| Coupling of external to internal respiration. | |
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MedLine Citation:
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PMID: 6421214 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Oxygen is required to generate chemical energy (ATP) to allow muscle contraction. The amount of chemical energy required is directly proportional to the work rate performed. Early in exercise, the muscle creatine phosphate and oxygen stores, primarily in the form of oxymyoglobin and oxyhemoglobin (oxygen content of venous blood decreases), are used for energy. This allows time for cardiac output and ventilation to increase to satisfy the total O2 requirement. Steady-state time depends on the level of work relative to the anaerobic threshold (AT). For work rates below the AT, steady-state for VO2 is achieved by 3 min and by 4 min for VCO2 and VE. For work rates above the AT, steady-states are considerably delayed or not achieved. For purposes of description of the pattern of external respiration (gas exchange at the lungs), three phases are defined. Phase I is the initial increase in VO2 and VCO2 at the start of exercise, lasting approximately 15 s. Because the gas exchange ratio (R) typically doesn't change during Phase I, the initial increase in VO2 and VCO2 must be due primarily to an increase in pulmonary blood flow and proportional increase in ventilation (cardiodynamic phase). Phase II is the exponential-like increase in VO2 and VCO2, which follow Phase I and terminates in a steady-state or asymptotic value (Phase III). At moderate work, VO2 increases more rapidly than VCO2 during Phase II (CO2 stores increase). Therefore, R decreases before it increases to the steady-state. Below the AT, the rate of external respiration equals the rate of internal respiration during Phase III.(ABSTRACT TRUNCATED AT 250 WORDS) |
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Authors:
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K Wasserman |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: The American review of respiratory disease Volume: 129 ISSN: 0003-0805 ISO Abbreviation: Am. Rev. Respir. Dis. Publication Date: 1984 Feb |
Date Detail:
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Created Date: 1984-03-22 Completed Date: 1984-03-22 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 0370523 Medline TA: Am Rev Respir Dis Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: S21-4 Citation Subset: AIM; IM; S |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Carbon Dioxide
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metabolism Cardiovascular Physiological Phenomena Citric Acid Cycle Energy Metabolism Humans Kinetics Muscles / metabolism Oxygen / metabolism Oxygen Consumption* Physical Exertion Pulmonary Gas Exchange Respiration* |
| Grant Support | |
ID/Acronym/Agency:
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HL 11907/HL/NHLBI NIH HHS |
| Chemical | |
Reg. No./Substance:
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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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