| The contribution of intrapulmonary shunts to the alveolar-to-arterial oxygen difference during exercise is very small. | |
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MedLine Citation:
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PMID: 18339692 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Exercise is well known to cause arterial PO2 to fall and the alveolar-arterial PO2 difference(Aa PO2 ) to increase. Until recently, the physiological basis for this was considered to be mostly ventilation/perfusion ((.)VA/(.)Q) inequality and alveolar-capillary diffusion limitation. Recently, arterio-venous shunting through dilated pulmonary blood vessels has been proposed to explain a significant part of the Aa PO2 during exercise. To test this hypothesis we determined venous admixture during 5 min of near-maximal, constant-load, exercise in hypoxia (in inspired O2 fraction, FIO2 , 0.13), normoxia (FIO2 , 0.21) and hyperoxia (FIO2 , 1.0) undertaken in balanced order on the same day in seven fit cyclists ((.)VO2max, 61.3 +/- 2.4 ml kg(-1) min(-1); mean +/- S.E.M.). Venous admixture reflects three causes of hypoxaemia combined: true shunt, diffusion limitation and ((.)VA/(.)Q) inequality. In hypoxia, venous admixture was 22.8 +/- 2.5% of the cardiac output; in normoxia it was 3.5 +/- 0.5%; in hyperoxia it was 0.5 +/- 0.2%. Since only true shunt accounts for venous admixture while breathing 100% O2, the present study suggests that shunt accounts for only a very small portion of the observed venous admixture, Aa PO2 and hypoxaemia during heavy exercise. |
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Authors:
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Ioannis Vogiatzis; Spyros Zakynthinos; Robert Boushel; Dimitris Athanasopoulos; Jordan A Guenette; Harrieth Wagner; Charis Roussos; Peter D Wagner |
Publication Detail:
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Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't Date: 2008-03-13 |
Journal Detail:
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Title: The Journal of physiology Volume: 586 ISSN: 1469-7793 ISO Abbreviation: J. Physiol. (Lond.) Publication Date: 2008 May |
Date Detail:
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Created Date: 2008-05-02 Completed Date: 2008-06-04 Revised Date: 2009-11-18 |
Medline Journal Info:
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Nlm Unique ID: 0266262 Medline TA: J Physiol Country: England |
Other Details:
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Languages: eng Pagination: 2381-91 Citation Subset: IM |
Affiliation:
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Medical School of Athens University, Department of Critical Care and Pulmonary Services, Evangelismos Hospital, Athens, Greece. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Oxygen
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metabolism* Physical Endurance / physiology* Physical Exertion / physiology* Pulmonary Alveoli / physiology* Pulmonary Artery / physiology* Pulmonary Gas Exchange / physiology* |
| Grant Support | |
ID/Acronym/Agency:
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HL84281/HL/NHLBI NIH HHS |
| Chemical | |
Reg. No./Substance:
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7782-44-7/Oxygen |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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