PFT Pulmonary Function Test

A doctor performs a pulmonary function test to measure air taken into and exhaled from the lungs.  In order to accurately measure the ability of the lungs, the patient must not have had any outside stimulation from smoking, heavy eating or asthma drugs, for several hours before the test.

Wear loose-fitting clothing to the test to make breathing as easy as possible. If you wear dentures, be sure to keep them in during the test. This will help you form a tight seal around the rubber mouthpiece of the test machine.

Some ventilation tests may require wearing a nose clip to make sure no air passes in or out of the nose during the test. You will be asked to breathe in different patterns including exhaling as fast as possible after inhaling normally, and inhaling and exhaling deeply. You may be asked to breathe in specific non-harmful amounts of helium, nitrogen or pure oxygen. Some tests may be performed in a small enclosure or testing booth, which has a controlled atmosphere. The accuracy and value of the test is very dependent on you doing your best to cooperate and follow the technician's instructions during your breathing efforts.

Lung function is measured with a spirometer. The spirometer consists of a tube attached to a small machine that measures the force of the exhaled air. The patient is asked to take deep breaths and exhale forcefully into the tube. The test will last for up to 45 minutes, because three or more repetitions must be administered to assure the validity of the results.

After ventilation testing, you may feel lightheaded from breathing in and out rapidly. You will be able to rest between tests. But if you have severe pulmonary disease, a longer period of rest may be needed after the tests are over. If you have trouble breathing during a test, you should immediately tell the technician. Usually, no special follow-up care is needed after a pulmonary function test.

In addition, pulmonary function tests are important to assess the health of a person's lungs before chest surgery.

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Pulmonary function tests are used:

• to help diagnose and evaluate lung disease,
• to determine the appropriateness and effectiveness of new and current treatments, and
• to measure how severely the lung is damaged.

There are two general types of pulmonary function tests:

• ventilation tests
• arterial blood gas studies

Pulmonary function tests can be divided into 6 parts:

1. Air flow This is the key to detecting obstruction. The patient is instructed to breath out as hard and fast and completely as possible from a full inspiration.
2. Maximum voluntary ventilation This is a test of the patients ability to breath in and out as hard and fast as possible for 10 seconds (liters/min).
3. lung volumes This test may be performed using helium dilution technique or by body plethysmography.
4. diffusion of carbon monoxide This is a test of the ability of inhaled carbon monoxide to diffuse into the pulmonary circulation.
5. flow volume loop Graphic display of simultaneously obtained lung volume versus airflow can be useful to get an overall view of the pulmonary function. Most importantly however, it can suggest upper airway obstructions.
6. arterial blood gases Acid base balance is examined and the Alveolar: arterial oxygen gradient are calculated.