Document Detail


Augmented hypoxic cerebral vasodilation in men during 5 days at 3,810 m altitude.
MedLine Citation:
PMID:  8926248     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The fractional increase in cerebral blood flow (CBF) velocity (VCBF) from the control value with 5-min steps of isocapnic hypoxia and hyperoxic hypercapnia was measured by transcranial Doppler in six sea-level native men before and during a 5-day sojourn at 3,810 m altitude to determine whether cerebral vasoreactivity to low arterial O2 saturation (SaO2) gradually increased [as does the hypoxic ventilatory response (HVR)] or diminished (adapted, in concert with known slow fall of CBF) at altitude. A control resting PCO2 value was chosen each day during preliminary hyperoxia to set ventilation at 140 ml.kg-1.min-1 for this and the parallel HVR study, attempting to establish control cerebrospinal fluid (CSF) and brain extracellular fluid pH values unaltered by acclimatization. The relationship of CBF to SaO2 was nonlinear, steepening at a lower SaO2. A hyperbolic equation was used to describe hypoxic cerebrovascular reactivity: fractional VCBF = x[60/ (SaO2-40)-1], where X is the fractional increase of VCBF at 70%.X rose from 0.346 +/- 0.104 (SD) at sea level to 0.463 +/- 0.084 on altitude day 5 (P < 0.05 by paired t-test, justified by the a priori experimental plan). For comparison with CO2 sensitivity, from these X values, we estimate the rise in CBF in response to a 1% fall in SaO2 at 80% to be 1.30% at sea level and 1.74% after 5 days at altitude. CBF sensitivity to increased end-tidal PCO2 rose from 4.01 +/- 0.62%/Torr at sea level to 5.12 +/- 0.79%/Torr on day 5 (P < 0.05), as expected, at the lower PCO2 due to the logarithmic relationship of PCO2 to CSF pH. This change was not significant after correction to log PCO2. We conclude that the cerebral vascular response to acute isocapnic hypoxia may increase during acclimatization at high altitude. The mechanism is unknown but is presumably unrelated to the parallel carotid chemosensitization that, in these subjects, increased the HVR by 60% in the same 5-day period from 0.91 +/- 0.38 to 1.46 +/- 0.59 l.min-1.% fall in SaO2-1).
Authors:
J B Jensen; B Sperling; J W Severinghaus; N A Lassen
Related Documents :
15453998 - Physiological basis for recommendations regarding exercise during pregnancy at high alt...
6311778 - Effect of prolonged exercise at altitude on the renin-aldosterone system.
11723998 - Operation everest iii (comex'97): the effect of simulated sever hypobaric hypoxia on li...
3555798 - Environmental considerations for exercise.
10679148 - Fertilizing potential of mouse spermatozoa cryopreserved in a medium containing whole e...
21922258 - Stimulated and voluntary fatiguing contractions of quadriceps femoris similarly disturb...
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  80     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  1996 Apr 
Date Detail:
Created Date:  1996-11-27     Completed Date:  1996-11-27     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:  1214-8     Citation Subset:  IM; S    
Affiliation:
Department of Clinical Physiology and Nuclear Medicine, Bispebjerg Hospital, Copenhagen, Denmark.
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Descriptor/Qualifier:
Adult
Aged
Altitude*
Anoxia / physiopathology*
Blood Flow Velocity / physiology*
Cerebrovascular Circulation / physiology*
Humans
Hypercapnia / physiopathology
Male
Middle Aged
Time Factors

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


Previous Document:  Cardiomyoplasty: degeneration of the assisting skeletal muscle.
Next Document:  Dietary fat modifies exercise-dependent glucose transport in skeletal muscle.