Postural and Conditional Variations of Nasal Patency in Patients under General Anesthesia Approximating Sleep as Assessed with Acoustic Rhinometry

Abstract

Nasal obstruction is a known risk factor associated with obstructive sleep apnea (OSA). Multiple methods of measuring nasal abnormalities including anterior and posterior rhinomanometry and acoustic rhinometry (AR) have been used to better quantify the relationship. These measurements are usually used in the sitting and awakening situation, which differ from the situations in the supine position and while asleep. The goal of this study was to evaluate the nasal patency in patients under general anesthesia approximating sleep as assessed with AR. The nasal minimal cross-sectional area (MCSA) and nasal volume in 50 patients who underwent general anesthesia were compared with subjects in the sitting, supine, and supine position under general anesthesia using AR to measure the nasal dimensions and patency. MCSA and nasal volume decreased more significantly in the supine than in the sitting subjects and these decrements were shown more in the supine position under general anesthesia than in the supine position without anesthesia. Furthermore, regarding nasal volume, the difference between in the sitting and in the supine was larger than the difference between in the supine position with and without general anesthesia. These results suggested that the decrements regarding nasal volume under positional change were greater than those under conditional change. The positional variation can affect the airway patency hydrodynamically and these alterations indicate the relationship of the pathophysiology in patients with OSA.