How does the FEV1/FVC ratio typically differ in obstructive versus restrictive lung diseases?

In the context of lung diseases, the FEV1/FVC ratio is a critical measure used to differentiate between obstructive and restrictive patterns of lung pathology.

In obstructive lung diseases, such as asthma or chronic obstructive pulmonary disease (COPD), airflow limitation is primarily characterized by a decrease in FEV1 (forced expiratory volume in one second) while FVC (forced vital capacity) may remain normal or decrease to a lesser extent. Because of this disproportionate reduction in FEV1 relative to FVC, the FEV1/FVC ratio is reduced. This change indicates that the individual has difficulty expelling air from the lungs quickly, leading to a predominance of airway obstruction.

In contrast, restrictive lung diseases, such as pulmonary fibrosis or obesity hypoventilation syndrome, involve a reduction in lung volumes due to restrictions in lung expansion. Both FEV1 and FVC are reduced in this scenario, but the FEV1/FVC ratio can remain normal or may even be increased, indicating that both values are affected proportionately.

The correct choice reflects that in obstructive diseases, the FEV1 is significantly reduced compared to the FVC, resulting in a decreased ratio, while in restrictive diseases, the ratio remains normal as