Document Detail

Respiratory oxygen cost for dead space challenge is characteristically increased during exercise in patients with chronic heart failure: does it further decrease exercise capacity?
MedLine Citation:
PMID:  9330126     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Although the work of the respiratory muscles is markedly increased during exercise in patients with chronic heart failure, the role of this abnormality in exercise intolerance is still controversial. This issue may be clarified directly by dead space challenge, as this technique increases minute ventilation. Therefore, in this study, the effects of an external dead space on exercise ventilation, gas exchange data, and exercise capacity in patients with chronic heart failure were examined. METHODS AND RESULTS: Dead space challenge was performed by adding an external dead space to the airway in 20 patients with chronic heart failure and 10 normal subjects. Two hours after completion of the control maximal bicycle exercise, the second exercise was performed under application of an external dead space equivalent to 10% of peak tidal volume. Respiratory gas exchange data were collected during exercise. Aerobic exercise capacity was assessed from the exercise time and the time to anaerobic threshold. The sensation of exertional dyspnea was assessed using Borg's rating scale. As compared with data during the control exercise, minute ventilation was increased by approximately 25% with the external dead space throughout exercise in both groups. A parallel 20% increase in systemic oxygen uptake was observed in the heart failure group, likely reflecting an increase in respiratory muscle work. This response was not observed in the normal group. Despite an additional increase in respiratory muscle work, neither aerobic exercise capacity nor exertional dyspnea was exacerbated in the heart failure group by the external dead space. CONCLUSIONS: Dead space challenge appears to be a unique technique that characteristically increases the work of respiratory muscles during exercise in patients with chronic heart failure. By use of this technique, it was demonstrated that an increase in respiratory muscle work is not important in reducing exercise capacity of patients with chronic heart failure.
T Kurotobi; H Sato; H Yokoyama; D Li; Y Koretsune; Y Ohnishi; M Karita; H Takeda; T Kuzuya; M Hori
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of cardiac failure     Volume:  3     ISSN:  1071-9164     ISO Abbreviation:  J. Card. Fail.     Publication Date:  1997 Sep 
Date Detail:
Created Date:  1997-11-14     Completed Date:  1997-11-14     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  9442138     Medline TA:  J Card Fail     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  181-8     Citation Subset:  IM    
First Department of Medicine, Osaka University School of Medicine, Japan.
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MeSH Terms
Cardiac Output, Low / complications,  physiopathology*
Chronic Disease
Dyspnea / etiology,  physiopathology*
Exercise Test
Middle Aged
Oxygen Consumption*
Respiratory Dead Space
Respiratory Function Tests
Respiratory Muscles / metabolism*,  physiopathology*

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

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