Functional MRI of the pharyngeal airway

描述(申请人提供)：咽部呼吸道的通畅性取决于咽部横截面积、顺应性和形状。舌外肌肉和咽壁肌肉在调节这些机械特性方面起着主要作用。腭咽似乎是最容易塌陷的区域，最近的数据表明，顺应性和临界塌陷压力(Pcrit)在人类和低等哺乳动物的腭咽吻尾方向上是不同的。在获得磁共振图像的同时，将分离大鼠的咽部，并系统地改变咽压。将获得长达15，1.0 mm的横断面，分别穿过腭咽和口咽部尾部，并计算每个层面的横截面积。然后将获得每个切片的压力：面积关系，这将允许推导区域咽部顺应性和Pcrit。通过将对照图像与电刺激舌肌或咽壁肌肉时获得的图像进行比较，评估咽肌活动对这些变量的影响。几何分析将使我们能够描述每个轴位切片的横径与前后径的比率(即，呼吸道的“椭圆度”)，以及咽部限流段(FLS)的位置。假说是：1)顺应性是区域性的，在腭咽部的值最高；2)咽前支位于腭咽部；3)腭咽部的形状是最椭圆形的；4)舌或咽缩窄肌的激活会降低区域的顺应性和Pcrit，并使气道变得不那么椭圆形(即，将使气道变硬)。这些实验将提供有关咽部的几何和内在机械特性以及咽部肌肉收缩所发生的变化的独特信息。这些数据可能有助于指导旨在利用呼吸道压力变化和/或植入性咽肌神经刺激器来缓解睡眠期间呼吸道阻塞的治疗策略。

DESCRIPTION (provided by applicant): The patency of the pharyngeal airway depends on pharyngeal cross-sectional area, compliance and shape. The extrinsic tongue muscles and the muscles of the pharyngeal wall play a major role in modulating these mechanical properties. The velopharynx appears to be the region most susceptible to collapse, and recent data suggest that compliance and the critical collapsing pressure (Pcrit) vary along the rostral-caudal extent of the velopharynx in humans and lower mammals. The rat pharynx will be isolated and pharyngeal pressure will be changed systematically while magnetic resonance images are obtained. Up to 15, 1.0 mm axial slices through the velopharynx and caudal oropharynx will be obtained, and the cross-sectional area of each slice computed. The pressure: area relation will then be obtained for each slice, which will allow derivation of regional pharyngeal compliance and Pcrit. The influence of pharyngeal muscle activity on these variables is evaluated by comparing control images with those obtained while the tongue or pharyngeal wall muscles are stimulated electrically. Geometric analyses will allow us to describe the ratio of the lateral to the anterior-posterior diameters of each axial slice (i.e., the "ellipticity" of the airway), and the location of the flow-limiting segment (FLS) of the pharynx. The hypotheses are: 1) compliance is regionally dependent, with the highest values in the velopharynx; 2) the FLS is located in the velopharynx; 3) the shape of the velopharynx is most elliptical at the FLS; 4) activation of tongue or pharyngeal constrictor muscles will decrease regional compliance and Pcrit, and make the airway less elliptical (i.e., will "stiffen" the airway). These experiments will provide unique information on the geometry and intrinsic mechanical properties of the pharynx, and the changes that occur with pharyngeal muscle contraction. The data may help to guide treatment strategies that are aimed at using airway pressure changes and/or implantable pharyngeal muscle nerve stimulators to alleviate airway obstruction during sleep.