School of Mechanical Engineering, Kyungpook National University, Daegu, South Korea.
IIHR-Hydroscience and Engineering, University of Iowa, Iowa City, Iowa.
J Appl Physiol (1985). 2020 Oct 1;129(4):732-747. doi: 10.1152/japplphysiol.00176.2020. Epub 2020 Aug 6.
This study aims to develop a one-dimensional (1D) computational fluid dynamics (CFD) model with dynamic airway geometry that considers airway wall compliance and acinar dynamics. The proposed 1D model evaluates the pressure distribution and the hysteresis between the pressure and tidal volume () in the central and terminal airways for healthy and asthmatic subjects. Four-dimensional CT images were captured at 11-14 time points during the breathing cycle. The airway diameter and length were reconstructed using a volume-filling method and a stochastic model at respective time points. The obtained values for the airway diameter and length were interpolated via the Akima spline to avoid unboundedness. A 1D energy balance equation considering the effects of wall compliance and parenchymal inertance was solved using the efficient aggregation-based algebraic multigrid solver, a sparse matrix solver, reducing the computational costs by around 90% when compared with the generalized minimal residual solver. In the versus displacement in the basal direction (-coordinate), the inspiration curve was lower than the expiration curve, leading to relative hysteresis. The dynamic deformation model was the major factor influencing the difference in the workload in the central and terminal airways. In contrast, wall compliance and parenchymal inertance appeared only marginally to affect the pressure and workload. The integrated 1D model mimicked dynamic deformation by predicting airway diameter and length at each time point, describing the effects of wall compliance and parenchymal inertance. This computationally efficient model could be utilized to assess breathing mechanism as an alternative to pulmonary function tests. This study introduces a one-dimensional (1D) computational fluid dynamics (CFD) model mimicking the realistic changes in diameter and length in whole airways and reveals differences in lung deformation between healthy and asthmatic subjects. Utilizing computational models, the effects of parenchymal inertance and airway wall compliance are investigated by changing ventilation frequency and airway wall elastance, respectively.
本研究旨在开发一种具有动态气道几何形状的一维(1D)计算流体动力学(CFD)模型,该模型考虑气道壁顺应性和腺泡动力学。所提出的 1D 模型评估了健康和哮喘受试者的中央和终末气道中的压力分布和压力与潮气量()之间的滞后关系。在呼吸周期的 11-14 个时间点采集了四维 CT 图像。使用体积填充法和随机模型在各个时间点重建气道直径和长度。通过 Akima 样条插值获得的气道直径和长度值,以避免无界性。通过有效的基于聚合的代数多重网格求解器求解考虑壁顺应性和实质惯性的 1D 能量平衡方程,稀疏矩阵求解器,与广义最小残差求解器相比,计算成本降低了约 90%。在基底方向(-坐标)上的位移与相比,吸气曲线低于呼气曲线,导致相对滞后。动态变形模型是影响中央和终末气道工作量差异的主要因素。相比之下,壁顺应性和实质惯性仅略微影响压力和工作量。集成的 1D 模型通过预测每个时间点的气道直径和长度来模拟动态变形,描述了壁顺应性和实质惯性的影响。这种计算效率高的模型可用于评估呼吸机制,作为肺功能测试的替代方法。本研究介绍了一种模拟整个气道直径和长度真实变化的一维(1D)计算流体动力学(CFD)模型,并揭示了健康和哮喘受试者之间肺部变形的差异。通过改变通气频率和气道壁弹性,利用计算模型分别研究实质惯性和气道壁顺应性的影响。