title: Correlation between alveolar ventilation and electrical properties of lung parenchyma.
abstract: One key problem in modern medical imaging is linking measured data and actual physiological quantities. In this article we derive such a link between the electrical bioimpedance of lung parenchyma, which can be measured by electrical impedance tomography (EIT), and the magnitude of regional ventilation, a key to understanding lung mechanics and developing novel protective ventilation strategies. Two rat-derived three-dimensional alveolar microstructures obtained from synchrotron-based x-ray tomography are each exposed to a constant potential difference for different states of ventilation in a finite element simulation. While the alveolar wall volume remains constant during stretch, the enclosed air volume varies, similar to the lung volume during ventilation. The enclosed air, serving as insulator in the alveolar ensemble, determines the resulting current and accordingly local tissue bioimpedance. From this we can derive a relationship between lung tissue bioimpedance and regional alveolar ventilation. The derived relationship shows a linear dependence between air content and tissue impedance and matches clinical data determined from a ventilated patient at the bedside.
authors.affiliation: Institute for Computational Mechanics, Technische Universität München, Boltzmannstrasse 15, D-85748 Garching b. München, Germany.
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Roth
authors.forename: Andreas
authors.initials: A
authors.lastname: Ehrl
authors.forename: Tobias
authors.initials: T
authors.lastname: Becher
authors.forename: Inéz
authors.initials: I
authors.lastname: Frerichs
authors.forename: Johannes C
authors.initials: JC
authors.lastname: Schittny
authors.forename: Norbert
authors.initials: N
authors.lastname: Weiler
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Wall
mesh_terms: D000818:Animals; D017097:Electric Impedance; D020342:Finite Element Analysis; D011650:Pulmonary Alveoli / Q000166:cytology* / Q000502:physiology*; D012123:Pulmonary Ventilation; D051381:Rats; D014054:Tomography