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
Sinusoidal forcing at frequencies up to 17 cycles/sec was applied to the anesthetized, apneic dog by a body respirator. Forcing pressure and volume displacement were displayed in quadrature on an oscilloscope and planimetric integration of these loops indicated an increase in energy dissipated by total respiratory resistance per liter of air displaced, due to turbulence and changing airway geometry, with increasing frequency. Nonlinear resistance was calculated and the differential coefficient, dP/dV (dynamic resistance), was determined at 10° intervals throughout the respiratory cycle, at each of three frequencies in four dogs. Total respiratory resistance is a “nonohmic” dependent variable and changes progressively throughout the cycle. Submitted on October 20, 1961
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