Reduced blood flow through intrapulmonary arteriovenous anastomoses at rest and during exercise in lowlanders during acclimatization to high altitude
Boulet, Lindsey M
Lovering, Andrew T
Tymko, Michael M
Day, Trevor A
Anh Nguyen, Trang
Ainslie, Philip N
Foster, Glen E
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Blood flow through intrapulmonary arteriovenous anastomoses (QIPAVA ) is elevated during exercise at sea level (SL) and at rest in acute normobaric hypoxia. Following high altitude (HA) acclimatization, resting QIPAVA is similar to SL, but it is unknown if this is true during exercise at HA. We reasoned that exercise at HA (5,050 m) would exacerbate QIPAVA due to heightened pulmonary arterial pressure. Using a supine cycle ergometer, seven healthy adults free from intracardiac shunts underwent an incremental exercise test at SL (25, 50, 75% of SL VO2peak ) and at HA (25, 50% of SL VO2peak ). Echocardiography was used to determine cardiac output (Q) and pulmonary artery systolic pressure (PASP) and agitated saline contrast was used to determine QIPAVA (bubble score; 0-5). The principal findings were: (1) Q was similar at SL-rest (3.9 +/- 0.47 l min-1 ) compared with HA-rest (4.5 +/- 0.49 l min-1 ; P = 0.382), but increased from rest during both SL and HA exercise (P < 0.001); (2) PASP increased from SL-rest (19.2 +/- 0.7 mmHg) to HA-rest (33.7 +/- 2.8 mmHg; P = 0.001) and, compared with SL, PASP was further elevated during HA exercise (P = 0.003); (3) QIPAVA was increased from SL-rest (0) to HA-rest (median = 1; P = 0.04) and increased from resting values during SL exercise (P < 0.05), but were unchanged during HA exercise (P = 0.91), despite significant increases in Q and PASP. Theoretical modeling of microbubble dissolution suggests that the lack of QIPAVA in response to exercise at HA is unlikely caused by saline contrast instability.
Boulet, L.M., Lovering, A.T., Tymko, M.M., Day, T.A., Stembridge, M., Nguyen, T.A., Ainslie, P.N. and Foster, G.E. (2017) 'Reduced blood flow through intrapulmonary arteriovenous anastomoses during exercise in lowlanders during acclimatization to high altitude', Experimental Physiology, doi:10.1113/EP086182
This article was published in Experimental Physiology on 30 March 2017 (online), available at http://dx.doi.org/10.1113/EP086182
Cardiff Metropolitan University (Grant ID: Cardiff Metropolian (Internal))
Gouvernement du Canada | Natural Sciences and Engineering Research Council of Canada (Conseil de Recherches en Sciences Naturelles et en Génie du Canada): Glen E Foster, 2014-05643
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