Neuromuscular respiratory failure and airway clearance — structured clinical encounter

Station 1 — recognition

The examiner asks what unifies this boy's symptoms. I explain that neuromuscular disease attacks breathing in two separate ways, and that both are present here. The morning headaches and daytime sleepiness are the symptoms of nocturnal hypoventilation from weak inspiratory muscles, and the recurrent chest infections with a weak cough are the consequence of an ineffective cough from weak expiratory and bulbar muscles. His lungs themselves are normal. [1] [2]

Station 2 — monitoring

Asked how I would confirm and monitor each problem, I set out four measurements. Forced vital capacity sitting and supine assesses the pump and flags diaphragm weakness; peak cough flow assesses the cough and predicts secretion-clearance failure; overnight oximetry with transcutaneous or end-tidal carbon dioxide detects nocturnal hypoventilation before daytime hypercapnia; and a morning bicarbonate or blood gas confirms chronic carbon dioxide retention. I would trend all four over time. [1] [7]

Station 3 — the two treatments

Asked about treatment, I describe two parallel ladders. For the hypoventilation I would start nocturnal non-invasive ventilation, which reverses the morning headaches and daytime sleepiness and rests the muscles. For the weak cough I would introduce airway clearance, from manual assisted cough and breath stacking or lung volume recruitment to mechanical insufflation-exsufflation, so clearance is in place before the next infection. I would also assess for the associated cardiomyopathy. [6] [2]

Station 4 — the chest-infection plan

The examiner asks what should happen when he next gets a chest infection. I state the governing rule: clear the secretions and support ventilation, do not merely give oxygen. The plan intensifies airway clearance and non-invasive ventilation, starts antibiotics early, monitors carbon dioxide rather than oxygen alone, and has a low threshold for admission, because oxygen alone masks the rising carbon dioxide and ignores the retained secretions that are the real danger. [1] [3]

Station 5 — the family and the future

Finally I counsel the family that with anticipatory respiratory care many boys with Duchenne muscular dystrophy now reach adulthood, and that the plan is a home programme with monitoring, non-invasive ventilation and a cough assist machine, trained carers, a written illness action plan and planned transition to adult services. The single rule I want them to hold is to clear secretions and ventilate rather than simply give oxygen when he is unwell. [2] [3]