A new estimator to minimize the error due to breathing in the measurement of respiratory impedance

The authors present a novel respiratory impedance estimator to minimize the error due to breathing. Its practical reliability was evaluated in a simulation using realistic signals. These signals were generated by superimposing pressure and flow records obtained in two conditions: (1) when applying forced oscillation to a resistance-inertance-elastance (RIE) mechanical model; (2) when healthy subjects breathed through the unexcited forced oscillation generator. Impedances computed (4-32 Hz) from the simulated signals with the estimator resulted in a mean value which was scarcely biased by the added breathing (errors less than 1% in the mean R, I and E) and had a small variability (coefficients of variation of R, I, and E of 1.34, 3.5, and 9.6%, respectively). The results suggest that the proposed estimator reduces the error in measurement of respiratory impedance without appreciable extra computational cost.