Parameter Estimation of Respiratory Impedance Measured by Forced Complex-wave Oscillations

Respiratory impedance data measured using the forced oscillation method were analyzed using an equivalent circuit model and the following conclusions were obtained: 1) Use of the complex wave oscillation method provided a measurement range of over 9 cmH_2O/1/s with a resolution of 0.13 cmH_2O/1/s.2) The respiratory system was expressed as a two-compartment model. By expressing the circuit characteristics as phasor loci, a method was shown whereby individual impedance parameter values could be derived from the measured impedance phasor loci. 3) Under enflurane anesthesia, the model parameter values were derived as R_1=1.2, R_2=1.6 cmH_2O/1/s, C_1=0.02, C_2=0.041/cmH_2O and L=0.065cmH_2O/1/s^2.