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Burtscher M, Viscor G. How important is V̇O 2max when climbing Mt. Everest (8,849 m)? Respir Physiol Neurobiol 2021; 297:103833. [PMID: 34952230 DOI: 10.1016/j.resp.2021.103833] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Revised: 12/12/2021] [Accepted: 12/20/2021] [Indexed: 11/18/2022]
Abstract
The maximal rate of oxygen uptake (V̇O2max) of humans declines with increasing altitude, but represents the upper limit of aerobic endurance performance at low and high altitude as well. Before Reinhold Messner and Peter Habeler climbed Mt. Everest first (1978) without supplemental oxygen, physiologists have doubted whether this would be possible due to insufficient V̇O2max remaining when approaching the summit (8849 m). Subsequently, several studies evaluated the decline in the V̇O2max levels at real and simulated extreme altitudes. However, the potential influence of the preexisting individual sea level V̇O2max remained largely unconsidered. Based on available studies and case observations, here we discuss the observed and expected decline of V̇O2max up to 8849 m dependent on the individual sea level V̇O2max. It is concluded that a high sea level V̇O2max and an only moderate decline of arterial oxygen saturation and associated V̇O2max with increasing altitude, due to appropriate acclimatization and ascent strategies, enable certain mountaineers to climb 8,000er summits and even the Everest without supplemental oxygen.
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Affiliation(s)
- Martin Burtscher
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria.
| | - Ginés Viscor
- Physiology Section, Department of Cell Biology, Physiology and Immunology, Faculty of Biology, University of Barcelona, Barcelona, Spain
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2
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Ilardo MA, Moltke I, Korneliussen TS, Cheng J, Stern AJ, Racimo F, de Barros Damgaard P, Sikora M, Seguin-Orlando A, Rasmussen S, van den Munckhof ICL, Ter Horst R, Joosten LAB, Netea MG, Salingkat S, Nielsen R, Willerslev E. Physiological and Genetic Adaptations to Diving in Sea Nomads. Cell 2019; 173:569-580.e15. [PMID: 29677510 DOI: 10.1016/j.cell.2018.03.054] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 01/01/2018] [Accepted: 03/21/2018] [Indexed: 12/30/2022]
Abstract
Understanding the physiology and genetics of human hypoxia tolerance has important medical implications, but this phenomenon has thus far only been investigated in high-altitude human populations. Another system, yet to be explored, is humans who engage in breath-hold diving. The indigenous Bajau people ("Sea Nomads") of Southeast Asia live a subsistence lifestyle based on breath-hold diving and are renowned for their extraordinary breath-holding abilities. However, it is unknown whether this has a genetic basis. Using a comparative genomic study, we show that natural selection on genetic variants in the PDE10A gene have increased spleen size in the Bajau, providing them with a larger reservoir of oxygenated red blood cells. We also find evidence of strong selection specific to the Bajau on BDKRB2, a gene affecting the human diving reflex. Thus, the Bajau, and possibly other diving populations, provide a new opportunity to study human adaptation to hypoxia tolerance. VIDEO ABSTRACT.
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Affiliation(s)
- Melissa A Ilardo
- Centre for GeoGenetics, University of Copenhagen, Copenhagen 1350, Denmark
| | - Ida Moltke
- Department of Biology, University of Copenhagen, Copenhagen 2200, Denmark
| | - Thorfinn S Korneliussen
- Centre for GeoGenetics, University of Copenhagen, Copenhagen 1350, Denmark; Department of Zoology, University of Cambridge, Cambridge, CB2 3EJ, UK
| | - Jade Cheng
- Department of Integrative Biology, University of California at Berkeley, Berkeley, CA 94720, USA
| | - Aaron J Stern
- Department of Integrative Biology, University of California at Berkeley, Berkeley, CA 94720, USA; Department of Computational Biology, University of California at Berkeley, Berkeley, CA 94720, USA
| | - Fernando Racimo
- Centre for GeoGenetics, University of Copenhagen, Copenhagen 1350, Denmark
| | | | - Martin Sikora
- Centre for GeoGenetics, University of Copenhagen, Copenhagen 1350, Denmark
| | - Andaine Seguin-Orlando
- Centre for GeoGenetics, University of Copenhagen, Copenhagen 1350, Denmark; Danish National High-throughput DNA Sequencing Centre, University of Copenhagen 1353, Denmark
| | - Simon Rasmussen
- Bioinformatics, Technical University of Denmark, Lyngby 2800, Denmark
| | - Inge C L van den Munckhof
- Department of Internal Medicine and Radboud Center for Infectious Diseases (RCI), Radboud University Medical Center, Nijmegen 6525, the Netherlands
| | - Rob Ter Horst
- Department of Internal Medicine and Radboud Center for Infectious Diseases (RCI), Radboud University Medical Center, Nijmegen 6525, the Netherlands
| | - Leo A B Joosten
- Department of Internal Medicine and Radboud Center for Infectious Diseases (RCI), Radboud University Medical Center, Nijmegen 6525, the Netherlands
| | - Mihai G Netea
- Department of Internal Medicine and Radboud Center for Infectious Diseases (RCI), Radboud University Medical Center, Nijmegen 6525, the Netherlands; Department for Genomics and Immunoregulation, Life and Medical Sciences Institute (LIMES), University of Bonn, Bonn 53115, Germany
| | | | - Rasmus Nielsen
- Centre for GeoGenetics, University of Copenhagen, Copenhagen 1350, Denmark; Department of Integrative Biology, University of California at Berkeley, Berkeley, CA 94720, USA.
