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This is a brief introduction to how you should interpret the values you got from a pulmonary function test at the doctors office. This article is focused on Chronic Obstructive Pulmunary Disease and look at

the values most important for this condition.

Did you know you can perform a pulmonary function test at home?

First of all, when you take a pulmonary function test, the person coaching you must be experienced and know how a correct test is performed and also be able to judge if the blow was satisfactory or not. Each session must give 3 different blows that meet the guidelines of the American Thorasic Society. Basically this means that the two best blows should not differ than more 5%. This shouldn’t be your concern and you must trust the professional coacher on this matter. The technique and quality of the test is essential to make a valid pulmonary function test interpretation.

To keep it simple we will look at only three parameters generated from a pulmonary function test, two of the values are measured and the third is calculated.

The values generated at the pulmonary function test are compared to a reference-guide. The reference-guide is based on sex, age, length and race. Your values are compared to the reference-guide and healthcare professionals often talk about how many percentage you have compared to the reference (the predicted value). If you are spot on the reference value you have  100%. The predicted value is calculated and based on statistics, so some people may have 90% or less naturally while others have 120% or more. It is important to remember that one value says nothing, we need the complete picture in order to know how to interpret the pulmonary function test.

• First we take a look at the value called FEV1. FEV1 is short for Forced Exspiratory Volume during the first second of the blow. This value is commonly known as lung-function. FEV1 tells us about the elasticity of the lungs. The better elasticity the higher value. A person with severe COPD has a very poor elasticity while a young, healthy non-smoker have a great elasticity in the lungs. You could compare this with a ballon (great elasticity) and a plastic bag (no elasticity), this example shows the two extremes and most of us are somewhere in between.

• The next value is FVC. FVC is short for Forced Volume Capacity. This is the total amount of air you exhale during the blow. To get this value correct you should blow no less than 6 seconds but preferably until you are out of air completely. This value is commonly known as lung-capacity.

• The third value is not measured but calculated from the two parameters above and it is refered to as FEV1%FVC. This calculated value tells us how many percentage of the total volume(FVC) you exspire during the first second of the blow (FEV1). This value is not related to any references and should always be above 70%, meaning that from all the air you exhale during the test more than 70% should be exhaled during the first second of the test. If the value is below 70% it’s natural to suspect some sort of obstructive condition.

 

We will be looking for links to different reference-guides and post them here. We use Reference values for spirometry of the European Coal and Steel Community. Different doctors prefer different references and you should now wich they use in order to make an pulmonary function test interpretation.