3 Pulmonary Function Tests to Help Diagnose Your Condition

For patients who visit Fivestar Pulmonary Associates to get to the bottom of worrisome lung or airway symptoms, pulmonary function testing is an early step in our evaluation process. Our expert team may use one or more of these simple medical tests to investigate:

• Cough (especially if it’s productive)
• Shortness of breath (dyspnea); wheezing
• Difficulty taking a deep or full breath 
• Chest tightness, pain, or pressure
• The effect smoking is having on your lungs

Pulmonary function tests assess how well your lungs work. They can help us diagnose suspected lung disease, and once diagnosed, these same tests can help us monitor the progression of the disease and evaluate the effectiveness of your treatment plan. 

In conjunction with oxygen evaluation tests (pulse oximetry, blood gas test) and imaging tests (chest X-ray), pulmonary function tests provide helpful insight into your lung and respiratory health. Let’s take a closer look at three invaluable tests. 

1. Spirometry 

Spirometry is a simple lung function test that measures how much air you can breathe in and out of your lungs, as well as how easily and quickly you can blow the air out of your lungs. 

How it works

During spirometry, you sit upright with a clip on your nose and breathe into a mouthpiece connected to a spirometer. We repeat the test a minimum of three times to ensure your results are accurate and reproducible; we may also repeat the test after you breathe in a medicine that helps open your airway to see if your breathing improves. 

Test results 

The spirometer records the total amount of air exhaled after a maximal breath (forced vital capacity, or FVC); the amount of air exhaled in the first second of forced expiration (forced expiratory volume in one second, or FEV1) and airflow obstruction (FEV1/FVC ratio). Low FVC, FEV1, or FEV1/FVC values can indicate an underlying lung disease.

What it’s used for

We can use spirometry to diagnose — and later evaluate the progression and treatment efficacy of — asthma, chronic obstructive pulmonary disease (COPD), interstitial lung disease, bronchiectasis, and cystic fibrosis. 

2. Lung volume test

A lung volume test assesses how much air your lungs can hold and the amount of air remaining in your lungs after you exhale. Essentially, it measures the various amounts of air in your lungs after different points of inhalation and exhalation.

How it works

A lung volume test is very similar to spirometry, except that you sit in a small room with clear walls. You can see and speak to our team throughout the test. You wear a nose clip to ensure all air movement goes through the mouthpiece.

After you take a few quick, shallow breaths, you breathe normally through the mouthpiece. Next, you breathe in fully and blow out to empty your lungs as much as possible. Finally, you take some slow, deep breaths in and out. 

Test results 

The clear, airtight chamber you sit in during lung volume testing is connected to a machine that measures the air pressure changes inside the box as you breathe. 

These variations are compared to normal values for someone of the same gender, age, and height. Abnormal results may be an indication of lung disease and often call for further testing. 

What it’s used for

Lung volume testing helps us diagnose asthma, COPD, and interstitial lung disease. Periodic post-diagnosis lung volume testing helps us see how well your treatment plan is working and if your disease is steady or progressing. 

3. Diffusion capacity test

A diffusion capacity test checks how easily oxygen moves from your lungs to your blood when you breathe. It measures the transfer of gases (oxygen and carbon dioxide) from inhaled air to your bloodstream — or the “diffusing capacity for carbon monoxide” (DLCO) of your lungs.

How it works

During diffusion capacity testing, you wear a mask and breathe in air (oxygen and nitrogen) that contains a small amount of carbon monoxide (not enough to harm you) and a tracer gas (like methane). You hold your breath for 10 seconds, then exhale. 

A machine that’s connected to the mouthpiece measures how much carbon monoxide remains in the exhaled air and, therefore, how much has passed from your lungs to your blood. This test is often performed in conjunction with spirometry. 

Test results 

Low DLCO results mean your lungs aren’t transferring oxygen to your blood efficiently. This might be because of a problem with your lungs or an issue with your heart. For example, your heart might not be pumping well enough, or your lungs may have less surface area for gas exchange due to scarring or inflammation. 

What it’s used for

We use diffusion capacity testing to help diagnose and evaluate COPD, asthma, interstitial lung disease, sarcoidosis, and cystic fibrosis. 

Get to the bottom of your symptoms

Do you have worrisome lung or airway symptoms? We can help. Take our online COPD Assessment Test (CAT) and our Asthma Control Test, then schedule an evaluation at your nearest Fivestar Pulmonary Associates office in Allen, McKinney, or Plano, Texas, today.