Lung Function Testing Made Simple (Spirometry)

A lung function test (also called spirometry) is a simple breathing test that checks how well your lungs are working.

During the test you will be asked to:

• Take the biggest breath you can.
• Seal your lips around a mouthpiece.
• Blow out as hard and as fast as possible until your lungs feel empty.
• Repeat the test several times to make sure the results are accurate.
• Sometimes repeat the test after using an inhaler to see if your breathing improves.

The test is painless and usually takes 15–30 minutes.

Your healthcare provider may recommend spirometry to:

• Find out why you're short of breath.
• Investigate a persistent cough or wheeze.
• Diagnose conditions such as asthma or COPD.
• Monitor how well your lungs are working over time.
• Check whether your inhaler or other treatment is helping.

Think of it as a fitness test for your lungs.

 Different lung function tests measure different aspects of how well your lungs work. 

What it means

Your lungs are working as expected for someone of your age, height, sex and background.

Simple explanation

"Your breathing test is normal. Air moves in and out of your lungs as expected."

What it means

Your airways are narrowed, making it harder to blow air out quickly.

This pattern is commonly seen in:

• Asthma
• COPD

Simple explanation

"The airways are narrower than normal, so it takes longer to empty your lungs."

 What it means

Your lungs cannot fully expand, so they hold less air than expected.

This may occur with:

• Lung scarring (fibrosis)
• Some muscle conditions
• Obesity
• Chest wall disorders

Simple explanation

"Your lungs are a little smaller or stiffer, so they can't fill with as much air."

What it means

There are signs of both narrowed airways and reduced lung size.

Simple explanation

"There are two problems happening at once—the airways are narrowed and the lungs cannot fully expand."

Measures how much air you can blow out in the first second.

Think of it as:

"How quickly your lungs can empty."

Lower values may mean your airways are narrowed.

Measures the total amount of air you can blow out after taking a full breath in.

Think of it as:

"How much air your lungs can hold."

Compares how much air comes out in the first second with the total amount you blow out.

Think of it as:

"How easily air can leave your lungs."

• Normal ratio: Airways are likely open.
• Low ratio: Airways may be narrowed or blocked.

Your healthcare provider will explain your results and decide whether you need:

• No further treatment if your lungs are working normally. 
• An inhaler or changes to your current treatment. 
• More breathing tests. 
• A chest X-ray or CT scan if more information is needed. 
• Advice about quitting smoking, exercise, or pulmonary rehabilitation if appropriate.

Think of your lungs like a balloon:

• 🎈 Normal: The balloon fills and empties easily. 
• 🚧 Obstructive: The balloon opening is narrow, so air gets out slowly. 
• 📦 Restrictive: The balloon can't stretch fully, so it holds less air. 
• 🔄 Mixed: The balloon doesn't stretch well, and the opening is narrow too. 

This simple comparison can make it easier to understand what your lung function results mean.

No single test tells the whole story. 

Your healthcare provider may use one or several lung function tests to understand:

• How well your lungs are working 
• Why you are experiencing breathing problems 
• Whether your treatment is working 
• How your lung condition changes over time