Center for Biomedical Engineering, Brown University, Providence, RI, 02912, USA; Research Service, Providence VA Medical Center, Providence, RI, 02908, USA.
Department of Mechanical Engineering, Widener University, Chester, PA, 19013, USA.
Comput Biol Med. 2022 Jun;145:105446. doi: 10.1016/j.compbiomed.2022.105446. Epub 2022 Mar 25.
Biomechanical relationships involving lingual myoanatomy, contractility, and bolus movement are fundamental properties of human swallowing. To portray the relationship between lingual deformation and bolus flow during swallowing, a weakly one-way solid-fluid finite element model (FEM) was derived employing an elemental mesh aligned to magnetic resonance diffusional tractography (Q-space MRI, QSI) of the human tongue, an arbitrary Lagrangian-Eulerian (ALE) formulation with remeshing to account for the effects of lingual surface (boundary) deformation, an implementation of patterned fiber shortening, and a computational visualization of liquid bolus flow. Representing lingual tissue deformation in terms of its 2D principal Lagrangian strain in the mid-sagittal plane, we demonstrated that the swallow sequence was characterized by initial superior-anterior expansion directed towards the hard palate, followed by sequential, radially directed, contractions of the genioglossus and verticalis to promote lingual rotation (lateral perspective) and propulsive displacement. We specifically assessed local bolus velocity as a function of viscosity (perfect slip conditions) and observed that a low viscosity bolus (5 cP) exhibited maximal displacement, surface spreading and local velocity compared to medium (110 cP, 300 cP) and high (525 cP) viscosity boluses. Analysis of local nodal velocity revealed that all bolus viscosities exhibited a bi-phasic progression, with the low viscosity bolus being the most heterogeneous and fragmented and the high viscosity bolus being the most homogenous and cohesive. Intraoral bolus cohesion was depicted in terms of the distributed velocity gradient, with higher gradients being associated with increased shear rate and bolus fragmentation. Lastly, we made a sensitivity analysis on tongue stiffness and contractility by varying the degree of extracellular matrix (ECM) stiffness through effects on the Mooney-Rivlin derived passive matrix and by varying maximum tetanized isometric stress, and observed that a graded increase of ECM stiffness was associated with reduced bolus spreading, posterior displacement, and surface velocity gradients, whereas a reduction of global contractility resulted in a graded reduction of obtainable accommodation volume, absent bolus spreading, and loss of posterior displacement. We portray a unidirectionally coupled solid-liquid FEM which associates myoarchitecture-based lingual deformation with intra-oral bolus flow, and deduce that local elevation of the velocity gradient correlates with bolus fragmentation, a precondition believed to be associated with aspiration vulnerability during oropharyngeal swallowing.
生物力学关系涉及舌肌解剖结构、收缩性和食团运动，这些都是人类吞咽的基本特性。为了描述吞咽过程中舌变形和食团流动之间的关系，我们采用了一种弱单向固液有限元模型（FEM），该模型使用与磁共振扩散轨迹（Q 空间 MRI，QSI）对齐的元素网格来表示人舌，采用任意拉格朗日-欧拉（ALE）公式并重新网格化来考虑舌表面（边界）变形的影响，实现纤维图案缩短，并对液体食团流动进行计算可视化。根据中矢状面的二维主要拉格朗日应变来表示舌组织变形，我们证明吞咽序列的特征是最初朝向硬腭的上-前扩张，随后是颏舌肌和垂直肌的顺序、放射状收缩，以促进舌旋转（侧视）和推进位移。我们专门评估了粘度（完美滑动条件）作为局部食团速度的函数，并观察到与中粘度（110 cP，300 cP）和高粘度（525 cP）食团相比，低粘度（5 cP）食团具有最大的位移、表面扩散和局部速度。局部节点速度分析表明，所有食团粘度都表现出双相进展，低粘度食团最不均匀和碎片化，高粘度食团最均匀和凝聚。口内食团内聚度用分布速度梯度来描述，较高的梯度与较高的剪切率和食团碎片化相关。最后，我们通过影响基于 Mooney-Rivlin 的被动基质来改变细胞外基质（ECM）刚度的程度，以及通过改变最大强直等长应力，对舌刚度和收缩性进行了敏感性分析，观察到 ECM 刚度的逐渐增加与食团扩散、后向位移和表面速度梯度的减少有关，而整体收缩性的降低则导致可获得的容纳体积逐渐减少，食团扩散消失，后向位移丢失。我们描述了一种单向固液耦合 FEM，该模型将基于肌构筑的舌变形与口腔内食团流动相关联，并推断出速度梯度的局部升高与食团碎片化相关，这是一种被认为与口咽吞咽期间吸入脆弱性相关的前提条件。
