Radial and longitudinal compartmental analysis of gas transport during high-frequency ventilation.
Radial and longitudinal compartmental analysis of gas transport during high-frequency ventilation.
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高频通气期间气体传输的径向和纵向隔室分析。
DOI：
10.1152/jappl.1986.60.4.1134
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Butler,JP
中科院分区：
文献类型：
--
作者：
Gavriely,N;Butler,JP
基于弥散物理原理，提出了低潮气量 (VT)、高频通气 (HFV) 的气体交换模型。这些是速度分布的不均匀性和流体组分以扩散方式的不可逆混合。使用数值方法将这些原理纳入定量模型。对称分叉支气管树模型的气道在径向方向上被分成两个同心层，这两个同心层代表由速度分布的不均匀性引起的运动分散。层之间的混合与扩散率和局部尺寸成比例。在模型中测试了频率 (f)、VT、速度分布形状和支气管模型配置的影响，并与现有实验数据进行了有利的比较。该模型预测，对于频率相关的速度剖面，示踪剂交换速率与 f 的平方根和 VT-V0 的平方成正比，其中 V0 是气体交换为零时的恒定小体积。预计循环内不对称混合对气体交换的影响比不对称速度分布的影响更大。预计在较高 VT 值的情况下，假设为湍流流态时的气体交换会比层流和通过分子扩散率混合时的气体交换少。人们发现该模型具有说教性、灵活性，并且能够对影响两个基本分散过程之一的因素组合进行建模。
A model of gas exchange by low-tidal-volume (VT), high-frequency ventilation (HFV) is presented, based on the physical principles of dispersion. These are the nonuniformity of the velocity profile and the nonreversible mixing of fluid components in a diffusive manner. A numerical method was used to incorporate these principles into a quantitative model. The airways of a symmetrically bifurcating bronchial-tree model were partitioned in the radial direction into two concentric layers representing the kinematic dispersion by nonuniformity of the velocity profile. Mixing between the layers was invoked in proportion to the diffusivity and local dimensions. The effects of frequency (f), VT, shape of the velocity profile, and bronchial-model configuration were tested in the model, with favorable comparison to available experimental data. The model predicts that for a frequency-dependent velocity profile, the rate of tracer exchange is proportional to the square root of f and to the square of VT-V0, where V0 is a constant small volume under which gas exchange was nil. Intracycle asymmetric mixing is predicted to have a stronger effect on gas exchange than asymmetric velocity profile. Gas exchange when turbulent-flow regime is assumed is predicted to be less for the higher VT values than with laminar flow and with mixing by molecular diffusivity. This model was found to be didactic, flexible, and capable of modeling combinations of factors affecting either one of the two fundamental processes of dispersion.