A 54-year-old man presents to his primary care provider with dyspnea and a cough. He is a non- smoker with no relevant occupational exposures. His pulmonary function test results are as follows. What can be the most probable diagnosis? Pre-Bronchodilator (BD)Post – BDTestActualPredicted% PredictedActual% ChangeFVC (L)3.194.22764.0025FEV1 (L)2.183.39642.8330FEV1/FVC (%)6880 714

**Core Concept**
The patient's pulmonary function test (PFT) results suggest an obstructive lung disease, characterized by a reduced FEV1/FVC ratio and a significant improvement in FEV1 after bronchodilator administration. This indicates airway obstruction that can be partially reversed by bronchodilators.

**Why the Correct Answer is Right**
The patient's FEV1/FVC ratio of 68% (pre-BD) and 71% (post-BD) is below the normal range (typically > 80%), indicating airway obstruction. The significant improvement in FEV1 after bronchodilator administration (ΔFEV1 = 1.0 L) suggests that the obstruction is reversible. This pattern is characteristic of asthma or chronic obstructive pulmonary disease (COPD), but given the patient's non-smoking status and lack of occupational exposures, asthma is more likely.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the patient's PFT results do not show a restrictive pattern, characterized by a low total lung capacity (TLC) and a low FEV1/FVC ratio.
* **Option B:** This option is incorrect because the patient's FEV1/FVC ratio is not significantly improved after bronchodilator administration, which is not typical of restrictive lung diseases.
* **Option C:** This option is incorrect because the patient's PFT results do not show a mixed obstructive-restrictive pattern, characterized by a low TLC and a low FEV1/FVC ratio.

**Clinical Pearl / High-Yield Fact**
In patients with asthma or COPD, a significant improvement in FEV1 after bronchodilator administration is a key diagnostic feature. This improvement is typically > 12% and > 200 mL, which is not seen in restrictive lung diseases.

**Correct Answer:** C.

✓ Correct Answer: B. Moderate Airflow Obstruction.