(381) Phenotypes of Velopharyngeal Tube Law in Obstructive Sleep Apnea

Introduction: Different modes of upper airway (UA) collapse are routinely observed in patients with obstructive sleep apnea (OSA) during drug induced sedated endoscopy (DISE). These different modes of collapse may reflect differences in UA biomechanical properties with potential implications for therapy selection.

Methods: The area-pressure relationship (tube law) of the velopharynx was quantified during DISE in 17 OSA patients via step reductions in nasal mask pressure. The minimal area of the velopharyngeal airspace was estimated from video endoscopy, while the intraluminal pressure was recorded with a catheter. The tube law was quantified for nasal mask pressures from 0 to 16 cmH2O at mid-inspiration (tube law A) and mid-expiration (tube law B) in all patients. The tube law was also quantified during multiple points of the breathing cycle at a constant nasal mask pressure of 0 or 4 cmH2O (tube law C) in three patients representing different phenotypes.

Results: Tube laws A and B revealed three phenotypes, namely collapse during inspiration (phenotype 1, 4 patients), collapse during expiration (phenotype 2, 2 patients), and collapse during both inspiration and expiration (phenotype 3, 11 patients). Tube law C revealed that phenotype 3 displays a nearly constant airway size (i.e., low pharyngeal compliance) during the breathing cycle, while phenotypes 1 and 2 display sizeable changes in airway size (i.e., high pharyngeal compliance) during the breathing cycle.

Conclusions: Three phenotypes of velopharyngeal collapse were observed, namely collapse driven by a negative lumen pressure with high intra-breath pharyngeal compliance (phenotype 1) or low intra-breath pharyngeal compliance (phenotype 3), or expiratory collapse (phenotype 2). Future studies should investigate how these phenotypes of UA collapse affect therapeutic outcomes.