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Nocturnal Hypoventilation in COPD — SCE Palliative Medicine MCQ

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HardRespiratory SymptomsNocturnal Hypoventilation in COPDSCE Palliative Medicine

A patient with severe COPD receiving nocturnal oxygen has morning headaches, hypersomnolence and a bicarbonate of 31 mmol/L. Overnight oximetry shows recurrent desaturation. What is the most appropriate next investigation?

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Correct answer: A — Respiratory polygraphy with consideration of transcutaneous carbon-dioxide monitoring

The symptoms, desaturation pattern and raised bicarbonate suggest COPD–OSAHS overlap with possible nocturnal hypoventilation. Respiratory polygraphy is the diagnostic sleep test, and transcutaneous carbon-dioxide monitoring helps identify hypoventilation and guide CPAP versus non-invasive ventilation. Oximetry alone cannot distinguish obstructive events from hypoventilation; simply increasing oxygen may worsen carbon-dioxide retention.

Reference: NICE NG202: COPD–OSAHS overlap syndrome: https://www.nice.org.uk/guidance/ng202/chapter/3-copdosahs-overlap-syndrome