Central Sleep Apnea

Central sleep apnoea (CSA) is recurrent cessation of ventilation during sleep because of absent or reduced respiratory effort, from instability in ventilatory control or impaired respiratory drive.

Types

• Cheyne-Stokes respiration with CSA: crescendo decrescendo breathing in heart failure (prevalence 30 to 40% in heart failure with reduced ejection fraction), stroke, atrial fibrillation.
• High altitude periodic breathing.
• Opioid induced CSA (ataxic breathing, in 30% of chronic opioid users).
• Primary (idiopathic) CSA; CSA due to medical conditions (renal failure, brainstem lesions, Chiari malformation); treatment emergent CSA after starting CPAP.
• Mechanisms: hypocapnia below apnoeic threshold with high loop gain, prolonged circulation time.
• Consequences: sleep fragmentation, nocturnal hypoxia, sympathetic activation, arrhythmia, poorer prognosis in heart failure.

• Witnessed apnoea without snoring, fatigue, insomnia, awakenings with breathlessness (paroxysmal nocturnal dyspnoea), daytime sleepiness (less than OSA), morning headache.
• Features of heart failure, atrial fibrillation, stroke, opioid use, high altitude.
• Cheyne Stokes pattern may be observed while awake in advanced heart failure.

• Polysomnography showing at least 5 central apnoeas/hypopnoeas per hour, over 50% of events being central, absent respiratory effort; Cheyne Stokes pattern (crescendo decrescendo with cycle length 60 seconds or more).
• Daytime blood gas (PaCO2 low in CSA with Cheyne Stokes, high in hypercapnic CSA from neuromuscular disease).
• Evaluate causes: echocardiography and BNP, rhythm monitoring, brain MRI (brainstem, Chiari), medication review (opioids, baclofen), renal function, neurological examination.

• Treat the underlying cause: optimise heart failure therapy (ACE inhibitor/sacubitril, beta blocker, MRA, SGLT2 inhibitor, diuretics), rate/rhythm control; reduce or switch opioids; descend from altitude.
• Positive airway pressure: CPAP may reduce central apnoea in heart failure (benefit if AHI falls under 15), but does not improve survival overall.
• Adaptive servo ventilation is contraindicated in heart failure with ejection fraction 45% or less and predominant CSA (SERVE HF showed increased cardiovascular mortality); it can be used in CSA with preserved function, opioid induced and treatment emergent CSA.
• Supplemental oxygen at night (2 to 3 L/min) reduces events and improves hypoxaemia in heart failure.
• Acetazolamide 250 mg at night (or 3 to 4 mg/kg) for altitude and primary CSA; theophylline 200 to 300 mg at night (limited, arrhythmia risk).
• Phrenic nerve stimulation (remedē system) for moderate to severe CSA reduces apnoea index.
• Bilevel ST ventilation for hypercapnic CSA (neuromuscular disease, opioid).
• Follow up with repeat polysomnography titration.