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This Article Full Text Full Text (PDF) All Versions of this Article: 586/18/4559    most recent jphysiol.2008.159350v2 jphysiol.2008.159350v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Lovering, A. T. Articles by Eldridge, M. W. PubMed PubMed Citation Articles by Lovering, A. T. Articles by Eldridge, M. W. Related Collections Integrative

¹ Department of Human Physiology, University of Oregon, Eugene, OR, USA
² Department of Population Health Sciences, John Rankin Laboratory of Pulmonary Medicine
³ Department of Pulmonary Function
⁴ Department of Pediatrics
⁵ Biomedical Engineering, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA

The 100% oxygen (O₂) technique has been used to detect and quantify right-to-left shunt for more than 50 years. The goal of this study was to determine if breathing 100% O₂ affected intrapulmonary arteriovenous pathways during exercise. Seven healthy subjects (3 females) performed two exercise protocols. In Protocol I subjects performed an incremental cycle ergometer test (60 W + 30 W/2 min; breathing room air, ) and arteriovenous shunting was evaluated using saline contrast echocardiography at each stage. Once significant arteriovenous shunting was documented (bubble score = 2), workload was held constant for the remainder of the protocol and was alternated between 1.0 (hyperoxia) and 0.209 (normoxia) as follows: hyperoxia for 180 s, normoxia for 120 s, hyperoxia for 120 s, normoxia for 120 s, hyperoxia for 60 s and normoxia for 120 s. For Protocol II, subjects performed an incremental cycle ergometer test until volitional exhaustion while continuously breathing 100% O₂. In Protocol I, shunting was seen in all subjects at 120–300 W. Breathing oxygen for 1 min reduced shunting, and breathing oxygen for 2 min eliminated shunting in all subjects. Shunting promptly resumed upon breathing room air. Similarly, in Protocol II, breathing 100% O₂ substantially decreased or eliminated exercise-induced arteriovenous shunting in all subjects at submaximal and in 4/7 subjects at maximal exercise intensities. Our results suggest that alveolar hyperoxia prevents or reduces blood flow through arteriovenous shunt pathways.

(Received 7 July 2008; accepted after revision 31 July 2008; first published online 7 August 2008)
Corresponding author A. T. Lovering: Department of Human Physiology, 1240 University of Oregon, Eugene, OR 97403-1240, USA.  Email: lovering{at}uoregon.edu