Which statement correctly distinguishes FEV1 from VC?

• A. FEV1 is the volume expired in the first second; VC is the maximal expiration after a maximal inspiration.
• B. FEV1 is the total lung capacity; VC is residual volume.
• C. FEV1 and VC measure the same parameter.
• D. FEV1 is the inspiratory capacity; VC is tidal volume.

Answer: (A)

The key idea is that FEV1 and vital capacity measure different things: how fast air flows out in a short interval versus how much air can be exhaled in total after a full inhale.

FEV1 is the volume of air that a person can forcefully exhale in the first second of a forced expiratory effort. It reflects airway caliber and the rapidity of exhalation, making it a useful indicator of airway resistance and obstructive patterns.

Vital capacity, on the other hand, is the maximum amount of air that can be exhaled after a maximal inhalation. It represents the total usable volume that can be moved in and out of the lungs from full inspiration to full expiration, not the rate at which air leaves the lungs.

This distinction is what the statement captures: FEV1 is the volume expired in the first second, while vital capacity is the maximal expiration after a maximal inspiration. The other ideas mix up what each parameter measures—for example, total lung capacity and residual volume describe different, larger or leftover volumes, and inspiratory capacity or tidal volume refer to other aspects of breathing.