Oncologists use various tests and tissue biopsies to diagnose lung cancer with certainty. Following a lung cancer diagnosis, health care teams often order pulmonary function tests (PFTs) to assess breathing patterns, which can guide treatment plans and surgical decisions.

Can a pulmonary function test detect lung cancer? The answer is no — they are used to evaluate how well your lungs function while you’re living with lung cancer and undergoing treatment. Although these breath tests cannot currently diagnose lung cancer, ongoing clinical trials are researching how other breath tests might detect certain molecules in the breath, known as volatile organic compounds (VOCs), that could indicate lung cancer at an early stage.

Here’s what you need to know about the different types of PFTs used today to assess lung function in people with lung cancer.

Current Breath Tests for Lung Cancer

When a person is first diagnosed with lung cancer, the pulmonologist (a doctor who specializes in the lungs) may want to conduct a pulmonary function test (also known as a breath test). The test results can help guide the pulmonologist in determining the most appropriate treatment.

Types of PFTs used for lung cancer include:

• Plethysmography
• Spirometry
• Diffusion testing

Plethysmography

Initially, people diagnosed with lung cancer may undergo a test known as a whole-body plethysmography, a body box plethysmography, or simply a body plethysmography. During this test, you’ll sit in a clear enclosed chamber. If you feel claustrophobic (uncomfortable in a confined space), let your technician know, and they can make accommodations. Inside the chamber, you’ll breathe into a mouthpiece while wearing nose clips. For around 15 minutes, the technician will guide you through different breathing patterns, from long, deep breaths to short, quick ones.

During the test, the air inside the box reflects the pressure and volume of each breath. The device measures not only the direct feedback from breathing into the mouthpiece but also the shifts in the air around you.

The technician will compare your results in lung capacity and airflow resistance to those of average healthy lungs. Lung surgery for cancer typically removes some healthy lung tissue, which may affect normal breathing. Plethysmography results can help your health care team determine the safest treatment moving forward. For instance, if your lungs are unlikely to handle the stress of surgery, your pulmonologist may recommend chemotherapy or radiation therapy instead.

Spirometry

Throughout your lung cancer treatment, your pulmonologist may ask you to take routine spirometry tests. Spirometry assesses how much you inhale and exhale and how quickly. The test results can help your doctors evaluate how well your treatment is working.

For this test, you will be seated in front of the spirometer and wear a nose clip while breathing into the machine’s mouthpiece. Your technician will ask you to take a deep breath, then forcefully exhale all the air out of your lungs into the mouthpiece. The amount of air you inhale and exhale and the time it takes provide the following types of important information.

Forced Expiratory Volume in 1 Second

The amount of air that you breathe out in the first second is called forced expiratory volume in 1 second (FEV1). FEV1 is decreased in many lung conditions, such as chronic obstructive pulmonary disease (COPD). This flow rate also decreases slightly each year as you age, so older individuals typically have a lower FEV1 than younger ones. Reduced FEV1 more than would be expected for your age is a strong predictor of lung cancer risk.

Forced Vital Capacity

Forced vital capacity (FVC) is the total amount of air you can exhale. FVC decreases in many of the same lung diseases but is not a good indicator of lung cancer risk or severity on its own.

Ratio of FEV1 to FVC

The most important indicator of lung function is the ratio of FEV1 to FVC. A decreased FEV1/FVC ratio compared to normal spirometry values is associated with an increased risk of lung cancer.

This test allows your pulmonologist to collect data on your FVC and FEV1, essentially measuring the force and practical strength of your lungs.

Lung Diffusion Testing

Both spirometry and body plethysmography evaluate how well you inhale and exhale air into your lungs. Another critical factor is your lungs’ ability to absorb oxygen once it enters the alveoli (lung sacs), known as diffusion.

A major test to assess lung diffusion in people with lung cancer is called diffusing capacity of the lungs for carbon monoxide (DLCO). Instead of inhaling room air, you inhale carbon monoxide, a gas that binds to red blood cells more strongly than oxygen does. During a 10-second breath-hold, DLCO measures how much carbon monoxide you absorb in that period. The higher the DLCO, the better your lung diffusion.

Oncologists and surgeons may consider your DLCO along with your FEV1/FVC ratio to determine if you’re a high-risk candidate for lung cancer surgery.

Preparing for a Breath Test

There are a few things to keep in mind while preparing for a PFT. On the day of the test, make sure you haven’t taken any medication to regulate your breathing unless advised by your doctor. If you smoke, refrain from smoking before the test. Additionally, avoid eating a large meal before the test.

What Are the Risks of PFTs?

Breath tests are noninvasive, so there is very little risk involved. However, during rapid breathing cycles, it is common to experience lightheadedness and shortness of breath. If the tests become difficult, you may also cough. If this happens, ask your technician for some time to rest.

It is also important to be mindful of risk factors that might interfere with these breathing tests. For example, if you have recently undergone surgery or have heart problems, talk to your pulmonologist for approval before beginning the test.

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Have you undergone breathing tests for lung cancer? What do you think about the future of breathing tests, and would you ever take part in a clinical trial? Share your thoughts in the comments below or by posting on your Activities page.