title: Towards a theoretical understanding of stroke volume estimation with impedance cardiography.
abstract: In electrical impedance cardiography, Kubicek's formula is often used to measure stroke volume from thoracic impedance variations synchronously to heart activity. To calculate stroke volume from impedance variations, the so-called outflow problem should be adequately solved. This outflow problem refers to the joint causes of impedance change due to blood entering the aorta from the heart, as well as blood leaving the aorta due to arterial runoff. The aim of this study was to investigate the Kubicek formula as a solution of the outflow problem. Kubicek's formula was theoretically investigated using a simple model of the volume-conducting properties of the thorax (two-cylinder model), as well as the hemodynamics of the systemic circulation (three-element "windkessel" model). The mathematical analysis showed that the outflow problem was not solved by the Kubicek formula. Moreover, this theoretical result was experimentally confirmed.
authors.affiliation: Department of Clinical Physics and Informatics, University Hospital Vrije Universiteit, Amsterdam, The Netherlands.
authors.forename: T J
authors.initials: TJ
authors.lastname: Faes
authors.forename: E
authors.initials: E
authors.lastname: Raaijmakers
authors.forename: J H
authors.initials: JH
authors.lastname: Meijer
authors.forename: H G
authors.initials: HG
authors.lastname: Goovaerts
authors.forename: R M
authors.initials: RM
authors.lastname: Heethaar
mesh_terms: D000328:Adult; D002307:Cardiography, Impedance / Q000379:methods*; D017097:Electric Impedance; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D013318:Stroke Volume; D013909:Thorax; D014947:Wounds and Injuries / Q000503:physiopathology