EFFECTS OF SURFACE-TENSION AND VISCOSITY ON AIRWAY REOPENING
EFFECTS OF SURFACE-TENSION AND VISCOSITY ON AIRWAY REOPENING
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DOI：
10.1152/jappl.1990.69.1.74
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发表时间：
1990-07-01
影响因子：
3.3
通讯作者：
SOLWAY, J
中科院分区：
文献类型：
--
作者：
GAVER, DP;SAMSEL, RW;SOLWAY, J
我们在一个实验室模型中研究了气道开放，该模型旨在模拟气道衬里液对合的支气管壁。我们使用不同表面张力（γ）和粘度（μ）的内衬流体测量了不同半径（R）的薄壁聚乙烯管中气道开放速度（U）和所施加的气道开放压力之间的关系。施加轴向壁张力（T）以改变表观壁柔度特性，并改变衬里膜厚度（H）。增加μ或γ或降低R或T导致气道开放压力增加。H的影响与T有关：T较小时，开启压力随H的减小而略有增加; T较大时，开启压力与H无关。使用量纲分析，我们发现，粘性和表面张力的相对重要性取决于毛细管数（Ca = microU/伽马）。当Ca较小时，开放压力约为8 γ/R，并作为在气道开放开始之前必须超过的表观“屈服压力”。当Ca较大（Ca大于0.5）时，粘性力明显地增加到总打开压力。基于这些结果，气道开放时间的预测表明，气道关闭可以持续通过相当大的一部分吸气时，衬里流体粘度或表面张力升高。
We studied airway opening in a benchtop model intended to mimic bronchial walls held in apposition by airway lining fluid. We measured the relationship between the airway opening velocity (U) and the applied airway opening pressure in thin-walled polyethylene tubes of different radii (R) using lining fluids of different surface tensions (gamma) and viscosities (mu). Axial wall tension (T) was applied to modify the apparent wall compliance characteristics, and the lining film thickness (H) was varied. Increasing mu or gamma or decreasing R or T led to an increase in the airway opening pressures. The effect of H depended on T: when T was small, opening pressures increased slightly as H was decreased; when T was large, opening pressure was independent of H. Using dimensional analysis, we found that the relative importance of viscous and surface tension forces depends on the capillary number (Ca = microU/gamma). When Ca is small, the opening pressure is approximately 8 gamma/R and acts as an apparent “yield pressure” that must be exceeded before airway opening can begin. When Ca is large (Ca greater than 0.5), viscous forces add appreciably to the overall opening pressures. Based on these results, predictions of airway opening times suggest that airway closure can persist through a considerable portion of inspiration when lining fluid viscosity or surface tension are elevated.