Characterization of Pulmonary Circulation during Mechanical Ventilation

本研究在假设肺除了具有Windkessel理论所解释的优点（通过脉动循环降低流动阻力）外，还具有抑制交流电中串联和并联共振等能量损失的功能，并将肺循环模拟到电路模型中进行。通过将离体灌注兔肺的肺动脉输入阻抗与六元灯模型拟合，考察肺循环的特征。因此，最大似然模型是Landes模型和Goldwyn-Watt模型的结合，该模型具有近端和外围段，对应于串联和并联谐振电路。推测循环是由近段的流量导联和外周段的压力导联控制的。研究了分析压力-体积曲线（pv曲线）的新方法。其基本理论是：我们可以从大数定律估计肺泡容积的频率分布服从正态分布。另一方面，考虑空心球（如肺）受外力时的连续性方程，在均匀压缩和可压缩情况下有两种解。那么，当条件为可压缩流体时，体积函数应显示为对数压力。因此，动态法测得的pv曲线肺泡容积分布必须用对数正态分布来解释。结果在对数正态分布的概率图纸上绘制容积与总肺活量的比值，识别出两条交叉的直线。这个交叉点是pv曲线的下拐点。本研究对这些进行了检验。

This study was performed by simulating pulmonary circulation to the electric circuit model on the hypothesis that a lung has the function to restrain an energy loss such as the series and the parallel resonance in the altemating current, in addition to the merit explained by Windkessel theory (decrease of the flow resistance by pulsatile circulation). A characterization of pulmonary circulation was examined by fitting the pulmonary arterial input impedance of the isolated perfusion rabbit lung to the six-element lamp model. As a result, the maximum likelihood model was the combination of Landes model and Goldwyn-Watt's model, which was provided with a proximal and a peripheral segment, corresponding to the series and the parallel resonance circuit. It was speculated that the circulation was controlled with flow lead in the proximal segment and with pressure lead in the peripheral segment.And, new method to analyze the pressure volume curve (PV-curve) was examined. The fundamentally theory is following: we can estimate that the frequency distribution of the volume of alveoli obeys a normal distribution from the law of large numbers. On the other hand, considering the equation of continuity in the hollow sphere receiving extemal force (as lung), there are two solves at the cases of the uniform compression and the compressible process. Then, the volume function should be revealed as logarithmic pressure when the condition is a compressible fluid. Therefore, the alveoli volume distribution of PV-curve measured by a dynamical method has to be explained in the logarithmic nomal distribution. As a result plotting the volume ratio to total lung capacity on the probability graph paper of logarithmic normal distribution, two crossed linear lines are recognized. And this crossing point is the lower inflection point (LIP) of the PV-curve. These were inspected by this study.