[Polyfrequent oscillometry measurement of airway resistance including the associated phase angle].

In 52 subjects aged between 28 and 80 years (healthy subjects, patients with obstructive and restrictive pulmonary disease), the airway resistance including the associated phase angle was investigated employing the forced oscillation technique at various frequencies (8, 12 and 16 Hz). Measurements were performed using a device manufactured by the firm of Custo, which makes possible the direct determination of oscillatory pressure and alternating flow at the mouth. With the aid of the phase angle, the airway resistance Rfo was calculated in approximation on the basis of the recorded impedance. As a reference unit, a body plethysmograph manufactured by the firm of Jaeger was employed. The short-term intra-individual variability of the oscillatory resistance measurements was, at 15%, within the fluctuation range of Rtot. The best agreement of Rfo and Rtot was achieved at 8 Hz (r = 0.83). With increasing frequency, the correlation decreased appreciably. Even in the presence of normal Rfo, negative phase angles indicated a disturbance of the mechanics of respiration. In comparison with the oscillatory resistance the determination with a bridge circuit, the reference values measured were compatible with those obtained with whole-body plethysmography. Direct measurement of Rfo and the associated phase angle, compares favourably with the reference tube technique in terms of the lack of complexity of the apparatus and a reduction in operator effort, and is thus a measuring system that is suitable for use in the doctor's office.