Changes in site of obstruction in obstructive sleep apnea patients according to sleep position: a DISE study.

OBJECTIVES/HYPOTHESIS This study aimed to evaluate changes in obstruction site in obstructive sleep apnea (OSA) patients according to sleep position. STUDY DESIGN Prospective case series. METHODS Eighty-five patients who had undergone level 1 sleep study and drug-induced sleep endoscopy in the supine and lateral positions were included. Obstruction sites were classified as soft palate (SP), tongue base (TB), lateral wall (LW), and larynx (LX). Subgroup analysis was performed according to lateral apnea-hypopnea index (AHI): those with an AHI of ≥ 10 (lateral obstructors, LO) and those with an AHI of < 10 (lateral nonobstructors, LNO). RESULTS Prevalence in obstruction site of SP, TB, and LX decreased significantly after change from supine to lateral position (P < 0.05). However, the prevalence of LW obstruction was not affected by position change. LW collapse in moderate OSA decreased (from 66.7% to 35.9%) after change to lateral sleep, whereas it persisted in severe OSA patients (81.6%-89.5%). In the lateral position, persistent obstruction at the LW was observed more frequently in the LO group compared to the LNO group (83.3% vs. 33.3%). CONCLUSION When sleep posture is changed from supine to lateral, obstruction due to structures such as tongue base and larynx improves dramatically. Obstruction in lateral position is mostly due to obstruction at the oropharyngeal LWs. Therefore, position dependency is mostly determined by LW collapsibility. Evaluating the changes of the upper airway according to sleep position can further characterize the upper airway collapsibility and can be used for tailored treatment planning.