Skip Navigation

  • PRINT  | 

What To Expect During Lung Function Tests

Breathing Tests

Spirometry might be done in your doctor's office or in a special lung function laboratory (lab). Lung volume measurement and lung diffusion capacity tests are done in a special lab or clinic. For these tests, you sit in a chair next to a machine that measures your breathing. For spirometry, you sit or stand next to the machine.

Before the tests, a technician places soft clips on your nose. This allows you to breathe only through a tube that's attached to the testing machine. The technician will tell you how to breathe into the tube. For example, you might be asked to breathe normally, slowly, or rapidly.

Some tests require deep breathing, which might make you feel short of breath, dizzy, or light-headed, or it might make you cough.


For this test, you take a deep breath and then exhale as fast and as hard as you can into the tube. With spirometry, your doctor may give you medicine to help open your airways. Your doctor will want to see whether the medicine changes or improves the test results.

Lung Volume Measurement

For body plethysmography, you sit in a clear glass booth and breathe through the tube attached to the testing machine. The changes in pressure inside the booth are measured to show how much air you can breathe into your lungs.

For other tests, you breathe in nitrogen or helium gas and then exhale. The gas that you breathe out is measured.

Lung Diffusion Capacity

During this test, you breathe in gas through the tube, hold your breath for 10 seconds, and then rapidly blow it out. The gas contains a small amount of carbon monoxide, which won't harm you.

Tests To Measure Oxygen Level

Pulse oximetry is done in a doctor's office or hospital. An arterial blood gas test is done in a lab or hospital.

Pulse Oximetry

For this test, a small sensor is attached to your finger or ear using a clip or flexible tape. The sensor is then attached to a cable that leads to a small machine called an oximeter. The oximeter shows the amount of oxygen in your blood. This test is painless and no needles are used.

Arterial Blood Gas

During this test, your doctor or technician inserts a needle into an artery, usually in your wrist, and takes a sample of blood. You may feel some discomfort when the needle is inserted. The sample is then sent to a lab where its oxygen level is measured.

After the needle is removed, you may feel mild pressure or throbbing at the needle site. Applying pressure to the area for 5 to 10 minutes should stop the bleeding. You'll be given a small bandage to place on the area.

Rate This Content:
Last Updated: September 17, 2012