Spirometry — Obstructive Pattern (COPD)

A 62-year-old male smoker presents with progressive dyspnea and cough. Spirometry shows FEV1/FVC = 0.65 with FEV1 = 45% predicted. The flow-volume loop demonstrates a concave expiratory limb and reduced PEFR. Post-bronchodilator testing (400 μg salbutamol, repeated after 15 minutes) shows an increase in FEV1 of 8% and 150 mL. The feature marked **D** in the diagram — absence of significant bronchodilator reversibility — is most consistent with which diagnosis?

A 58-year-old male smoker (40 pack-years) presents with progressive dyspnea on exertion and chronic productive cough for 3 years. Post-bronchodilator spirometry is performed. The structure marked **A** in the diagram shows a reduced FEV1/FVC ratio of 0.62. Which of the following best describes the pathophysiological basis for this finding in COPD?