Document Detail

Corrected end-tidal P(CO(2)) accurately estimates Pa(CO(2)) at rest and during exercise in morbidly obese adults.
MedLine Citation:
PMID:  22878275     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Obesity affects lung function and gas exchange and imposes mechanical ventilatory limitations during exercise that could disrupt the predictability of Pa(CO(2)) from end-tidal P(CO(2)) (P(ETCO(2))), an important clinical tool for assessing gas exchange efficiency during exercise testing. Pa(CO(2)) has been estimated during exercise with good accuracy in normal-weight individuals by using a correction equation developed by Jones and colleagues (P(JCO(2)) = 5.5 + 0.9 x P(ETCO(2)) – 2.1 x tidal volume). The purpose of this project was to determine the accuracy of Pa(CO(2)) estimations from P(ETCO(2)) and P(JCO(2)) values at rest and at submaximal and peak exercise in morbidly obese adults.
METHODS: Pa(CO(2)) and P(ETCO(2)) values from 37 obese adults (22 women, 15 men; age, 39 ± 9 y; BMI, 49 ± 7; [mean ± SD]) were evaluated. Subjects underwent ramped cardiopulmonary exercise testing to volitional exhaustion. P(ETCO(2)) was determined from expired gases simultaneously with temperature-corrected arterial blood gases (radial arterial catheter) at rest, every minute during exercise, and at peak exercise. Data were analyzed using paired t tests.
RESULTS: P(ETCO(2)) was not significantly different from Pa(CO(2)) at rest (P(ETCO(2)) = 37 ± 3 mm Hg vs Pa(CO(2)) = 38 ± 3 mm Hg, P = .14). However, during exercise, P(ETCO(2)) was significantly higher than Pa(CO(2)) (submaximal: 42 ± 4 vs 40 ± 3, P < .001; peak: 40 ± 4 vs 37 ± 4, P < .001, respectively). Jones’ equation successfully corrected P(ETCO(2)), such that P(JCO(2)) was not significantly different from Pa(CO(2)) (submax: P(JCO(2)) = 40 ± 3, P = .650; peak: 37 ± 4, P = .065).
CONCLUSION: P(JCO(2)) provides a better estimate of Pa(CO(2)) than P(ETCO(2)) during submaximal exercise and at peak exercise, whereas at rest both yield reasonable estimates in morbidly obese individuals. Clinicians and physiologists can obtain accurate estimations of Pa(CO(2)) in morbidly obese individuals by using P(JCO(2)).
Vipa Bernhardt; Santiago Lorenzo; Tony G Babb; Gerald S Zavorsky
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Chest     Volume:  143     ISSN:  1931-3543     ISO Abbreviation:  Chest     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-03-15     Completed Date:  2013-06-20     Revised Date:  2014-02-04    
Medline Journal Info:
Nlm Unique ID:  0231335     Medline TA:  Chest     Country:  United States    
Other Details:
Languages:  eng     Pagination:  471-7     Citation Subset:  AIM; IM    
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MeSH Terms
Body Mass Index
Carbon Dioxide / metabolism*
Exercise / physiology*
Linear Models
Lung / metabolism,  physiopathology
Middle Aged
Models, Biological
Obesity, Morbid / metabolism,  physiopathology*
Oxygen / metabolism*
Pulmonary Gas Exchange / physiology*
Rest / physiology*
Tidal Volume / physiology
Grant Support
Reg. No./Substance:
142M471B3J/Carbon Dioxide; S88TT14065/Oxygen

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

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