What is central sleep apnea?

Central Sleep Apnea: Definition, Diagnosis, and Management

Central sleep apnea (CSA) is characterized by recurrent episodes of apnea during sleep resulting from temporary loss of ventilatory effort due to central nervous system or cardiac dysfunction, in contrast to obstructive sleep apnea where airflow obstruction occurs despite breathing effort. 1

Pathophysiology

• CSA occurs when there is a temporary withdrawal of respiratory center stimulation to the inspiratory muscles, resulting in absence of airflow without respiratory effort 2
• Unlike obstructive sleep apnea (OSA), where airway obstruction occurs despite continued respiratory effort, CSA involves a fundamental failure of the central drive to breathe 3
• Common in patients with congestive heart failure (CHF), particularly manifesting as Cheyne-Stokes respiration with a characteristic crescendo-decrescendo breathing pattern 4

Types of Central Sleep Apnea

1. CSA with Cheyne-Stokes Respiration:

   • Characterized by a crescendo-decrescendo breathing pattern
   • Common in heart failure patients
   • Patients may report paroxysmal nocturnal dyspnea, orthopnea, and chest discomfort 4

2. CSA with normocapnia and ventilatory instability:

   • Often occurs at high altitude or with spontaneous nocturnal hyperventilation
   • Hypocapnic alkalosis leads to loss of ventilatory drive 3

3. CSA with hypercapnia:

   • Associated with conditions like central alveolar hypoventilation (Ondine's curse) or obesity-hypoventilation syndrome
   • Represents failure of chemoreceptor sensitivity 5

Risk Factors and Prevalence

• Heart failure (most common association)
• Atrial fibrillation
• Stroke or neurological disorders affecting the brainstem
• Chronic opioid medication use
• Advanced age (>60 years)
• Certain cardiac medications 4, 6

While OSA is common (affecting up to 15% of men and 5% of women), CSA is relatively rare in the general population but highly prevalent in specific populations, particularly those with cardiovascular disease 2, 6

Diagnostic Criteria and Assessment

• Polysomnography is the gold standard for diagnosis 1
• Diagnostic criteria for CSA require:
  • Multiple episodes of apnea (complete cessation of breathing) during sleep
  • Absence of respiratory effort during these episodes
  • At least 5 central apneas per hour of sleep 1
• For Cheyne-Stokes respiration, at least 3 consecutive central apneas/hypopneas with the characteristic crescendo-decrescendo breathing pattern 4

Clinical Presentation

• Unlike OSA patients who often present with excessive daytime sleepiness, CSA patients more commonly report:
  • Insomnia
  • Frequent awakenings
  • Fatigue
  • Depression
  • Morning headaches
  • Less commonly, frank hypersomnolence 5

Complications

• Increased cardiovascular morbidity and mortality
• Pulmonary hypertension
• Cardiac arrhythmias
• Worsening of heart failure
• Neurocognitive impairment
• Decreased quality of life 2, 6

Management Approaches

Management depends on the type of CSA and underlying cause:

1. Treatment of underlying conditions:

   • Optimize heart failure management (most important for CSA with Cheyne-Stokes respiration)
   • Address neurological disorders
   • Consider medication adjustments if opioids or other medications are contributing factors 4

2. Positive airway pressure therapies:

   • For CSA with normocapnia: Adaptive servo-ventilation (ASV) is recommended
   • For CSA with hypercapnia: Non-invasive ventilation is required 3
   • CPAP may be beneficial in some cases, particularly when there is a mixed component with OSA 6

3. Supplemental oxygen:

   • Can reduce central apneas in many cases
   • Target oxygen saturation ≥92% 4, 5

4. Pharmacologic approaches:

   • Acetazolamide has shown short-term benefit but variable long-term results
   • Caution with respiratory stimulants in heart failure patients 5

5. Advanced therapies:

   • Phrenic nerve stimulation has shown improvement in sleep metrics and quality of life 6

Clinical Pearls and Pitfalls

• CSA in heart failure may be a marker of worsening cardiac function requiring optimization of cardiac therapy 4
• Nocturnal desaturation is a stronger predictor of pulmonary hypertension than apnea-hypopnea index alone 4
• CSA with a central AHI >30/hour has been associated with worse survival in heart failure patients 4
• Avoid aggressive suppression of Cheyne-Stokes respiration in heart failure as it may be a compensatory mechanism 4
• Monitor for complications including pneumonia in patients with altered respiratory patterns 4

Central sleep apnea remains a challenging condition to diagnose and treat effectively, requiring careful assessment of underlying causes and tailored therapeutic approaches based on the specific type and associated conditions.