| | - Eske Willerslev
- Centre for GeoGenetics, University of Copenhagen, Copenhagen 1350, Denmark; Department of Zoology, University of Cambridge, Cambridge, CB2 3EJ, UK; Wellcome Trust, Sanger Institute, Hinxton CB10 1SA, UK.
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Abstract
The Caudwell Xtreme Everest (CXE) expedition in the spring of 2007 systematically studied 222 healthy volunteers as they ascended from sea level to Everest Base Camp (5300 m). A subgroup of climbing investigators ascended higher on Everest and obtained physiological measurements up to an altitude of 8400 m. The aim of the study was to explore inter-individual variation in response to environmental hypobaric hypoxia in order to understand better the pathophysiology of critically ill patients and other patients in whom hypoxaemia and cellular hypoxia are prevalent. This paper describes the aims, study characteristics, organization and management of the CXE expedition.
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Curiositas. THE ULSTER MEDICAL JOURNAL 2016; 85:55-6. [PMID: 27158167 PMCID: PMC4847832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
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Gilbert-Kawai E, Sheperdigian A, Adams T, Mitchell K, Feelisch M, Murray A, Peters M, Gilbert-Kawai G, Montgomery H, Levett D, Kumar R, Mythen M, Grocott M, Martin D. Design and conduct of Xtreme Everest 2: An observational cohort study of Sherpa and lowlander responses to graduated hypobaric hypoxia. F1000Res 2015; 4:90. [PMID: 26064476 PMCID: PMC4448741 DOI: 10.12688/f1000research.6297.1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/07/2015] [Indexed: 11/20/2022] Open
Abstract
Objective: Oxygen availability falls with ascent to altitude and also as a consequence of critical illness. Because cellular sequelae and adaptive processes may be shared in both circumstances, high altitude exposure (‘physiological hypoxia’) assists in the exploration of the response to pathological hypoxia. We therefore studied the response of healthy participants to progressive hypobaric hypoxia at altitude. The primary objective of the study was to identify differences between high altitude inhabitants (Sherpas) and lowland comparators. Methods: We performed an observational cohort study of human responses to progressive hypobaric hypoxia (during ascent) and subsequent normoxia (following descent) comparing Sherpas with lowlanders. Studies were conducted in London (35m), Kathmandu (1300m), Namche Bazaar (3500m) and Everest Base Camp (5300m). Of 180 healthy volunteers departing from Kathmandu, 64 were Sherpas and 116 were lowlanders. Physiological, biochemical, genetic and epigenetic data were collected. Core studies focused on nitric oxide metabolism, microcirculatory blood flow and exercise performance. Additional studies performed in nested subgroups examined mitochondrial and metabolic function, and ventilatory and cardiac variables. Of the 180 healthy participants who left Kathmandu, 178 (99%) completed the planned trek. Overall, more than 90% of planned testing was completed. Forty-four study protocols were successfully completed at altitudes up to and including 5300m. A subgroup of identical twins (all lowlanders) was also studied in detail. Conclusion: This programme of study (Xtreme Everest 2) will provide a rich dataset relating to human adaptation to hypoxia, and the responses seen on re-exposure to normoxia. It is the largest comprehensive high altitude study of Sherpas yet performed. Translational data generated from this study will be of relevance to diseases in which oxygenation is a major factor.
