In adults with Obstructive Sleep Apnea (OSA), where does upper airway collapse most commonly occur, in the retropalatal or retroglossal region?

Upper Airway Collapse in Adults with Obstructive Sleep Apnea

In adults with obstructive sleep apnea (OSA), upper airway collapse occurs most commonly in the retropalatal region, with the velopharynx being the primary site of obstruction in the majority of patients. 1, 2

Anatomical Sites of Collapse

• The primary site of airway collapse is most frequently located in the velopharynx (retropalatal region), but can also occur in the oro- and/or hypopharynx (retroglossal region) 1
• In a study of 18 patients with OSA, 56% had collapse confined to the velopharyngeal or retropalatal segment of the upper airway during NREM sleep, while the remaining 44% demonstrated collapse of the retroglossal segment 2
• Multiple levels of obstruction are common in OSA patients, with collapse occurring at both the retropalatal level and behind the tongue base in the large majority of apneic patients 1

Factors Influencing Site of Collapse

• The retropalatal airway is narrower and more collapsible than the retroglossal airway 3
• Compared to the retroglossal airway, the retropalatal airway has greater absolute and relative compliances, making it more susceptible to collapse 3
• Anatomical predictors of retropalatal collapse include:
  • Increased proportion of volumetric pharyngeal soft tissues to the surrounding cervicomandibular bony frame 4
  • Enlarged soft tissues of the lateral wall and soft palate 4
  • Decreased volume of the nasopharynx and pharyngeal cavity 4

Clinical Implications

• Understanding the site of airway collapse is crucial for surgical planning and outcomes 1
• Surgical success with uvulopalatopharyngoplasty (UPPP) can only be anticipated when pharyngeal collapse is limited to the retropalatal area, which is rarely the case in obese patients or those with severe sleep apnea 1
• The percentage of patients attaining UPPP success was 52% in cases of isolated oropharyngeal obstruction compared with only 5% in situations of associated retrolingual narrowing 1
• Patients with retropalatal and retroglossal collapse have only a 5% success rate with isolated palatal procedures 5

Diagnostic Considerations

• The site of airway closure can be determined during sleep with:
  • Placement of catheters attached to pressure transducers in the esophagus and at different levels in the pharyngeal airway 1
  • Imaging the upper airway with a fiberoptic scope 1
  • Fast acquisition MRI or computed axial tomography scans 1
  • Dynamic MRI during natural sleep 6

Sleep State Effects

• During REM sleep, collapse may occur in a more caudal segment of the upper airway than during NREM sleep 2
• In a study of 9 patients, 7 demonstrated more caudal collapse during REM compared to NREM sleep 2

Types of Obstruction Patterns

• Recent dynamic MRI studies have identified four types of airway obstruction:
  • Type A: Retropalatal obstruction caused by the soft palate separated from the tongue (28.6% of cases) 6
  • Type BI and BII: Retropalatal obstructions caused by the soft palate attached to the tongue (57.1% of cases) 6
  • Type C: Combined retropalatal and retroglossal obstruction caused by the soft palate and the tongue (14.3% of cases) 6

Surgical Considerations

• Multilevel surgery may be necessary for patients with obstruction at multiple sites 1
• Success rates for isolated soft palate procedures are generally poor (approximately 50% success rate) and even lower in patients with multi-level obstruction 5
• Surgical procedures dedicated to the soft palate have been essentially studied in selected mild to moderate OSA populations with predominant oropharyngeal narrowing 1
• Failure of UPPP is usually attributed to secondary sites of obstruction located more caudally in the upper airway or to persistent retropalatal collapse 1