Pulmonary Function Tests FAQ
What are lung function tests used for?
Lung function tests are a series of noninvasive procedures that measure how your lungs function. They provide information about air flow in and out of your lungs.
Doctors use these tests to diagnose conditions such as allergies, infections, chronic lung conditions and other diseases. In addition, your doctor may use these tests to evaluate treatment for conditions such as asthma and chronic obstructive pulmonary disease (COPD), as well as assess the health of your lungs before you undergo surgery.
What do lung function tests measure?
Lung function testing involves a series of different procedures that assess the health and capacity of your lungs. Measurements may include the amount of air inhaled and exhaled during normal breathing (tidal volume), how much air your lungs can hold (total lung capacity) and other breathing abilities.
Normal lung function measurements vary from person to person. Your doctor will compare your test results with the expected average in someone of the same age, height, sex and race. If you have previous testing, your doctor will compare your results to earlier measurements.
Is there anything I need to do to prepare for testing?
Because these are noninvasive, painless tests that don’t require sedation of any kind, there’s no prior preparation necessary for most people. You can eat and drink before the test, but we recommend you don’t eat a heavy meal or exercise vigorously before your appointment.
Depending on your medical condition, your doctor may ask you to follow special instructions before testing, such as:
- Medications. If you take breathing medications to help open the airways (bronchodilators), it may affect testing. You may be asked not to take these medications before your appointment. Talk to your doctor about any medications or supplements you’re taking.
- Smoking. Avoid smoking for 12 hours before testing.
- Pregnancy or gastrointestinal issues. Notify your doctor if you’re pregnant or if you have abdominal swelling, both of which can affect your ability to breathe deeply.
Is there any paperwork I need to fill out before I come in for my test?
Where do I go for the test?
- Mountain View campus – The pulmonary diagnostics lab, located in the old main hospital.
- Los Gatos campus – The pulmonary diagnostics lab in the main hospital.
What equipment is used during testing?
Some tests use a spirometer, a device you breathe into (through a mouthpiece) that measures the amount of air and how quickly you’re able to inhale and exhale. Spirometry also allows your doctor to measure oxygen and carbon dioxide levels when you breathe.
Your doctor may also use plethysmography to determine how much air you can hold in your lungs during rest. This involves sitting in an air-tight box — about the size of a telephone booth — and breathing into a mouthpiece. As you breathe into the mouthpiece, it changes the pressure and amount of air in the compartment, which helps determine of the amount of air in your lungs.
What can I expect during testing?
Before testing begins, you’ll be asked to loosen tight clothing and remove jewelry or other objects that may interfere with testing. Also, you’ll be asked to empty your bladder before the procedure.
The types of tests you’ll undergo will depend on your condition and the tests your doctor orders. You’ll be monitored for faintness, dizziness, difficulty breathing or other issues throughout testing. Tests may be performed sitting or standing, depending on your doctor’s instructions.
Generally, during testing you can expect:
- You’ll wear a nose clip to ensure you breathe through your mouth, rather than your nose.
- You’ll be given a sterile mouthpiece for the spirometer and asked to perform a variety of breathing exercises, such as deep and shallow breathing, or slow and fast breathing. Depending on your specific testing, you may be asked to repeat breathing exercises several times.
- If your testing includes plethysmography, you’ll perform a series of breathing exercises while sitting inside the compartment.
- You may be given a bronchodilator medication (to open airways) during testing and asked to repeat breathing exercises after the medication has taken effect.
Are there any special instructions I should follow after my procedure?
Unless your doctor tells you otherwise, you can resume your regular diet, medications and activities after testing. If you have a lung condition, you may feel tired after the procedure.
Are there any risks associated with lung function testing?
Because tests are noninvasive, it's safe for most people. Complications could include faintness or light headedness due to hyperventilation. If you have asthma, the deep-breathing exercises could cause breathing difficulties.
Your doctor may not recommend lung function testing if:
- You’ve had recent eye surgery, since testing causes additional pressure to develop inside your eyes.
- You’ve had recent chest or abdominal surgery, which would make it difficult to take deep breaths without straining the tissue around the surgical area.
- You have active tuberculosis or a respiratory infection, which can affect your ability to perform breathing exercises.
- You have an unstable heart condition or chest pain, or you’ve had a recent heart attack or an aneurysm, which makes you ineligible for testing.
How and when will I get the results of my test?
Your doctor will receive a copy of the results 48 to 72 after the test and will share them with you.