Neuromuscular Respiratory Failure

Question 1

Why do patients with neuromuscular disease develop respiratory failure?

Answer 1

Weakness of respiratory muscles (diaphragm and accessory muscles of respiration)

Hypotonia of bulbar muscles

Coexistent anatomical abnormalities (scoliosis or rigid spine)

Decreased central respiratory drive

Question 2

Clinical features of neuromuscular respiratory failure

Answer 2

Dyspnoea when lying flat (weakness of diaphragm)

Overtly breathless

Use of accessory muscles

Unable to complete sentences or take deep breaths

Paradoxical abdominal motion

Hypoxaemia + hypercarbia may produce mental clouding or somnolence

Presence or absence of bulbar weakness

Tall, thin face (congenital myopathy, myotonic dystrophy)

Ptosis or ophthalmoparesis (mitochondrial disorder, myasthenia)

Fasciculation (motor neurone disease)

Paraspinal muscle wasting (acid maltase deficiency)

Skin rash (dermatomyositis)

Question 3

Investigations in neuromuscular respiratory failure

Answer 3

Vital capacity

Mouth pressures

Arterial blood gases

Chest x-ray

Overnight respiratory monitoring

Question 4

Management of neuromuscular respiratory failure

Answer 4

Emergency intubation & ventilation