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This Article Full Text (PDF) Free All Versions of this Article: chest.07-0619v1 132/3/977    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to My Personal Article Archive Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hansen, J. E. Articles by Wasserman, K. Search for Related Content PubMed PubMed Citation Articles by Hansen, J. E. Articles by Wasserman, K.

Mixed-expired and end-tidal CO₂ distinguish between ventilation and perfusion defects during exercise testing in lung and heart diseases

¹Los Angeles Biomedical Research Institute, Harbor-UCLA Medical Center, Respiratory and Critical Care Division of Physiology and Medicine, Department of Medicine, University of California at Los Angeles, Torrance, CA 90509 ²Department of Chest Diseases, Faculty of Medicine, Baskent University, Ankara, Turkey ³Department of Respiratory Medicine, Ruttonjee Hopsital, Hong Kong SAR

jhansen{at}labiomed.org

Abstract

Background: Mismatching of ventilation to perfusion is found in patients with COPD, left ventricular failure (LVF), and pulmonary vascular diseases. Such mismatching may be due to ventilation or perfusion defects or both. Our primary hypothesis was that pressures of mixed expired (PECO₂), end-tidal PCO₂ (PETCO₂) and their ratios, would differ between groups during exercise testing, depending on whether the ventilation/perfusion abnormality was dominantly caused by airways or perfusion defects.

Methods: We collected incremental cycle ergometry tests from 25 normal subjects and 3 groups of 25 patients, each group with uncomplicated COPD, LVF, or primary pulmonary arterial hypertension (PAH). We compared PECO₂, PETCO₂ and their ratios at rest, unloaded pedaling, anaerobic threshold, and peak exercise.

Results: Although each patient group had mean peak O₂ uptake of approximately 50% of predicted normal, each group's levels and patterns of change of PECO₂, PETCO₂, and their ratios were surprisingly distinctive. As hypothesized, the COPD group always had markedly lower ratios of PECO₂/PETCO₂ than all other groups (p<0.001). In addition LVF had slightly lower PECO₂/PETCO₂ ratios at heavy exercise than normal (p<0.05). At all times, except for COPD PETCO₂ at peak exercise, each group had significantly lower PETCO₂ and PECO₂ than normal subjects (p<0.001). With PAH, the PETCO2 decline with exercise was distinctive.

Conclusions: The levels and changes in PECO₂, PETCO₂, and their ratios during cardiopulmonary exercise testing are distinctive and explained by the differing pathophysiologies of ventilation/perfusion mismatching in these disorders.

Key Words: Ventilation-perfusion ratio • Pulmonary circulation • Exercise test • Congestive heart failure • COPD • Pulmonary artery hypertension