| Summary: | Objective: To quantitatively examine changes in the upper airway caliber of normal subjects at graded negative inspiratory pressures generated during nasopharyngoscopy with a Müller maneuver.Study Design: Eighteen normal subjects prospectively underwent nasopharyngoscopy with Müller maneuvers. Subjects performed graded and maximal effort Müller maneuvers while sitting upright, and maximal-effort Müller maneuvers in the supine position. Two regions of the upper airway--the retropalatal and retroglossal--were examined.Methods: Images from the endoscopic examination were objectively analyzed by adjusting manually traced airway contours using full-width, half-maximum edge detection algorithm software. The adjusted tracings' area and dimensions through the airway centroid were measured.Results: Müller maneuvers performed at -40 cm H2O resulted in a 64%+/-17% (P = .0001) reduction in upper airway area that consisted of a 51%+/-20% (P = .0001) reduction in the lateral dimension and a 21%+/-24% (P = .0026) reduction in antero-posterior dimension. Müller maneuvers in the retroglossal region did not significantly reduce airway area (P = .575), but demonstrated an altered airway conformation that consisted of lateral narrowing and an increase in antero-posterior dimension. Changes in body position did not result in significant differences in either airway caliber or airway dimension.Conclusions: Airway caliber during forced inspiration is mediated primarily through changes in the lateral pharyngeal walls. This study has also shown that antero-posterior and lateral airway structures are largely independent in their response to Müller maneuvers. Similarly, the retropalatal and retroglossal regions of the upper airway respond differently to forced negative intraluminal pressure.
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