Which statement best describes the relationship between FVC and FEV1?

Which statement best describes the relationship between FVC and FEV1?

• A. FVC is the total volume exhaled during a full maximal expiration; FEV1 is the amount exhaled in the first second.
• B. FVC measures the amount inhaled in the first second.
• C. FEV1 equals FVC.
• D. FEV1 is the total air exhaled.

Answer: (A)

The essential idea is how these two spirometry measures relate to the air you can move out of your lungs during a forced expiration. FVC, or forced vital capacity, is the total amount of air you can exhale forcefully after a full, maximal inhalation. FEV1, the forced expiratory volume in one second, is how much of that air comes out in the first second of that same forced exhalation. So FEV1 is a portion of FVC, not the whole amount, and they describe different parts of the exhalation. That’s why the best description is that FVC is the total volume exhaled during a full maximal expiration, while FEV1 is the amount exhaled in the first second. The other statements misrepresent either what FVC or FEV1 measure (for example, inhaled air, or claiming they are equal, or that FEV1 is the total exhaled). In healthy lungs, FEV1 is typically a large fraction of FVC, but not equal to it.

The essential idea is how these two spirometry measures relate to the air you can move out of your lungs during a forced expiration. FVC, or forced vital capacity, is the total amount of air you can exhale forcefully after a full, maximal inhalation. FEV1, the forced expiratory volume in one second, is how much of that air comes out in the first second of that same forced exhalation. So FEV1 is a portion of FVC, not the whole amount, and they describe different parts of the exhalation.

That’s why the best description is that FVC is the total volume exhaled during a full maximal expiration, while FEV1 is the amount exhaled in the first second. The other statements misrepresent either what FVC or FEV1 measure (for example, inhaled air, or claiming they are equal, or that FEV1 is the total exhaled). In healthy lungs, FEV1 is typically a large fraction of FVC, but not equal to it.