How does a positional device cause treatment-emergent central apneas in patients with positional Obstructive Sleep Apnea (OSA)?

How Positional Devices Cause Treatment-Emergent Central Apneas in Positional OSA

Positional therapy devices can cause treatment-emergent central apneas in positional OSA patients by altering upper airway mechanics and ventilatory control, similar to how CPAP therapy can unmask complex sleep apnea syndrome in some patients. 1

Mechanism of Treatment-Emergent Central Apneas

When using positional therapy for positional OSA (POSA), several physiological changes can occur:

1. Altered Upper Airway Mechanics:

   • Positional devices force patients to sleep in non-supine positions, which changes upper airway dynamics
   • This sudden change in airway patency can lead to ventilatory instability

2. Ventilatory Control System Response:

   • Similar to what happens with CPAP or mandibular advancement devices, the resolution of obstructive events can unmask underlying central respiratory control instability
   • When obstructive events are reduced, the ventilatory control system may become more sensitive to CO₂ levels

3. Complex Sleep Apnea Unmasking:

   • In some patients, the treatment of obstructive events reveals an underlying predisposition to central apneas
   • This phenomenon has been documented with various OSA treatments including CPAP, mandibular advancement devices, and even surgical interventions 1

Risk Factors for Developing Treatment-Emergent Central Apneas

Patients more likely to develop central apneas with positional therapy include:

• Those with a high apnea index in the lateral position 2
• Patients with unstable respiratory control systems
• Individuals with comorbidities affecting respiratory drive
• Patients who may have undiagnosed complex sleep apnea syndrome (CompSAS)

Clinical Implications

The European Respiratory Society guidelines note that positional therapy using vibratory devices is recommended for mild to moderate position-dependent OSA with non-supine AHI <15 events/hour 3, 4. However, this recommendation doesn't account for the potential development of treatment-emergent central apneas.

Important considerations:

• Approximately 35% of positional OSA patients may change to non-positional OSA in follow-up studies 2
• Patients with a higher apnea index in the lateral position are more likely to develop non-positional OSA patterns 2
• The current definition of complex sleep apnea syndrome should be broadened to include cases unmasked by non-CPAP treatments 1

Monitoring and Management

For patients using positional therapy:

• Follow-up sleep studies should be performed to document individual success 4
• Monitor for emergence of central apneas when transitioning from supine to non-supine positions
• Consider alternative treatments if central apneas develop or if positional therapy proves ineffective
• Long-term compliance should be secured through follow-up studies 4

Conclusion

While positional therapy can be effective for positional OSA (reducing AHI by approximately 54% in short-term studies 5), clinicians should be aware of the potential for treatment-emergent central apneas. This phenomenon, similar to complex sleep apnea unmasked by CPAP, requires careful monitoring and may necessitate adjustment of treatment approach in affected patients.