1. Systemic oxygen extraction during exercise at high altitude
- Author
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D.S. Martin, A. Cobb, P. Meale, K. Mitchell, M. Edsell, M.G. Mythen, M.P.W. Grocott, Tom Adams, Lindsay Biseker, Adam Booth, Oliver Burdall, Alexandra Cobb, Andrew Cumpstey, Steve Dauncey, Mark Edsell, James Farrant, Martin Feelisch, Bernadette Fernandez, Oliver Firth, Edward Gilbert, Daniel Grant, Michael Grocott, Phil Hennis, Laura Jackson, Will Jenner, Jildou van der Kaaij, Maryam Khosravi, Edith Kortekaas, Denny Levett, Zeyn Mahomed, Daniel Martin, Paula Meale, Jim Milledge, Kay Mitchell, Damian Mole, Oliver Moses, Michael Mythen, Fabio Rigat, Alasdair O'Doherty, Alex Salam, Matt Sanborn, Adam Sheperdigian, Fiona Shrubb, Jo Simpson, Nick Talbot, Liesel Wandrag, Savini Wijesingha, Wilby Williamson, Tom Woolley, and Heng Yow
- Subjects
Adult ,Male ,Acclimatization ,chemistry.chemical_element ,Oxygen ,Hypoxemia ,Animal science ,Oxygen Consumption ,Translational Research ,medicine ,Humans ,Peak exercise ,exercise ,business.industry ,hypoxia ,Altitude ,Significant difference ,Effects of high altitude on humans ,Oxygen uptake ,Anesthesiology and Pain Medicine ,blood gas analysis ,chemistry ,Anesthesia ,physiology ,Female ,medicine.symptom ,business ,Oxygen extraction - Abstract
Background Classic teaching suggests that diminished availability of oxygen leads to increased tissue oxygen extraction yet evidence to support this notion in the context of hypoxaemia, as opposed to anaemia or cardiac failure, is limited. Methods At 75 m above sea level, and after 7–8 days of acclimatization to 4559 m, systemic oxygen extraction [C(a−v)O2] was calculated in five participants at rest and at peak exercise. Absolute [C(a−v)O2] was calculated by subtracting central venous oxygen content (CcvO2) from arterial oxygen content ( C a O 2 ) in blood sampled from central venous and peripheral arterial catheters, respectively. Oxygen uptake ( V ˙ O 2 ) was determined from expired gas analysis during exercise. Results Ascent to altitude resulted in significant hypoxaemia; median (range) S p O 2 87.1 (82.5–90.7)% and P a O 2 6.6 (5.7–6.8) kPa. While absolute C(a−v)O2 was reduced at maximum exercise at 4559 m [83.9 (67.5–120.9) ml litre−1 vs 99.6 (88.0–151.3) ml litre−1 at 75 m, P=0.043], there was no change in oxygen extraction ratio (OER) [C(a−v)O2/CaO2] between the two altitudes [0.52 (0.48–0.71) at 4559 m and 0.53 (0.49–0.73) at 75 m, P=0.500]. Comparison of C(a−v)O2 at peak V ˙ O 2 at 4559 m and the equivalent V ˙ O 2 at sea level for each participant also revealed no significant difference [83.9 (67.5–120.9) ml litre1 vs 81.2 (73.0–120.7) ml litre−1, respectively, P=0.225]. Conclusion In acclimatized individuals at 4559 m, there was a decline in maximum absolute C(a−v)O2 during exercise but no alteration in OER calculated using central venous oxygen measurements. This suggests that oxygen extraction may have become limited after exposure to 7–8 days of hypoxaemia.
- Published
- 2014