Comparison of two forced oscillation techniques.

The forced oscillation technique developed by Korn et al. in 1979 (Siregnost FD 5) overestimates the measured resistances by about 20% in the range of resistance values met in healthy subjects and in patients. This is due to an overestimation of the impedance of the side tubing used for calibration. In addition, the device that we investigated introduces a phase shift of 9 degrees between pressure and flow.