Document Detail

The increased ventilatory response to exercise in pregnancy reflects alterations in the respiratory control systems ventilatory recruitment threshold for CO2.
MedLine Citation:
PMID:  20227527     Owner:  NLM     Status:  MEDLINE    
We tested the hypothesis that the magnitude of the pregnancy-induced increase in exercise hyperpnea is predictable based on the level at which Pa CO2 is regulated at rest. We performed a detailed retrospective analysis of previous data from 25 healthy young women who performed exercise and rebreathing tests in the third trimester (TM(3); 36.5+/-0.2 weeks gestation; mean+/-SEM) and again 20.4+/-1.7 weeks post-partum (PP). At rest, arterialized venous blood was obtained for the estimation of Pa CO2, [H(+)] and [HCO(3)(-)]; and serum progesterone ([P(4)]) and 17beta-estradiol ([E(2)]) concentrations. Duffin's modified hyperoxic rebreathing procedure was used to evaluate changes in central ventilatory chemoreflex control characteristics at rest. Breath-by-breath ventilatory and gas exchange variables were measured at rest and during symptom-limited incremental cycle exercise tests. At rest in TM(3) compared with PP: Pa CO2, [H(+)], [HCO(3)(-)] and the central chemoreflex ventilatory recruitment threshold for Pa CO2 (VRT CO2) decreased, while ventilation (V E), [P(4)], [E(2)] and central chemoreflex sensitivity (V ES) increased (all p<or=0.001). The slope of the linear relation between V E and V CO2 during exercise was significantly higher in TM(3) vs. PP (31.2+/-0.6 vs. 27.5+/-0.5, p<0.001). The magnitude of this change in the VE-V CO2 slope correlated significantly with concurrent reductions in each of the VRT CO2 (R(2)=0.619, p<0.001), Pa CO2 (R(2)=0.203, p=0.024) and [HCO(3)(-)] (R(2)=0.189, p=0.030); and was independent (p>0.05) of changes in [P(4)], [E(2)] and V ES. In conclusion, the increased ventilatory response to exercise in pregnancy can be explained, in large part, by reductions in the respiratory control system's resting Pa CO2 equilibrium point as manifest primarily by reductions in the VRT CO2.
Dennis Jensen; Katherine A Webb; Denis E O'Donnell
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-03-19
Journal Detail:
Title:  Respiratory physiology & neurobiology     Volume:  171     ISSN:  1878-1519     ISO Abbreviation:  Respir Physiol Neurobiol     Publication Date:  2010 Apr 
Date Detail:
Created Date:  2010-04-23     Completed Date:  2010-10-28     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101140022     Medline TA:  Respir Physiol Neurobiol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  75-82     Citation Subset:  IM    
Copyright Information:
(c) 2010 Elsevier B.V. All rights reserved.
Respiratory Investigation Unit, Department of Medicine, Queen's University c/o Kingston General Hospital, Kingston, Ontario, Canada.
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MeSH Terms
Carbon Dioxide / blood*
Estradiol / blood
Exercise / physiology*
Exercise Test / methods
Longitudinal Studies
Oxygen / blood
Pregnancy / physiology*
Pregnancy Trimester, Third
Progesterone / blood
Pulmonary Gas Exchange / physiology*
Pulmonary Ventilation / physiology*
Reflex / physiology*
Rest / physiology
Retrospective Studies
Time Factors
Reg. No./Substance:
124-38-9/Carbon Dioxide; 50-28-2/Estradiol; 57-83-0/Progesterone; 7782-44-7/Oxygen

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

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