If you’ve recently had a lung function test, you’re not alone in heading straight to Google afterward. Seeing a page filled with numbers, percentages, and unfamiliar abbreviations can raise more questions than answers, especially if you’re managing ongoing symptoms or a chronic heart or lung condition.
At PulseAir Heart and Lung Centre, we often remind patients of this: spirometry results are helpful, but they’re only meaningful when interpreted in context. Here’s a clear, patient‑first guide to understanding what those lung test results are measuring and why follow‑up matters.
What Is a Lung Function Test?
A lung function test, most commonly spirometry, measures how well your lungs move air in and out. During the test, you’re asked to take a deep breath and blow forcefully into a mouthpiece connected to a machine.
Spirometry is often ordered when:
- You’re experiencing shortness of breath, coughing, or wheezing
- A provider wants to evaluate asthma or COPD
- Symptoms don’t match imaging or exam findings
- A specialist needs baseline measurements or follow‑up data
At a lung centre, spirometry is one piece of a much larger diagnostic picture.
The Three Spirometry Numbers Patients Ask About Most
FEV1 (Forced Expiratory Volume in One Second)
This measures how much air you can forcefully exhale in the first second of blowing out.
- Lower values may suggest narrowed airways
- It’s often used to assess airflow limitation
FVC (Forced Vital Capacity)
This is the total amount of air you can fully exhale after taking your deepest breath.
- Reduced FVC may point to lung restriction or reduced lung volume
- It helps determine how much air your lungs can hold and release
FEV1/FVC Ratio
This compares how much air comes out in the first second versus the total amount exhaled.
- A lower ratio can indicate obstruction
- A normal or high ratio with low volumes may suggest restriction
Each number tells a different part of the story, and none should be read on its own.
What Do “Predicted” Percentages Actually Mean?
Your results are often shown as a percentage of predicted values. These predictions are based on large population studies and take into account factors such as:
- Age
- Height
- Sex
- Biological reference standards
In general, results between 80% and 120% of predicted are commonly considered within expected limits. However, this doesn’t automatically mean everything is normal—or abnormal.
A specialist looks at:
- Patterns across all measurements
- How results align with symptoms
- Whether results change over time
When Results Are Labelled “Normal,” “Mild,” or “Moderate”
Spirometry reports often include terms like:
- Normal
- Mild obstruction
- Moderate obstruction
These categories describe measurement patterns, not diagnoses.
For example:
- “Mild obstruction” may explain symptoms, or may not
- “Normal” results don’t rule out asthma or other conditions
- Severity labels don’t predict how you’ll feel day to day
This is why interpretation matters just as much as the numbers themselves.
How Specialists Use Lung Test Results to Narrow Down Causes
Obstructive Patterns
When airflow is limited, specialists may consider conditions such as:
- Asthma
- Chronic obstructive pulmonary disease (COPD)
Additional testing or medication trials may be needed to clarify the cause.
Restrictive Patterns
Lower lung volumes with preserved airflow ratios can suggest:
- Chest wall or muscle limitations
- Lung tissue changes
- Cardiac or systemic contributors
Further evaluation is often required.
Mixed or Unclear Patterns
Sometimes results don’t fit neatly into one category. In these cases, a specialist may recommend:
- Repeat spirometry
- Full pulmonary function testing
- Imaging or cardiopulmonary assessment
Why a Single Lung Test Rarely Tells the Whole Story
Spirometry reflects how your lungs functioned on that specific day. Results can be influenced by:
- Technique and effort
- Recent illness
- Medication use
- Fatigue or pain
That’s why lung specialists look beyond a single test and consider:
- Symptom history
- Physical exams
- Imaging results
- Changes over time
When Repeat or Follow‑Up Testing Is Recommended
Repeat testing may be advised to:
- Monitor progression of a known condition
- Evaluate response to inhalers or other therapies
- Confirm borderline or unexpected findings
- Establish a reliable baseline
Consistent follow‑up helps ensure care decisions are based on accurate, meaningful data.
Moving Forward With Clarity and Support
Lung test results aren’t meant to be decoded alone. They’re tools that help guide diagnosis, treatment, and long‑term management when interpreted by experienced specialists.
At PulseAir Heart and Lung Centre, we provide comprehensive pulmonary function testing, expert interpretation, and coordinated follow‑up care for patients with known or suspected heart and lung conditions. If you have questions about your results or have been referred for further evaluation, our team is here to help you understand what comes next.
Questions? Get In Touch with Us Today