Basser P J, McMahon T A, Griffith P
Biomedical Engineering and Instrumentation Branch, National Institutes of Health, Bethesda, Maryland 20892.
J Biomech Eng. 1989 Nov;111(4):288-97. doi: 10.1115/1.3168381.
An instability resembling an avalanche is proposed as the mechanism by which mucus is expelled from the respiratory tract during cough. The cough event was simulated in a model airway. In these experiments, air was forced through a channel whose walls were lined with a non-Newtonian material rheologically similar to tracheal mucus. Frames from high-speed cine photographs showed an unstable event which began as an undulation of the free surface and progressed to a catastrophic clearance of the channel. Measurements of the longitudinal pressure gradient support the hypothesis that the clearance event is initiated when the total stress applied to the mucus analog exceeds its finite yield stress. A continuum model predicts that yielding occurs within the bottom layers of the mucus analog. Calculations based upon estimates of tracheal geometry and air flow show that the clearance event studied here would be expected to occur during a cough but not during normal breathing. Experiments also show that a lubricant introduced between the channel walls and the mucus blanket can reduce the air flow rate required to precipitate the clearance.
一种类似雪崩的不稳定性被认为是咳嗽时呼吸道排出黏液的机制。在一个模拟气道中对咳嗽过程进行了模拟。在这些实验中，空气被强制通过一个通道，该通道的壁面衬有流变学上类似于气管黏液的非牛顿材料。高速电影照片的画面显示了一个不稳定事件，该事件始于自由表面的波动，并发展为通道的灾难性清空。纵向压力梯度的测量结果支持了这样一种假设，即当施加在黏液类似物上的总应力超过其有限屈服应力时，清空事件就会开始。一个连续介质模型预测，屈服发生在黏液类似物的底层。基于气管几何形状和气流估计的计算表明，这里研究的清空事件预计会在咳嗽时发生，而不是在正常呼吸时发生。实验还表明，在通道壁和黏液层之间引入润滑剂可以降低引发清空所需的气流速度。
