Pulmonary function tests (PFTs) are non-invasive tests that show how well the lungs are working. The tests measure lung volume, capacity, rates of flow, and gas exchange. This information can help your physician diagnose and decide the treatment of certain lung disorders.
Obstructive. This is when air has trouble flowing out of the lungs due to resistance. This causes a decreased flow of air.
Restrictive. This is when the chest muscles can’t expand enough. This creates problems with air flow.
Spirometry. A spirometer is a device with a mouthpiece hooked up to a small electronic machine.
Plethysmography. You sit or stand inside an air-tight box that looks like a short, square telephone booth to do the tests.
Tidal volume (VT). This is the amount of air inhaled or exhaled during normal breathing.
Minute volume (MV). This is the total amount of air exhaled per minute.
Vital capacity (VC). This is the total volume of air that can be exhaled after inhaling as much as you can.
Functional residual capacity (FRC). This is the amount of air left in lungs after exhaling normally.
Residual volume. This is the amount of air left in the lungs after exhaling as much as you can.
Total lung capacity. This is the total volume of the lungs when filled with as much air as possible.
Forced vital capacity (FVC). This is the amount of air exhaled forcefully and quickly after inhaling as much as you can.
Forced expiratory volume (FEV). This is the amount of air expired during the first, second, and third seconds of the FVC test.
Forced expiratory flow (FEF). This is the average rate of flow during the middle half of the FVC test.
Peak expiratory flow rate (PEFR). This is the fastest rate that you can force air out of your lungs.
Normal values for PFTs vary from person to person. The amount of air inhaled and exhaled in your test results are compared to the average for someone of the same age, height, sex, and race. Results are also compared to any of your previous test results. If you have abnormal PFT measurements or if your results have changes, you may need other tests.
There are many different reasons why pulmonary function tests (PFTs) may be done. They are sometimes done in healthy people as part of a routine physical. Or you may have PFTs if your healthcare provider needs help to diagnose you with a health problem such as:
PFTs may be used to check lung function before surgery or other procedures in patients who have lung or heart problems, who are smokers, or who have other health conditions. Another use of PFTs is to assess treatment for asthma, emphysema, and other chronic lung problems. Your physician may also have other reasons to advise PFTs.
Because pulmonary function testing is not an invasive procedure, it is safe and quick for most people. But the person must be able to follow clear, simple directions.
All procedures have some risks. The risks of this procedure may include:
In some cases, a person shouldn’t have PFTs. Reasons for this can include:
Your risks may vary depending on your general health and other factors. Ask your physician which risks apply most to you. Talk with him or her about any concerns you have.
The clinical staff will explain the procedure to you. Ask him or her any questions you have.
Tell your healthcare provider if you take any medicines. This includes prescriptions, over-the-counter medicines, vitamins, and herbal supplements.
Make sure to:
If you have a history of lung or breathing problems, you may be tired after the tests. You will be given a chance to rest afterwards. Your physician will talk with you about your test results.