Respiratory impedance and volume flow at high frequency in dogs

Abstract
Sinusoidal forcing at frequencies up to 11 cycle/sec was applied to the anesthetized, apneic dog in a body respirator. Using an oscilloscope and the Lissajous patterns displayed by the simultaneous recording of driving pressure and volume flow, the frequency (resonant; mean, 5.4 cycle/sec) at which there was zero phase shift was determined. By analogy with an inductance-resistance-capacitance network, inertance (mean, .041 cm H2O/liter/sec2) was derived from static compliance (mean, .022 liter/cm H2O) and resonant frequency. Impedance at each frequency and damping ratio (mean, 1.57) was calculated. Tissue resistance was found to be 19% of the total resistance (mean, 4.3 cm H2O/liter/sec). A nomogram was constructed to facilitate the determination of inertance and the coding of data as electrical analogues. Submitted on September 16, 1960

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