Central sleep apnoea and hypoventilation syndromes — branching viva

Opening — framing the problem

The examiner begins: a term baby breathes normally while awake but becomes shallow, cyanosed and hypercapnic the moment he sleeps, and cannot be weaned despite a normal heart and clear lungs. Talk me through your reasoning. [1] [3]

I would frame this as a disorder of the control of breathing until proven otherwise, because the breathing is adequate awake and fails in sleep, when the wakefulness drive is withdrawn and only the deficient chemoreceptor drive remains. The normal heart and lungs argue against a cardiac or pulmonary cause, and the failure to wean with a well-looking awake baby is the classic mismatch of central hypoventilation. [1] [3]

Branch A — confirming and stabilising

How would you confirm the diagnosis and stabilise the baby? [1]

I would send PHOX2B genetic testing to confirm congenital central hypoventilation syndrome, which also predicts severity through the repeat length and mutation type, and I would arrange attended polysomnography with carbon dioxide monitoring. To stabilise, the principle is to ventilate rather than merely oxygenate: I would provide assisted ventilation to clear carbon dioxide and monitor carbon dioxide directly, because oxygen alone can correct the saturation while the carbon dioxide climbs to narcosis. [1] [15]

Branch B — long-term support

The genetics confirm congenital central hypoventilation syndrome. What does lifelong management look like? [4]

Management is lifelong assisted ventilation matched to dependence: mask non-invasive ventilation for sleep-only hypoventilation, tracheostomy with a home ventilator for greater needs or in infancy, and diaphragm pacing for selected children needing daytime support. Around this sits multisystem surveillance for pulmonary hypertension, autonomic dysrhythmia and Hirschsprung disease, a home ventilation programme with an emergency plan, and cautious anaesthesia given the sensitivity to respiratory depressants. [4] [8] [13]

Branch C — the ROHHAD pivot

Now a five-year-old presents with rapid weight gain over months, then hypothalamic features and sleep hypoventilation. What is your concern? [6]

This timeline of rapid-onset obesity followed by hypothalamic dysfunction, hypoventilation and autonomic dysregulation is ROHHAD until excluded, and I would actively search for an associated neural crest tumour with cross-sectional and metaiodobenzylguanidine imaging, because roughly forty per cent of cases are ROHHAD-NET. Management is to confirm and support the hypoventilation, treat any tumour, manage the endocrine and autonomic complications, and consider immunomodulation in refractory disease. [6] [7]

Closing — the safety rule

Give me the single safety rule you would write on this child's emergency plan. [1]

Ventilate, do not merely oxygenate, and measure carbon dioxide rather than trust the oxygen saturation, because these children lack the air hunger that would otherwise warn us; avoid sedatives and opioids that further blunt the drive. [1] [13]