Gavriely N, Shee T R, Cugell D W, Grotberg J B
Department of Physiology and Biophysics, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa.
J Appl Physiol (1985). 1989 May;66(5):2251-61. doi: 10.1152/jappl.1989.66.5.2251.
We studied flutter in collapsible tubes as a possible mechanism for the generation of respiratory wheezes. The pressure-flow relationships and the wall oscillations of thick-walled [wall thickness (h)-to-lumen radius (r) ratio 1:1.7 to 1.3] self-supporting latex and Silastic tubes mounted between rigid pipes were measured. A high-impedance vacuum pump was connected to the downstream end. Upstream and downstream valves were used to control corresponding resistances. We found loud honking sounds and tube wall oscillations that occurred only when the tubes were buckled and flow limiting, i.e., when the flow became constant and independent of downstream driving pressure. The overall range of oscillatory frequencies was 260-750 Hz for airflow, presenting as sharp peaks of power on the frequency spectrum. The oscillatory frequencies (f) were higher at higher fluid velocities (u) and with narrower distance between opposing flattened walls (2b), resulting from increasing downstream suction pressure and the transmural pressure becoming more negative. The effect of u and b on f for a latex tube (h-to-r ratio 1:1.7) were found to be f = 228 + 0.021 (u/b). These relationships were valid throughout the range of oscillations in this tube (283-720 Hz) and with flow rates of 12-64 l/min. The experimental data were compared with predictions of the fluid dynamic flutter theory and the vortex-induced wall vibrations mechanism. We conclude that viscid flutter in soft tubes is the more probable mechanism for the generation of oscillations in the soft tube model and is a possible mechanism for the generation of respiratory wheezes.
我们研究了可塌陷管中的颤振，将其作为产生呼吸性哮鸣音的一种可能机制。测量了安装在刚性管之间的厚壁（壁厚（h）与管腔半径（r）之比为1:1.7至1.3）自支撑乳胶管和硅橡胶管的压力-流量关系及管壁振荡。一个高阻抗真空泵连接到下游端。上游和下游阀门用于控制相应的阻力。我们发现只有当管子发生弯曲且流量受限，即当流量变得恒定且与下游驱动压力无关时，才会出现响亮的喇叭声和管壁振荡。气流振荡频率的总体范围为260 - 750 Hz，在频谱上呈现为尖锐的功率峰值。在较高的流体速度（u）以及相对扁平壁之间的距离（2b）更窄时，振荡频率（f）更高，这是由于下游吸力压力增加以及跨壁压力变得更负所致。对于乳胶管（h与r之比为1:1.7），发现u和b对f的影响为f = 228 + 0.021（u/b）。这些关系在该管的整个振荡范围内（283 - 720 Hz）以及流速为12 - 64 l/min时都是有效的。将实验数据与流体动力学颤振理论和涡激壁振动机制的预测进行了比较。我们得出结论，软质管中的粘性颤振是软质管模型中产生振荡的更可能机制，并且是产生呼吸性哮鸣音的一种可能机制。
