What is the primary characteristic of the lungs in emphysema?

In emphysema, the primary characteristic is a decrease in lung elasticity. This condition results from damage to the alveoli, the tiny air sacs in the lungs where gas exchange occurs. When the alveoli lose their elasticity, they become less capable of returning to their original size after inhalation, which makes it difficult for the lungs to expel air effectively. This reduced ability to recoil leads to air trapping and diminished airflow, especially during exhalation.

While other options describe changes that may occur in lung function or structure, they do not capture the hallmark of emphysema as accurately. For instance, the airways do not primarily become narrower; instead, damage to the alveoli increases the compliance of the lungs but reduces their elastic recoil. Additionally, in emphysema, alveoli do not multiply; rather, they can become destructed and merge together, which diminishes the total surface area available for gas exchange. Lastly, carbon dioxide levels typically increase, not drop, due to the impaired ability to exhale it effectively, which is a significant issue in emphysema.