Development of new respirator using the Taylor dispersion effect

高频振荡是使用比死腔小的潮气量和高频率的人工呼吸方法。由于潮汐体积小，很难用对流输运来解释这种方法，因此泰勒弥散被认为是最重要的机制之一，即轴向对流和横向混合的相互作用。然而，泰勒色散如何在实际气道中对气体运输起作用并不明显。本研究的目的是研究泰勒色散的贡献，在高频振荡，以阐明气体传输现象的实验研究的速度分布和有效扩散系数的振荡流在气道模型。最后，设计了一种高效的高频振荡人工呼吸器。特别地，研究了侧向混合对轴向气体输运的影响，并指出侧向混合对轴向气体输运的影响取决于主导Taylor弥散的流动状态。首先，将气道模型修正为产生共振的直管模型。在共振频率附近的湍流的存在下，在轴向方向上的有效气体扩散率增强。其次，将气道模型修改为非对称和非对称分叉模型，模拟气道内分叉的平均几何形状。有效气体扩散率再次增加，由于二次流诱导的分叉网站。因此，利用增强气体扩散效应来开发高效的人工呼吸器。

High frequency oscillation is the artificial respiratory method using a smaller tidal volume than the dead space and high frequency. As this method can be hardly explained by convection transport because of the small tidal volume, Taylor dispersion is considered to be one of the most important mechanisms, that is an interaction between axial convection and lateral mixing. However, it is not obvious how Taylor dispersion plays a role for the gas transport in actual airways. The purpose of this study is to examine the contribution of Taylor dispersion during high-frequency oscillation to elucidate the gas transport phenomena with experimental investigation of velocity profiles and effective diffusivities in the oscillatory flow in the airway model. Finally we develop the design of efficient artificial respirator with high-frequency oscillation. Especially, the effect of lateral mixing on the axial gas transport is examined that is depend upon the flow state that dominates Taylor dispersion.Firstly, the airway model is modified to the straight pipe emerging the resonance. The effective gas diffusivity in the axial direction is enhanced with the presence of turbulence near the resonant frequency. Secondly, the airway model is modified to the asymmetrical and asymmetrical bifurcation modeling the averaged geometry of bifurcation in the airways. The effective gas diffusivity is again augmented due to the secondary flow induced in the bifurcation sites. Thus the augmented gas dispersion effect is utilized to develop the efficient artificial respirator.