Complex central sleep apnea (CompSAS), also termed treatment-emergent central sleep apnea, is a clinical phenomenon where central apneas (cessation of breathing without respiratory effort) emerge or persistently appear during CPAP titration in patients initially presenting with obstructive sleep apnea (OSA). The phenomenon was recognized after CPAP became widely used; central events are seen in 5-15% of OSA patients during initial CPAP treatment, with majority resolving over weeks but a subset developing persistent CompSAS. Pathophysiology involves a hypersensitive ventilatory response system (high loop gain), periodic breathing tendencies, and unmasking of underlying central control instability.
Risk factors and associated conditions include: heart failure (especially with reduced ejection fraction or atrial fibrillation), prior stroke, opioid use, high altitude exposure, male sex, older age, and possibly idiopathic. Cheyne-Stokes respiration with central sleep apnea (CSR-CSA) is a specific pattern seen in heart failure characterized by crescendo-decrescendo breathing pattern with central apneas at the nadir, distinct from but overlapping with CompSAS.
Treatment options for complex CSA include: continued CPAP therapy with extended observation (some patients adapt and central events resolve), bilevel positive airway pressure with backup rate (BPAP-ST/BPAP with timed mode), adaptive servo-ventilation (ASV) — provides variable pressure support proportional to detected hypoventilation, very effective for CompSAS but contraindicated in heart failure with EF ≤45% (SERVE-HF trial showed increased mortality), transvenous phrenic nerve stimulation (Remede System) — implanted device that stimulates the phrenic nerve to maintain regular breathing, FDA-approved for moderate-severe CSA, oxygen supplementation (low-flow continuous oxygen reduces central events in selected cases, especially CSR-CSA), and pharmacologic options (acetazolamide — induces metabolic acidosis stimulating respiration; theophylline; sedatives like temazepam in select cases). Comprehensive evaluation requires multidisciplinary sleep medicine and cardiology team, careful echocardiographic assessment, optimization of underlying conditions (heart failure management, opioid weaning if applicable), and individualized treatment selection based on EF, CSA pattern, comorbidities, and response.