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Neuromuscular respiratory failure — SCE Respiratory MCQ

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HardRespiratory physiologyNeuromuscular respiratory failureSCE Respiratory

A 57-year-old man with motor neurone disease reports orthopnoea and morning headaches. Sitting FVC is 71% predicted but supine FVC falls to 48% predicted; SNIP is 28 cmH2O. Overnight oximetry shows sustained desaturation and transcutaneous CO2 rises overnight. Chest radiograph is clear. What is the most likely underlying cause?

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Correct answer: D — Respiratory muscle weakness causing nocturnal hypoventilation

The best answer is “Respiratory muscle weakness causing nocturnal hypoventilation”. The clinical pattern, physiology and imaging described are most consistent with Respiratory muscle weakness causing nocturnal hypoventilation. The competing diagnoses may share individual findings, but do not account for the complete combination in the stem. The remaining choices—“COPD causing expiratory airflow obstruction”, “Interstitial lung disease causing diffusion failure”, “Pulmonary embolism causing acute dead-space ventilation”, “Asthma causing nocturnal bronchospasm”—are credible in related respiratory presentations, but each addresses a different diagnostic, staging or management decision and does not fit the decisive findings and pathway position in this stem.

Reference: NICE NG42 motor neurone disease: https://www.nice.org.uk/guidance/ng42/chapter/Recommendations