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Affiliation(s)
- Edward Gilbert-Kawai
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, W1T 7HA, UK
| | - Adam Sheperdigian
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, W1T 7HA, UK
| | - Thomas Adams
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, W1T 7HA, UK
| | - Kay Mitchell
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, W1T 7HA, UK ; Integrative Physiology and Critical Illness Group, Faculty of Medicine, University Hospital Southampton NHS Foundation Trust, Southampton, SO16 6YD, UK ; Anaesthesia and Critical Care Research Unit, University Hospital Southampton NHS Foundation Trust, Southampton, SO16 6YD, UK ; NIHR Southampton Respiratory Biomedical Research Unit, Southampton, CB2 3EG, UK
| | - Martin Feelisch
- Integrative Physiology and Critical Illness Group, Faculty of Medicine, University Hospital Southampton NHS Foundation Trust, Southampton, SO16 6YD, UK ; NIHR Southampton Respiratory Biomedical Research Unit, Southampton, CB2 3EG, UK
| | - Andrew Murray
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, W1T 7HA, UK ; Department of Physiology, Development & Neuroscience, University of Cambridge, Cambridge, CB2 3EG, UK
| | - Mark Peters
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, W1T 7HA, UK ; Critical Care Group Portex Unit, UCL, Institute of Child Health, London, WC1N 1EH, UK
| | - Grace Gilbert-Kawai
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, W1T 7HA, UK
| | - Hugh Montgomery
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, W1T 7HA, UK
| | - Denny Levett
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, W1T 7HA, UK
| | - Rajendra Kumar
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, W1T 7HA, UK ; Nepal Health Research Council, Kathmandu, Nepal
| | - Michael Mythen
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, W1T 7HA, UK
| | - Michael Grocott
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, W1T 7HA, UK ; Integrative Physiology and Critical Illness Group, Faculty of Medicine, University Hospital Southampton NHS Foundation Trust, Southampton, SO16 6YD, UK ; Anaesthesia and Critical Care Research Unit, University Hospital Southampton NHS Foundation Trust, Southampton, SO16 6YD, UK ; NIHR Southampton Respiratory Biomedical Research Unit, Southampton, CB2 3EG, UK
| | - Daniel Martin
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, W1T 7HA, UK
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Abstract
The military has always had an important role in high altitude research. This is due to the fact that mountainous regions often span borders and provide a safe haven to enemies. Deploying troops rapidly into high altitude environments presents major problems in terms of the development of high altitude illness. This paper examines the rationale for carrying out research at high altitude and the opportunities within the UK Defence Medical Services for carrying out this research.
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Affiliation(s)
- Adrian Mellor
- Defence Medical Services, Lichfield, UK MDHU Northallerton, Friarage Hospital, Northallerton, UK Cardiothoracic Anaesthesia, S Tees NHS Foundation Trust, Middlesbrough, UK Carnegie Institute of Sport, Physical Activity and Leisure, Leeds Metropolitan University, Leeds, UK
| | - D Woods
- Defence Medical Services, Lichfield, UK MDHU Northallerton, Friarage Hospital, Northallerton, UK Royal Victoria Infirmary, Newcastle upon Tyne, UK Carnegie Institute of Sport, Physical Activity and Leisure, Leeds Metropolitan University, Leeds, UK
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7
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Martin DS, Gilbert-Kawai E, Levett DZ, Mitchell K, Kumar Bc R, Mythen MG, Grocott MP. Xtreme Everest 2: unlocking the secrets of the Sherpa phenotype? EXTREME PHYSIOLOGY & MEDICINE 2013; 2:30. [PMID: 24229457 PMCID: PMC3853703 DOI: 10.1186/2046-7648-2-30] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 09/12/2013] [Indexed: 01/06/2023]
Abstract
Xtreme Everest 2 (XE2) was part of an ongoing programme of field, laboratory and clinical research focused on human responses to hypoxaemia that was conducted by the Caudwell Xtreme Everest Hypoxia Research Consortium. The aim of XE2 was to characterise acclimatisation to environmental hypoxia during a standardised ascent to high altitude in order to identify biomarkers of adaptation and maladaptation. Ultimately, this may lead to novel diagnostic and treatment strategies for the pathophysiological hypoxaemia and cellular hypoxia observed in critically ill patients. XE2 was unique in comparing participants drawn from two distinct populations: native ancestral high-altitude dwellers (Sherpas) and native lowlanders. Experiments to study the microcirculation, mitochondrial function and the effect that nitric oxide metabolism may exert upon them were focal to the scientific profile. In addition, the genetic and epigenetic (methylation and histone modification) basis of observed differences in phenotype was explored. The biological samples and phenotypic metadata already collected during XE2 will be analysed as an independent study. Data generated will also contribute to (and be compared with) the bioresource obtained from our previous observational high-altitude study, Caudwell Xtreme Everest (2007).
