Certified Respiratory Therapist Practice Exam

The correct choice is the diffusing capacity (DLCO) test, which plays a crucial role in distinguishing emphysema from other pulmonary conditions. Emphysema is characterized by the destruction of the alveoli, leading to a reduction in the surface area available for gas exchange, which directly impacts the diffusing capacity.

When a patient has emphysema, the DLCO results typically demonstrate a decrease due to this impaired gas exchange. In contrast, other lung diseases, such as asthma or chronic bronchitis, might not show as significant a reduction in DLCO, or they may even present normal values depending on the specific pathophysiology involved.

By measuring how well oxygen passes from the lungs to the blood, DLCO provides valuable information that helps clinicians differentiate emphysema—where there is alveolar destruction and reduced gas exchange efficiency—from other lung diseases that may not have the same impact on diffusion capacity.