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Increased blood‐oxygen binding affinity in Tibetan and Han Chinese residents at 4200 m
Author(s) -
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
Publication year - 2014
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2014.080820
Subject(s) - altitude (triangle) , effects of high altitude on humans , oxygen saturation , hypoxia (environmental) , oxygen , sea level , zoology , medicine , cardiology , chemistry , endocrinology , biology , anatomy , geography , cartography , geometry , mathematics , organic chemistry
New FindingsWhat is the central question of this study? Is Tibetan and Chinese highlanders’ blood oxygen‐binding affinity ( P 50 ) different from that of other populations (at altitude or sea level), and does Tibetan P 50 relate to haemoglobin concentration and/or exercise capacity at altitude?What is the main finding and its importance? Tibetans and Chinese at 4200 m have slightly lower P 50 than sea‐level residents. During maximal exercise at 4200 m, reduced P 50 does not enhance pulmonary gas exchange, impair systemic oxygen extraction or affect peak exercise capacity. 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 P 50 reliably.High‐altitude natives are challenged by hypoxia, and a potential compensatory mechanism could be reduced blood oxygen‐binding affinity ( P 50 ), as seen in several high‐altitude mammalian species. In 21 Qinghai Tibetan and nine Han Chinese men, all resident at 4200 m, standard P 50 was calculated from measurements of arterial P O 2and 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 P 50 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, P < 0.01). There was no relationship between P 50 and haemoglobin concentration (the latter ranging from 15.2 to 22.9 g dl −1 in Tibetans). During peak exercise, P 50 was not associated with alveolar–arterial P O 2difference or peak O 2 uptake per kilogram. There appears to be no apparent benefit of a lower P 50 in this adult high‐altitude Tibetan population.