What best describes emphysema?

Emphysema is a chronic lung condition that primarily affects the air sacs, known as alveoli, in the lungs. The defining characteristic of emphysema is the enlargement and destruction of these air sacs, which leads to reduced surface area for gas exchange. This enlargement occurs because the walls of the alveoli break down, causing them to merge into fewer, larger sacs, which decreases the lung's ability to oxygenate blood and remove carbon dioxide effectively.

This condition is most commonly associated with long-term exposure to irritants such as cigarette smoke and environmental pollutants, and it is a key component of chronic obstructive pulmonary disease (COPD). The distinguishing feature of emphysema compared to other pulmonary conditions is this abnormal enlargement of the air sacs rather than inflammation, fluid accumulation, or increased mucus, which characterize different respiratory issues.