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Affiliation(s)
- Daniel S Martin
- UCL Centre for Altitude, Space and Extreme Environment Medicine, Portex Unit, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK.
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8
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Martin DS, Gilbert-Kawai ET, Meale PM, Fernandez BO, Cobb A, Khosravi M, Mitchell K, Grocott MPW, Levett DZH, Mythen MG, Feelisch M. Design and conduct of 'Xtreme Alps': a double-blind, randomised controlled study of the effects of dietary nitrate supplementation on acclimatisation to high altitude. Contemp Clin Trials 2013; 36:450-9. [PMID: 24028941 DOI: 10.1016/j.cct.2013.09.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 08/29/2013] [Accepted: 09/02/2013] [Indexed: 01/05/2023]
Abstract
The study of healthy human volunteers ascending to high altitude provides a robust model of the complex physiological interplay that emulates human adaptation to hypoxaemia in clinical conditions. Nitric oxide (NO) metabolism may play an important role in both adaptation to high altitude and response to hypoxaemia during critical illness at sea level. Circulating nitrate and nitrite concentrations can be augmented by dietary supplementation and this is associated with improved exercise performance and mitochondrial efficiency. We hypothesised that the administration of a dietary substance (beetroot juice) rich in nitrate would improve oxygen efficiency during exercise at high altitude by enhancing tissue microcirculatory blood flow and oxygenation. Furthermore, nitrate supplementation would lead to measurable increases in NO bioactivity throughout the body. This methodological manuscript describes the design and conduct of the 'Xtreme Alps' expedition, a double-blind randomised controlled trial investigating the effects of dietary nitrate supplementation on acclimatisation to hypobaric hypoxia at high altitude in healthy human volunteers. The primary outcome measure was the change in oxygen efficiency during exercise at high altitude between participants allocated to receive nitrate supplementation and those receiving a placebo. A number of secondary measures were recorded, including exercise capacity, peripheral and microcirculatory blood flow and tissue oxygenation. Results from this study will further elucidate the role of NO in adaption to hypoxaemia and guide clinical trials in critically ill patients. Improved understanding of hypoxaemia in critical illness may provide new therapeutic avenues for interventions that will improve survival in critically ill patients.
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Affiliation(s)
- Daniel S Martin
- UCL Centre for Altitude, Space and Extreme Environment Medicine, Portex Unit, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK; University College London, Division of Surgery and Interventional Science, 9th Floor, Royal Free Hospital, Pond Street, London NW3 2QG, UK.
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HEGGIE VANESSA. Experimental physiology, Everest and oxygen: from the ghastly kitchens to the gasping lung. BRITISH JOURNAL FOR THE HISTORY OF SCIENCE 2013; 46:123-147. [PMCID: PMC3607278 DOI: 10.1017/s0007087412000775] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Often the truth value of a scientific claim is dependent on our faith that laboratory experiments can model nature. When the nature that you are modelling is something as large as the tallest terrestrial mountain on earth, and as mysterious (at least until 1953) as the reaction of the human body to the highest point on the earth's surface, mapping between laboratory and ‘real world’ is a tricky process. The so-called ‘death zone’ of Mount Everest is a liminal space; a change in weather could make the difference between a survivable mountaintop and a site where the human respiratory system cannot maintain basic biological functions. Predicting what would happen to the first human beings to climb that high was therefore literally a matter of life or death – here inaccurate models could kill. Consequently, high-altitude respiratory physiology has prioritized not the laboratory, but the field. A holistic, environmentally situated sort of science used a range of (often non-scientific) expertise to prove the laboratory wrong time after time. In so doing, Everest was constructed paradoxically both as a unique field site which needed to be studied in vivo, and as a ‘natural laboratory’ which could produce generalizable knowledge about the human (male) body.
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Affiliation(s)
- VANESSA HEGGIE
- Department of History and Philosophy of Science, University of Cambridge, Free School Lane, Cambridge, CB2 3RH, UK.
