HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 99/1/224    most recent 01230.2004v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Manohar, M. Articles by Goetz, T. E. Search for Related Content PubMed PubMed Citation Articles by Manohar, M. Articles by Goetz, T. E.

Intrapulmonary arteriovenous shunts of >15 µm in diameter probably do not contribute to arterial hypoxemia in maximally exercising Thoroughbred horses

Departments of Veterinary Biosciences and Clinical Medicine, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois

Submitted 1 November 2004 ; accepted in final form 10 March 2005

The present study examined whether Thoroughbred horses performing strenuous exercise exhibit intrapulmonary arteriovenous shunting that may contribute to the observed arterial hypoxemia. Experiments were carried out on seven healthy, exercise-trained Thoroughbreds at rest, maximal exercise (galloping at 14 m/s on a 3.5% uphill grade for 120 s), and submaximal exertion (8 m/s on a 3.5% uphill grade for 150 s). Along with blood gas/hemodynamic parameters, intrapulmonary arteriovenous shunting was studied by injecting 15-µm-diameter microspheres, labeled with different stable isotopes, into the right atrium while simultaneous blood samples were being withdrawn at a constant rate from the pulmonary artery and the aorta. Arterial hypoxemia was observed only during maximal exercise. Also, despite significant pulmonary arterial hypertension during submaximal and maximal exertion, 15-µm microspheres did not traverse the pulmonary microcirculation to appear in the aortic blood. Thus our findings did not support a role for intrapulmonary arteriovenous shunts of >15 µm in diameter in the exercise-induced arterial hypoxemia in racehorses. Interestingly, our observation that, in going from 30 to 120 s of maximal exertion, arterial O₂ tension had remained unchanged despite significant reductions in mixed venous blood O₂ tension, hemoglobin-O₂ saturation, and O₂ content also discounts the importance of intrapulmonary arteriovenous shunts in causing arterial hypoxemia. This is because, assuming that a constant fraction of total pulmonary blood flow bypasses the gas-exchange areas of the equine lungs via intrapulmonary arteriovenous shunts during 30–120 s of maximal exertion, the observed significant reductions in mixed venous blood oxygenation should cause a significant reduction in arterial O₂ tension, which was not the case in our horses. Thus it is suggested that intrapulmonary arteriovenous shunting probably does not contribute to the exercise-induced arterial hypoxemia in racehorses.

blood gas tensions during exertion; arterial desaturation during exercise; pulmonary microcirculation; microspheres

This article has been cited by other articles:

				A. T. Lovering, L. M. Romer, H. C. Haverkamp, D. F. Pegelow, J. S. Hokanson, and M. W. Eldridge Intrapulmonary shunting and pulmonary gas exchange during normoxic and hypoxic exercise in healthy humans J Appl Physiol, May 1, 2008; 104(5): 1418 - 1425. [Abstract] [Full Text] [PDF]

				M. K. Stickland, A. T. Lovering, and M. W. Eldridge Exercise-induced Arteriovenous Intrapulmonary Shunting in Dogs Am. J. Respir. Crit. Care Med., August 1, 2007; 176(3): 300 - 305. [Abstract] [Full Text] [PDF]