Document Detail


Comparison of the end-tidal arterial PCO2 gradient during exercise in normal subjects and in patients with severe COPD.
MedLine Citation:
PMID:  7750309     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We undertook the present study with the following objectives: (1) to compare the difference between the end-tidal and the arterial carbondioxide concentration (P[ETa] CO2) gradients at rest and during exercise in normal subjects and patients with COPD; and (2) to analyze the factors contributing to this gradient. We studied seven normal subjects and seven patients with COPD using a symptom-limited exercise test on a cycle ergometer. Our results show that the P(ET-a)CO2 increased progressively as the individuals went from rest to higher workloads in both the normal group and in the COPD group. The P(ET-a)CO2 in patients with COPD both at rest (-3.24 +/- 2.78 mm Hg) and during exercise (1.03 +/- 2.23 mm Hg) is significantly lower than that in normal individuals at rest (1.84 +/- 3.68 mm Hg) and during exercise (10.3 +/- 6.5 mm Hg) (p < 0.01). However, the slope for the relationship between the P(ET-a)CO2 and the workload is actually significantly steeper in the patients with COPD. Although the P(ET-a)CO2 correlated significantly with the workload in both normal subjects (r = 0.63, p < 0.001) and patients (r = 0.55, p < 0.005), the P(ET-a)CO2 was much more closely correlated with the ratio of dead space to tidal volume (VD/VT) (r values of -0.86 and -0.77, respectively). Moreover, when multiple regression analysis was performed, addition of any other physiologic measure (eg, oxygen consumption [VO2], carbon dioxide production [VCO2], minute ventilation [VE], or workload) as a second independent variable after the VD/VT did not improve the correlation. This indicates that the correlation between the P(ET-a)CO2 and the workload is probably related to the dependence of the VD/VT on the workload. The PaCO2 in normal subjects and in the COPD group correlated significantly with the partial pressure of end-tidal carbon dioxide (PETCO2). Using multiple regression analysis, with the PaCO2 as the dependent variable and the PETCO2 (along with other physiologic measures) as the independent variables, we found that the standard error of the estimate was still above 2.1 mm Hg in normal subjects and in patients with COPD. We conclude that (1) during exercise, the P(ET-a)CO2 in normal subjects and in patients with COPD increases significantly, (2) the P(ET-a)CO2 gradient is more closely correlated with the VD/VT than any other physiologic variable, and (3) changes in the PETCO2 during exercise are not correlated closely with changes in the PaCO2.
Authors:
Z Liu; F Vargas; D Stansbury; S A Sasse; R W Light
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Chest     Volume:  107     ISSN:  0012-3692     ISO Abbreviation:  Chest     Publication Date:  1995 May 
Date Detail:
Created Date:  1995-06-19     Completed Date:  1995-06-19     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  0231335     Medline TA:  Chest     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1218-24     Citation Subset:  AIM; IM    
Affiliation:
Department of Medicine, Veterans Affairs Medical Center, Long Beach, CA 90822, USA.
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MeSH Terms
Descriptor/Qualifier:
Adult
Arteries / physiology
Carbon Dioxide / blood*
Case-Control Studies
Exercise / physiology*
Humans
Lung Diseases, Obstructive / blood,  physiopathology*
Male
Middle Aged
Regression Analysis
Tidal Volume
Chemical
Reg. No./Substance:
124-38-9/Carbon Dioxide
Comments/Corrections
Comment In:
Chest. 1996 Sep;110(3):865-6   [PMID:  8797451 ]

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


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