Spirometry is a tool that plays an important role in chronic obstructive pulmonary disease (COPD) — from the moment your doctor thinks you have COPD all the way through its treatment and management.

It’s used to help diagnose and measure breathing difficulties, like shortness of breath, cough, or mucus production.

Spirometry can detect COPD even in its earliest stage, even before any obvious symptoms are noticeable.

Along with diagnosing COPD, this test can also help track progression of the disease, assist in staging, and even help to determine treatments that might be most effective.

Spirometry testing is done in the doctor’s office using a machine called a spirometer. This device measures your lung function and records the results, which are also displayed on a graph.

Your doctor will ask you to take a deep breath and then blow out into the mouthpiece on the spirometer as hard and fast as you can.

It will measure the total amount that you were able to exhale, called the forced vital capacity (FVC), as well as how much was exhaled in the first second, called the forced expiratory volume in 1 second (FEV1).

Your FEV1 is also influenced by other factors including your age, sex, height, and ethnicity. The FEV1 is calculated as a percentage of the FVC (FEV1/FVC).

Just as that percentage was able to confirm a diagnosis of COPD, it will also let your doctor know how the disease is progressing.

Your doctor will use the spirometer to regularly monitor your lung function and help track the progression of your disease.

The test is used to help determine COPD staging and, depending on your FEV1 and FVC readings, you’ll be staged based on the following:

COPD stage 1

The first stage is considered mild. Your FEV1is equal to or greater than the predicted normal values with an FEV1/FVC less than 70 percent.

In this stage, your symptoms are most likely to be very mild.

COPD stage 2

Your FEV1 will fall between 50 percent and 79 percent of the predicted normal values with an FEV1/FVC of less than 70 percent.

Symptoms, like shortness of breath after activity and cough and sputum production, are more noticeable. Your COPD is considered to be moderate.

COPD stage 3

Your FEV1 falls somewhere between 30 percent and 49 percent of the normal predicted values and your FEV1/FVC is less than 70 percent.

In this severe stage, shortness of breath, fatigue, and a lower tolerance to physical activity are usually noticeable. Episodes of COPD exacerbation are also common in severe COPD.

COPD stage 4

This is the most severe stage of COPD. Your FEV1is less than 30 percent of normal predicted values or less than 50 percent with chronic respiratory failure.

At this stage, your quality of life is greatly impacted and exacerbations can be life-threatening.

Regular use of spirometry for progression tracking is important when it comes to COPD treatment.

Each stage comes with its own unique issues, and understanding what stage your disease is at allows your doctor to recommend and prescribe the best possible treatment.

While staging helps create standard treatments, your doctor will take your spirometer results into consideration along with other factors to create a treatment that’s personalized to you.

They’ll consider factors like other health conditions you may have as well as your current physical condition when it comes to rehabilitation therapy such as exercise.

Your doctor will schedule regular tests and use the spirometer results to make adjustments to your treatment as needed. These can include recommendations for medical treatments, lifestyle changes, and rehabilitation programs.

Spirometry, along with assisting in staging and treatment recommendations, also lets your doctor check to see whether or not your treatment is working.

The results of your tests can tell the doctor if your lung capacity is stable, improving, or decreasing so that adjustments to treatment can be made.

COPD is a chronic condition that can’t yet be cured. But treatments and lifestyle changes can help reduce your symptoms, slow progression, and improve your quality of life.

A spirometry test is a tool you and your doctor can use to determine which COPD treatments are right for you at each stage of the disease.