Document Detail


Ventilatory constraints during exercise in patients with chronic heart failure.
MedLine Citation:
PMID:  10669670     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We examined the degree of ventilatory constraint in patients with a history of chronic heart failure (CHF; n = 11; mean +/- SE age, 62 +/- 4 years; cardiac index [CI], 2.0 +/- 0.1; and ejection fraction [EF], 24 +/- 2%) and in control subjects (CTLS; n = 8; age, 61 +/- 5 years; CI, 2.6 +/- 0.3) by plotting the tidal flow-volume responses to graded exercise in relationship to the maximal flow-volume envelope (MFVL). Inspiratory capacity (IC) maneuvers were performed to follow changes in end-expiratory lung volume (EELV) during exercise, and the degree of expiratory flow limitation was assessed as the percent of the tidal volume (VT) that met or exceeded the expiratory boundary of the MFVL. CHF patients had significantly (p < 0.05) reduced baseline pulmonary function (FVC, 76 +/- 4%; FEV(1), 78 +/- 4% predicted) relative to CTLS (FVC, 99 +/- 4%; FEV(1), 102 +/- 4% predicted). At peak exercise, oxygen consumption (VO(2)) and minute ventilation (V(E)) were lower in CHF patients than in CTLS (VO(2), 17 +/- 2 vs 32 +/- 2 mL/kg/min; VE, 56 +/- 4 vs 82 +/- 6 L/min, respectively), whereas VE/carbon dioxide output was higher (42 +/- 4 vs 29 +/- 5). In CTLS, EELV initially decreased with light exercise, but increased as VE and expiratory flow limitation increased. In contrast, the EELV in patients with CHF remained near residual volume (RV) throughout exercise, despite increasing flow limitation. At peak exercise, IC averaged 91 +/- 3% and 79 +/- 4% (p < 0.05) of the FVC in CHF patients and CTLS, respectively, and flow limitation was present over > 45% of the VT in CHF patients vs < 25% in CTLS (despite the higher VE in CTLS). The least fit and most symptomatic CHF patients demonstrated the lowest EELV, the greatest degree of flow limitation, and a limited response to increased inspired carbon dioxide during exercise, all consistent with VE constraint. We conclude that patients with CHF commonly breathe near RV during exertion and experience expiratory flow limitation. This results in VE constraint and may contribute to exertional intolerance.
Authors:
B D Johnson; K C Beck; L J Olson; K A O'Malley; T G Allison; R W Squires; G T Gau
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Chest     Volume:  117     ISSN:  0012-3692     ISO Abbreviation:  Chest     Publication Date:  2000 Feb 
Date Detail:
Created Date:  2000-03-03     Completed Date:  2000-03-03     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0231335     Medline TA:  Chest     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  321-32     Citation Subset:  AIM; IM    
Affiliation:
Divisions of Cardiovascular, Department of Internal Medicine, Mayo Clinic and Foundation, Rochester, MN 55905, USA. johnson.bruce@mayo.edu
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MeSH Terms
Descriptor/Qualifier:
Adult
Aged
Carbon Dioxide / blood
Exercise Test*
Female
Heart Failure / diagnosis*,  physiopathology
Humans
Lung Volume Measurements*
Male
Middle Aged
Oxygen / blood
Residual Volume / physiology
Stroke Volume / physiology
Ventilation-Perfusion Ratio / physiology
Ventricular Dysfunction, Left / diagnosis,  physiopathology
Work of Breathing / physiology
Grant Support
ID/Acronym/Agency:
MO1-RR00585/RR/NCRR NIH HHS
Chemical
Reg. No./Substance:
124-38-9/Carbon Dioxide; 7782-44-7/Oxygen

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


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