PFT Interpretation Chart
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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.
A PFT Interpretation Chart is generally set out as a flowchart, stepping 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 are providing the best care for their patients.
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.
Printable PFT Interpretation Chart PDF
Access our free PFT Interpretation Chart here to improve respiratory conditions
How does a PFT Interpretation Chart work?
This Printable PFT Interpretation Chart works like a roadmap for your decision-making once you have your patient’s pulmonary function test results. To ensure you’re following the flowchart correctly, just follow the steps below which provide a written version of the diagram.
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 gives a measure of the percentage of lung capacity that can be forcibly expired in one second and is useful in determining the extent of obstructive lung disease.
The first step in the flowchart is therefore determining if the FEV₁/VC ratio is above the lower limit of normal (LLN) value. This will determine which branch we move down for the next step.
Step 2. Vital capacity - VC
Next, we 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 is above LLN, this indicates obstruction. However, if the VC is below the LLN we need to move onto the next step to determine the type of disorder.
Step 3. Total lung capacity- TLC
Next, we will look at the total lung capacity- TLC, to further narrow down the range of diagnoses. By comparing the TLC to the LLN for the TLC, we will be able to determine whether the disorder is restrictive, obstructive, or mixed.
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 further specify the patient’s disorder, if present.
Step 5. Next Steps
We have left space for notes on the patient’s results, whether this is noting down the actual values, or just any additional information on the pulmonary function tests. This section can also be used for your assessment of the patient’s disease or any next steps for treatment.
PFT Interpretation Chart Example (sample)
To make sure you’ve got this diagram straight in your head, we’ve created a sample PFT Interpretation Chart PDF for you to download and have a look at. This sample indicates the path taken through the flowchart diagram for a patient with PFT results within normal ranges for each of the four values described above.
Download this free PFT Interpretation Chart PDF example here
When would you use this PFT Interpretation Chart?
This PFT Interpretation Chart Template is designed to be used once the pulmonary function tests are completed. This means after the spirometry has been completed and you have the results for FEV₁/VC, VC, TLC, and DLCO.
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 getting familiar with pulmonary function tests and the implications of the different parameter values.
Next steps
Following the identification of a pulmonary disorder using this free PFT Interpretation Chart, the next steps involve tailoring 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 to gauge the effectiveness of the treatment, allowing for necessary adjustments. Additionally, the patient will be educated on self-management techniques to ensure their respiratory symptoms are controlled.
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.
Commonly asked questions
FEV₁/VC (Forced Expiratory Volume in one second divided by vital capacity) is a key pulmonary function test parameter that assesses the proportion of the vital capacity expelled in the first second of a forced expiration, helping diagnose and classify lung diseases. This ratio can be used to distinguish between obstructive or restrictive lung disorders, as a FEV₁/VC less than the LLN indicates an obstructive or mixed disorder rather than a restrictive disorder.
Pulmonary function tests (PFTs) are typically completed using a spirometer, which measures the volume of air a person inhales or exhales, providing valuable information about lung function and capacity.
Vital Capacity (VC) is measured during PFTs by having the individual inhale as deeply as possible and then exhale forcefully and completely into the spirometer, allowing the assessment of the maximum amount of air a person can exhale after a maximal inhalation.
