Document Detail

Exercise-induced intrapulmonary arteriovenous shunting in healthy humans.
MedLine Citation:
PMID:  15107409     Owner:  NLM     Status:  MEDLINE    
We hypothesized that increasing exercise intensity recruits dormant arteriovenous intrapulmonary shunts, which may contribute to the widened alveolar-arterial oxygen difference seen with exercise. Twenty-three healthy volunteers (13 men and 10 women, aged 23-48 yr) with normal lung function and a wide range of fitness (mean maximal oxygen uptake = 126% predicted; range = 78-200% predicted) were studied by agitated saline contrast echocardiography (4-chamber apical view). All 23 subjects had normal resting contrast echocardiograms without evidence of intracardiac or intrapulmonary shunting. However, with cycle ergometer exercise, 21 of 23 (91%) of the subjects showed a delayed (>3 cardiac cycles) appearance of contrast bubbles in the left heart. This pattern is consistent with passage of contrast bubbles through the pulmonary circulation. Because the contrast bubbles are known to be significantly larger than pulmonary capillaries, we propose that they are traveling through direct arteriovenous intrapulmonary shunts. In all cases, the intrapulmonary shunting developed at submaximal oxygen uptakes [%maximal oxygen uptake = 59 +/- 20 (SD)] and once evident persisted at all subsequent work rates. Within 3 min of exercise termination, the contrast echocardiograms with bubble injection showed no evidence of intrapulmonary shunting. These dynamic shunts will contribute significantly to the widened alveolar-arterial oxygen difference seen with exercise. They may also act as a protective parallel vascular network limiting the rise in regional pulmonary vascular pressure while preserving cardiac output during exercise.
Marlowe W Eldridge; Jerome A Dempsey; Hans C Haverkamp; Andrew T Lovering; John S Hokanson
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.     Date:  2004-04-23
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  97     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2004 Sep 
Date Detail:
Created Date:  2004-08-30     Completed Date:  2005-02-10     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  797-805     Citation Subset:  IM    
John Rankin Laboratory of Pulmonary Medicine, University of Wisconsin, Medical School, Madison, Wisconsin 53792-4108, USA.
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MeSH Terms
Adaptation, Physiological / physiology
Blood Flow Velocity
Exercise Test
Heart Ventricles / physiopathology*,  ultrasonography
Lung / blood supply*,  physiology*,  ultrasonography
Middle Aged
Oxygen Consumption / physiology*
Physical Endurance / physiology*
Physical Exertion / physiology*
Pulmonary Artery / physiopathology,  ultrasonography
Pulmonary Circulation / physiology*
Pulmonary Gas Exchange / physiology
Pulmonary Veins / physiopathology,  ultrasonography
Respiratory Function Tests
Grant Support
R01 HL-15469-33/HL/NHLBI NIH HHS; T32 HL-07654-16/HL/NHLBI NIH HHS

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