Journal of Applied Physiology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

J Appl Physiol 71: 1025-1031, 1991;
8750-7587/91 $5.00
This Article
Right arrow Full Text (PDF)
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Cotton, R. B.
Right arrow Articles by Olsson, T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Cotton, R. B.
Right arrow Articles by Olsson, T.

Journal of Applied Physiology, Vol 71, Issue 3 1025-1031, Copyright © 1991 by American Physiological Society

ARTICLES

Origin of cardiac-related thoracic electrical impedance variations in lambs

R. B. Cotton, D. P. Lindstrom, H. W. Sundell, J. W. Hammon Jr, A. Silberberg and T. Olsson
Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.

Cardiac-related deflections in thoracic electrical impedance have been thought to correlate sufficiently well with cardiac stroke volume to be used as the basis for a noninvasive estimation of cardiac output. To determine more precisely the physiological origin of the impedance deflection (DZ), we regarded right ventricular stroke volume (SVa) as the sum of two components: 1) that part of SVa responsible for the transient increment in pulmonary blood volume within a cardiac cycle, SVa-v and 2) the remaining part of SVa, (SVa-SVa-v). SVa-v was measured in lambs by integration of the difference between pulmonary arterial and pulmonary venous flow. SVa and its components were varied experimentally by opening and closing an aorticocaval shunt or by inflating and deflating a cuff implanted around the pulmonary artery. DZ was measured using a tetrapolar disk electrode system. Multivariate linear regression analysis revealed that SVa-v had a significant positive effect on DZ, and, at the same time, (SVa-SVa-v) had a significant negative effect on DZ. In the pulmonary artery occluder model, the positive effect of SVa-v dominated the opposing negative effect of (SVa - SVa-v) so that the net effect of SVa on DZ was positive and significant. In the aorticocaval shunt model, these effects opposed each other to the extent that there was no significant correlation between SVa and DZ. These results shed new light on the physiological origin of DZ. They also demonstrate that use of DZ to measure acute changes in cardiac output may yield misleading results. Changes or the lack of changes in thoracic electrical impedance do not necessarily reflect cardiac output status.




HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Visit Other APS Journals Online