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

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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