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Cerebral hypoperfusion modifies the respiratory chemoreflex during orthostatic stress.
MedLine Citation:
PMID:  23330653     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The respiratory chemoreflex is known to be modified during orthostatic stress though the underlying mechanisms remain to be established. To detremine the potential role of cerebral hypoperfusion, we examined the relationship between changes in middle cerebral artery mean blood velocity (MCA Vmean) and pulmonary ventilation (VE) from supine control to lower body negative pressure (LBNP, -45mmHg) at different carbon dioxide (CO2) levels (0, 3.5, 5% CO2). The regression line of the linear relationship between VE and end tidal CO2 (PETCO2) shifted leftwards during orthostatic stress without any change in sensitivity (1.36 ± 0.27 at supine to 1.06 ± 0.21 l/min/mmHg during LBNP; P=0.087). In contrast, the relationship between MCA Vmean-PETCO2 was not shifted by LBNP induced-changes in PETCO2. However, changes in VE from rest to LBNP were more related to changes in MCA Vmean than changes in PETCO2. These findings demonstrate for the first time that postural reductions in CBF modified the central respiratory chemoreflex by moving its operating point. An orthostatically induced-decrease in CBF likely attenuated the "washout" of CO2 level from the brain causing hyperpnea subsequent to activation of the central chemoreflex.
Authors:
Shigehiko Ogoh; Hidehiro Nakahara; Kazunobu Okazaki; Damian M Bailey; Tadayoshi Miyamoto
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-21
Journal Detail:
Title:  Clinical science (London, England : 1979)     Volume:  -     ISSN:  1470-8736     ISO Abbreviation:  Clin. Sci.     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-21     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7905731     Medline TA:  Clin Sci (Lond)     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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