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Obesity hypoventilation syndrome — SCE Respiratory MCQ

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HardSleep MedicineObesity hypoventilation syndromeSCE Respiratory

A 58-year-old woman with BMI 47 kg/m2 has morning headaches, ankle oedema and daytime somnolence. Sleep study shows OSAHS; awake ABG on air shows pH 7.37, PaCO2 7.1 kPa and PaO2 8.4 kPa. Bicarbonate is 34 mmol/L. What is the most likely diagnosis?

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Correct answer: A — Obesity hypoventilation syndrome

Obesity with awake hypercapnia and sleep-disordered breathing defines obesity hypoventilation syndrome after excluding other causes. Uncomplicated OSAHS does not have daytime hypercapnia. Primary pulmonary hypertension and nocturnal asthma would not explain the chronic compensated ventilatory failure.

Reference: NICE NG202