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Obesity Hypoventilation Syndrome — RACP Adult Medicine MCQ

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ModerateRespiratoryObesity Hypoventilation SyndromeRACP Adult Medicine

A 55-year-old woman with obesity hypoventilation syndrome (BMI 48) has daytime somnolence and a morning ABG showing pH 7.34, PaCO₂ 55 mmHg, PaO₂ 52 mmHg, and HCO₃ 32 mmol/L. Overnight oximetry shows significant desaturation. What is the recommended respiratory support?

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Correct answer: B — Non-invasive ventilation (BiPAP)

Obesity hypoventilation syndrome (OHS) with daytime hypercapnia and hypoxaemia requires non-invasive ventilation (BiPAP/bilevel PAP) as first-line respiratory support. NIV provides both inspiratory pressure support (corrects hypoventilation) and expiratory pressure (treats upper airway obstruction). The HOT-HMV trial showed NIV improved ventilatory failure and quality of life. CPAP alone may be adequate for mild OHS without significant hypercapnia but is insufficient here.

Reference: TSANZ – 2020 – Domiciliary NIV Guidelines; eTG – 2025 – Respiratory