Medical Tests for Diagnosing and Monitoring COPD

A number of medical tests can be used to diagnose your COPD, monitor your progress, and determine your treatment needs. These may include lung function tests, tests to determine your need for extra oxygen, and imaging tests, like chest x-rays.

Spirometry

Spirometry is the main lung function test used to diagnose COPD, to monitor your response to treatment, and to measure the severity of your disease. The test measures your ability to force air out of your lungs. Spirometry can detect COPD even if you do not have symptoms.

To take this test, you breathe into a machine called a spirometer. You take a deep breath in through a mouthpiece and blow it out as quickly and completely as possible. The test is usually repeated a couple of times to get an accurate reading. The spirometry test is sometimes done before and after you take a bronchodilator medication to gauge how much of your blocked airflow is reversible.

Two spirometer readings are most relevant to people with COPD:

• Forced Vital Capacity, often abbreviated as FVC, is the total amount of air that you can forcibly exhale after taking a full breath.

• Forced Expiratory Volume, or FEV1, is the amount of air that you can force out in one second.

Your doctor uses these two readings to determine your stage of COPD and to monitor the progression of your disease. Keep in mind, though, that your lung function readings may not be related to the kind of symptoms you have.

Arterial Blood Gas

An arterial blood gas test is used to measure how much oxygen and carbon dioxide are in your blood. It tells your doctor how severe your COPD is and whether or not you need supplemental oxygen.

The test uses blood drawn from an artery-usually on the wrist, but sometimes in the elbow or the groin. With an arterial blood draw, oxygen and carbon dioxide levels are measured before they are depleted by the body's tissues.

Drawing blood from an artery hurts more than collecting blood from a vein because the arteries are deeper and have more nerves. You may be given a local anesthetic to make this test more comfortable.

Pulse oximetry is a test that measures how much oxygen is carried in the blood. Pulse ox, as it is sometimes called, is used to monitor the effect of exercise on your blood's ability to carry oxygen. It can help determine whether you need extra oxygen.

The test is done by placing a special probe on your finger or earlobe. The pulse oximeter uses light waves to measure how well your blood is carrying oxygen. Pulse oximetry can be done while you are at rest, while walking or while sleeping.

Chest X-ray

A chest x-ray produces an image of your heart and lungs. Chest x-rays are not good at diagnosing COPD. Your doctor may order a chest x-ray to look at the condition of your lungs, to check for specific characteristics related to COPD, or to rule out other conditions, like pneumonia or lung cancer, that may be causing breathing problems.