A Handy Guide To Help Interpret Spirometer Readings

Check out this helpful guide to find out how you and your doctor can interpret spirometry readings and what this may mean for your lung condition in the future.

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A spirometry test is used to test how well your lungs are functioning. But the results can be a little confusing. Read on to find out how to compare your readings with normal predicted values and how to interpret FVC, FEV1 and FEV1/FVC Ratio results.

If you have been diagnosed with a respiratory disease, like asthma or COPD – Chronic Obstructive Pulmonary Disease, you may be well aware of the spirometry test and its use in the diagnosis of such conditions.

But it can be difficult to understand the many different results provided, and how best to interpret all of these readings.

Read this handy guide to find out just how your and your doctor can interpret Bluetooth Spirometry readings and what this may mean in the long term for your lung condition.

What Is A Spirometry Test Used For?

A Bluetooth Spirometer is a test to see how well your lungs work. Usually the test itself will be conducted with your GP or a practice nurse at your doctor’s surgery but it can be performed anywhere.

The test is a helpful way for healthcare professionals to check your lungs and airways in order to effectively diagnose a lung condition, such as asthma, COPD and restrictive lung disease (such as interstitial pulmonary fibrosis).

A spirometry test measures the volume of air you both inhale and exhale, and how quickly you exhale.

There are crucial measurements derived from a spirometry test and these include:

Forced vital capacity (FVC)

Forced expiratory volume (FEV)

Forced expiratory volume in one second (FEV1)
Total lung capacity (TLC)

What Do Normal, Values In A Spirometry Test Mean?

Results are given in litres per minute and percentages.

Normal readings for this test are different depending on the person and they are based on the following factors:

Age

Height

Race

Gender

Your doctor will work out the predicted normal values for you before you undertake the test.

Once the test is complete, they will then evaluate your test score against the predicted value. To get a normal result? You will need to obtain a score that is 80% or more of the predicted value.

If you want to gain an idea of what your normal value looks like, you can use a very clever device, called a spirometry calculator.

Here, you can enter your own individual details – or if you know your spirometry readings already – and the calculator will work out what % of the normal, predicted values your results are.

As the spirometry test measures two key factors…

Forced vital capacity (FVC)

Forced expiratory volume in one second (FEV1).

…your doctor will look at these figures as a combined number known as the FEV1/FVC ratio.

If your airways are obstructed, the amount of air you will be able to quickly exhale from your lungs will be lower than normal.

The FEV1/FVC ratio will therefore be lower.

.After you have your spirometry test, your doctor compares your test results to the normal, predicted values from people who are similar to you in age, height, weight, gender and ethnicity.

Generally speaking, normal results will have an FVC and a FEV1 above 80 percent predicted with a FEV1/FVC ratio that is greater than 70 percent.

This can come across as a little confusing, so read on to find out how best to interpret these results:

Interpreting Your Spirometry Results

After your spirometry test, your doctor will look at your results and begin to interpret them. There are several methods your doctor may choose to interpret your results.

In order to diagnose asthma, you will have a low FEV1 and low FEV1/FVC reading. This is due it being more difficult for the air to leave the lungs. This means that is an airway obstruction.

Obstructive lung diseases include asthma and COPD (chronic obstructive pulmonary disease).

When spirometry is used in conjunction with a bronchodilator test, this usually means that patients will take four puffs of an albuterol inhaler, wait for 15-20 mins and then further readings will be taken.

The results of which help to separate asthma from COPD.

If the FEV1 reading increases by 12% albuterol, it means that the airway blockage is reversible. This reversibility is a sign of asthma.

If the numbers for your FVC or FEV1 are decreased, your doctor will then need to look more closely into the results of your test.
Your doctor will move on to look at the % (percent) predicted for both your

FVC and FEV1.

They will begin with looking at the % for your Forced vital capacity (FVC). This is to work out whether it’s in the normal range.

If your FVC is lower than normal, something is obstructing your airways/breathing. This could be due to an obstructive lung disease.
The results will be different in both children and adults.

For children (aged 5-18), these are as follows:

Percentage of predicted FVC value is:

80% or greater

NORMAL RESULT

Percentage of predicted FVC value is:

Less than 80%

ABNORMAL RESULT

For adults, these are as follows:

Percentage of predicted FVC value is:

Greater than or equal to the lower limit amount of normal

NORMAL RESULT

Percentage of predicted FVC value is:

Less than the lower limit amount of normal

NORMAL RESULT

Your doctor will likely then look into the % for your Forced expiratory volume in one second (FEV1), again as a way to see if this in the normal range.
This particular measurement will tell your doctor the severity of any breathing issues. If your FEV1 is lower than normal, this could mean that you have a significant breathing obstruction.
As it can be measured quickly and easily at all stages of disease, FEV1 is strongly recommended as the measurement of choice in COPD as:
According to guidelines from the American Thoracic Society, the figures below show what’s considered normal and abnormal when it comes to your FEV1 spirometry test results: