PFT Interpretation Chart

What is a pulmonary function test (PFT)?

Lung function tests, also known as pulmonary function tests, are a type of clinical examination that gauges patients' lung function (whether they are inhaling and exhaling oxygen normally). They play a crucial role in diagnosing and monitoring interstitial lung disease and in preoperative pulmonary evaluation for conditions such as lung cancer and thoracic surgery. More specifically, they help determine the kind of respiratory conditions they might be dealing with or developing, such as asthma, pulmonary fibrosis, and Chronic Obstructive Pulmonary Disease (COPD).

They come in different types but are always non-invasive breathing tests, meaning the clinician conducting the test won’t insert tools or instruments into the patient's body. The most common type of Pulmonary Function Testing is the Spirometry Test.

The measurements of the PFT Test, more specifically, the Spirometry Test, will give healthcare professionals a clear picture of a patient’s lung capacity, airflow limitations, and if their lungs are afflicted with obstructive airways or restrictive lung disease.

What is a PFT Interpretation Chart?

Pulmonary function tests, or PFTs, are a series of assessments designed to measure a patient’s respiratory function. These tests typically include vital capacity (VC), forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), diffusion capacity of carbon monoxide (DLCO), or total lung capacity (TLC).

While these results are reasonably simple to obtain through spirometry, clinical knowledge, and decision-making skills are required in their interpretation.

As there are many potential causes for abnormal PFT results, and each disease’s presentation can differ in which PFT results it impacts, this PFT Interpretation Chart can serve as a visual guide through the woods of interpreting PFT results and helps healthcare practitioners identify various lung conditions by analyzing lung volumes.

As an example of its application, obstructive lung diseases, such as asthma, chronic bronchitis, emphysema, and bronchiectasis, can be identified by looking for signs of hyperinflation, alterations in the functional residual capacity (FRC), an increase in residual volume (RV), total lung capacity (TLC) percentage, and RV-to-TLC ratio.

Generally, A PFT Interpretation Chart is a flowchart that steps the clinician through the result interpretation process in a series of “yes/no” decisions. This flowchart simplifies the diagnosis and decision-making process and provides the clinician with a standardized tool to ensure they provide the best patient care.

So, if you’ve been struggling with getting obstructive and restrictive disorders mixed up, read on to learn how to use Carepatron’s PFT Interpretation Chart based on the flowchart created by the American Thoracic Society (ATS).

How does a PFT Interpretation Chart work?

This Printable PFT Interpretation Chart is a roadmap for decision-making once you have your patient’s pulmonary function test results. To ensure you’re following the flowchart correctly, go through the steps below:

Step 1: FEV₁ / VC ratio

The first step involves looking at your patient's ratio of forced expiratory volume in one second (FEV₁) divided by their vital capacity (VC). This ratio measures the percentage of lung capacity that can be forcibly expired in one second and is useful in determining the extent of obstructive lung disease. 

Therefore, the first step in the flowchart is to determine if the FEV₁/VC, or FEV1/FVC ratio according to the ATS, is above the lower limit of normal (LLN) value. This will determine which branch you move down for the next step.

Step 2: Vital capacity (VC)

Next, you will consider the vital capacity of the lungs—VC. If the VC is above the lower limit of normal values, and the FEV₁/VC ratio is also above the lower limit of normal, then you have a normal spirometry result for these tests. If the VC is below the lower limit of normal but the FEV₁/VC is normal, this could still be either an obstructive or restrictive disorder.

If FEV₁/VC was below the LLN and the VC was above the LLN, this indicates obstruction. However, if the VC is below the LLN, you must move on to the next step to determine the type of disorder.

Step 3: Total lung capacity (TLC)

Next, you will examine total lung capacity (TLC) to narrow the range of diagnoses further. You can determine whether the disorder is restrictive, obstructive, or mixed by evaluating lung volume, including TLC. Comparing the TLC to the LLN for the TLC will help confirm the presence of restriction or hyperinflation.

Step 4: Transfer factor (DLCO)

The last step is looking at the transfer factor, or the diffusion of carbon monoxide, called DLCO. DLCO allows us to specify the patient's disorder further if present.

Step 5: Next steps

We have left space for notes on the patient's results, whether this is noting the actual values or just any additional information on the pulmonary function tests. This section can also be used to assess the patient's disease or any next steps for treatment. 

Next steps

After identifying a pulmonary disorder using this free PFT Interpretation Chart, the next step is to tailor a personalized treatment strategy. 

Pulmonologists may prescribe specific medications, such as bronchodilators or anti-inflammatory drugs, and suggest lifestyle adjustments to optimize the patient's respiratory health. 

Regular monitoring and follow-up PFTs will then help gauge the treatment's effectiveness, allowing for necessary adjustments. Additionally, the patient will be educated on self-management techniques to control their respiratory symptoms. 

If the patient's PFT results are inconclusive, further diagnostic testing may be required, such as imaging, laboratory tests, or referral to a respiratory specialist. 

 In more severe cases, surgery or urgent care may be needed. The next steps will depend on the patient's individual medical history, the severity and type of their disorder, and the evidence-based best practice in their area. 

Who can benefit from using the PFT Interpretation Chart?

This PFT Interpretation Chart Template is designed to be used once the pulmonary function testing is completed. Practitioners who may find this PFT Interpretation Chart useful for interpreting the results of their patient’s PFT include:

• Anaesthesiologists
• Occupational medicine specialists
• Pulmonary specialists
• Primary care physicians
• Respiratory therapists
• Sports medicine practitioners.

Additionally, this chart can be useful for interns or students who are still familiar with pulmonary function tests and the implications of the different parameter values.