A 68-year-old male with a 40-pack-year smoking history prese…

A 68-year-old male with a 40-pack-year smoking history presents with chronic productive cough, increased work of breathing, and mild peripheral cyanosis. Physical exam reveals bilateral wheezes and rhonchi. Chest X-ray shows increased bronchovascular markings and cardiomegaly. Arterial blood gas analysis reveals: pH: 7.34 PaCO₂: 58 mmHg PaO₂: 60 mmHg HCO₃⁻: 30 mEq/L Which of the following is the most likely diagnosis?