Getting the right diagnosis through lung function tests

Changes in health, including lung health, can be daunting. If you’re experiencing symptoms such as shortness of breath, a repetitive cough and phlegm or mucus, talking to your doctor to find out the cause is the best place to start.

The symptoms of Chronic Obstructive Pulmonary Disease (COPD) can overlap with other conditions, including asthma, so to get the right treatment, proper assessment and diagnosis is important. If you are concerned about a change in symptoms, talk to your doctor about undergoing some tests.

Why are lung function tests important in the diagnosis and treatment of COPD?

Lung function tests assist in the diagnosis and management of COPD. They measure how well and how much air you breathe in and out of your lungs. They can also show how well oxygen enters your body, and how much air you have in your lungs. Your doctor may ask you some questions about your symptoms and then you may do a simple, and non-invasive breathing test to screen for potential airway obstruction, such as is common in COPD and asthma. If a lower than expected result is returned your doctor will then undertake a more detailed assessment, such as spirometry.

What is spirometry?

Spirometry is a breathing test used to determine what kind of respiratory condition is present. It’s always required for a diagnosis of COPD and is used to differentiate COPD from other conditions, such as asthma, which require different treatment approaches. This test measures the amount of air you can breathe in and out, and how quickly you’re able to breathe air out. Typically, if you have COPD, you will take longer to breathe all your air out.

Spirometry is done by breathing into a machine called a spirometer. You will be asked to take your biggest breath in and to breathe all the air out as fast as you can into the machine. This needs to be done several times and your best result is recorded.

The test is often repeated after you have taken some breathing medicines to find out if your lung function improves with these medicines. It can take up to 20 minutes to complete the tests.

Spirometry will be used to monitor your COPD and to check how well your treatment is working.

What should I know before having spirometry?

There are several things you may need to know in preparation for your test. It’s important to be guided by your doctor and ask them questions if you’re unsure about anything. The information can be overwhelming but your doctor will go through all of this on the day or before the testing.

• You may be asked to not take your COPD medicines on the day of the test. However, if you feel really breathless, take your medicines and let the person conducting your test know when you last used them.
• The person conducting the spirometry test will give you instructions on how to do the test. If you do not understand them, ask for the instructions to be repeated or for a demonstration on how the test should be undertaken.
• You can sometimes become light-headed during the test. If this happens, stop breathing into the machine and let the person conducting your test know.
• As effort is required to do this test, you may get tired. This is not unusual. To get the best results, you will be asked to do the test several times. Spirometry results vary according to a person’s age, height, whether they are male or female, and their ethnic background.

What do the results mean?

There are different measurements taken to assess your lung function however the most common measures taken during spirometry are:

1. Forced Expiratory Volume in one second (FEV1). This is the maximum amount of air that can be expelled from the lungs during the first second of breathing out following a maximal breath in.
2. Vital Capacity (VC). This is the maximum amount of air that can be expelled from the lungs while breathing out following a maximal breath in.
3. Forced Vital Capacity (FVC). This is the maximum amount of air that can be expelled from the lungs while breathing out forcefully. VC and FVC are equal in a normal lung but can differ in patients who have a chronic lung condition.
4. FEV1/FVC. This measures how much air is blown out in the first second proportional to the total amount blown out of the lung. So it shows how quickly the lungs can be emptied. People with healthy lungs can usually blow out 70% to 90% of their air in the first second.