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Wilson MH, Davagnanam I, Holland G, Dattani RS, Tamm A, Hirani SP, Kolfschoten N, Strycharczuk L, Green C, Thornton JS, Wright A, Edsell M, Kitchen ND, Sharp DJ, Ham TE, Murray A, Holloway CJ, Clarke K, Grocott MP, Montgomery H, Imray C. Cerebral venous system and anatomical predisposition to high-altitude headache. Ann Neurol 2013; 73:381-9. [DOI: 10.1002/ana.23796] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 09/12/2012] [Accepted: 10/29/2012] [Indexed: 01/03/2023]
Affiliation(s)
| | - Indran Davagnanam
- Lysholm Department of Neuroradiology; National Hospital for Neurology and Neurosurgery; London
| | - Graeme Holland
- Centre for Altitude, Space, and Extreme Environment Medicine; University College London; London
| | - Raj S. Dattani
- Centre for Altitude, Space, and Extreme Environment Medicine; University College London; London
| | - Alexander Tamm
- Centre for Altitude, Space, and Extreme Environment Medicine; University College London; London
| | | | - Nicky Kolfschoten
- Centre for Altitude, Space, and Extreme Environment Medicine; University College London; London
| | - Lisa Strycharczuk
- Lysholm Department of Neuroradiology; National Hospital for Neurology and Neurosurgery; London
| | - Cathy Green
- Lysholm Department of Neuroradiology; National Hospital for Neurology and Neurosurgery; London
| | - John S. Thornton
- Lysholm Department of Neuroradiology; National Hospital for Neurology and Neurosurgery; London
| | | | | | - Neil D. Kitchen
- Department of Neurosurgery; National Hospital for Neurology and Neurosurgery; London
| | - David J. Sharp
- The Traumatic Brain Injury Centre; St Mary's Hospital; Imperial College; London; W1 2NY
| | - Timothy E. Ham
- The Traumatic Brain Injury Centre; St Mary's Hospital; Imperial College; London; W1 2NY
| | - Andrew Murray
- Department of Physiology, Development, and Neuroscience; University of Cambridge; Cambridge
| | | | - Kieran Clarke
- Department of Physiology; University of Oxford; Oxford
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Abstract
This article is a review of the rationale and methodology of a translational study conducted at altitude investigating the potential role of nitrate supplements to improve tolerance to hypoxia, and a discussion of the applicability of the findings to intensive care medicine.
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Affiliation(s)
- Steve Dauncey
- FY1 in Anaesthetics, St John's Hospital, Livingston, Scotland
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12
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Ji LD, Qiu YQ, Xu J, Irwin DM, Tam SC, Tang NLS, Zhang YP. Genetic adaptation of the hypoxia-inducible factor pathway to oxygen pressure among eurasian human populations. Mol Biol Evol 2012; 29:3359-70. [PMID: 22628534 DOI: 10.1093/molbev/mss144] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Research into the mechanisms of human adaptation to the hypoxic environment of high altitude is of great interest to the fields of human physiology and clinical medicine. Recently, the gene EGLN1, from the hypoxia-inducible factor (HIF) pathway, was identified as being involved in the hypoxic adaptation of highland Andeans and Tibetans. Both highland Andeans and Tibetans have adapted to an extremely hypoxic habitat and less attention has been paid to populations living in normoxic conditions at sea level and mild-hypoxic environments of moderate altitude, thus, whether a common adaptive mechanism exists in response to quantitative variations of environmental oxygen pressure over a wide range of residing altitudes is unknown. Here, we first performed a genome-wide association study of 35 populations from the Human Genome Diversity-CEPH Panel who dwell at sea level to moderate altitude in Eurasia (N = 691; 0-2,500 m) to identify the genetic adaptation profile of normoxic and mild-hypoxic inhabitants. In addition, we systematically compared the results from the present study to six previously published genome-wide scans of highland Andeans and Tibetans to identify shared adaptive signals in response to quantitative variations of oxygen pressure. For normoxic and mild-hypoxic populations, the strongest adaptive signal came from the mu opioid receptor-encoding gene (OPRM1, 2.54 × 10(-9)), which has been implicated in the stimulation of respiration, while in the systematic survey the EGLN1-DISC1 locus was identified in all studies. A replication study performed with highland Tibetans (N = 733) and sea level Han Chinese (N = 748) confirmed the association between altitude and SNP allele frequencies in OPRM1 (in Tibetans only, P < 0.01) and in EGLN1-DISC1 (in Tibetans and Han Chinese, P < 0.01). Taken together, identification of the OPRM1 gene suggests that cardiopulmonary adaptation mechanisms are important and should be a focus in future studies of hypoxia adaptation. Furthermore, the identification of the EGLN1 gene from the HIF pathway suggests a common adaptive mechanism for Eurasian human populations residing at different altitudes with different oxygen pressures.
