Benkhadra Mehdi, Lenfant F, Bry J, Astruc K, Trost O, Ricolfi F, Girard C, Trouilloud P, Feigl G
Laboratory of Anatomy-INSERM U887, Faculté de Médecine, University of Burgundy, 7 Boulevard Jeanne d'Arc, Dijon, France.
Surg Radiol Anat. 2009 Aug;31(7):537-43. doi: 10.1007/s00276-009-0481-3. Epub 2009 Mar 10.
Cricoid pressure occludes the esophagus (E) by compressing it between the cricoid cartilage (CC) and the body of the sixth cervical vertebra (C6). This technique is used to prevent passive regurgitation during the induction of anesthesia in patients at high risk for regurgitation. Failures of this technique had been described and a possible displacement of the E relative to the CC had been reported, but there is no study about displacement during antero-posterior movements of the head.
The aim of our study was to evaluate the displacement of the CC relative to the cervical E, during flexion and extension movements of the head.
We retrospectively studied X-ray computed tomography (CT) images of 21 patients with suspected cervical trauma. Patients were in the supine position. In the first series of images, the head was positioned at maximal flexion by means of a support placed under the external occipital protuberance. In the second series of images, the head was maintained in extension by means of a support placed under the shoulders. Each position was obtained as far as possible within the limits of pain and restricted movement. In flexion and extension, we used the lowest slice from the cricoid cartilage. The variables measured were: diameters of CC (CD) and E (OD), left and right lateral displacements of E.
A total of 13 CT were analyzed. CD and OD as well as OD/OC ratios did not vary significantly in flexion and extension. We noticed 61.5 and 92.3% (respectively in flexion and in extension) of left or right displacement: 23% of patients presented right displacement in both flexion and extension; 38.5% of patients did not present any right displacement in flexion or in extension; 61.5% of patients presented left displacement in both flexion and extension. More generally, almost 92% of patients presented displacement either in flexion or extension, or both.
In our study, it can be seen that the E is clearly displaced with regard to the CC, that this displacement is favored by extension. Only 2/13 patients have an "over than 3 mm" displacement in extension whereas 5/13 in flexion. So, even if there are more displacements in extension, they are inferior to 3 mm and may not be considered as significant considering the occlusion of E. According to our results, the extension position of the head produces more displacement of the E but should preserve the containment of the cricoid pressure if we consider the thickness of the E wall.
环状软骨压迫通过在环状软骨（CC）与第六颈椎椎体（C6）之间挤压食管（E）来阻塞食管。该技术用于防止反流高危患者在麻醉诱导期间发生被动反流。已有该技术失败的描述，并且有报道称食管相对于环状软骨可能发生移位，但尚无关于头部前后移动时移位情况的研究。
我们研究的目的是评估头部屈伸运动期间环状软骨相对于颈部食管的移位情况。
我们回顾性研究了21例疑似颈椎创伤患者的X线计算机断层扫描（CT）图像。患者处于仰卧位。在第一组图像中，通过在枕外隆突下方放置支撑物将头部置于最大屈曲位。在第二组图像中，通过在肩部下方放置支撑物使头部保持伸展位。每个位置尽可能在疼痛和活动受限的范围内获得。在屈伸位时，我们使用环状软骨的最低层面。测量的变量包括：环状软骨直径（CD）和食管直径（OD）、食管的左右侧移位。
共分析了13份CT图像。屈伸位时CD和OD以及OD/OC比值均无显著变化。我们注意到左右移位分别为61.5%（屈曲位）和92.3%（伸展位）：23%的患者在屈伸位时均出现右侧移位；38.5%的患者在屈曲位或伸展位均未出现右侧移位；61.5%的患者在屈伸位时均出现左侧移位。更普遍的是，几乎92%的患者在屈曲位或伸展位或两者均出现移位。
在我们的研究中，可以看出食管相对于环状软骨明显移位，伸展位时这种移位更明显。伸展位时只有2/13的患者移位“超过3毫米”，而屈曲位时有5/13的患者。所以，即使伸展位时移位更多，但它们小于3毫米，考虑到食管的阻塞情况，可能不被视为显著移位。根据我们的结果，头部伸展位会使食管产生更多移位，但如果考虑食管壁的厚度，应能保持环状软骨压迫的封堵作用。
