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Obesity hypoventilation syndrome — SCE Acute Medicine MCQ

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HardRespiratory medicineObesity hypoventilation syndromeSCE Acute Medicine

A 68-year-old man with COPD and obesity develops morning headaches and somnolence. During an admission for cellulitis, ABG on air shows pH 7.36, PaCO2 7.8 kPa, PaO2 7.9 kPa, HCO3- 34 mmol/L. Overnight oximetry shows sustained desaturation and serum bicarbonate has been high for months. What is the most likely diagnosis?

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Correct answer: E — Obesity hypoventilation syndrome with chronic hypercapnia

Daytime hypercapnia with obesity, raised bicarbonate and sleep-related hypoventilation suggests obesity hypoventilation syndrome, often overlapping with OSA and COPD. Isolated OSA does not usually cause persistent daytime hypercapnia. PE more typically causes acute hypocapnia unless massive with ventilatory failure.

Reference: BTS/ICS Ventilatory Management Guideline; NICE CKS Sleep apnoea