In emphysema, diffusion capacity is impaired due to what structural change?

In emphysema, diffusion capacity is impaired due to what structural change?

• A. Destruction of alveolar walls leading to reduced surface area for gas exchange
• B. Mucus blockage
• C. Increased diffusion capacity
• D. Normal diffusion capacity

Answer: (A)

Diffusion capacity reflects how easily gases move from the air into the blood across the alveolar–capillary membrane, and it depends mainly on the surface area available for exchange and the distance across which diffusion must occur. In emphysema, destruction of the alveolar walls destroys the tiny air sacs and the accompanying capillary network, so the total surface area for gas exchange falls. With less interface for diffusion, less gas can cross per unit time, so diffusion capacity decreases. Mucus blockage affects ventilation by narrowing or obstructing airways, not the alveolar surface area for gas transfer. A higher diffusion capacity would require more surface area, which isn’t the case in emphysema. Normal diffusion capacity would contradict the loss of alveolar walls.

Diffusion capacity reflects how easily gases move from the air into the blood across the alveolar–capillary membrane, and it depends mainly on the surface area available for exchange and the distance across which diffusion must occur. In emphysema, destruction of the alveolar walls destroys the tiny air sacs and the accompanying capillary network, so the total surface area for gas exchange falls. With less interface for diffusion, less gas can cross per unit time, so diffusion capacity decreases.

Mucus blockage affects ventilation by narrowing or obstructing airways, not the alveolar surface area for gas transfer. A higher diffusion capacity would require more surface area, which isn’t the case in emphysema. Normal diffusion capacity would contradict the loss of alveolar walls.