Which of the following is NOT classified as an obstructive lung disease?

The correct answer indicates that fibrosis is not classified as an obstructive lung disease. Fibrosis, particularly pulmonary fibrosis, is characterized by the thickening and scarring of lung tissue, which primarily leads to restrictive lung disease rather than obstructive lung disease. In restrictive lung disease, the lungs cannot expand fully, which limits the total volume of air that can be taken in, as opposed to obstructive diseases where airflow is impaired during expiration due to blockages or narrowing in the airways.

Obstructive lung diseases, such as bronchitis, emphysema, and chronic obstructive pulmonary disease (COPD), are characterized by difficulty in exhaling air due to obstruction. In bronchitis, inflammation and mucus buildup in the airways restrict airflow, whereas emphysema involves the destruction of alveolar walls, leading to the loss of elastic recoil and trapping of air in the lungs. COPD encompasses these conditions, further verifying their classification as obstructive lung diseases. Thus, fibrosis stands out clearly as it leads to different pathophysiological changes and clinical symptoms, emphasizing its distinction from the obstructive type.