鼻腔抵抗測定の基礎的条件

トランスジーサーの性能と限界の問題

抄録

Various methods are employed to assess the patency of the nasal cavities. Nasal resistance is evaluated by simultaneous measurements of the air flow and the pressure difference between the nostrils and pharynx. These values are transformed into the electrical signals by transducers, amplified and recorded. However, we are often annoyed with problems arising during and after the measurement, such as a loop formation of the pressure-flow curve. The purpose of this paper is to evaluate the exact function of the apparatus including the transducers and to clarify the limitation in analyzing the recorded data.
Two solenoid valves were connected in parallel using Y tube to the constant negative pres-sure source. Rectangular waves were led through the solenoid valves which were alternatively opened by a manual switch. Sinusoidal waves were produced by a respirator (Harvard Ap-paratus) equipped with phototransistor signals at zero flow point. Four transducers and one hot wire flowmeter were checked by the above mentioned airflow system. Diameter and length of the conduit pipes to the transducers were also varied. The mean values of the stabilizing time, rise time and overshoot were calculated from the curves recorded 10 times in each ex-perimental condition when the rectangular waves were measured. The time lags were determined comparing the recorded curve with the phototransistor signal when the sinusoidal waves were measured. Curves of the flow measurement recorded by a penumotachometer and the transducers prominently lagged behind the actual rectangular phenomena. The time lag of the hot wire flowmeter was much smaller, but significant time lapse was also needed for stabilization. The time lag of the pressure transducer was shorter as compared with the flow transducers, but overshoots were noted especially in cases of long and thick conduit pipes. Stabilizing and rise times were voluntarily elongated by narrowing the pipes. The loop formation of the pressure-flow curves on an oscilloscope is at least in part attributed to the phase difference of the measur-ing system, since it is apparent from our observations that the flow signal considerably lags behind the pressure signal.
It is required for the experimenter to have a good knowledge on the function and efficiency of transducers, use them exactly according to the description, and analyze the data within the limitation of their function.