PROPERTIES OF TISSUES SURROUNDING THE UPPER AIRWAY

The pathogenesis of obstructive sleep apnea (OSA) remains unknown. How ever, we are beginning to understand the mechanisms leading to sleep a pnea by evaluating the structure and function of the upper airway (UA) and the surrounding soft-tissue structures using sophisticated magnet ic-resonance-imaging techniques. Knowledge of the morphology and mecha nical behavior of the soft-tissue structures is essential for a comple te understanding of the physiology of the UA. Although the tongue and soft palate have bern considered tile most important UA soft-tissue st ructures, our data have highlighted the importance of the lateral phar yngeal walls in the mediating UA caliber. We have demonstrated that: ( 1) during wakefulness, the predominant anatomic abnormality underlying UA narrowing in patients with OSA is thickening of the lateral pharyn geal walls; (2) during respiration, there are significant changes in l ateral airway dimensions as well as in the thickness of the lateral wa lls; and (3) incremental levels of continuous positive airway pressure (CPAP) result in progressive thinning of the lateral pharyngeal walls . The dynamic biomechanical behavior of the lateral pharyngeal walls d uring wakefulness, sleep, and during apneas needs to be investigated.