Expiratory pharyngeal airway obstruction during sleep: a multiple element model

Area of Science:

• Sleep Medicine
• Respiratory Physiology
• Otolaryngology

Background:

• Obstructive sleep apnea (OSA) and snoring involve upper airway collapse during sleep.
• Airway obstruction in OSA is often considered inspiratory, but expiratory obstruction also occurs.
• Understanding expiratory mechanics is crucial for diagnosing and treating OSA.

Purpose of the Study:

• To investigate the segmental mechanics of expiratory airway obstruction in patients with snoring and mild OSA.
• To determine the primary sites and characteristics of expiratory collapse.

Main Methods:

• An experimental study involving 20 patients with snoring and mild OSA during sedated sleep.
• Simultaneous measurement of airflow, airway pressures, and airway areas (supraglottic/retroglossal and retropalatal).
• Experimental adjustment of nasal continuous positive airway pressure (nCPAP) and evaluation of airway mechanics during expiratory pressure drops.

Main Results:

• The supraglottic/retroglossal level was the predominant site of expiratory obstruction (65%), often combined with retropalatal obstruction (17.6%).
• Expiratory compliance was higher in the supraglottic/retroglossal segment than the retropalatal segment.
• Increased retropalatal collapse occurred during obstructed expiratory breaths compared to non-obstructed breaths.

Conclusions:

• The supraglottic/retroglossal region is frequently obstructed during expiration in OSA patients.
• Segmental airway interactions occur during expiration, with increased retropalatal collapse.
• Expiratory collapse may contribute to the severity of subsequent inspiratory obstruction in OSA.