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Pulmonary Function Lab

Evaluating Lung Function

There are different tests to help determine your lung function.

Complete PFT Examining Airways Exercise Tests Respiratory Strength Laboratory

Evaluating Lung Function with a Complete PFT

When you are having difficulty breathing, your doctor may order a group of pulmonary function tests known collectively as a “complete PFT,” to help make a diagnosis.

The tests include:

Spirometry to evaluate how fast and how much air is traveling through your airways when you intentionally exhale.
Lung volumes to measure how much air you can breathe in, breathe out and is left in your lungs after exhaling completely.
Diffusion capacity to measure how well oxygen passes through your lungs and enters the blood stream.

When you take each test, you will breathe through a mouthpiece into a testing device. A respiratory therapist will explain how you should breathe and coach you through the maneuver. You will perform the maneuver several times to ensure an accurate and reliable test result.

The tests together last about one hour.

Examining Airways and Lungs

Specially-trained respiratory therapists assist physicians in performing two procedures to inspect your airways and lungs: bronchoscopy and thoracoscopy.

Both procedures involve the use of a scope, which is a thin viewing tube. The tube is inserted into the body on one end and connected outside the body on the other end to a lighted viewing lens or digital camera. For bronchoscopy, a bronchoscope is inserted through the mouth or nose. For thoracoscopy, an endoscope is inserted through a small incision in the chest.

Your doctor may order a bronchoscopy to diagnose problems with your airways, lungs or lymph nodes in the chest. Bronchoscopy is used to remove an abnormal growth or foreign object in the airway, or to take tissue samples—a biopsy—to test for diseases.

The lab may use either a flexible bronchoscope or a rigid bronchoscope.

The flexible version is used more often and has several advantages. You need only local anesthesia, and insertion is more comfortable. Your doctor also can get a better view of your smallest airways because the scope is thinner and made of a material that can be maneuvered through the airway with greater ease.

Sometimes, however, the rigid version, which is made of a straight, hollow metal tube, is the better choice. It is used when bleeding in the airway could block the view or when an object that needs to be removed is particularly large. Larger tissue samples can be taken with the rigid bronchoscope. It is also used for special procedures such as widening the airway or destroying a growth using a laser.

You will receive general anesthesia when the doctor uses a rigid bronchoscope.

Your doctor may order a thorascopy to examine the lining of your lung to detect cancer cells that have spread there from another part of your body. The test is also used to remove fluid that has collected in the chest, a medical condition called pleural effusion.

When you undergo a thoracoscopy, you will receive local anesthesia and light sedation. If your doctor needs a tissue sample, an instrument will be inserted through the endoscope to retrieve it. The tissue sample is later evaluated by the hospital laboratory.

The procedure takes two to three hours. However, you must stay in the hospital for several hours, or in some cases overnight, after the thoracoscopy to recover.

Exercise Tests

Exercise tests help your doctor to:

Evaluate shortness of breath when you exert yourself.
Evaluate your endurance level.
Determine your cardiopulmonary fitness.
Compare your oxygen levels when you rest and when you exercise.

Our lab performs several types of exercise tests.

Oxygen helps your body to function. Most people get enough from the air they breathe. But some lung and heart diseases can affect your body’s ability to turn this oxygen into the energy that organs and tissues need to function properly.

If your body is not getting enough oxygen from the air, your doctor may ask you to use supplemental oxygen.

To determine if you need it and how much, your doctor may order two tests:

Oxygen desaturation study: A respiratory therapist clips an electronic device called a pulse oximeter to your finger, which measures how much oxygen is in your blood. Measurements are taken when you are at rest and when you are exerting yourself on a treadmill or stationary bike, or walking in a hallway. If the amount of oxygen in your blood is low, you may need supplemental oxygen. This test takes about 30 minutes.
Oxygen titration study: If you already use supplemental oxygen, your doctor may order this test to determine if you need to adjust the amount you use. Pulse oximeter readings are taken at rest and during exertion to pinpoint how much supplemental oxygen you need to maintain the appropriate oxygen saturation level in your bloodstream. This test takes about 30 minutes.

If heart or lung disease leaves you feeling breathless, your doctor may want you to begin a pulmonary rehabilitation program.

Before you begin rehabilitation, your doctor needs to know your exercise capacity—how much exertion your body can handle. To make this determination, the doctor may order you to take a six-minute walk test.

This test requires you to walk as far as you can up and down a hallway for six minutes. A respiratory therapist will ask you to rate your ability to breathe and level of fatigue on a scale of 1 to 10 during and after the test. The therapist also will measure your heart and respiratory rate, blood pressure and other indicators of your respiratory health.

Your doctor will use the results to assess your current endurance level before you start rehabilitation. The doctor likely will ask you to repeat the test several weeks or months later to determine how rehabilitation is affecting your health.

You might also take the walk test on a regular basis to help the doctor monitor your condition.

The test takes about 30 minutes.

A cardiopulmonary exercise test evaluates how your heart, lungs and muscles respond to exercise.

Your doctor may order this test for a variety of reasons, including:

Diagnosing heart, lung and circulatory diseases.
Assessing your readiness for surgery.
Developing an exercise prescription for your pulmonary rehabilitation program.

Before you begin the exercise portion of the test, the respiratory therapist will measure your blood pressure, heart rate and oxygen saturation, record an electrocardiogram and take blood from your artery.

Our lab typically uses a stationary bike during the exercise portion of the test. As you pedal the bike, you will encounter increasing amounts of resistance. The respiratory therapist will monitor your blood pressure, heart rate and oxygen saturation. An electrocardiogram is recorded throughout the test. You must continue to pedal until you feel as if you can pedal no more. When you reach your peak exercise point, the therapist will draw blood from your artery again.

After the blood draw, the exercise portion of the test is over. However, you will continue to pedal with very low resistance for several more minutes to allow your muscles to properly cool down.

In some situations, you will use a treadmill instead of a bike.

This test takes about two hours.

Please wear appropriate attire for the test. This includes:

Shoes suitable for pedaling an exercise bike or walking.
Shorts or pants.
A shirt, blouse or top that buttons or zips in the front (so the respiratory therapist can apply the electrocardiogram leads to your chest and adjust them while you are exercising).

Measuring Respiratory Muscle Strength

Neuromuscular diseases, such as muscular dystrophy or multiple sclerosis, can weaken the muscles you need to help you breathe.

If your doctor wants to evaluate the strength of your respiratory muscles, you will come to the lab to get an assessment of your maximal respiratory pressures. The test measures the force generated by the diaphragm and chest muscles when you forcefully breathe in and out.

The lab sometimes also refers to this test as maximum inspiratory and expiratory pressure measurements.

The evaluation takes about 15 minutes.