Definition of Complex Sleep Apnea (Treatment-Emergent Central Sleep Apnea)
Complex sleep apnea, also known as treatment-emergent central sleep apnea (TECSA), is defined as the emergence or persistence of central apneas (≥5 events per hour) when obstructive sleep apnea events are eliminated with positive airway pressure therapy, in the absence of other clear causes such as heart failure or opioid use. 1, 2
Core Diagnostic Criteria
The defining characteristics of TECSA include:
- Central apneas that appear or persist during PAP therapy for obstructive sleep apnea, specifically when obstructive events have been successfully treated 2, 3
- Central apnea index ≥5 events per hour during positive airway pressure treatment 3
- Absence of alternative explanations such as systolic heart failure, narcotic use, or other identifiable causes of central sleep apnea 3, 4
Key Polysomnographic Features
When TECSA occurs, specific patterns emerge on sleep studies:
- NREM sleep dominance of respiratory events, with spontaneous improvement during REM sleep 5
- Absence of respiratory effort during apneic events, distinguishing central from obstructive apneas 1
- Metronomic timing with either short (<30 seconds) or long (>60 seconds) cycle times 5
Clinical Context and Prevalence
- Prevalence ranges widely from 0.56% to 18% depending on the study population and diagnostic criteria used 2, 3
- Approximately 1% of patients starting CPAP therapy for obstructive sleep apnea develop TECSA, according to the American Academy of Sleep Medicine 1
- TECSA can emerge with any OSA treatment, not just CPAP—it has been documented after surgery (including nasal/sinus procedures), oral appliances, mandibular advancement devices, and even tracheostomy 5, 6
Pathophysiological Mechanisms
The underlying mechanisms driving TECSA include:
- Ventilatory control instability with oscillations in arterial CO₂ levels 2, 3
- CPAP-related increased CO₂ elimination that can destabilize respiratory control 3
- Activation of airway and pulmonary stretch receptors triggering central apneas 2, 3
- Low arousal threshold contributing to breathing instability 2
- Prolonged circulation time in some patients 2
Natural History and Clinical Significance
- TECSA is often self-limited, with resolution occurring spontaneously within 1-3 months of continued CPAP therapy in many patients 1, 2
- Prognosis is similar to obstructive sleep apnea when TECSA does occur 3
- Central apneas resolve in most patients on follow-up with continued CPAP therapy 3
Important Clinical Pitfall
Do not confuse TECSA with heart failure-associated central sleep apnea, which has distinct features including Cheyne-Stokes respiration pattern with longer cycle length (45-75 seconds), orthopnea, and paroxysmal nocturnal dyspnea 1. The American Academy of Sleep Medicine emphasizes that TECSA occurs in the absence of heart failure or other identifiable causes 1, 3.