Destruction of alveolar walls leading to decreased gas exchange describes which condition?

• A. Pneumonia
• B. Pulmonary Edema
• C. Emphysema
• D. Congestive Heart Failure

Answer: (C)

Understanding gas exchange hinges on the alveolar surface area and the integrity of the alveolar–capillary walls. When those walls are destroyed, as in emphysema, the tiny air sacs merge into larger air spaces, dramatically reducing the surface area available for oxygen and carbon dioxide diffusion and shrinking the capillary network involved in gas transfer. Elastic recoil is also lost, leading to airway collapse during expiration and air trapping, which further impairs efficient gas exchange. This combination explains the decreased gas exchange described.

Pneumonia involves infection that fills alveoli with fluid and inflammatory exudate, causing consolidation and impaired gas exchange without destroying alveolar walls. Pulmonary edema and congestive heart failure cause fluid accumulation in the interstitial space or alveoli, increasing diffusion distance rather than reducing surface area through wall destruction. Therefore, the description most accurately fits emphysema.