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Affiliation(s)
- Lin-Dan Ji
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
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13
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McMorrow RCN, Windsor JS, Hart ND, Richards P, Rodway GW, Ahuja VY, O’Dwyer MJ, Mythen MG, Grocott MPW. Closed and open breathing circuit function in healthy volunteers during exercise at Mount Everest base camp (5300 m). Anaesthesia 2012; 67:875-80. [DOI: 10.1111/j.1365-2044.2012.07152.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Anderson PJ, Miller AD, O'Malley KA, Ceridon ML, Beck KC, Wood CM, Wiste HJ, Mueller JJ, Johnson JB, Johnson BD. Incidence and Symptoms of High Altitude Illness in South Pole Workers: Antarctic Study of Altitude Physiology (ASAP). CLINICAL MEDICINE INSIGHTS-CIRCULATORY RESPIRATORY AND PULMONARY MEDICINE 2011; 5:27-35. [PMID: 21695160 PMCID: PMC3114308 DOI: 10.4137/ccrpm.s6882] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Introduction: Each year, the US Antarctic Program rapidly transports scientists and support personnel from sea level (SL) to the South Pole (SP, 2835 m) providing a unique natural laboratory to quantify the incidence of acute mountain sickness (AMS), patterns of altitude related symptoms and the field effectiveness of acetazolamide in a highly controlled setting. We hypothesized that the combination of rapid ascent (3 hr), accentuated hypobarism (relative to altitude), cold, and immediate exertion would increase altitude illness risk. Methods: Medically screened adults (N = 246, age = 37 ± 11 yr, 30% female, BMI = 26 ± 4 kg/m2) were recruited. All underwent SL and SP physiological evaluation, completed Lake Louise symptom questionnaires (LLSQ, to define AMS), and answered additional symptom related questions (eg, exertional dyspnea, mental status, cough, edema and general health), during the 1st week at altitude. Acetazolamide, while not mandatory, was used by 40% of participants. Results: At SP, the barometric pressure resulted in physiological altitudes that approached 3400 m, while T °C averaged −42, humidity 0.03%. Arterial oxygen saturation averaged 89% ± 3%. Overall, 52% developed LLSQ defined AMS. The most common symptoms reported were exertional dyspnea-(87%), sleeping difficulty-(74%), headache-(66%), fatigue-(65%), and dizziness/lightheadedness-(46%). Symptom severity peaked on days 1–2, yet in >20% exertional dyspnea, fatigue and sleep problems persisted through day 7. AMS incidence was similar between those using acetazolamide and those abstaining (51 vs. 52%, P = 0.87). Those who used acetazolamide tended to be older, have less altitude experience, worse symptoms on previous exposures, and less SP experience. Conclusion: The incidence of AMS at SP tended to be higher than previously reports in other geographic locations at similar altitudes. Thus, the SP constitutes a more intense altitude exposure than might be expected considering physical altitude alone. Many symptoms persist, possibly due to extremely cold, arid conditions and the benefits of acetazolamide appeared negligible, though it may have prevented more severe symptoms in higher risk subjects.
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Affiliation(s)
- Paul J Anderson
- Health Partners Occupational and Environmental Medicine Residency, St. Paul, MN, USA
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Holloway CJ, Montgomery HE, Murray AJ, Cochlin LE, Codreanu I, Hopwood N, Johnson AW, Rider OJ, Levett DZH, Tyler DJ, Francis JM, Neubauer S, Grocott MPW, Clarke K. Cardiac response to hypobaric hypoxia: persistent changes in cardiac mass, function, and energy metabolism after a trek to Mt. Everest Base Camp. FASEB J 2010; 25:792-6. [PMID: 20978235 DOI: 10.1096/fj.10-172999] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We postulated that changes in cardiac high-energy phosphate metabolism may underlie the myocardial dysfunction caused by hypobaric hypoxia. Healthy volunteers (n=14) were studied immediately before, and within 4 d of return from, a 17-d trek to Mt. Everest Base Camp (5300 m). (31)P magnetic resonance (MR) spectroscopy was used to measure cardiac phosphocreatine (PCr)/ATP, and MR imaging and echocardiography were used to assess cardiac volumes, mass, and function. Immediately after returning from Mt. Everest, total body weight had fallen by 3% (P<0.05), but left ventricular mass, adjusted for changes in body surface area, had disproportionately decreased by 11% (P<0.05). Alterations in diastolic function were also observed, with a reduction in peak left ventricular filling rates and mitral inflow E/A, by 17% (P<0.05) and 24% (P<0.01), respectively, with no change in hydration status. Compared with pretrek, cardiac PCr/ATP ratio had decreased by 18% (P<0.01). Whether the abnormalities were even greater at altitude is unknown, but all had returned to pretrek levels after 6 mo. The alterations in cardiac morphology, function, and energetics are similar to findings in patients with chronic hypoxia. Thus, a decrease in cardiac PCr/ATP may be a universal response to periods of sustained low oxygen availability, underlying hypoxia-induced cardiac dysfunction in healthy human heart and in patients with cardiopulmonary diseases.
