- Forced Expired Volume in the first second (FEV1):
This is a measure of how much of the FVC the subject exhaled in the first second. A normal person will exhale around 80% of their FVC in the first second.
This is the percent of the FVC that person exhaled in the first second (see above). Both measures are important to look at together because if the FVC is low, the FEV1 will also be low (as in restrictive diseases such as idiopathic pulmonary fibrosis; however in these diseases, the person’s ability to exhale is not usually compromised).