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until proven otherwise, because the breathing is adequate awake and fails in sleep, when the wakefulness drive is withdrawn and only the deficient chemoreceptor drive remains.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]}