Journal of Applied Physiology AJP: Renal Physiology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
QUICK SEARCH:   [advanced]


     

J Appl Physiol (February 24, 2005). doi:10.1152/japplphysiol.01248.2004
This Article
Right arrow Full Text (PDF) Free
Right arrow All Versions of this Article:
99/1/64    most recent
01248.2004v1
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 HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Steinback, C. D.
Right arrow Articles by Shoemaker, J. K.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Steinback, C. D.
Right arrow Articles by Shoemaker, J. K.
Submitted on November 5, 2004
Accepted on February 22, 2005

Carotid Distensibility, Baroreflex Sensitivity and Orthostatic Stress

Craig D. Steinback1, Deborah D. O'Leary2, Jason Bakker1, Angela D. Cechetto1, Hanif M. Ladak3, and J. Kevin Shoemaker4*

1 School of Kinesiology, The University of Western Ontario, London, Ontario, Canada
2 Department of Community Health Sciences, Brock University, St. Catharines, Ontario, Canada
3 Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada; Department of Electrical & Computer Engineering, The University of Western Ontario, London, Ontario, Canada; Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada
4 School of Kinesiology, The University of Western Ontario, London, Ontario, Canada; Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada

* To whom correspondence should be addressed. E-mail: kshoemak{at}uwo.ca.

In this study we tested the hypothesis that carotid arteries undergo rapid changes in distensibility on moving from the supine to head-up tilt (HUT) postures, and subsequently, that this change in cDa might be associated with concurrent reductions in cardiovagal baroreflex sensitivity (BRS). Thus, the effect of posture on carotid vascular mechanics and cardiovagal BRS with consideration for altered central hemodynamics (i.e. stroke volume (SV; Doppler ultrasound), was examined. Carotid pulse pressure (cPP; Millar transducer) and contra lateral B-mode ultrasound images were assessed at the carotid artery during supine and 60° HUT postures. From these measures, carotid distensibility (cDa) was calculated at 5 mmHg pressure increments experienced during the cardiac cycle (n=6). Carotid PP (n=9) was not different in the two postures. A smaller SV being ejected into a smaller carotid artery in HUT explained the maintenance of cPP in HUT. Also, compared with Supine, cDa was reset to a lower level in HUT (main effect of posture; P<0.05). Cardiovagal BRS (sequence method) was diminished in HUT versus Supine (P<0.05). A positive correlation was observed between the tilt-induced changes in maximal cDa (in early systole) and cardiovagal BRS (r2 = 0.75; P<0.05) but there was little predictive relationship between changes in carotid PP, systolic vessel dimensions, or average cDa and the corresponding change in BRS. The current results indicate that HUT elicits rapid changes in carotid artery mechanics and further suggest that reductions in the maximal cDa measured in early systole contribute to reduced cardiovagal BRS with HUT.




This article has been cited by other articles:


Home page
 Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
D. A. Salzer, P. J. Medeiros, R. Craen, and J. K. Shoemaker
Neurogenic-nitric oxide interactions affecting brachial artery mechanics in humans: roles of vessel distensibility vs. diameter
Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2008; 295(4): R1181 - R1187.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
Visit Other APS Journals Online
Copyright © 1948 by the American Physiological Society.