GAS DISPERSION IN VOLUME-CYCLED TUBE FLOW .2. TRACER BOLUS EXPERIMENTS
GAS DISPERSION IN VOLUME-CYCLED TUBE FLOW .2. TRACER BOLUS EXPERIMENTS
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DOI：
10.1152/jappl.1992.72.1.321
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发表时间：
1992-01-01
影响因子：
3.3
通讯作者：
GAVRIELY, N
中科院分区：
文献类型：
--
作者：
GAVER, DP;SOLWAY, J;GAVRIELY, N
提出了一种快速测量体积循环管流中局部气体弥散的新方法。在将示踪气体（氩气）的小团注入振荡流中之后，根据质谱仪进行的局部氩气浓度测量来评估示踪气体的轴向传输的时间平均有效扩散系数（[D（eff）/D]）。提出了两种方法用于从浓度测量值评估[D（eff）/D]：一种使用所有采样数据，另一种仅使用浓度的局部峰值。实验在两个管（半径= 0.85或1.0 cm）中在频率（0.42小于或等于f小于或等于8.5 Hz）和潮气量（7小于或等于VT小于或等于48 ml）的范围内进行。实验结果表明与Elad等人的理论预测非常一致（J.Appl.Physiol.72：312-320，1992）。在没有振荡的情况下（静态流体），所得的[D（eff）/D]收敛于分子扩散的结果。我们还表明，浓度数据可以在任何径向或轴向位置，不一定在示踪气体注入点，并得到[D（eff）/D]是独立的采样导管的空间位置。该方法具有类似的精度，并且比用于测量振荡流中的气体分散的先前方法快得多。这些测量的快速性可允许该方法用于肺系统内气体运输特性的体内评估。
We present a new method for rapid measurement of local gas dispersion in volume-cycled tube flow. After a small bolus of tracer gas (argon) was injected into the oscillating flow, the time-averaged effective diffusion coefficient ([D(eff)/D]) for axial transport of a tracer gas is evaluated from local argon concentration measurements taken by a mass spectrometer. Two methods are presented for the evaluation of [D(eff)/D] from the concentration measurements: one uses all the sampled data, and the other uses only the local peaks of the concentration. Experiments were conducted in two tubes (radius = 0.85 or 1.0 cm) over a range of frequencies (0.42 less-than-or-equal-to f less-than-or-equal-to 8.5 Hz) and tidal volumes (7 less-than-or-equal-to VT less-than-or-equal-to 48 ml). The experimental results show very good agreement with the theoretical predictions of Elad et al. (J. Appl. Physiol. 72: 312-320, 1992). In the absence of oscillations (static fluid), the resulting [D(eff)/D] converges to that of molecular diffusion. We also show that concentration data may be acquired at any radial or axial position, not necessarily at the tracer gas injection point, and the resulting [D(eff)/D] is independent of the spatial position of the sampling catheter. This method is of similar accuracy and is substantially faster than previous methods for measuring gas dispersion in oscillatory flows. The rapidity of these measurements may permit this method to be used for the in vivo assessment of gas transport properties within the pulmonary system.