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MND – Type 2 Respiratory Failure — SCE Neurology MCQ

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EasyPeripheral Neuropathy & NeuromuscularMND – Type 2 Respiratory FailureSCE Neurology

A 60-year-old man with known MND and progressive respiratory failure presents with morning headaches, daytime somnolence, and poor concentration. Overnight oximetry shows recurrent nocturnal desaturations. ABG shows PaCO₂ 7.2 kPa and PaO₂ 8.5 kPa. What do these findings indicate?

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Correct answer: C — Type 2 respiratory failure due to neuromuscular respiratory weakness

Raised PaCO₂ (hypercapnia) with low PaO₂ indicates type 2 (ventilatory) respiratory failure. In MND, this results from progressive diaphragmatic and intercostal muscle weakness causing hypoventilation. Morning headaches and daytime somnolence are classic symptoms of nocturnal hypercapnia. This is the indication for non-invasive ventilation (NIV), which is the most important intervention for survival and quality of life in MND with respiratory involvement. A: OSA causes desaturations but MND respiratory failure is the primary diagnosis here. C: Type 1 RF has normal/low PaCO₂. D: PE typically causes type 1 RF. E: Hyperventilation causes low PaCO₂.

Reference: NICE NG42 Motor Neurone Disease (2016)