Respiratory system inertance: investigation in a physical inertance model

Abstract

For analysis of respiratory system mechanics the very complex structure of the respiratory system is strongly simplified to a simple resistance-compliance-model. While for most patients this simplification seems sufficient, in patients with pulmonary disease this model is inappropriate. Additionally, to regional inhomogeneity throughout the lung, large volume accelerations due to the strongly decreased respiratory system compliance together with a mass increase of the patients’ lungs, i.e. an increased respiratory system inertance ${\mathit{I}}_{\mathrm{rs}}$ , result in a significant inertive pressure contribution. The aim of this study was to develop a physical inertance model, and its description by conventional methods of respiratory monitoring. Its parameters are adjustable within the physiological range, with ${\mathit{I}}_{\mathrm{rs}}$ between 0.06 and 0.2 mbar·s²·l⁻¹. The model proved well with static and dynamic analysis of respiratory system parameters. Using our physical model it is possible to evaluate new methods of respiratory monitoring and to investigate experimentally the interrelationship of respiratory system parameters.