Final answer:
In emphysema, the respiratory membrane undergoes a decrease in surface area for gas exchange due to damaged alveolar walls, leading to larger sacs and fewer alveoli.
Step-by-step explanation:
In patients with emphysema, the respiratory membrane undergoes significant changes that affect gas exchange within the lungs. One of the key changes is B) Decreased surface area for gas exchange. Emphysema damages the walls between the alveoli, causing them to lose their shape and become larger sacs. This results in a reduced number of alveoli and, consequently, a decreased surface area for gas exchange. The thickening of the respiratory membrane and increased elasticity are not typical of emphysema—instead, there is loss of elasticity. Furthermore, the diffusion capacity of the respiratory membrane is not enhanced; it is compromised due to the reduced surface area and destruction of the pulmonary capillaries.