Pulmonary Function Lab

What is it? 

A Pulmonary Function Lab is the location in a hospital where breathing tests are performed. This is where your spirometry, diffusing capacity (DLCO) and total lung capacity (TLC) tests will probably be performed.

What should you expect?

On the day of your appointment:

If you are taking any inhaled medications you may be asked to withhold them for a specific time period ahead of your appointment. Some Pulmonary Function tests cannot be performed if you have taken certain medications. You should be told if this is necessary when your appointment is made but if you have any questions you should call the Pulmonary Function Lab to be sure.

You should avoid eating, smoking and exercising immediately before your appointment.

Before the tests start:

Depending on which breathing tests the physician has ordered the tests may take up to an hour, or even longer. Please inform the lab staff if you have other appointments that will limit the time you have for testing.

If you use supplemental oxygen you should ask the lab staff whether supplemental oxygen can be provided for you during your visit. This is a common request and most labs should be able to accommodate your needs.

You will have your height and your weight measured. Height is a very important measurement because the expected values for your test results are based largely on your standing height.

Important: Your height should never be guessed or remembered. It should be measured every time you have a Pulmonary Function test. When it is measured it should be done with your shoes off and with you standing straight, looking directly ahead. If it is not possible to measure your standing height correctly for any reason then it is possible to estimate your height with a good degree of accuracy by measuring fingertip to fingertip distance (arm span).

You may be asked about your smoking habits and smoking history. You may be asked about medications you are taking, particularly inhaled medications.

During the tests:

For all breathing tests you will be asked to sit upright in a chair. You may be asked to loosen your bra or your belt if these could restrict your breathing. If you are using supplemental oxygen you will be asked to take your nasal cannula off during each test. You will have your nose clipped so that you will breathe only through your mouth and you will be asked to breath through a mouthpiece. It is important that you keep your lips snug on the mouthpiece in order to get a tight seal so that air does not leak.

During each test the staff person giving you the test should explain the test maneuver beforehand and should be coaching and encouraging you the entire time you are performing the test. You should not feel self-conscious if you have difficulty following the instructions. All pulmonary function tests require that you breathe in unusual and very specific ways and this often takes practice.

You will probably need to perform each breathing test more than once even when you perform it correctly. This is because reproducibility is an important factor when assessing test quality. The staff person who is performing your test should tell you each time whether you did the test correctly, or if not, which part of the test you need to improve.

You may become short of breath. You may become fatigued. You may become dizzy. You may become claustrophobic. This is all normal. There should be no lasting effects from any breathing test. If you become too tired, short of breath, or uncomfortable please take time to recover between tests. If you are using supplemental oxygen you can use it between tests if this will help you recover. You can drink water if your throat is uncomfortable or dry. Kleenex should be available if you start coughing.

The nose clip and the mouthpiece should both be new and clean at the start of your testing session. The staff person performing your tests should be wearing gloves or at a minimum should have performed hand hygiene before your testing session.

After the tests:

You can have a copy of your test results when your testing session is over. This report will not include an interpretation, just the test results. This is because the Pulmonary Function Lab is responsible for performing your tests, but one or more pulmonary physicians are responsible for interpreting the results.

What affects test quality?

Leaking air during any of the tests will reduce the accuracy of the test and the results can be underestimated or overestimated depending on the test. If you are having difficulty keeping your lips snug on the mouthpiece please ask if a different mouthpiece is available. Because the breathing tests can make you short of breath, or even claustrophobic, you may be tempted to take extra air in by breathing around the mouthpiece, or to loosen your nose clip so you can breathe through your nose. Try to not to do these things. Keep your lips snugly on the mouthpiece during each test until you are told you can come off the mouthpiece.

Poor motivation often produces poor quality and inaccurate results. It is best when you cooperate with the lab staff, follow their directions, and try to give a good effort for each test. Unlike many other hospital tests you may have, the quality and accuracy of pulmonary function tests depend entirely on the effort you put into them.

Creative Commons License
PFT Patient by Richard Johnston is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.