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We utilized novel three-dimensional volumetric analysis techniques with magnetic resonance imaging (MRI) to study the upper airway and surrounding soft-tissue structures. These MRI techniques allowed us to objectively quantify the volume of the tongue, soft palate, parapharyngeal fat pads, and lateral pharyngeal walls.We first validated our volumetric imaging techniques on a phantom and then demonstrated that our results were reliable and reproducible in normal subjects who did not lose weight. Finally, we studied 12 obese, nonapneic women during wakefulness before and after weight loss. We hypothesized that our novel magnetic-resonance computer-reconstruction techniques would allow us to detect small reductions in the volume of the tongue, soft palate, lateral pharyngeal walls, and parapharyngeal fat pads and increases in the volume of the upper airway with weight loss.University medical center.Normal controls and 12 obese nonapneic women.Weight loss.Following a mean 17.1+/-8.62 kg (17.3%) reduction in weight, upper airway volume increased (p = 0.06) in both the retropalatal and retroglossal regions. This increase in upper airway volume was mediated by significant reductions in the volume of the lateral pharyngeal wall (p = 0.0001) and parapharyngeal fat pads (p = 0.001). However, the volume of the tongue (p = 0.35) and soft palate (p = 0.39) were not reduced significantly with weight loss.These data indicate that volumetric MRI is a powerful tool to study anatomic changes in the upper airway and surrounding soft-tissue structures and is sensitive enough to detect changes in these structures.

Objective: To quantitatively examine changes in the upper airway caliber of normal subjects at graded negative inspiratory pressures generated during nasopharyngoscopy with a Muller maneuver. Study Design: Eighteen normal subjects prospectively underwent nasopharyngoscopy with Muller maneuvers. Subjects performed graded and maximal effort Muller maneuvers while sitting upright, and maximal-effort Muller 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: Muller 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. Muller 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 Muller maneuvers. Similarly, the retropalatal and retroglossal regions of the upper airway respond differently to forced negative intraluminal pressure. Key Words: Nasopharyngoscopy, Muller maneuver, normal subjects, upper airway, obstructive sleep apnea.