Which of the following lung disease types is associated with a decreased FEV1/FVC ratio?

• A. Restrictive lung disease
• B. Obstructive lung disease
• C. Interstitital lung disease
• D. Pulmonary fibrosis

Answer: (B)

The decreased FEV1/FVC ratio is a hallmark of obstructive lung diseases. In these conditions, there is a significant limitation in airflow, leading to a reduction in the forced expiratory volume in one second (FEV1) compared to the forced vital capacity (FVC). In obstructive lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD), the FEV1 is particularly affected due to obstruction in the airways, which causes difficulty in expelling air quickly.

In contrast, restrictive lung diseases, including conditions such as pulmonary fibrosis, may lead to a preserved or increased FEV1/FVC ratio, as both values can be reduced equally, but the FVC tends to decrease more drastically than FEV1, maintaining or slightly increasing the ratio. Thus, while a decrease in FEV1/FVC can indicate poor airway function typical of obstruction, any ratio analysis in restrictive cases does not illustrate the same pattern of airflow limitation.

Therefore, the association of a decreased FEV1/FVC ratio specifically aligns with obstructive lung disease, emphasizing how airflow limitation characterizes this type of respiratory pathology.