Department of Mechanical Engineering, School of Biomedical Engineering, Orthopaedic Bioengineering Research Laboratory, 300 West Drake Street, Colorado State University, Fort Collins, CO 80523, United States.
Department of Anesthesia, University of Iowa Roy J. and Lucille A. Carver College of Medicine, 451 Newton Road, 200 Medicine Administration Building, Iowa City, IA 52242, United States.
J Clin Anesth. 2022 Oct;81:110909. doi: 10.1016/j.jclinane.2022.110909. Epub 2022 Jun 20.
To minimize the risk of cervical spinal cord injury in patients who have cervical spine pathology, minimizing cervical spine motion during laryngoscopy and tracheal intubation is commonly recommended. However, clinicians may better aim to reduce cervical spinal cord strain during airway management of their patients. The aim of this study was to predict laryngoscope force characteristics (location, magnitude, and direction) that would minimize cervical spine motions and cord strains.
We utilized a computational model of the adult human cervical spine and spinal cord to predict intervertebral motions (rotation [flexion/extension] and translation [subluxation]) and cord strains (stretch and compression) during laryngoscopy.
Routine direct (Macintosh) laryngoscopy conditions were defined by a specific force application location (mid-C3 vertebral body), magnitude (48.8 N), and direction (70 degrees). Sixty laryngoscope force conditions were simulated using 4 force locations (cephalad and caudad of routine), 5 magnitudes (25-200% of routine), and 3 directions (50, 70, 90 degrees).
Under all conditions, extension at Oc-C1 and C1-C2 were greater than in all other cervical segments. Decreasing force magnitude to values reported for indirect laryngoscopes (8-17 N) decreased cervical extension to ~50% of routine values. The cervical cord was most likely to experience potentially injurious compressive strain at C3, but force magnitudes ≤50% of routine (≤24.4 N) decreased strain in C3 and all other cord regions to non-injurious values. Changing laryngoscope force locations and directions had minor effects on motion and strain.
The model predicts clinicians can most effectively minimize cervical spine motion and cord strain during laryngoscopy by decreasing laryngoscope force magnitude. Very low force magnitudes (<5 N, ~10% of routine) are necessary to decrease overall cervical extension to <50% of routine values. Force magnitudes ≤24.4 N (≤50% of routine) are predicted to help prevent potentially injurious compressive cord strain.
为了降低患有颈椎疾病的患者颈椎脊髓损伤的风险，通常建议在喉镜检查和气管插管过程中尽量减少颈椎运动。然而，临床医生可能更希望在患者的气道管理过程中减少颈椎脊髓的应变。本研究旨在预测能够最大限度减少颈椎运动和脊髓应变的喉镜力特征（位置、大小和方向）。
我们利用成人颈椎和脊髓的计算模型来预测喉镜检查过程中的椎间运动（旋转[屈伸]和平移[半脱位]）和脊髓应变（拉伸和压缩）。
常规直接（Macintosh）喉镜条件由特定的力施加位置（C3 椎体中部）、大小（48.8 N）和方向（70 度）定义。通过 4 个力位置（常规头侧和尾侧）、5 个力大小（常规的 25-200%）和 3 个方向（50、70、90 度）模拟了 60 种喉镜力条件。
在所有条件下，Oc-C1 和 C1-C2 的伸展均大于其他所有颈椎节段。将力大小减小到报道的间接喉镜值（8-17 N）可将颈椎伸展减小至常规值的约 50%。颈椎脊髓最有可能在 C3 处经历潜在的压迫性应变，但力大小≤常规值的 50%（≤24.4 N）可将 C3 和所有其他脊髓区域的应变降低至无害值。改变喉镜力的位置和方向对运动和应变的影响较小。
该模型预测，通过降低喉镜力的大小，临床医生可以在喉镜检查过程中最有效地减少颈椎运动和脊髓应变。非常低的力大小（<5 N，约为常规值的 10%）可将整体颈椎伸展减少至常规值的<50%。预测力大小≤24.4 N（常规值的≤50%）有助于防止潜在的压迫性脊髓应变。
