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01-11-2009 | Original Article

Identification of the human electrical impedance indifferent point: a surrogate for the volume indifferent point?

Authors: Sara S. Jarvis, James A. Pawelczyk

Published in: European Journal of Applied Physiology | Issue 4/2009

Abstract

Head-up tilt (HUT) redistributes ~700 mL of blood to the dependent regions. In a gravitational field, hydrostatic pressure is balanced against vascular compliance, resulting in a hydrostatic indifferent point (HIP) whose location should be coincident with an indifferent point for volume (VIP). Cardiac filling is determined by the hydrostatic gradient between the HIP/VIP and right atrium. We employed segmental impedance to examine blood volume redistribution during HUT and estimate the location of the VIP. During HUT, impedance increased in the chest and decreased in the lower abdomen, presumably due to blood volume shifts. Using a non-linear model to relate blood volume shifts to the hydrostatic gradient, we estimated the location of the electrical impedance indifferent point between the xyphoid process and iliac crest, at 64.5 ± 2.6% of an individual’s height. This method may provide a quantitative framework to assess the effects of blood volume distribution on tilt tolerance.

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Title: Identification of the human electrical impedance indifferent point: a surrogate for the volume indifferent point?
Authors: Sara S. Jarvis
James A. Pawelczyk
Publication date: 01-11-2009
Publisher: Springer-Verlag
Published in: European Journal of Applied Physiology / Issue 4/2009
Print ISSN: 1439-6319
Electronic ISSN: 1439-6327
DOI: https://doi.org/10.1007/s00421-009-1148-9

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Identification of the human electrical impedance indifferent point: a surrogate for the volume indifferent point?

Abstract

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