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What is FEV1?

When you have a Pulmonary Function Test (PFT) run, one of the measurements they take is your FEV1 or Forced Expiratory Volume in the first second.

the volume of air that you can forcefully blow out during the first second of the FVC. A decrease of the FEV1 compared to normal values (obtained from non-smoking, normal subjects your age, height and sex), may indicate a slowing of your flow rates. Chronic obstructive pulmonary diseases (COPD) such as emphysema (including emphysema associated with Alpha-1 Antitrypsin Deficiency), asthma, or chronic bronchitis can reduce flow rates.

Understanding PFTAlphaNet

Evaluating changes in FEV1 and DLCO over time can indicate the effectiveness of therapies, such as augmentation therapy, to slow down or prevent the lung destruction of Alpha-1.

You might hear an Alpha say, “I have only 30 percent lung function,” or “I’ve lost 70 percent of my lung function.” This type of interpretation of PFT measurements demonstrates a misunderstanding of PFT results. When an Alpha makes this type of statement, they are probably referring to their FEV1 value – a test result that can be expressed as a percent of the predicted normal value (and not the percent of an individual’s lung function).

Interpreting your test results can be somewhat complicated, but here is what you need to keep in mind as you evaluate your FEV1 results:

Example: If the predicted normal FEV1 for an individual of your size, age, and sex is 3.0 liters, and your FEV1 is 1.0 liter, your percent of the expected normal value would be 33 percent. This does not mean, however, that you have lost 67 percent of your lungs, or that only 33 percent of your lungs are functioning properly.

First, changes in FEV1 may not reflect what is going on in the lungs as a whole, especially in Alpha-1. There are Alphas who have virtually normal FEV1 measurements but severe emphysema, while others have very impaired FEV1 and only mild changes of emphysema on chest CT. (Below is a description of the chest CT test). This is because emphysema is a disease of the air sacs, while the FEV1 is much more reflective of what is going on in the bronchial tubes.

Second, even with disease in the bronchial tubes, it can take a lot of injury or blockage before the testing of FEV1 starts to produce abnormal values. Then, once the FEV1 starts to become abnormal, there is not an exact one-on-one relationship between the amount of injury to the lungs and value of the FEV1.

Still, within a particular individual, test results like the FEV1 are a good way of following whether or not someone’s condition has stabilized or is worsening.

Big Fat Reference Guide – AlphaNet