抄録
A fluidic respirator with on moving parts has several merits as follows.
1) The pressure of the oscillation at trachea are invariable when the compliance of lung varied.
2) The ratio of durations exhalation to inhalation is kept constant when the gas pressure and the compliance of lung are varied, so the inspirated gas volume is determined solely by the gas pressure supplied.
3) The voluntary breathings are not obstructed by the respirator.
4) No power sources are necessary, except gas sources O2 and N2O.
5) The weight is light and easy to deal with.
In addition, the effects of a lenitive for the tension of muscles can be observed by the change of frequency, because the frequency is changed by the compliance of lung. The demerit is to lose more than a half of gases supplied directly into the room air.
An asymmetric pattern of bistable device is chosen by the model lung experiments with reference to the matching of the minimum pressure in oscillation. By assuming a linearized relation of output pressure and flow in a fluidic device, a theoretical equation in the duration of inhalation is obtained. The relation between prssure and flow during exhalation is obtained by Bernoulli's equation referring to negative pressure made by the effect of jet entrainment. As the results, the frequency is proportional to A0/C√Ps, and the time ratio of exhalation to inhalation is proportional to l/√A0. These are obtained theoretically, where A0: cross sectional area of output chunnel in a fluidic device, C: compliance of lung, Ps: gas supply pressure to the respirator. Experimental results of the basic tests on model lung and the clinical tests are demonstrated, and the theoretical evaluations are made valid.
