Experimental analysis of fundamental mechanism of High Frequency Oscillatory Ventilation (HFOV) in micro-scale bronchial model

本研究的目的是对高频振荡通气（High Frequency oscillation Ventilation， HFOV）的呼吸机制进行实验分析，并评价其作为一种有效的临床人工呼吸方法。在本实验中，研究了呼吸支气管模型中微尺度振荡气流的详细结构。由于高频通气，HFOV手术从气管到肺泡的全肺通气或气体交换机制与正常呼吸时不同。高频通风产生复杂的振荡流动现象，包括流化、泰勒扩散、不同时间常数的异相效应等。对这些影响的分析有助于优化HFOV的临床条件。本研究的结果如下：(1)设计并制作了具有真实尺寸的微尺度呼吸支气管单分支和多分支模型。采用HFOV驱动产生了更多的通气气流。利用微型piv系统对HFOV驱动模型中振荡呼吸气流进行了定量流场分析，明确了母管和子管吸气和呼气阶段速度分布的发展过程。(2)随着呼吸频率的增加，理论上预测了两个子管之间以不同顺应性终止的钟摆流动的非同步流动。在本研究中，通过对呼吸支气管微通道模式下振荡气流的时间序列测量，定量验证了HFOV操作情况下特定气流的存在性。(3)研究了包括肺泡在内的肺端区呼吸流动数值模拟的实际条件。(4)采用水力类比的方法研究了高视场条件下气体交换中边界层振荡行为的非定常效应。少

The objective of the research is experimental analysis of respiration mechanism of HFOV (High Frequency Oscillatory Ventilation) which is evaluated as an efficient clinical method of artificial respiration. In this experiment, detailed structure of micro-scale oscillatory air flow in a model of respiratory bronchial has been investigated.The ventilation or gas exchange mechanism in whole lungs from trachea to alveoli by HFOV operation is different from it in the case of normal breathing because of very high frequency ventilation. The high frequency ventilation generates complicated oscillatory flow phenomena with streaming, Taylor's diffusion, out-of-phase effect by different time constant and so on. The analysis of these effects is useful to optimize the clinical condition of HFOV. The results obtained in this research are as follows.(1) Micro-scale single- and multi-bifurcation models of respiratory bronchial with real dimensions have been designed and manufactured. The respiratory v … More entilation air flows in the models were generated by using HFOV driver. The quantitative flow field analysis of oscillatory respiration air flow in the models functioned by HFOV driver has been experimentally carried out by using micro-PIV system, and the development process of velocity profiles in inspiration and expiration phases in parent tube and daughter tubes has been clarified.(2) With the increase in respiration frequency, the appearance of asynchronous flow as pendelluft flow between both daughter tubes terminated with different compliance had been predicted theoretically. In this research, the existence of the particular flow in the case of HFOV operation has been verified quantitatively by time series measurement of oscillatory air flow in micro channel mode of respiration bronchial.(3) Practical conditions for numerical simulation of respiration flow in end zone of lungs include alveoli have been investigated.(4) The unsteadiness effect of oscillatory boundary layer behavior in gas exchange in the case of HFOV operation has been investigated experimental]y by hydraulic analogy. Less