Grocott, Michael P.W., Martin, Daniel S., Levett, Denny Z.H., McMorrow, Roger, Windsor, Jeremy and Montgomery, Hugh E.. (2009) Arterial blood gases and oxygen content in climbers on Mount Everest. New England Journal Of Medicine , Vol.360 (No.2). pp. 140-149. ISSN 0028-4793

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Abstract

The partial pressure of atmospheric oxygen falls progressively as barometric pressure decreases with increasing altitude. Correspondingly, the ability to perform work (e.g., walking or climbing) diminishes with the decreased availability of atmospheric oxygen for aerobic respiration.1,2 At the summit of Mount Everest (8848 m [29,029 ft]), the highest point on the earth's surface, the partial pressure of inspired oxygen (PIO2) is believed to be very close to the limit that acclimatized humans can tolerate while maintaining functions such as ambulation and cognition.3 Hillary and Tenzing used supplemental oxygen to achieve the first ascent of Everest in 1953. It was not until 25 years after their ascent that the first ascent of Everest without supplemental oxygen was made by Messner and Habeler.4 Currently, less than 4% of persons who climb Everest do so without the use of supplemental oxygen (Salisbury R., Himalayan database: personal communication). The only published measurements of the partial pressure of oxygen in arterial blood (PaO2) at such a low barometric pressure were reported in two studies — Operation Everest II and Operation Everest III (Comex '97) — that were designed to simulate an ascent of Mount Everest by placing subjects in a hypobaric chamber.5,6 The subjects in the two studies had a mean (±SD) resting PaO2 of 30.3±2.1 mm Hg (4.04±0.28 kPa)5 and 30.6±1.4 mm Hg (4.08±0.19 kPa),6 respectively, at a barometric pressure equivalent to the summit of Mount Everest (253.0 mm Hg, or 33.73 kPa). Such profound hypoxemia was tolerable because the subjects had been gradually acclimatized to the simulated altitude over a period of 37 to 40 days. In 1981, the partial pressures of oxygen and carbon dioxide (PaCO2) at end expiration were measured in a single person on Everest's summit after the person had been breathing without supplemental oxygen for approximately 10 minutes.7 With the use of a classic Bohr integration, the PaO2 for this climber was estimated to be 28 mm Hg (3.73 kPa). We made direct field measurements of PaO2 and arterial oxygen content (CaO2) in climbers breathing ambient air at these extreme altitudes.

Item Type:	Journal Article
Divisions:	Faculty of Medicine > Warwick Medical School > Metabolic and Vascular Health Faculty of Medicine > Warwick Medical School
Journal or Publication Title:	New England Journal Of Medicine
Publisher:	Massachusetts Medical Society
ISSN:	0028-4793
Date:	8 January 2009
Volume:	Vol.360
Number:	No.2
Page Range:	pp. 140-149
Identification Number:	10.1056/NEJMoa0801581
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Description:	The members of the Caudwell Xtreme Everest Research Group are as follows: Investigators — V. Ahuja, G. Aref-Adib, R. Burnham, A. Chisholm, K. Clarke, D. Coates, M. Coates, D. Cook, M. Cox, S. Dhillon, C. Dougall, P. Doyle, P. Duncan, M. Edsell, L. Edwards, L. Evans, P. Gardiner, M. Grocott, P. Gunning, N. Hart, J. Harrington, J. Harvey, C. Holloway, D. Howard, D. Hurlbut, C. Imray, C. Ince, M. Jonas, J. van der Kaaij, M. Khosravi, N. Kolfschoten, D. Levett, H. Luery, A. Luks, D. Martin, R. McMorrow, P. Meale, K. Mitchell, H. Montgomery, G. Morgan, J. Morgan, A. Murray, M. Mythen, S. Newman, M. O'Dwyer, J. Pate, T. Plant, M. Pun, P. Richards, A. Richardson, G. Rodway, J. Simpson, C. Stroud, M. Stroud, J. Stygal, B. Symons, P. Szawarski, A. Van Tulleken, C. Van Tulleken, A. Vercueil, L. Wandrag, M. Wilson, J. Windsor; Scientific Advisory Group — B. Basnyat, C. Clarke, T. Hornbein, J. Milledge, J. West.
URI:	http://wrap.warwick.ac.uk/id/eprint/52007

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