What Are the Two Most Common Pulmonary Function Tests?

Maintaining healthy lungs is essential for overall well-being, but many lung conditions can develop slowly without obvious symptoms. When doctors need to evaluate how well your lungs are working, they often recommend pulmonary function tests (PFTs). These tests help measure breathing ability, airflow, lung capacity, and how efficiently oxygen moves through the lungs.



Among the different types of pulmonary function tests available, the two most common pulmonary function tests are spirometry and lung volume testing. These tests are widely used because they provide valuable information about lung performance and help healthcare providers diagnose and monitor respiratory conditions.

Whether someone is experiencing shortness of breath, persistent coughing, wheezing, or managing a chronic lung condition, pulmonary function testing can provide important insights into their respiratory health.

For professional evaluation and accurate testing, patients can learn more about pulmonary function tests and how these assessments support better lung care.

What Are Pulmonary Function Tests?

Pulmonary function tests are a group of non-invasive breathing tests designed to measure how effectively the lungs function. Unlike imaging tests such as X-rays or CT scans, PFTs focus on lung performance rather than appearance.

These tests evaluate several important aspects of respiratory health, including:

  • How much air the lungs can hold
  • How quickly air moves in and out of the lungs
  • How well oxygen passes from the lungs into the bloodstream
  • Whether airflow is restricted or reduced

Doctors commonly recommend pulmonary function testing for diagnosing or monitoring conditions such as:

  • Asthma
  • Chronic obstructive pulmonary disease (COPD)
  • Pulmonary fibrosis
  • Emphysema
  • Bronchitis
  • Other breathing disorders

Pulmonary function tests can also be used before surgery, to monitor treatment progress, or to evaluate unexplained breathing problems.

The Two Most Common Pulmonary Function Tests

Although several types of PFT tests exist, two tests are performed most frequently:

  1. Spirometry
  2. Lung Volume Testing

Both tests provide different information about lung function and are often used together to create a complete picture of respiratory health.

1. Spirometry: The Most Common Lung Function Test

Spirometry is the most widely used pulmonary function test and is often the first test doctors perform when evaluating breathing problems.

This test measures how much air a person can inhale and exhale and how quickly they can force air out of their lungs.

During a spirometry test, the patient breathes into a device called a spirometer. The machine records airflow measurements while the patient follows specific breathing instructions.

What Does a Spirometry Test Measure?

Spirometry mainly measures two important values:

Forced Vital Capacity (FVC)

Forced Vital Capacity refers to the total amount of air a person can forcefully exhale after taking the deepest breath possible.

A reduced FVC may indicate that the lungs cannot expand properly or that lung volume is limited.

Forced Expiratory Volume in One Second (FEV1)

FEV1 measures how much air a person can forcefully breathe out during the first second of exhalation.

This measurement helps identify airflow limitations commonly seen in conditions such as asthma and COPD.

Doctors often compare the FEV1 and FVC values to determine whether a breathing problem is caused by airway obstruction or restricted lung expansion.

Why Is Spirometry Performed?

A spirometry test may be recommended for:

  • Diagnosing asthma or COPD
  • Evaluating chronic cough
  • Investigating shortness of breath
  • Monitoring lung disease progression
  • Checking response to inhaler treatments
  • Assessing lung function before certain procedures

Because spirometry is quick, safe, and reliable, it remains one of the most important tools for respiratory health evaluation.

2. Lung Volume Testing: Measuring Total Lung Capacity

The second most common pulmonary function test is lung volume testing. While spirometry measures airflow, lung volume testing determines the actual amount of air inside the lungs.

This test provides information about lung capacity that cannot always be measured through regular spirometry.

Lung volume testing helps doctors understand whether someone has a restrictive lung condition, where the lungs cannot fully expand.

What Does Lung Volume Testing Measure?

Lung volume tests evaluate several measurements, including:

Total Lung Capacity (TLC)

Total Lung Capacity is the maximum amount of air the lungs can hold after taking the deepest possible breath.

A lower TLC may suggest restricted lung expansion caused by conditions affecting lung tissue or chest movement.

Residual Volume (RV)

Residual Volume refers to the amount of air remaining in the lungs after completely exhaling.

This measurement helps identify problems where air becomes trapped inside the lungs.

Functional Residual Capacity (FRC)

Functional Residual Capacity measures the amount of air remaining in the lungs after a normal breath out.

