Laboratory of Experimental Pneumology, IDIBELL, L’Hospitalet, Barcelona, Spain.
J Appl Physiol (1985). 2011 Mar;110(3):653-60. doi: 10.1152/japplphysiol.01115.2010. Epub 2010 Dec 16.
Lung tissue presents substantial nonlinear phenomena not accounted for by linear models; however, nonlinear approaches are less available. Our aim was to characterize the behavior of total harmonic distortion, an index of nonlinearity, in lung tissue strips under sinusoidal deformation at a single frequency as a function of strain amplitude and operational stress. To that end, lung parenchymal strips from healthy rats (n = 6) were subjected to sinusoidal deformation (1 Hz) at different strain amplitudes (Δε = 4, 8, 12, 16, and 20%) and operating stresses (σ(op) = 6, 8, 10, 12, 14, and 16 hPa). Additional rats (n = 9) were intratracheally instilled with saline or bleomycin (2.5 U/kg, 3 times 1 wk apart), killed 28 days after the last instillation, and their lung tissue strips were studied at 5 and 10 hPa σ(op) and 5% Δε. In both cases, harmonic distortion (HD%) of input (strain) and output (stress) signals were determined. In healthy strips, HD% increased linearly with Δε, stress amplitude, and minimum stress by cycle variations, but showed no significant change with σ(op) levels. A prediction model could be determined as a function of operational stress and stress amplitude. Harmonic distortion was significantly increased in bleomycin-treated strips compared with controls and showed positive correlation with E behavior in both normal and diseased strips. We concluded that HD% can be useful as a single and simple parameter of lung tissue nonlinearity.
肺组织表现出大量线性模型无法解释的非线性现象；然而，非线性方法的应用较少。我们的目的是描述总谐波失真（一种非线性指数）在单个频率下正弦变形时的行为，作为应变幅度和操作应力的函数。为此，我们对来自健康大鼠的肺实质条带（n=6）进行了正弦变形（1 Hz），应变幅度（Δε=4、8、12、16 和 20%）和操作应力（σ（op）=6、8、10、12、14 和 16 hPa）不同。另外 9 只大鼠（n=9）经气管内滴注生理盐水或博来霉素（2.5 U/kg，3 次，间隔 1 周），最后一次滴注后 28 天处死，研究其肺组织条带在 5 和 10 hPa σ（op）和 5%Δε时的情况。在这两种情况下，均测定输入（应变）和输出（应力）信号的谐波失真（HD%）。在健康的条带中，HD%随Δε、应力幅度和最小应力的周期性变化呈线性增加，但与σ（op）水平无显著变化。可以确定一个作为操作应力和应力幅度函数的预测模型。与对照组相比，博来霉素处理的条带中的谐波失真显著增加，并且在正常和患病条带中都与 E 行为呈正相关。我们得出结论，HD%可用作肺组织非线性的单一简单参数。
