What structural change occurs in lungs affected by emphysema?

In patients with emphysema, the primary structural change is a decrease in the surface area available for gas exchange. This occurs due to the destruction of the alveolar walls, which leads to the formation of larger, less effective air spaces instead of the small, numerous alveoli that are optimal for gas exchange. As the alveoli are damaged and coalesce, the overall surface area diminishes, impairing the lungs' ability to absorb oxygen and expel carbon dioxide efficiently. This reduced surface area is a hallmark of emphysema and is central to the disease's impact on respiratory function.

The other potential options do not accurately reflect the consequences of emphysema. For instance, an increase in elasticity or capacity is not characteristic of the diseased state; rather, the lungs can become less elastic. Similarly, enhanced gas exchange surfaces would be contrary to the condition since emphysema actually reduces the effectiveness of these surfaces. The formation of fibrotic tissue is more associated with other respiratory conditions, such as pulmonary fibrosis, rather than emphysema, which primarily involves destructive changes rather than an increase in fibrous tissue.