The FEV1/FVC ratio is typically expressed as a percentage. What is the normal range for this ratio?

• A. ≥ 60%
• B. ≥ 70-85%
• C. ≥ 80%
• D. ≥ 90%

Answer: (B)

The main idea here is how the FEV1/FVC ratio reflects airway function. This ratio shows what fraction of the total forced vital capacity is expelled in the first second of a forced expiratory maneuver. In healthy lungs, FEV1 is a large portion of FVC, so the ratio stays high. Obstructive diseases reduce FEV1 more than FVC, dropping the ratio, while restrictive diseases reduce both FEV1 and FVC but keep the ratio closer to normal or even higher.

In healthy adults, the ratio is typically around 0.75–0.85 when expressed as a percentage, corresponding to about 75–85%. Because this value tends to drift lower with age, a practical normal range is roughly 70–85%. That’s why a range like 70–85% best captures the usual variation seen in the population.

So the correct answer aligns with this broad, age-influenced normal window. The other options either set a value that's too low, or insist on a fixed high percentage that doesn’t account for natural variation with age.