[Oscillation method in respiratory function diagnosis of adults--integration and optimizing possibilities. 3. The phase angle].

The importance of the phase angle in oscillatory measurements of resistance depends on the presence or absence of an endobronchial obstruction. In case there is an obstruction, a negative phase angle is first of all an expression of the low compliance of the larger airways and points to an underestimation of the real flow resistance. If there is no obstruction one can state facts about the peripheral compliance, in particular taking into consideration the dependence of the phase signal on actual lung volume. It is recommended to supply the basic ventilation tests with an additional determination of a second angle (beta) from the inspiratory part of the psi/V-curve. That allows to separate normal persons and patients with lung fibrosis and emphysema.