Respiratory Conditions · USMLE Step 1

A patient with severe asthma has normal DLCO. This finding supports the diagnosis because:

  1. Alveolar walls remain intact
  2. Air trapping reduces diffusion
  3. Bronchioles collapse permanently
  4. Mucus plugs thicken the alveolar membrane
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Correct answer: Alveolar walls remain intact

Asthma affects airways but not alveoli, so DLCO is typically normal or increased. This helps distinguish asthma from emphysema.

Difficulty: Medium Question 6 of 20

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