Identification and assessment of constrictions in a branched tube system

This paper focuses on developing an analytical methodology, based on the frequency spectrum of the input acoustic impedance, to identify and assess the location and severity of constrictions in a branched-treelike tube system. The method is applied to two models, one is for the trachea with the first-generation asymmetric bronchi and the other is for the trachea with two-generation bronchi. To develop the methodology, a different size constriction is introduced at various locations along the branches and resonant frequencies are analyzed. Correlation is performed between the resonant frequencies and the location and size of these constrictions. For the two models, charts are generated which can be used to determine the location and size of a constriction just by observing the trend of various resonances. For the first model it is shown that in the frequency range of 1–4000 Hz the third and sixth resonances reflect constriction occurrence in the larger branch and the fourth and seventh reflect constriction in the smaller branch. However, for the second model it is indicated that constriction is reflected: in first branch by the sixth resonance, in the second branch by the seventh resonance, and in the third branch by the ninth resonance.