Pulmonary Function Test: Types, Process, Risks

A pulmonary function test is a relatively common medical procedure. As the name suggests, it is meant to check how your lungs are.

pulmonary function test

A pulmonary function test is a relatively common medical procedure. As the name suggests, it is meant to check how your lungs are. There are different pulmonary tests that serve different purposes. Here are just some of them.

What it is

As mentioned earlier, a pulmonary function test looks at the status of your lungs. It is an objective way to measure how well your lungs are functioning. It can also pinpoint concerns which are used as a basis for both diagnosis and proper intervention. This test is not only limited for people with current or potential lung problems. It can also be used as a post-surgery test or a diagnostic tool for those constantly exposed to a workplace which could be hazardous to the lungs. Some companies that deal with chemicals, for example, have a regular pulmonary function test as part of the health benefits of their employees.

There is really nothing to be too concerned about when you undergo such a test. Easily administered and non-invasive in nature, these tests cover pretty much everything where lungs are concerned. These include lung capacity, flow rates, oxygen and carbon dioxide exchange, and lung volume. Such essential information will help your doctor identify the severity of certain lung conditions and the best way to address them.

Different kinds

As said earlier, there are different kinds of pulmonary function tests that serve different purposes. Here are three of the most utilized types:

  • Spirometry

This primarily looks into your gas exchange. Are you breathing enough oxygen in? Are you exhaling enough carbon dioxide out? In this pulmonary function test, you will be using a spirometer. It is a mouthpiece that you inhale and exhale into as normally as you would. This mouthpiece is connected to a small electronic machine which then gives an accurate reading of your lung capacity to take in and expel gas. Basically, it will determine how well your lungs function.

This test is not for diagnosis alone. Apart from being a basis for diagnosis, this can be a comparative tool as well. It can compare your lung capacity before and after taking certain medication meant to relieve symptoms of lung problems. This test can also show how well you are responding to certain medications your doctor has prescribed. Spirometry is a common pulmonary function test for people suffering from asthma, pulmonary fibrosis, cystic fibrosis, COPD, and other lung disorders.

  • Plethysmography

If a spirometer checks your lung capacity to breathe gas in and out, this next type of pulmonary function test shifts its focus to the amount of gas in your lungs. To properly measure lung volume, you will have to be required to either sit or stand inside an airtight box that looks like a telephone booth. Here, you will have to inhale and exhale into a mouthpiece. Your doctor will then determine lung volume by measuring air pressure in the box. Aside from lung volume, this test can also help pinpoint the location of a blood clot if there is any. This test is usually prescribed if you have potential blood clots or if you exhibit symptoms of upper respiratory problems such as pain and difficulty while breathing and shortness of breath.

  • Diffusion capacity

The final type of pulmonary function test is meant to check the function of the alveoli. These are tiny air sacs found in the lungs where gaseous exchange occur. This test is prescribed by the doctor in order to identify how well your lungs are processing air. This is also the go-to test to show how well your lungs diffuses harmful gases such as carbon monoxide.


Not to belabor the point but a pulmonary function test is easy to take because you are not required to do much plus it is non-invasive. However, there are still some risks involved when undergoing this procedure. It essential to be aware of the following if you are about to take this test:

  • May cause dizziness
  • May cause cough
  • May feel out of breath
  • May trigger an asthma attack

Inform your doctor BEFORE taking the test if you have a history of aneurysm, if you have had surgery, if you have had a history of cardiovascular ailments, or if you have been diagnosed with tuberculosis and other respiratory disorders regardless of the severity.

You should also tell your doctor if any of these conditions apply to you. Each of these conditions may affect the results of whatever pulmonary function test that you took.

  • Pregnancy
  • Maintaining any form of medication especially pain relievers or bronchodilators
  • Exhaustion that might affect test results
  • Stomach bloating

When do you need it?

A doctor commonly asks a patient to undergo a pulmonary function test given the following situations:

  • Allergies
  • Respiratory disorders and infections
  • Injuries
  • Chronic lung problems (asthma, bronchitis, etc.)
  • Restrictive airway problems
  • Lung diseases such as asbestosis, sarcoidosis, and scleroderma
  • Constant smoking
  • History of cardiovascular illnesses

Preparing for a PFT

When you prepare for a pulmonary function test (PFT), there are some things you have to do. These include stopping any medication you are taking, to cease smoking before taking the test, and to avoid eating a lot on the day of the tests. Make sure you discuss preparations in detail with your physician. He/She might require added ways to better prepare for your PFT to ensure high accuracy in your test results.

A pulmonary function test is a routine test that many undergo. Given how safe and easy the test is done, taking it poses no problem at all except for rare occasions where certain risks have been identified. Consult your doctor about the best time to undergo such a routine. Early detection of lung concerns can definitely expedite the healing process as well. For optimum lung health, take that needed pulmonary function test as soon as possible.

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