Respiratory gaseous flow measurement is one of an unsteady gas flow measurement and becoming very important. It has a wide field of application, for example, a measurement of lung function, an evaluation of respiratory gas exchange, a grasp of medical condition and so on. Especially, the evaluation of the absolute quantity and the analysis of the breathing waveform pattern are very important in the respiratory gaseous flow measurement. However, the dynamic characteristics of the respiratory gaseous flow meter has not been quantitatively measured and evaluated in the actual unsteady flows. There is substantial literature dealing with the measurement of unsteady gas flow. Most of these studies generated unsteady mass flows by using piston cylinders. Clearly, in these studies, substantial efforts must have been required in order to minimize the sensitivity dependence of density fluctuation on pressure and temperature variations. On the other hand, the dynamic characteristic evaluation of the gaseous flow meter which reproduced the sinusoidal waveform with only a single frequency component in the measurement frequency band was typically enough. However, the respiratory airflow waveform with the various frequency components and the shapes is complicated. Moreover, we already know that the respiratory waveform pattern changes by a state of health and activities. To solve these problems, this paper deals with the development of unsteady gas flow generator for the various breathing waveform reproduction. At first, we carry out the survey on the respiratory gaseous flow. Based on the research background and the above mentioned survey, we develop and introduce the unsteady gas flow generator which can generate the various respiratory flows. And we show the effectiveness of the developed unsteady gas flow generator. Moreover, we conduct the performance evaluation of the developed unsteady gas flow generator and the uncertainty analysis.

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