AJRCCM Articles in Press. Published on 31-March-2015 as 10.1164/rccm.201501-0157OC

Page 1 of 44

Pulmonary Gas Exchange Abnormalities in Mild COPD: Implications for Dyspnea and Exercise Intolerance Amany F. Elbehairy1,2, Casey E. Ciavaglia1, Katherine A. Webb1, Jordan A. Guenette3, Dennis Jensen4, Sahar M. Mourad2, J. Alberto Neder1, Denis E. O’Donnell1; on behalf of the Canadian Respiratory Research Network. Affiliations: Respiratory Investigation Unit, Department of Medicine, Queen’s University & Kingston General Hospital, Kingston, ON, Canada. 2 Department of Chest Diseases, Faculty of Medicine, Alexandria University, Alexandria, Egypt. 3 Department of Physical Therapy and UBC Centre for Heart Lung Innovation, University of British Columbia and St. Paul’s Hospital, Vancouver, BC, Canada. 4 Department of Kinesiology and Physical Education, McGill University, Montreal, QC, Canada. 1

Correspondence to: Dr. Denis O’Donnell, 102 Stuart Street, Kingston, Ontario, Canada K7L 2V6; tel: 1-613-548-2339; fax: 1-613-549-1459; e-mail: [email protected] Author’s contributions: All authors played a role in the content and writing of the manuscript. In addition: DEO was the principal investigator and contributed the original idea for the study; DEO, AFE and KAW had input into the study design and conduct of study; AFE and CEC collected the data; AFE performed data analysis and prepared it for presentation. Sources of support: Ontario Thoracic Society; William Spear / Richard Start Endowment Fund, Queen’s University; The Canadian Respiratory Research Network (CRRN). The CRRN is supported by grants from the Canadian Institutes of Health Research (CIHR) - Institute of Circulatory and Respiratory Health; Canadian Lung Association (CLA)/Canadian Thoracic Society (CTS); British Columbia Lung Association; and Industry Partners Boehringer-Ingelheim Canada Ltd, AstraZeneca Canada Inc., and Novartis Canada Ltd. Financial support to Amany F. Elbehairy was provided by an Egyptian Ministry of Higher Education and Scientific Research Scholarship. Jordan A. Guenette was supported by a Scholar Award from the Michael Smith Foundation for Health Research. Dennis Jensen was supported by a Chercheurs-Boursiers Junior 1 salary award from the Fonds de Recherche du Québec-Santé and by a William Dawson Research Scholar Award. The funders had no role in the study design, data collection and analysis, or preparation of the manuscript. Running head: Pulmonary gas exchange abnormalities in mild COPD Subject descriptor number: 8.14 Gas Exchange Body of text word count: 3,513 This article has an online data supplement, which is accessible from this issue’s table of content online at www.atsjournals.org

Copyright © 2015 by the American Thoracic Society

AJRCCM Articles in Press. Published on 31-March-2015 as 10.1164/rccm.201501-0157OC

AT A GLANCE COMMENTARY What is the current scientific knowledge on this subject? Heterogeneous mechanical and pulmonary gas exchange impairment can exist in smokers with only minor spirometric abnormalities but their precise clinical relevance remains unknown. The presence of a high ventilatory equivalent for CO2, suggesting reduced ventilatory efficiency, has consistently been reported in several recent exercise studies in mild COPD but the underlying mechanisms and consequences for exercise tolerance are poorly understood. What does this study add to the field? Increased physiological dead space and wasted ventilation were the most consistent pulmonary gas exchange abnormalities during exercise in the patients with mild COPD. While effective alveolar ventilation and arterial blood gas homeostasis were adequately preserved by compensatory increases in minute ventilation, this forced earlier dynamic respiratory mechanical constraints, greater dyspnea and exercise intolerance in these patients despite a largely preserved FEV1.

1

Copyright © 2015 by the American Thoracic Society

Page 2 of 44

AJRCCM Articles in Press. Published on 31-March-2015 as 10.1164/rccm.201501-0157OC

Page 3 of 44

ABSTRACT Background: Several studies in mild COPD have shown higher than normal ventilatory equivalent for carbon dioxide (⩒E/⩒CO2) during exercise. Our objective was to examine pulmonary gas exchange abnormalities and the mechanisms of high ⩒E/⩒CO2 in mild COPD and its impact on dyspnea and exercise intolerance. Methods: Twenty-two subjects (11 GOLD grade-1B COPD patients, 11 age-matched healthy controls) undertook physiological testing and a symptom-limited incremental cycle exercise test with arterial blood gas collection. Results: Patients (post-bronchodilator FEV1: 94±10 %predicted; mean±SD) had evidence of peripheral airway dysfunction and reduced peak oxygen uptake compared to controls (80±18 versus 113±24 %predicted; p

Pulmonary Gas Exchange Abnormalities in Mild Chronic Obstructive Pulmonary Disease. Implications for Dyspnea and Exercise Intolerance.

Several studies in mild chronic obstructive pulmonary disease (COPD) have shown a higher than normal ventilatory equivalent for carbon dioxide ([Formu...
1MB Sizes 0 Downloads 13 Views