Spirometry Explained: Your Guide to the Lung‑Function Test

Ever wonder why doctors ask you to blow into a tube? That’s spirometry – a quick, painless way to measure how well your lungs move air in and out. It’s not just for asthma patients; anyone with breathing concerns can benefit. The numbers you get help doctors spot early problems and decide if treatment is needed.

What Happens During a Spirometry Test

First, you’ll sit upright and get a mouthpiece that fits snugly over a small filter. You’ll take a deep breath, then exhale as hard and fast as possible until you can’t push any more air out. The machine records the volume and speed of that breath. Most clinics do three tries, and the best two are kept for analysis.

There’s no special prep, but avoid heavy meals, smoking, or vigorous exercise for a couple of hours beforehand. If you have a cold, the test might be postponed because congestion can skew the results. The whole process takes about 10 minutes.

Understanding Your Spirometry Results

Doctors look at two key numbers: FEV1 (the amount of air you can force out in the first second) and FVC (the total amount of air you can exhale after a full inhalation). The ratio of FEV1 to FVC tells whether you have an obstructive pattern (like COPD) or a restrictive pattern (like fibrosis).

Numbers are compared to predicted values based on age, gender, height, and ethnicity. If your FEV1 is less than 80% of the predicted value, it signals reduced lung capacity. A low FEV1/FVC ratio (<0.70) usually points to obstruction. Your doctor will explain what the specific percentages mean for you.

Beyond diagnosis, spirometry helps track disease progression and evaluate how well a medication works. If you start a new inhaler, repeat testing after a few weeks shows whether your lung function is improving.

It’s normal to feel a bit light‑headed after blowing hard, but that passes quickly. If you ever feel dizzy or chest pain during the test, tell the technician right away – they’ll stop and reassess.

In short, spirometry is a simple, cost‑effective tool that gives a clear picture of your breathing health. Knowing the basics helps you feel confident when your doctor recommends the test, and it lets you understand the numbers they discuss with you.