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Affiliation(s)
- Cameron J Holloway
- 1 Department of Physiology, Anatomy, and Genetics, Sherrington Bldg., University of Oxford, Oxford OX1 3PT, UK.
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16
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Abstract
The Caudwell Xtreme Everest (CXE) expedition involved the detailed study of 222 subjects ascending to 5300 m or higher during the first half of 2007. Following baseline measurements at sea level, 198 trekker-subjects trekked to Everest Base Camp (EBC) following an identical ascent profile. An additional group of 24 investigator-subjects followed a similar ascent to EBC and remained there for the duration of the expedition, with a subgroup of 14 collecting data higher on Everest. This article focuses on published data obtained by the investigator-subjects at extreme altitude (>5500 m). Unique measurements of peak oxygen consumption, middle cerebral artery diameter and blood velocity, and microcirculatory blood flow were made on the South Col (7950 m). Unique arterial blood gas values were obtained from 4 subjects at 8400 m during descent from the summit of Everest. Arterial blood gas and microcirculatory blood flow data are discussed in detail.
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Levett DZH, Martin DS, Wilson MH, Mitchell K, Dhillon S, Rigat F, Montgomery HE, Mythen MG, Grocott MPW. Design and conduct of Caudwell Xtreme Everest: an observational cohort study of variation in human adaptation to progressive environmental hypoxia. BMC Med Res Methodol 2010; 10:98. [PMID: 20964858 PMCID: PMC2988011 DOI: 10.1186/1471-2288-10-98] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Accepted: 10/21/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The physiological responses to hypoxaemia and cellular hypoxia are poorly understood, and inter-individual differences in performance at altitude and outcome in critical illness remain unexplained. We propose a model for exploring adaptation to hypoxia in the critically ill: the study of healthy humans, progressively exposed to environmental hypobaric hypoxia (EHH). The aim of this study was to describe the spectrum of adaptive responses in humans exposed to graded EHH and identify factors (physiological and genetic) associated with inter-individual variation in these responses. METHODS DESIGN Observational cohort study of progressive incremental exposure to EHH. SETTING University human physiology laboratory in London, UK (75 m) and 7 field laboratories in Nepal at 1300 m, 3500 m, 4250 m, 5300 m, 6400 m, 7950 m and 8400 m. PARTICIPANTS 198 healthy volunteers and 24 investigators trekking to Everest Base Camp (EBC) (5300 m). A subgroup of 14 investigators studied at altitudes up to 8400 m on Everest. MAIN OUTCOME MEASURES Exercise capacity, exercise efficiency and economy, brain and muscle Near Infrared Spectroscopy, plasma biomarkers (including markers of inflammation), allele frequencies of known or suspected hypoxia responsive genes, spirometry, neurocognitive testing, retinal imaging, pupilometry. In nested subgroups: microcirculatory imaging, muscle biopsies with proteomic and transcriptomic tissue analysis, continuous cardiac output measurement, arterial blood gas measurement, trans-cranial Doppler, gastrointestinal tonometry, thromboelastography and ocular saccadometry. RESULTS Of 198 healthy volunteers leaving Kathmandu, 190 reached EBC (5300 m). All 24 investigators reached EBC. The completion rate for planned testing was more than 99% in the investigator group and more than 95% in the trekkers. Unique measurements were safely performed at extreme altitude, including the highest (altitude) field measurements of exercise capacity, cerebral blood flow velocity and microvascular blood flow at 7950 m and arterial blood gas measurement at 8400 m. CONCLUSIONS This study demonstrates the feasibility and safety of conducting a large healthy volunteer cohort study of human adaptation to hypoxia in this difficult environment. Systematic measurements of a large set of variables were achieved in 222 subjects and at altitudes up to 8400 m. The resulting dataset is a unique resource for the study of genotype:phenotype interactions in relation to hypoxic adaptation.
