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Near Infra-Red Spectroscopy And Arterial Oxygen Extraction At Altitude

  • Christopher B. Wolff
  • Neil Richardson
  • Oliver Kemp
  • Anya Kuttler
  • Roger McMorrow
  • Nigel Hart
  • Christopher HE Imray
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 599)

Abstract

The ratio of oxygenated to total haemoglobin (Hb), or rSO2, obtained by near infra-red spectroscopy (NIRS), includes both arterial and venous blood of the region examined. The relationship of arterial oxygen extraction, E, and saturation, SaO2, to rSO2 can be expressed, for normally functioning tissue, as E = 1.39(1 - rSO2/SaO2). Cerebral E, at rest, is constant at lower altitudes but is reduced at 5000 m. This corresponds to constant values of E for SaO2 values above 90% (approximately). E declines linearly for lower SaO2 values, either including measurement at high altitude or at sea level with a reduced inspiratory oxygen concentration. In addition to measurements of brain NIRS resting oxygen extraction of liver, muscle and kidney have also been calculated from NIRS measurements made, on normal inspired air, at sea level and after acute ascent to 2400 m and 5050 m. At 5050 m E was reduced for all four regions but at 2400 m was the same as at sea level for brain, liver and muscle; for the kidney E was elevated at 2400 m. Cerebral oxygen extraction was calculated for rest and the full range of exercise. It was constant at sea level for the lower levels of exercise and, if the calculated extraction value assumptions still hold at lower SaO2 values, reduced for the higher work rates at intermediate altitudes. The present study confirms constancy of oxygen extraction and hence the ratio of oxygen delivery to oxygen consumption (1/E), within physiological limits, and appears to show where those limits lay and, to some extent, show how matters change beyond ordinary physiological limits.

Keywords

Oxygen Delivery Cerebral Oxygen Oxygen Extraction Moderate Altitude Arterial Oxygen Content 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. 1.
    C. B. Wolff, Cerebral blood flow and oxygen delivery at high altitude, High Altitude Medicine and Biology 1( 1), 33-38 ( 2000).PubMedCrossRefGoogle Scholar
  2. 2.
    C. B. Wolff, P. Barry and D. J. Collier, Cardiovascular and respiratory adjustments at altitude sustain cerebral oxygen delivery – Severinghaus revisited, Comp. Bioch. and Physiol. Part A 132, 221-229 ( 2002).CrossRefGoogle Scholar
  3. 3.
    C. B. Wolff, and C. H. E. Imray, Partitioning of arterial and venous volumes in the brain under hypoxic conditions, Adv. Exp. Med.. Biol. 540, 19-23 ( 2004).Google Scholar
  4. 4.
    P. W. McCormick, M. Stewart, M. G. Goetting and G. Balakrishnan, Regional cerebrovascular oxygen saturation measured by optical spectroscopy in humans. Stroke 22, 596-602 ( 1991).PubMedGoogle Scholar
  5. 5.
    M. Beasley, C. Chan, H. Hoar, C. Knickenberg, P. Forster, C. Imray and T. And Cerebral, hepatic, renal, skeletal muscle and peripheral oxygenation at 0m, 2400m and 5050m, High Altitude Medicine & Biology 2( 1), p96 A71, ( 2001) (abstract).Google Scholar
  6. 6.
    C. H. E Imray, S. D. Myers, K. T. S. Pattinson, A. R. Bradwell, C. W. Chan, S. Harris, P. Collins and A. D. Wright, Effect of exercise on cerebral perfusion in humans at high altitude. J. Appl. Physiol. 99( 2), 699-706 ( 2005).PubMedCrossRefGoogle Scholar
  7. 7.
    C.B. Wolff, Cardiac output, oxygen consumption and muscle oxygen delivery in submaximal exercise: normal and low O2 states. Adv. Exp. Med. Biol. 510, 279-284 ( 2003).PubMedGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  • Christopher B. Wolff
    • 1
  • Neil Richardson
  • Oliver Kemp
  • Anya Kuttler
  • Roger McMorrow
  • Nigel Hart
  • Christopher HE Imray
    • 2
  1. 1.Applied Physiology Block 9St Thomas’s HospitalLondon, SE1 7EHUK
  2. 2.Coventry and Warwickshire County Vascular UnitUniversity Hospitals Coventry and WarwickshireCoventry CV2 2DHUK

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