Pulmonary Function Tests (PFTs)

This information describes why you are having pulmonary function tests (PFTs) and what to expect before, during, and after your tests.

PFTs are breathing tests that measure how your lungs are working. The results will show how much air your lungs can take in and how the air flows in your lungs.

Reasons for Having PFTs

You may have a PFT to see how your lungs are working before surgery, diagnose or evaluate lung disease, or monitor the side effects of cancer treatment.

Before surgery, PFTs may be done to:

  • See if there are issues with your lungs that could interfere with anesthesia (medication used to make you sleepy for surgery).
  • See how much air your lungs can hold.

PFTs may be done to help your doctor:

  • See if your lungs are working normally.
  • Diagnose lung disease.
  • Determine if you’re having trouble breathing if your lungs are not working normally.
  • Check the status of chronic (long-term) lung disease
    • The 2 major patterns of lung disease are obstructive and restrictive. In obstructive lung disease, there is a decrease in the flow of air. Examples include emphysema or asthma. In restrictive lung disease, the amount of air the lung can fill up with is limited. Examples are fibrosis or scarring.

PFTs may be used to monitor the side effects of cancer treatment, such as:

  • Radiation in the area of your lung(s).
  • Some chemotherapy medications.
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The Day of Your PFTs

On the day of and prior to your PFTs:

  • Do not eat a large meal before testing. If you feel hungry, eat a light meal a few hours before the test.
  • Take all your medications as usual, unless your doctor gives you other instructions.
  • Do not have any caffeine, such as coffee, tea, or chocolate, for 4 hours before your test.
  • Please arrive on time for your appointment.
  • Write any additional instructions from your healthcare provider here:

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During Your PFTs

A pulmonary technologist will perform your PFTs. You will sit in a pulmonary analyzer, which is a machine that will measure the amount, force, and speed of your breathing. You will wear a nose clip to keep air from going through your nose while you blow into a mouthpiece. Your technologist will tell you to take deep, shallow, slow, or quick breaths at different periods during the test. Your doctor may request a complete test or only parts of the test.

The effort you make can have a big influence on the results of the test. You will be asked to repeat sections of the test to get the most accurate results. You may be asked to inhale a medication called a bronchodilator to open your airways. Inhaling a bronchodilator will help your doctor determine if you might benefit from specific medication(s).

PFTs take about 45 minutes to 1 hour.

Arterial blood gas test

You may have some blood drawn to measure the amount of oxygen and carbon dioxide in your blood. This is called an arterial blood gas test. It is the only part of the PFTs that may hurt.

If you have an arterial blood gas test, you may get a medication to numb your wrist and then blood will be drawn from your radial artery. After the blood is drawn, a snug elastic bandage will be put on your wrist.

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After Your PFTs

  • If you had blood drawn for the arterial blood gas test, keep the bandage on for at least 4 hours after your test. You may feel some tingling or numbness at the site. This should only last until the next morning.
  • You may go back to your regular diet.
  • There are no restrictions on your activities.
  • Your healthcare provider will explain the results of your test and what it means for your overall care. If you have any questions or concerns, talk with your doctor or nurse.
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