Use of ventilator driven forced oscillations for characterizing human respiratory mechanics at low frequencies

Frequency domain and offline and online time domain techniques are compared to estimate respiratory mechanical properties using standard ventilator waveforms at low frequencies. Both methods are shown to yield consistent parameter estimates for a simple series RC model and pure sine wave input. However, they could not accurately predict frequency dependence of respiratory resistance from 0 to 1 Hz when using a step flow waveform. This behavior is traced to signal-to-noise limitations and nonlinearities