In obstructive lung disease, the FEV1/FVC ratio is typically:

In obstructive lung disease, the FEV1/FVC ratio is typically:

• A. Normal
• B. Increased
• C. Decreased
• D. Unchanged

Answer: (C)

Obstructive processes mainly limit expiratory airflow, so the amount you can blow out in the first second (FEV1) falls more than the total exhaled volume (FVC). This disproportionate drop lowers the FEV1/FVC ratio. FVC may be normal or reduced, and air trapping can occur, but the hallmark is that FEV1 is reduced relative to FVC, producing a decreased ratio. In contrast, restrictive patterns reduce both volumes more or less equally, keeping the ratio normal or even higher. That’s why a decreased FEV1/FVC ratio is typical in obstructive lung disease.

Obstructive processes mainly limit expiratory airflow, so the amount you can blow out in the first second (FEV1) falls more than the total exhaled volume (FVC). This disproportionate drop lowers the FEV1/FVC ratio. FVC may be normal or reduced, and air trapping can occur, but the hallmark is that FEV1 is reduced relative to FVC, producing a decreased ratio. In contrast, restrictive patterns reduce both volumes more or less equally, keeping the ratio normal or even higher. That’s why a decreased FEV1/FVC ratio is typical in obstructive lung disease.