[Use of multi-frequency oscillation method in the respiratory mechanics perimeter diagnosis]

Oscillatory resistance Rrs and reactance Xrs curves were measured in the frequency range 4-25 Hz at FRC-level and at the course of vital capacity manoeuvres. The 55 subjects investigated were separated into the three groups healthy subjects and patients with restrictive and obstructive lung diseases by means of the parameters airway resistance Raw and lung compliance CL estimated by body-plethysmography and esophageal pressure technique, respectively. In accordance with the Raw- and CL-values in each group the parameters Rrs and Xrs demonstrate at FRC-level a different frequency dependent behaviour. An enhancement of Raw in patients with COLD causes a drop of Rrs(f) and a displacement of the whole Xrs-curve into the negative direction. Conversely, the reduction of CL in patients with fibrosis leads to a significant decrease of Xrs-values at lower frequencies without marked changes in the Rrs-curves. An additional enhancement of Raw and a further reduction of CL can be induced by decrease and increase of lung volume VL in comparison with the FRC-level. These alterations can be detected also in the frequency dependent shape of the Rrs- and Xrs-curves. Because of this inverse influence of VL on Raw and CL the diagnostic differentiation between patients with mild obstructive and restrictive lung diseases can be improved by a simultaneous evaluation of the volume and frequency dependence of oscillatory parameters.