Increased blood‐oxygen binding affinity in Tibetan and Han Chinese residents at 4200 m. Issue 12 (1st December 2014)

• Record Type: Journal Article
• Authors: Simonson, T. S.; Wei, G.; Wagner, H. E.; Wuren, T.; Bui, A.; Fine, J. M.; Qin, G.; Beltrami, F. G.; Yan, M.; Wagner, P. D.; Ge, Ri Li
• Is Part Of: Experimental physiology. Volume 99:Issue 12(2014:Dec.)
• Page Start: 1624
• Page End: 1635
• Publication Date: 2014-12-01
• Subjects: Physiology, Experimental -- Periodicals; 571.0724
• DOI: 10.1113/expphysiol.2014.080820
• Languages: English
• ISSNs: 0958-0670

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="eph1515-sec-0010" sec-type="section"> <title>New Findings</title> <p> <list id="eph1515-list-0001" list-type="bullet"> <list-item> <p> <bold>What is the central question of this study?</bold> </p> <p>Is Tibetan and Chinese highlanders' blood oxygen‐binding affinity (<italic>P</italic><sub>50</sub>) different from that of other populations (at altitude or sea level), and does Tibetan <italic>P</italic><sub>50</sub> relate to haemoglobin concentration and/or exercise capacity at altitude?</p> </list-item> <list-item> <p> <bold>What is the main finding and its importance?</bold> </p> <p>Tibetans and Chinese at 4200 m have slightly lower <italic>P</italic><sub>50</sub> than sea‐level residents.</p> <p>During maximal exercise at 4200 m, reduced <italic>P</italic><sub>50</sub> does not enhance pulmonary gas exchange, impair systemic oxygen extraction or affect peak exercise capacity.</p> <p>Oxygen saturation measurements based upon forehead oximetry are sufficiently reduced during exercise at altitude (and accurate compared with those obtained from arterial blood by co‐oximetry) to determine <italic>P</italic><sub>50</sub> reliably.</p> </list-item> </list> </p> </sec> <sec id="eph1515-sec-0020" sec-type="section"> <p>High‐altitude natives are challenged by hypoxia, and a potential compensatory mechanism could be reduced blood oxygen‐binding affinity (<italic>P</italic><sub>50</sub>), as seen in several high‐altitude mammalian species. In 21 Qinghai Tibetan and nine Han Chinese men, all resident at 4200 m, standard <italic>P</italic><sub>50</sub> was calculated from measurements of arterial <inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgh3m42s9q2" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:09580670:eph1515:equation:eph1515-math-0001" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>P</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:msub></mml:math></alternatives></inline-formula> and forehead oximeter oxygen saturation, which was validated in a separate examination of 13 healthy subjects residing at sea level. In both Tibetans and Han Chinese, standard <italic>P</italic><sub>50</sub> was 24.5 ± 1.4 and 24.5 ± 2.0 mmHg, respectively, and was lower than in the sea‐level subjects (26.2 ± 0.6 mmHg, <italic>P</italic> < 0.01). There was no relationship between <italic>P</italic><sub>50</sub> and haemoglobin concentration (the latter ranging from 15.2 to 22.9 g dl<sup>−1</sup> in Tibetans). During peak exercise, <italic>P</italic><sub>50</sub> was not associated with alveolar–arterial <inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgh3m42s9rm" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:09580670:eph1515:equation:eph1515-math-0002" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>P</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:msub></mml:math></alternatives></inline-formula> difference or peak O<sub>2</sub> uptake per kilogram. There appears to be no apparent benefit of a lower <italic>P</italic><sub>50</sub> in this adult high‐altitude Tibetan population.</p> </sec> </abstract>