Department of Mechanical and Aerospace Engineering, Carleton University, 1125 Colonel By Drive, Ottawa, ON, Canada K1S 5B6.
U.S. Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, MD, 21005-5066, USA.
J Mech Behav Biomed Mater. 2022 Jun;130:105181. doi: 10.1016/j.jmbbm.2022.105181. Epub 2022 Mar 26.
Finite element models of thoracic injury often treat the lung as a bulk homogeneous and isotropic material, which reduces the computational costs associated with such investigations. Ignoring the heterogeneous structure of the lung may be computationally expedient, but this simplification may inadvertently fail to capture the true lung strain dynamics. In the present work, a series of direct impact experiments were performed on porcine lungs, inflated to a relevant expiratory pressure, and monitored using high-speed X-ray imaging. The lungs were instrumented with radiopaque markers within the parenchyma and tertiary bronchi to monitor the resulting deformation mechanics. The deformation mechanics demonstrate a high degree of strain localization related to the structural heterogeneity of the lung. The relative motion of the tertiary bronchi was measured during the impact event, and used to estimate the parenchyma tissue strains in the inter-bronchial regions. These were shown to exceed the trans-lobe strains by a factor 3 to 5 times higher in their tensile, compressive, and shear strain responses. Our results demonstrate that the lung parenchyma and bronchial tissues form a heterogeneous structure with a substantial stiffness differential that cannot be appropriately modelled as a homogeneous and isotropic monolithic mass without loss of accuracy and predictive relevance.
胸部损伤的有限元模型通常将肺视为均匀各向同性的整体材料，从而降低了与这些研究相关的计算成本。忽略肺的不均匀结构在计算上可能很方便，但这种简化可能会无意中无法捕捉到真实的肺应变动力学。在本工作中，对充气至相关呼气压力的猪肺进行了一系列直接冲击实验，并使用高速 X 射线成像进行监测。在肺实质和三级支气管内放置不透射线的标记物来监测由此产生的变形力学。变形力学显示出与肺的结构异质性相关的高度应变局部化。在冲击事件期间测量了三级支气管的相对运动，并用于估计支气管间区域的肺实质组织应变。结果表明，在拉伸、压缩和剪切应变响应中，它们的应变值比跨叶应变高 3 到 5 倍。我们的结果表明，肺实质和支气管组织形成了一种具有显著刚度差异的不均匀结构，如果不适当建模为均匀各向同性的整体块状质量，就会失去准确性和预测相关性。
