What is positional obstructive sleep apnea (OSA)?

Definition of Positional Obstructive Sleep Apnea (OSA)

Positional obstructive sleep apnea is defined as a condition where the apnea-hypopnea index (AHI) in the supine position is at least twice as high as the AHI in the non-supine position. 1

Key Characteristics

• Prevalence: Approximately 50% of OSA patients have positional OSA 1
• Diagnostic criteria:
  • Supine AHI at least twice as high as non-supine AHI 1
  • Most studies require minimal non-supine sleep time (ranging from 15 minutes to 1 hour or 30% of total sleep time) 1
  • Some definitions include an additional criterion of non-supine AHI being below a certain threshold (typically <15 events/hour) 1

Pathophysiology

The positional dependence of OSA occurs due to several anatomical and physiological factors:

• Body position affects the cross-section and closing pressures of the pharynx 1
• Supine sleeping position decreases the lateral dimension of the upper airway 1
• Ventilatory drive is dependent on body position 1
• Hypopharyngeal collapse (particularly at the tongue base and epiglottis) is the primary site that improves with change from supine to lateral position 2

Patient Characteristics

Patients with positional OSA tend to have:

• Lower overall AHI compared to non-positional OSA patients 1
• Younger age 1
• Lower BMI (less obesity) 1
• Higher prevalence in men (75%) compared to women (43%) 3

Clinical Implications

1. Diagnostic considerations:

   • Sleep position should be documented during polysomnography 1
   • The "first night effect" during sleep studies may lead to over-estimation of POSA cases 3
   • Sleep position assessment questionnaires may help identify true positional OSA patients 3

2. Treatment options:

   • Positional therapy can be considered for mild to moderate positional OSA 1
   • Modern vibratory positional devices show better adherence than traditional methods like tennis ball technique 1
   • CPAP remains more effective at reducing AHI but has lower compliance compared to positional therapy 1

Treatment Efficacy and Recommendations

• Positional therapy effectiveness:

  • Moderate reductions in AHI but clearly inferior to CPAP 1
  • Better compliance compared to CPAP (additional 2.5 hours per night) 1
  • Fewer side effects compared to CPAP 1

• Current recommendations:

  • The European Respiratory Society suggests either vibratory positional therapy or CPAP for patients with mild or moderate position-dependent OSA with non-supine AHI <15 events/hour 1
  • For mild positional OSA, either vibrational positional therapy or mandibular advancement devices (MAD) may be used 1
  • Traditional positional therapy methods (tennis ball technique, backpacks) have poor long-term compliance (only 29% after 2 years) 1

Pitfalls and Caveats

1. Long-term adherence:

   • Traditional positional therapy methods have poor long-term compliance 1
   • Vibratory devices show better adherence but still require follow-up 1

2. Effectiveness limitations:

   • If positional therapy is used, sleep studies should be performed to document individual success 1
   • Long-term compliance should be secured by follow-up studies 1

3. Patient selection:

   • Not all patients normalize AHI when non-supine, so correction of OSA by position should be documented with polysomnography before initiating this form of treatment 1
   • Positional therapy is not recommended for severe OSA or patients with significant non-supine AHI 1

Positional OSA represents an important subtype of sleep apnea that may benefit from targeted therapy approaches. Proper identification through comprehensive sleep studies and appropriate treatment selection based on disease severity and patient characteristics can improve outcomes for these patients.