Document Detail

Cardiovascular and cerebrovascular responses to acute isocapnic and poikilocapnic hypoxia in humans.
MedLine Citation:
PMID:  18263856     Owner:  NLM     Status:  MEDLINE    
We examined the cardiovascular and cerebrovascular responses to acute isocapnic (IH) and poikilocapnic hypoxia (PH) in 10 men (25.7 +/- 4.2 yr, mean +/- SD). Heart rate (HR), mean arterial pressure (MAP), and mean peak middle cerebral artery blood flow velocity (Vp) were measured continuously during two randomized protocols of 20 min of step IH and PH (45 Torr). HR was elevated during both IH (P < 0.01) and PH (P < 0.01), with no differences observed between conditions. MAP was modestly elevated across all time points during IH but only became elevated after 5 min during PH. During IH, Vp was elevated from baseline throughout the exposure with a consistent hypoxic sensitivity of approximately 0.34 cm x s(-1).%desaturation(-1) (P < 0.05). The Vp response to PH was biphasic with an initial decrease from baseline occurring at 79 +/- 23 s, followed by a subsequent elevation, becoming equivalent to the IH response by 10 min. The nadir of the PH response exhibited a hypoxic sensitivity of -0.24 cm x s(-1) x % desaturation(-1). When expressed in relation to end-tidal Pco2, a sensitivity of -1.08 cm x s(-1).Torr(-1) was calculated, similar to previously reported sensitivities to euoxic hypocapnia. Cerebrovascular resistance (CVR) was not changed during IH. During PH, an initial increase in CVR was observed. However, CVR returned to baseline by 20 min of PH. These data show the cerebrovascular response to PH consists of an early hypocapnia-mediated response, followed by a secondary increase, mediated predominantly by hypoxia.
Craig D Steinback; Marc J Poulin
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Publication Detail:
Type:  Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't     Date:  2007-11-29
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  104     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2008 Feb 
Date Detail:
Created Date:  2008-02-11     Completed Date:  2008-04-04     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  482-9     Citation Subset:  IM    
Dept. of Physiology and Biophysics, Faculty of Medicine, Univ. of Calgary, HMRB-212, 3330 Hospital Dr., NW, Calgary, Alberta, Canada T2N 4N1.
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MeSH Terms
Alkalosis, Respiratory / physiopathology
Anoxia / physiopathology*
Blood Flow Velocity
Blood Pressure
Cerebrovascular Circulation*
Heart Rate
Hypocapnia / physiopathology*
Middle Cerebral Artery / physiopathology*
Pulmonary Ventilation
Time Factors
Vascular Resistance

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

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