Non-linear Effects in the Respiratory Impedance

  • Clara Mihaela Ionescu
Part of the Series in BioEngineering book series (SERBIOENG)


This chapter describes the non-linear effects in the respiratory signals and in the related measurement instrumentation during FOT tests. In order to do so, some improvements are brought to the classical FOT device and a mechanical, piston-based prototype FOT device is introduced. This prototype overcomes the limitations of the loudspeaker and allows generation of multisine signals below 4 Hz. The principle of sending detection lines in the frequency domain for characterizing odd and even non-linear contributions from a non-linear system are introduced to the reader as a theoretical basis for the further discussion of this chapter. Two detection methods are presented: a robust method based on multiple measurements and a fast method based on a single measurement. After having discussed the pitfalls of non-linear distortions from the measuring device itself, we discuss the non-linear contributions in the respiratory signals: pressure and flow. The non-linear effects are further quantified by means of a novel evaluation index. Then the variations in this novel index are analyzed in groups of asthma patients, COPD patients, and healthy volunteers. Finally, the link between the non-linear distortions and the lumped fractional order model parameters is introduced, thus completing the puzzle of this book.


Frequency Response Function Excitation Signal Breathing Frequency Prototype Device Feedforward Compensation 
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Copyright information

© Springer-Verlag London 2013

Authors and Affiliations

  • Clara Mihaela Ionescu
    • 1
  1. 1.Department of Electrical Energy, Systems and AutomationGhent UniversityGentBelgium

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