Motor neurone disease (MND) is a devastating and progressive neurological disorder in which degeneration of motor neurones results in weakness and wasting of the dependent muscles. The prevalence of MND is approximately five per 100 000 and approximately 30% of patients have primary bulbar symptoms.1 Half of the patients die within 36 months of experiencing the first symptom.

Presentation with ventilatory failure is recognised but uncommon,2 occurring in less than 5% of cases3; however, abnormalities of respiratory muscle function are frequently detectable.4 ,5 As the condition progresses respiratory muscle strength diminishes4 ,6; indeed, the rate of change in respiratory function is the only measurable parameter which predicts survival.1 When the load placed on the respiratory muscle pump exceeds the capacity of the respiratory muscles, then the patient is at risk of ventilatory failure. Initially abnormalities may be present only in sleep7 or on exercise8 but, frequently, established ventilatory failure ensues. Ventilatory failure is usually manifest by dyspnoea which may be worse on lying flat (if diaphragm weakness is prominent) or sitting upright (if expiratory muscle weakness predominates). More commonly there is generalised weakness and then there are no clear cut postural symptoms. Direct questioning may elicit symptoms suggestive of disordered sleep architecture—for example, daytime somnolence, difficulty concentrating, or “respiratory” nightmares—or carbon dioxide retention—for example, morning headache. Examination may show paradoxical abdominal motion during respiration. This indicates substantial diaphragm weakness9 combined with preservation of enough upper thoracic musculature to generate sufficient negative intrathoracic pressure to cause inward abdominal motion. In more advanced disease paradoxical motion may be difficult to elicit and the patient may simply appear tachypnoeic without useful rib cage movement. In established MND patients may also complain of choking symptoms; most commonly this represents swallowing difficulties. However, …