These measurements help physicians understand lung mechanics and identify abnormalities.

Why Is Lung Volume Testing Important?

Lung volume testing is especially useful when doctors need additional information beyond spirometry.

It can help diagnose:

  • Pulmonary fibrosis
  • Chest wall disorders
  • Neuromuscular conditions affecting breathing
  • Restrictive lung diseases
  • Severe lung damage

By measuring lung capacity directly, this test provides a clearer picture of how well the lungs expand and function.

Spirometry vs Lung Volume Testing: Key Differences

While both tests evaluate lung function, they focus on different areas.


How Are Pulmonary Function Tests Performed?

Pulmonary function testing is generally simple and painless. The exact procedure depends on the type of test being performed.

A typical PFT appointment may include:

  1. The patient receives instructions from a healthcare professional.
  2. The patient sits comfortably and may wear a nose clip during testing.
  3. The patient breathes into specialized equipment.
  4. Different breathing patterns are recorded.
  5. Results are analyzed by healthcare providers.

The testing process usually takes between 30 minutes and an hour, depending on how many measurements are required.

How Should You Prepare for a Pulmonary Function Test?

Proper preparation can help ensure accurate results.

Before a PFT test, patients may be advised to:

  • Avoid heavy meals before testing
  • Wear comfortable clothing
  • Avoid smoking before the appointment
  • Follow instructions about inhaler or medication use
  • Inform the healthcare provider about current symptoms or medical conditions

Always follow the specific preparation instructions provided by your healthcare professional.

What Do Pulmonary Function Test Results Mean?

Pulmonary function test results show how well the lungs are performing compared with expected values based on factors such as:

  • Age
  • Height
  • Sex
  • Overall health

Abnormal results do not always mean a serious condition exists. Doctors interpret results along with symptoms, medical history, and other diagnostic information.

Common patterns include:

Obstructive Pattern

This occurs when air has difficulty leaving the lungs due to narrowed airways.

Common causes include:

  • Asthma
  • COPD
  • Chronic bronchitis

Restrictive Pattern

This occurs when the lungs cannot fully expand or hold normal amounts of air.

Possible causes include:

  • Pulmonary fibrosis
  • Chest wall problems
  • Certain muscle disorders

Who Needs Pulmonary Function Testing?

Doctors may recommend pulmonary function tests for people experiencing:

  • Persistent coughing
  • Wheezing
  • Shortness of breath
  • Chest tightness
  • Reduced exercise tolerance
  • Unexplained breathing difficulties

They may also be recommended for people who:

  • Work around respiratory hazards
  • Have a history of smoking
  • Need monitoring for chronic lung conditions
  • Require pre-surgical lung evaluation

Benefits of Early Lung Function Testing

Early detection of lung problems can make a significant difference in treatment outcomes.

Benefits of pulmonary function testing include:

  • Identifying breathing problems early
  • Helping doctors choose appropriate treatments
  • Tracking disease progression
  • Measuring treatment effectiveness
  • Improving long-term respiratory care

Regular monitoring can help patients and healthcare providers make informed decisions about managing lung health.

Frequently Asked Questions About Pulmonary Function Tests

What are the two most common pulmonary function tests?

The two most common pulmonary function tests are spirometry and lung volume testing. Spirometry measures airflow, while lung volume testing measures the total amount of air the lungs can hold.

Is a pulmonary function test painful?

No. Pulmonary function tests are non-invasive and painless. Patients simply breathe into specialized equipment while following instructions.

How long does a pulmonary function test take?

Most pulmonary function tests take around 30 minutes to one hour, depending on the number of tests required.

Can pulmonary function tests diagnose asthma?

Yes. Spirometry is commonly used to help diagnose asthma by identifying airflow limitations and measuring changes after medication.

Are pulmonary function tests safe?

Yes. PFTs are considered safe for most people. Some individuals may experience temporary shortness of breath or lightheadedness during forceful breathing exercises.

Final Thoughts

The two most common pulmonary function tests—spirometry and lung volume testing—play an important role in understanding how well the lungs work. Spirometry focuses on airflow, while lung volume testing evaluates lung capacity and expansion.

These tests help healthcare providers diagnose respiratory conditions, monitor treatment progress, and create personalized care plans. If you are experiencing breathing issues or need a detailed evaluation of your lung health, pulmonary function testing can provide valuable information about your respiratory function.

Early assessment and proper monitoring can help protect lung health and improve quality of life.

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