What To Expect During Lung Function Tests

Breathing Tests

Spirometry tests may be done in your doctor's office or in a special lung function lab. Your doctor may ask you to use a peak flow meter in the office and suggest that you also do the test at home. The lung volume measurement and lung diffusion capacity tests are done in a special lab or clinic.

For the lung volume measurement and lung diffusion capacity 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 may be asked to breathe normally, slowly, or rapidly.

The deep breathing done in some of the tests may make you feel short of breath, dizzy, or lightheaded, or it may make you cough.

Spirometry

In 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 a medicine that helps open your airways. Your doctor will want to see whether it changes or improves the test results.

Peak Flow Meter

In this test, you take a deep breath and then exhale as fast and as hard as you can into a small, hand-held device that's connected to a mouthpiece.

Lung Volume Measurement

For this test, 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.

Sometimes you breathe in nitrogen or helium gas and then breathe it out. The gas that you exhale is then 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. Arterial blood gas tests are done in a lab or hospital.

Pulse Oximetry

During this test, a small light is placed over your fingertip, earlobe, or toe using a clip or flexible tape. It's 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 small 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 oxygen level of the blood sample is then checked in a lab.

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 will be given a small bandage to place on the area.