Measurement of Respiratory Input Impedance Using the Interrupter Technique – A Model Study

Respiratory input impedance contains information about the state of pulmonary mechanics in the frequency domain. In this paper the possibility of respiratory impedance measurement by interrupter technique as well as the accuracy of this approach are assessed. Transient states of flow and pressure recorded during expiratory flow interruption are simulated with a complex model for the respiratory system and then used to calculate the impedance. The results of computations are compared to the known impedance of the model, showing that the proposed algorithm yields satisfactory accuracy from 10 to 400 Hz, particularly in the range between 20 and 150 Hz.