AN ALTERNATIVE METHOD FOR MEASURING HUMAN RESPIRATORY IMPEDANCE

The Forced Oscillation Technique (FOT) denotes a non-invasive lima function test which serves as a medical diagnostic tool to measure human respiratory impedance. The FOT principle is based on superimposing air pressure oscillations onto the normal breathing waves of the subject, measuring both air flow and an pressure at the mouth and analyzing the data with signal processing techniques which apply to linear systems. The motivation to eliminate the need for flow measurement arises from i) economic reasons, because measurement of an flow in this case requires the presence of an expensive component, the pneumotachograph, in the FOT device and innovative aspects, The present work assessed the possibility that the requirement to measure flow could be eliminated if the transformation from excitation signal to measured pressure in the FOT device (given by the internal impedances of the device) is known. This conceptual solution was theoretically proven by analyzing the electrical circuit which models these transformations. Measurements were conceived and performed in order to estimate these quantities.