Lab Reports Decoded

Spirometry Explained: The 3 Numbers That Reveal Lung Health (Video)

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Read the full written guide: Spirometry (PFT) Report: FEV1, FVC and the Ratio Explained →

In this video we break down a spirometry report into three simple numbers, FVC, FEV1, and their ratio. You’ll learn what each metric means and how doctors use them to spot airway narrowing or reduced lung capacity.

We also share quick tips on how to prepare for the test and the key threshold that flags obstruction. This guide is for everyday understanding, not medical advice.

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Transcript

Ever wonder why doctors focus on three numbers in a breathing test?

Ever wonder why doctors focus on three numbers in a breathing test?

Spirometry Basics

You’ll walk away knowing the three key numbers that doctors look at in a breathing test.

What spirometry measures

Spirometry asks you to take your biggest breath, seal a mouthpiece, and blow out as hard and fast as you can. A nose clip stops air from escaping the other way. Imagine emptying a balloon through a straw.

Three key numbers

Your report boils down to three values. FVC tells how much total air you can force out after a full inhalation. FEV1 measures the volume expelled in the first second. The FEV1/FVC ratio compares the two and shows whether the airway is narrowed.

Obstruction threshold

A ratio below about 0.70, or under the lab’s lower limit of normal, points to an obstructive pattern like asthma or COPD.

Obstructive vs restrictive

Obstructive means the airways are pinched, so air leaves slowly. FEV1 drops more than FVC, pulling the ratio down. Restrictive means the lungs can’t fill fully, so both FVC and FEV1 are low but the ratio stays normal or even high. Common causes include asthma, smoking-related COPD, and lung scarring.

Reversibility cutoff

If after a reliever inhaler the FEV1 improves by at least 12% and 200 mL, the test flags significant reversibility, a clue toward asthma.

How to prepare

To get reliable numbers, avoid coughing or stopping early, and give three good blows. Labs often grade the effort from A to F; a low grade may mean the test should be repeated. Ask your doctor about holding reliever meds, skip smoking for an hour, skip a heavy meal, and skip intense exercise for 30 minutes before the test.

The one key takeaway

The one key takeaway: watch the FEV1/FVC ratio. If it falls below about 0.70, it signals an obstructive pattern, and a rise of 12% after a bronchodilator suggests asthma.

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Read the full guide

Read the complete guide on thecareonline.com. This is general information, not medical advice.

Nothing on The Care Online is medical advice. Traditional practices are described as tradition, not as fact. Take a persistent or serious concern to a qualified professional. See how videos and posts are made on our methodology page.