Lung Function

Looking to optimize lung care? Discover the essentials of Lung Function Test for healthcare professionals. Explore diagnostic insights and patient well-being.

By Olivia Sayson on Jul 18, 2024.


Fact Checked by Ericka Pingol.

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What is a Lung Function Test?

A lung function test, a pulmonary function test, is a fundamental diagnostic tool for evaluating lung health and diagnosing respiratory conditions. The primary test, spirometry, measures lung capacity and air expulsion force, serving as an effective screening tool for conditions like COPD and asthma that impact lung volumes and airways.

Lung volume testing offers even more precise measurements of total lung air, including residual air after a standard breath. Meanwhile, a diffusing capacity test assesses how efficiently oxygen travels from the lungs into the bloodstream.

For individuals experiencing unexplained breathlessness or unusual symptoms, exercise testing is a valuable tool for identifying underlying issues. This typically involves treadmill or stationary bike activities while monitoring vital signs.

Lung function tests are minimally invasive and conducted by skilled pulmonary function technicians. Results are compared to age, height, and gender-based normal values. Abnormal results may suggest a lung problem, while normal results provide reassurance.

These tests are essential resources for healthcare professionals, enabling accurate diagnosis, monitoring, and treatment of respiratory conditions, ultimately contributing to overall lung health and well-being.

How Does it Work?

A Printable Lung Function Test helps measure various parameters that help diagnose and monitor respiratory conditions. Here's how it works:

Step 1: Patient Preparation

Before the test, the patient should follow certain pre-test guidelines, such as refraining from smoking and short-acting inhaler use. These guidelines ensure accurate results.

Step 2: Spirometry

This is a key component of the test. It involves the patient taking a deep breath and exhaling forcefully into a spirometer device. The test measures parameters like Forced Vital Capacity (FVC) and Forced Expiratory Volume in one second (FEV1).

Step 3: Lung Volume Testing

This assesses Total Lung Capacity (TLC) and Residual Volume (RV), which provide insights into lung efficiency.

Step 4: Diffusing Capacity Test

This measures the lung's ability to transfer gases, particularly carbon monoxide (DLCO), helping to diagnose conditions like pulmonary fibrosis.

Step 5: Exercise Testing and Asthma Testing

If necessary, exercise testing may be conducted to evaluate lung function during physical activity. Specific asthma tests may also be performed to diagnose or monitor asthma.

When Would You Use This Test?

Healthcare practitioners rely on lung function or pulmonary function tests as essential diagnostic tools in various clinical scenarios. These tests are most commonly employed when evaluating patients with suspected or known respiratory conditions. For individuals presenting with symptoms like shortness of breath, wheezing, chronic cough, or unexplained chest discomfort, lung function tests become indispensable. They help identify and diagnose conditions such as asthma, chronic obstructive pulmonary disease (COPD), interstitial lung diseases, and restrictive lung disorders. 

Lung function tests are crucial in monitoring the progression of known respiratory conditions, determining treatment efficacy, and making informed decisions regarding therapeutic interventions.

In preoperative assessments, lung function tests gauge a patient's ability to tolerate surgery, especially in cardiac or pulmonary procedures. Lung function tests have applications in occupational medicine, particularly for workers exposed to potentially harmful substances or respiratory hazards. These tests can detect early signs of lung impairment due to occupational exposure and inform employers and workers about necessary protective measures.

In sports medicine, lung function tests are employed to assess the fitness level and exercise tolerance of athletes and physically active individuals. Exercise testing, a subtype of lung function testing, is used to determine an individual's aerobic capacity and potential limitations during physical activity. 

What do the Results Mean?

Interpreting the results of the Free Lung Function Test is essential for healthcare professionals to diagnose and manage respiratory conditions effectively. Common results provide valuable insights into a patient's lung health.

When a patient's lung function falls within the expected range, it indicates that their lung capacity and airway function are generally healthy. This suggests no immediate concerns regarding respiratory conditions. Normal results can offer reassurance to the patient and their healthcare provider, but they don't necessarily rule out underlying issues, especially in early-stage or intermittent conditions.

Abnormal results may signify a range of respiratory problems. Reduced lung capacity or airflow may indicate conditions like asthma, chronic obstructive pulmonary disease (COPD), or interstitial lung disease. Elevated lung volumes can be associated with restrictive lung diseases or conditions like obesity hypoventilation syndrome. It's important to note that abnormal results are not definitive diagnoses; they prompt further investigation, potentially including additional tests, imaging, or consultation with a specialist.

In some cases, patients may have lung function tests that yield varying results, with some within the normal range and others falling outside it. This variability can be due to factors like asthma exacerbations, recent respiratory infections, or changes in medication. It emphasizes the importance of considering the broader clinical context when interpreting results and making diagnostic and treatment decisions.

Research & Evidence

Lung function tests have a rich history of research and evidence supporting their clinical utility. These tests have evolved over time, thanks to continuous scientific exploration and validation.

The history of lung function testing can be traced back to the early 20th century when scientists like Ernest Hickling and J.S. Haldane developed the concept of spirometry. Over the years, advancements in technology and methodologies have refined the accuracy and reliability of these tests. Research has demonstrated their effectiveness in diagnosing various respiratory conditions, including asthma, COPD, and interstitial lung diseases, providing essential data to guide clinical decision-making.

The evidence supporting lung function tests is robust and spans numerous clinical studies, validating their diagnostic and prognostic value. For instance, spirometry has been extensively studied, and its role in identifying airway obstruction and monitoring disease progression is well-documented. 


  • Pellegrino R, Viegi G, Brusasco V, et al. Interpretative strategies for lung function tests. Eur Respir J. 2005;26(5):948-968.
  • Enright PL, Beck KC, Sherrill DL. Repeatability of spirometry in 18,000 adult patients. Am J Respir Crit Care Med. 2004;169(2):235-238.
  • Hansen JE, Sun XG, Wasserman K. Spirometric criteria for airway obstruction: use percentage of FEV1/FVC ratio below the fifth percentile, not <70%. Chest. 2007;131(2):349-355.
Who Typically Requests A Lung Function Test?
Who Typically Requests A Lung Function Test?

Commonly asked questions

Who Typically Requests A Lung Function Test?

A doctor, usually a pulmonologist or primary care physician, requests a Lung Function Test if they suspect a respiratory issue or want to monitor a known lung condition.

How Are Lung Function Tests Used?

During a Lung Function Test, you'll breathe into a machine called a spirometer, which measures how much air your lungs can h

How Long Does A Lung Function Test Take?

A Lung Function Test typically takes 15 to 30 minutes, although it may vary depending on the specific tests needed and the patient's ability to cooperate.

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