| The effects of inspiratory intrathoracic pressure production on the cardiovascular response to submaximal exercise in health and chronic heart failure. | |
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MedLine Citation:
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PMID: 16997896 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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We sought to determine whether the normal inspiratory intrathoracic pressures (P(ITP)) produced during exercise contribute to the blunted cardiac output and locomotor limb blood flow responses observed in chronic heart failure (CHF). Five chronically instrumented dogs exercised on a treadmill at 2.5 mile/h at 5% grade while healthy or after the induction of tachycardia-induced CHF. We observed several key differences in the cardiovascular responses to changes in the inspiratory P(ITP) excursion between health and CHF; namely, 1) removing approximately 70% of the normally produced inspiratory P(ITP) excursion during exercise (with 15 cmH(2)O inspiratory positive pressure ventilation) significantly reduced stroke volume (SV) in healthy animals by 5 +/- 2% (P < 0.05) but significantly increased SV and cardiac output (Q(TOT)) in animals with CHF by 5 +/- 1% (P < 0.05); 2) doubling the magnitude of the inspiratory P(ITP) excursion had no effect on SV or Q(TOT) in healthy animals but significantly reduced steady-state Q(TOT) and SV in animals with CHF by -4 +/- 3% and -10 +/- 3%, respectively; 3) removing the majority of the normally produced inspiratory P(ITP) excursion had no effect on blood flow distribution in healthy animals but increased hindlimb blood flow (9 +/- 3%, P < 0.05) out of proportion to the increases in Q(TOT); and 4) the only similarity between healthy and CHF animals was that increasing the inspiratory P(ITP) excursion significantly reduced steady-state locomotor limb blood flow by 5 +/- 2% and 6 +/- 3%, respectively (P < 0.05 for both). We conclude that 1) the normally produced inspiratory P(ITP) excursions are required for a maximal SV response to submaximal exercise in healthy animals but detrimental to the SV and Q(TOT) responses to submaximal exercise in CHF, 2) the respiratory muscle ergoreflex tonically restrains locomotor limb blood flow during submaximal exercise in CHF, and 3) excessive inspiratory muscle work further compromises cardiac function and blood flow distribution in both health and CHF. |
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Authors:
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Jordan D Miller; Curtis A Smith; Sarah J Hemauer; Jerome A Dempsey |
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Publication Detail:
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Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't Date: 2006-09-22 |
Journal Detail:
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Title: American journal of physiology. Heart and circulatory physiology Volume: 292 ISSN: 0363-6135 ISO Abbreviation: Am. J. Physiol. Heart Circ. Physiol. Publication Date: 2007 Jan |
Date Detail:
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Created Date: 2007-01-10 Completed Date: 2007-02-20 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 100901228 Medline TA: Am J Physiol Heart Circ Physiol Country: United States |
Other Details:
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Languages: eng Pagination: H580-92 Citation Subset: IM |
Affiliation:
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Univ. of Iowa, 200 Hawkins Dr., 340B Eckstein Medical Research Bldg., Iowa City, IA 52242, USA. jordan-miller@uiowa.edu |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Airway Resistance Animals Cardiac Output* Dogs Exercise Test Female Heart Failure / physiopathology* Inhalation* Physical Exertion* Reference Values Stroke Volume* Thorax / physiopathology* |
| Grant Support | |
ID/Acronym/Agency:
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R01-HL-015469/HL/NHLBI NIH HHS; T32-HL-007654/HL/NHLBI NIH HHS |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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