From the Department of Anesthesia, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, Iowa (B.J.H., R.P.F., M.M.T.); Foundation for Orthopaedic Research and Education, Tampa, Florida (B.G.S.); and Department of Mechanical Engineering, School of Biomedical Engineering, Orthopaedic Bioengineering Research Laboratory, Colorado State University, Fort Collins, Colorado (C.M.P.).
Anesthesiology. 2014 Aug;121(2):260-71. doi: 10.1097/ALN.0000000000000263.
Laryngoscopy and endotracheal intubation in the presence of cervical spine instability may put patients at risk of cervical cord injury. Nevertheless, the biomechanics of intubation (cervical spine motion as a function of applied force) have not been characterized. This study characterized and compared the relationship between laryngoscope force and cervical spine motion using two laryngoscopes hypothesized to differ in force.
Fourteen adults undergoing elective surgery were intubated twice (Macintosh, Airtraq). During each intubation, laryngoscope force, cervical spine motion, and glottic view were recorded. Force and motion were referenced to a preintubation baseline (stage 1) and were characterized at three stages: stage 2 (laryngoscope introduction); stage 3 (best glottic view); and stage 4 (endotracheal tube in trachea).
Maximal force and motion occurred at stage 3 and differed between the Macintosh and Airtraq: (1) force: 48.8 ± 15.8 versus 10.4 ± 2.8 N, respectively, P = 0.0001; (2) occiput-C5 extension: 29.5 ± 8.5 versus 19.1 ± 8.7 degrees, respectively, P = 0.0023. Between stages 2 and 3, the motion/force ratio differed between Macintosh and Airtraq: 0.5 ± 0.2 versus 2.0 ± 1.4 degrees/N, respectively; P = 0.0006.
The relationship between laryngoscope force and cervical spine motion is: (1) nonlinear and (2) differs between laryngoscopes. Differences between laryngoscopes in motion/force relationships are likely due to: (1) laryngoscope-specific cervical extension needed for intubation, (2) laryngoscope-specific airway displacement/deformation needed for intubation, and (3) cervical spine and airway tissue viscoelastic properties. Cervical spine motion during endotracheal intubation is not directly proportional to force. Low-force laryngoscopes cannot be assumed to result in proportionally low cervical spine motion.
在颈椎不稳定的情况下进行喉镜检查和气管插管可能会使患者面临颈椎脊髓损伤的风险。然而，插管的生物力学（作为力的函数的颈椎运动）尚未得到描述。本研究使用两种喉镜来描述和比较插管力与颈椎运动之间的关系，这两种喉镜假设在力上有所不同。
14 名接受择期手术的成年人进行了两次插管（Macintosh，Airtraq）。在每次插管过程中，记录喉镜力、颈椎运动和声门视图。力和运动参考插管前的基线（第 1 阶段），并在三个阶段进行描述：第 2 阶段（喉镜引入）；第 3 阶段（最佳声门视图）；第 4 阶段（气管内导管在气管中）。
最大力和运动发生在第 3 阶段，Macintosh 和 Airtraq 之间存在差异：（1）力：分别为 48.8 ± 15.8 与 10.4 ± 2.8 N，P = 0.0001；（2）枕骨-C5 伸展：分别为 29.5 ± 8.5 与 19.1 ± 8.7 度，P = 0.0023。在第 2 阶段和第 3 阶段之间，Macintosh 和 Airtraq 之间的运动/力比存在差异：分别为 0.5 ± 0.2 与 2.0 ± 1.4 度/N，P = 0.0006。
喉镜力与颈椎运动之间的关系是：（1）非线性的；（2）不同的喉镜之间存在差异。喉镜在运动/力关系上的差异可能归因于：（1）喉镜特定的颈椎延伸需要插管；（2）喉镜特定的气道位移/变形需要插管；（3）颈椎和气道组织的粘弹性。在气管插管过程中，颈椎运动与力不成正比。不能假设低力喉镜会导致颈椎运动成比例地降低。
