Document Detail


The influence of alternating current frequency on flow related admittance changes of blood: a concept for improvement of impedance cardiography.
MedLine Citation:
PMID:  7749358     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Impedance cardiography is based on admittance changes induced by volume changes of the intrathoracic blood vessels, but also by the longitudinal orientation of red blood cells induced by flow. An experiment was set up to separate these two phenomena and to study their frequency dependence. Admittance changes of flowing blood with variable haematocrit, of a saline solution and of plasma were measured in an in vitro set-up. Four different alternating current frequencies were used: 100 kHz, 5 MHz, 15 MHz and 20 MHz. The measured admittance appeared to be dependent on blood flow: when blood flow increased, admittance in the longitudinal direction increased. This increase was stronger for higher haematocrits, probably due to the longitudinal orientation of the blood cells. At higher frequencies, the orientation effect of the red cells became negligibly small. No frequency or flow dependent admittance change was detected when saline or plasma was used as the perfusate. It is concluded that the orientation effect can be neglected at high frequencies. Impedance cardiography in this range will give more reliable information about volume changes.
Authors:
P M de Vries; J W Langendijk; P M Kouw
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Physiological measurement     Volume:  16     ISSN:  0967-3334     ISO Abbreviation:  Physiol Meas     Publication Date:  1995 Feb 
Date Detail:
Created Date:  1995-06-22     Completed Date:  1995-06-22     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  9306921     Medline TA:  Physiol Meas     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  63-9     Citation Subset:  IM    
Affiliation:
Free University, Department of Internal Medicine, Amsterdam, The Netherlands.
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MeSH Terms
Descriptor/Qualifier:
Blood Flow Velocity / physiology*
Cardiography, Impedance*
Hematocrit
Humans
Research Design

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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