Maksym G N, Bates J H
Department of Biomedical Engineering, McGill University, Montréal, Québec, Canada.
Ann Biomed Eng. 1997 Nov-Dec;25(6):1000-8.
The quasistatic and dynamic pressure volume characteristics of the lungs were measured in five anesthetized, paralyzed open-chest rats. Psuedo-random volume perturbations over a frequency range of 0.25 to 25 Hz and having peak-peak amplitudes of 1 to 4 ml were applied after the lungs were allowed to expire against 0.2, 0.4, 0.6, and 0.8 kPa positive end-expiratory pressure (PEEP). The lung mechanics were partitioned in two ways: a linear dynamic block followed by a static nonlinearity (Wiener model) and a static nonlinearity ahead of a linear dynamic block (Hammerstein model). It was found that a Hammerstein model featuring a third-order polynomial static nonlinearity and a linear impulse response function of 1-sec duration accounted for the greatest amount of the output variance (98.8 +/- 0.6%, mean +/- SD from perturbations of 4 ml amplitude and PEEP = 0.8 kPa). The static nonlinear behavior matched the measured quasistatic pressure volume behavior obtained at the same amplitude and at the same level of PEEP, provided that all direct current gain of the model was located within the static nonlinearity. Under these conditions, the linear resistance was inversely dependent on the PEEP, whereas little PEEP or amplitude dependence of the linear compartment elastance was observed. Thus, of the two block-structured models tested, the Hammerstein model accounted better for the large amplitude nonlinear mechanical behavior. However, neither model could account for the dependence of the linear block resistance on PEEP.
在五只麻醉、麻痹且开胸的大鼠身上测量了肺的准静态和动态压力-容积特性。在肺以0.2、0.4、0.6和0.8 kPa呼气末正压（PEEP）呼气后，施加频率范围为0.25至25 Hz、峰峰值幅度为1至4 ml的伪随机容积扰动。肺力学以两种方式进行划分：一个线性动态模块后接一个静态非线性模块（维纳模型），以及一个静态非线性模块在前、线性动态模块在后（哈默斯坦模型）。结果发现，一个具有三阶多项式静态非线性和1秒持续时间线性脉冲响应函数的哈默斯坦模型解释了最大比例的输出方差（98.8±0.6%，来自幅度为4 ml且PEEP = 0.8 kPa扰动的均值±标准差）。如果模型的所有直流增益都位于静态非线性模块内，那么静态非线性行为与在相同幅度和相同PEEP水平下测得的准静态压力-容积行为相匹配。在这些条件下，线性阻力与PEEP成反比，而线性腔室弹性对PEEP或幅度的依赖性很小。因此，在测试的两种块结构模型中，哈默斯坦模型能更好地解释大幅度非线性力学行为。然而，两种模型都无法解释线性模块阻力对PEEP的依赖性。
