the lungs. There are three basic types of breathing tests. These series of tests compile a complete pulmonary function test (the most common test ordered).

1. Spirometry: You will be asked to inhale deeply and exhale forcefully into a piece of equipment called a spirometer. The amount of air you inhale and the rate you exhale will give useful information about the health of your lungs. You may also be given inhaled medication (bronchodilator) and then retested to determine if the medication might be helpful.

2. Lung Volume Measurements: This test will measure the greatest amount of air that you can inhale and exhale through a mouthpiece. You will also be asked to perform a test sitting inside a large box for a brief period of time to measure your total lung volume.

3. Diffusing Capacity (DLCO): This test evaluates how well your lungs transfer the oxygen in the air to your blood stream. The amount of red blood cells (hemoglobin) in your blood can affect this measurement. Therefore, you may be asked to have some blood drawn to assist in a more accurate interpretation of this test.

Reasons for Procedure

• 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

How long will the test take?

Each type of pulmonary function test takes about 20 minutes. If your doctor has ordered a “complete” test, it will take about an hour. If your doctor also asked for assessment of bronchodilator response (complete B/A) it will probably take about 1 ½ hours.

Is there any preparation?

Do not take any inhaled medication for about 4-6 hours before this test. Other medications may be taken as usual.

Risk Factors for Complications During the Procedure

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

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 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.

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.

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

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 lung condition or disease, you’ll be given a bronchodilator or other medication.

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.

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