Computational model for forced expiration from asymmetric normal lungs.
Computational model for forced expiration from asymmetric normal lungs.
复制标题
不对称正常肺强制呼气的计算模型。
DOI：
10.1114/1.1588651
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发表时间：
2003
影响因子：
3.8
通讯作者：
Lutchen,KennethR
中科院分区：
文献类型：
--
作者：
Polak,AdamG;Lutchen,KennethR
我们提出了一个通过基于形态测量的非对称支气管树来预测最大呼气的计算模型。建立了一个具有Horsfield几何结构的计算模型，包括波速限制，并考虑了来自几个独立的肺泡室的独立气流。通过求解描述沿气道分支的静压损失的非线性微分方程组，计算准静态条件下的空气流量值。对后续肺容量的计算得到了半动态最大呼气流量-容量(MEFV)曲线。模拟结果表明，该模型捕捉到了强迫呼气过程中活体观察到的主要现象：大部分肺活量的流量-容量曲线的努力独立性、受限流量与阻塞点下游的呼吸道特性的独立性、肺区域压力和容量的特征差异以及呼气过程中其变异性的形状。对限流机理有了一些新的认识。首先，在支气管树的各个分支中，血流限制在略有不同的时刻开始，但在很短的一段时间后，所有区域的血流都以并行的方式受到限制。因此，对于大多数过期的肺容量，口腔内的总流量是有限的。其次，每个气道分支贡献了它们自己的流量-体积形状，正是这些单独的流量构成了测量的MEFV曲线。第三，中心气道的异质性在整个血流的调节中起着至关重要的作用。第四，支气管树的不对称性是局部体积变异性的非重力成分。最后，增加的不均一性产生的结果不能用支气管树的对称结构来解释或重新创建。
We present a computational model to predict maximal expiration through a morphometry-based asymmetrical bronchial tree. A computational model with the Horsfield-like geometry of the airway structure, including wave-speed flow limitation and taking into consideration separate airflows from several independent alveolar compartments has been derived. The airflow values are calculated for quasistatic conditions by solving a system of nonlinear differential equations describing static pressure losses along the airway branches. Calculations done for succeeding lung volumes result in the semidynamic maximal expiratory flow–volume (MEFV) curve. Simulations performed show that the model captures the main phenomena observedin vivoduring forced expiration: effort independence of the flow–volume curve for the most of vital capacity, independence of limited flow on the properties of airways downstream to the choke points, characteristic differences of lung regional pressures and volumes, and a shape of their variability during exhalation. Some new insights into the flow limitation mechanism were achieved. First, flow limitation begins at slightly different time instants in individual branches of the bronchial tree, however after a short period of time, all regional flows are limited in a parallel fashion. Hence, total flow at the mouth is limited for most of the expired lung volume. Second, each of the airway branches contribute their own flow–volume shape and just these individual flows constitute the measured MEFV curve. Third, central airway heterogeneity can play a crucial role in modification of the entire flow. Fourth, the bronchial tree asymmetry is responsible for a nongravitational component of regional volume variability. Finally, increased inhomogeneity yields results that cannot be explained nor re-created with the use of a symmetrical structure of the bronchial tree.©2003 Biomedical Engineering Society.PAC2003: 8719Uv, 8710+e, 8718Bb