A 45-year-old man with long-standing COPD presents with worsening dyspnea. ABG shows pH 7.32, PaCO₂ 60 mmHg, PaO₂ 55 mmHg. Which primary physiological abnormality explains his chronic hypercapnia?
A
Increased alveolar ventilation
B
Reduced diffusion capacity for carbon dioxide
C
Alveolar hypoventilation due to loss of elastic recoil
D
Impaired hemoglobin binding to carbon dioxide