Why do central apneas emerge in patients with positional obstructive sleep apnea (OSA) effectively treated with a positional device?

Emergence of Central Apneas in Positional OSA Treated with Positional Devices

Central apneas may emerge in positional obstructive sleep apnea (OSA) effectively treated with positional devices due to ventilatory control instability unmasked when the obstructive component is resolved, similar to the "complex sleep apnea" phenomenon seen with CPAP therapy. This represents a treatment-emergent central sleep apnea that requires careful monitoring and potential adjustment of therapy.

Mechanisms of Central Apnea Emergence

• Resolution of Upper Airway Obstruction: When positional therapy successfully eliminates obstructive events by preventing supine sleep, the underlying ventilatory control instability may become apparent 1

• Sleep Stage Transitions: Positional therapy may alter sleep architecture, potentially increasing transitions between sleep stages which are vulnerable periods for central apneas

• Changes in Sleep Depth: Positional therapy can affect the distribution of sleep stages, with some studies showing increases in deep sleep (4-17%) and REM sleep (1-10%) 1

• Ventilatory Control Sensitivity: Patients with OSA often have heightened chemoreceptor sensitivity that becomes evident when obstructive events are eliminated

Risk Factors for Developing Central Apneas

• Pre-existing ventilatory instability: Patients with underlying tendency toward central apneas
• Higher baseline AHI: More severe OSA may be associated with greater ventilatory control instability
• Comorbidities: Heart failure, stroke, or other neurological conditions
• Medication use: Opioids or other respiratory depressants

Clinical Implications

1. Monitoring Requirements:

   • Follow-up sleep studies are essential when using positional therapy to document individual success 1
   • Regular assessment for emergence of central events is recommended

2. Treatment Modifications:

   • If central apneas emerge and are clinically significant, consider:
     • Adjusting the positional device
     • Switching to CPAP or BiPAP therapy
     • Adding supplemental oxygen if appropriate

3. Patient Selection:

   • Positional therapy is most effective in patients who are younger, have lower AHI, and are less obese 1
   • Consider the risk of central apnea emergence in patient selection

Efficacy and Adherence Considerations

• Positional therapy can reduce AHI by approximately 54% in appropriate candidates 2
• Modern vibratory positional devices show improved adherence (73.7% of nights) compared to older techniques 3
• Positional therapy may be equivalent to CPAP in normalizing AHI in carefully selected patients with positional OSA 4, 5

Treatment Algorithm for Positional OSA

1. Initial Assessment:

   • Confirm positional OSA (supine AHI at least twice as high as non-supine AHI)
   • Ensure non-supine AHI <15 events/hour 1

2. Treatment Selection:

   • For mild to moderate positional OSA: Consider vibratory positional device 1
   • For severe OSA: CPAP remains first-line therapy 6

3. Follow-up Monitoring:

   • Objective assessment of treatment efficacy with follow-up sleep study
   • Monitor for emergence of central apneas
   • Assess daytime symptoms and adherence

4. If Central Apneas Emerge:

   • Evaluate clinical significance (frequency, oxygen desaturations)
   • Consider transition to CPAP if central events are significant
   • Consider referral to sleep specialist for complex cases

Remember that while positional therapy can be effective for carefully selected patients, it is generally considered inferior to CPAP for overall treatment efficacy 1. The emergence of central apneas represents an important clinical consideration that requires appropriate monitoring and management to ensure optimal patient outcomes.