Which lung disease is characterized by a decreased FEV1/FVC ratio?

The decreased FEV1/FVC ratio is a hallmark of obstructive lung disease. In this condition, airflow limitation occurs, primarily affecting the expiration of air from the lungs. This obstruction leads to a significant reduction in the forced expiratory volume in one second (FEV1), which is the volume of air expelled in the first second of a forced expiratory maneuver. Although the forced vital capacity (FVC)—the total amount of air that can be forcibly exhaled—may also be decreased, it is not reduced at the same rate as FEV1. Consequently, the ratio (FEV1/FVC) falls below the normal range, typically indicated as being less than 70%.

In contrast, other lung diseases, such as restrictive lung diseases, interstitial lung diseases, and pneumoconiosis, may present with a normal or increased FEV1/FVC ratio due to the decrease in both FEV1 and FVC, with FVC decreasing proportionately more than FEV1. Therefore, while these conditions may impair lung function, they do not exhibit the specific hallmark of a decreased FEV1/FVC ratio associated with obstructive lung disease.