A 71-year-old man with advanced COPD develops morning headaches and somnolence. Arterial blood gas on room air shows pH 7.34, PaCO2 62 mm Hg, and

Question

A 71-year-old man with advanced COPD develops morning headaches and somnolence. Arterial blood gas on room air shows pH 7.34, PaCO2 62 mm Hg, and bicarbonate 33 mEq/L. Which of the following is the most likely explanation for this patient's findings?

Accepted Answer

Chronic alveolar hypoventilation with renal bicarbonate retention

Answer

Primary hyperventilation syndrome

Answer

Pulmonary embolism with respiratory alkalosis

Answer

Metabolic alkalosis from vomiting alone

Answer

Acute salicylate toxicity

Chronic hypercapnic respiratory failure — USMLE Step 3 MCQ

A 71-year-old man with advanced COPD develops morning headaches and somnolence. Arterial blood gas on room air shows pH 7.34, PaCO2 62 mm Hg, and bicarbonate 33 mEq/L. Which of the following is the most likely explanation for this patient's findings?