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Pulmonary Function Tests

If you want to take a group of tests to know how well your lungs work, pulmonary function tests are the primary answer. There are several other tests that focus on types like skin, but the results of this test show you how well you’re able to breathe and if your lungs are effective enough to be able to bring in oxygen to the rest of the body.

How Pulmonary Function Tests are Performed

A spirometer is used when you breathe into the mouthpiece and is called a spirometry test. Breathing normally and quietly are common test measurements. Other tests might need to require forced inhalation and exhalation. To see how your test results change, you may be asked to inhale a different gas or medicine.

Long Volume Measurement

Lung volume measurement can be done in two ways:

  • The most accurate long volume measurement is body plethysmography. The technologist asks you to breathe in and out, as you are directed towards an airtight box.
  • Another lung volume is when you breathe nitrogen or helium gas through a tube.

A tracer gas, a harmful gas, may be asked for you to breathe in for a short amount of time to measure diffusion capacity. The measured air you breathe out is the concentration of the gas. Inhaled and exhaled gas is different in terms of how effectively the gas travels from the lungs into the blood. The doctor can estimate the rate at which lungs move through oxygen from the air into the bloodstream for this test.

How to Prepare for Pulmonary Function Tests

Do not eat a heavy meal or smoke 4-6 hours before the test. Before the test, you will get additional instructions on what to do and not do on the days before your test. You will also get specific instructions if you need to stop using bronchodilators or other inhaled machines. Breathing in medicine may be needed before or during the test.


You may experience some temporary shortness of breath or lightheadedness during the test, as it involves forced breathing and rapid breathing. During pulmonary function tests, you will breathe through a tight-fitting mouthpiece and also acquire nose clips for the procedure. A part of the test may feel uncomfortable and claustrophobic.

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