The usefulness of the method of sine wave oscillating pressure for measuring total respiratory flow resistance in human subjects and guinea pigs

Abstract

The validity and the applicability of a sine wave oscillation method for measuring total respiratory flow resistance (viscous resistance of chest lung system) are discussed with a series of experiments by using bodyplethysmograph in man and guinea pig.The principle of this method, which was introduced by DuBois and developed by Mead, is that the total respiratory flow resistance can be estimated by the bodyplethysmograph through which the sine wave pressure is imposed to the chest lung system to attain a resonant state (to get zero value of the reactance in the simulated electrical R-L-C circuit) by adjusting the frequency of the wave.The results obtained by using the bodyplethysmographs and the pressure imposing device which are designed by the author are as follows.1. The frequency of the sine wave oscillation with which the reactance of the chest lung system becomes zero, was found to be 7∼9c.p.s. in both man and guinea pig. And over 12c.p.s. the impedance of the system showed a steep rise.2. By analysing the flow and its imposed pressure curves, it was found that the total respiratory flow resistance showed continuous change according to a various stage of the flow curve.3. Used an artificial mouth piece resistor with known resistance of three kinds in man, the frequencies 7∼9c.p.s. also showed the most pertinent reproducibility, and the impedance was overestimated by the below or above frequencies of this range.4. In applying to the short term inhalation study of low concentration of sulfur dioxide (1.5∼2.0ppm) in man, this technique revealed rapid response and individual difference of the sensitivity of the total respiratory flow resistance after few seconds of the exposure.5. In long term exposure of guinea pigs to 0.1ppm of toluene diisocyanate vapor without any surgical treatment, the animals showed a repeated day to day response with different individual sensitivity, and when sodium chloride aerosols were added the response of the total respiratory flow resistance was affected in meaningful pattern.From the results above, it can be said that this procedure is a relevant and sensitive method to evaluate a behavior of the respiratory air way in both man and guinea pig particulary in short or long term study of various environmental toxic materials.