Effects of the Body Position Changes on Upper Airway Caliber in Obstructive Sleep Apnea during Sleep

Sohn, Jung Ho; Choi, Young Jun; Lee, Chang Min; Jang, Hyun Uk; Kim, Jae Hyuk; Lee, Kyu Yup; Kim, Jung Soo

Abstract

BACKGROUND AND OBJECTIVES
Obstructive sleep apnea (OSA) is the intermittent cessation of breathing during sleep due to the collapse of the pharyngeal airway. Pharyngeal collapsibility and oropharyngeal caliber are affected by the respiratory cycle and the body position. Several methods have been used to evaluate the states of upper airway in patients with OSA according to body positions during wakefulness, but there were no reports about the upper airway states according to body positions during sleep. The aim of this study is to evaluate the states of upper airway in patients with OSA according to body position changes during sleep. MATERIALS AND METHOD: Using a multi detector CT, we studied 10 patients with OSA. Each patient was scanned at supine position during the awake state and then induced to sleep using Midazolam. According to body positions (supine, decubitus, and prone), images were acquired during sleep state. The following 4 transverse levels were obtained to evaluate the minimal cross sectional area, collapsibility index, and airway volume: 1) high retropalate level, 2) low retropalate level, 3) high retroglossal level, 4) low retroglossal level. RESULTS: During sleep, the upper airway cross sectional area was decreased and the airway wall collapsibility was increased. Cross sectional area and airway volume were larger at prone and decubitus positions than supine position. Airway wall collapsibility index was lower at prone and decubitus positions than at the supine position. CONCLUSION: In this study, we confirm that the upper airway collapsibility decreases and the airway caliber increases according to body position changes (prone, decubitus) during sleep. Furthermore, the decubitus position is better than the prone position for improving upper airway patency during sleep.