Corrected end-tidal p co 2 accurately estimates pa co 2 at rest and during exercise in morbidly obese adults

Vipa Bernhardt, Santiago Lorenzo, Tony G. Babb, Gerald S. Zavorsky

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

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 effi ciency 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 5.5 1 0.9 3 P ETCO 2 - 2.1 3 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 signifi cantly different from Pa CO 2 at rest (P ETCO 2 5 37 - 3 mm Hg vs Pa CO 2 5 38 - 3 mm Hg, P 5 .14). However, during exercise, P ETCO 2 was signifi cantly 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 signifi cantly different from Pa CO 2 (submax: P JCO 2 5 40 - 3, P 5 .650; peak: 37 - 4, P 5 .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 . CHEST 2013; 143(2):471-477

Original languageEnglish (US)
Pages (from-to)471-477
Number of pages7
JournalCHEST
Volume143
Issue number2
DOIs
StatePublished - Feb 2013

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Critical Care and Intensive Care Medicine
  • Cardiology and Cardiovascular Medicine

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