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Affiliation(s)
- Denny Z H Levett
- Centre for Altitude Space and Extreme Environment Medicine, UCL Institute of Human Health and Performance, First Floor, Charterhouse Building, UCL Archway Campus, Highgate Hill, London, N19 5LW, UK
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Koch SP, Habermehl C, Mehnert J, Schmitz CH, Holtze S, Villringer A, Steinbrink J, Obrig H. High-resolution optical functional mapping of the human somatosensory cortex. FRONTIERS IN NEUROENERGETICS 2010; 2:12. [PMID: 20616883 PMCID: PMC2899520 DOI: 10.3389/fnene.2010.00012] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Accepted: 05/26/2010] [Indexed: 11/19/2022]
Abstract
Non-invasive optical imaging of brain function has been promoted in a number of fields in which functional magnetic resonance imaging (fMRI) is limited due to constraints induced by the scanning environment. Beyond physiological and psychological research, bedside monitoring and neurorehabilitation may be relevant clinical applications that are yet little explored. A major obstacle to advocate the tool in clinical research is insufficient spatial resolution. Based on a multi-distance high-density optical imaging setup, we here demonstrate a dramatic increase in sensitivity of the method. We show that optical imaging allows for the differentiation between activations of single finger representations in the primary somatosensory cortex (SI). Methodologically our findings confirm results in a pioneering study by Zeff et al. (2007) and extend them to the homuncular organization of SI. After performing a motor task, eight subjects underwent vibrotactile stimulation of the little finger and the thumb. We used a high-density diffuse-optical sensing array in conjunction with optical tomographic reconstruction. Optical imaging disclosed three discrete activation foci one for motor and two discrete foci for vibrotactile stimulation of the first and fifth finger, respectively. The results were co-registered to the individual anatomical brain anatomy (MRI) which confirmed the localization in the expected cortical gyri in four subjects. This advance in spatial resolution opens new perspectives to apply optical imaging in the research on plasticity notably in patients undergoing neurorehabilitation.
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Affiliation(s)
- Stefan P Koch
- Berlin NeuroImaging Center, Charité Universitätsmedizin Berlin Berlin, Germany
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19
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Edwards LM, Murray AJ, Tyler DJ, Kemp GJ, Holloway CJ, Robbins PA, Neubauer S, Levett D, Montgomery HE, Grocott MP, Clarke K. The effect of high-altitude on human skeletal muscle energetics: P-MRS results from the Caudwell Xtreme Everest expedition. PLoS One 2010; 5:e10681. [PMID: 20502713 PMCID: PMC2873292 DOI: 10.1371/journal.pone.0010681] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Accepted: 04/23/2010] [Indexed: 01/28/2023] Open
Abstract
Many disease states are associated with regional or systemic hypoxia. The study of healthy individuals exposed to high-altitude hypoxia offers a way to explore hypoxic adaptation without the confounding effects of disease and therapeutic interventions. Using 31P magnetic resonance spectroscopy and imaging, we investigated skeletal muscle energetics and morphology after exposure to hypobaric hypoxia in seven altitude-naïve subjects (trekkers) and seven experienced climbers. The trekkers ascended to 5300 m while the climbers ascended above 7950 m. Before the study, climbers had better mitochondrial function (evidenced by shorter phosphocreatine recovery halftime) than trekkers: 16±1 vs. 22±2 s (mean ± SE, p<0.01). Climbers had higher resting [Pi] than trekkers before the expedition and resting [Pi] was raised across both groups on their return (PRE: 2.6±0.2 vs. POST: 3.0±0.2 mM, p<0.05). There was significant muscle atrophy post-CXE (PRE: 4.7±0.2 vs. POST: 4.5±0.2 cm2, p<0.05), yet exercising metabolites were unchanged. These results suggest that, in response to high altitude hypoxia, skeletal muscle function is maintained in humans, despite significant atrophy.
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Affiliation(s)
- Lindsay M Edwards
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, Oxfordshire, United Kingdom.
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Martin DS, Goedhart P, Vercueil A, Ince C, Levett DZH, Grocott MPW. Changes in sublingual microcirculatory flow index and vessel density on ascent to altitude. Exp Physiol 2010; 95:880-91. [PMID: 20418348 DOI: 10.1113/expphysiol.2009.051656] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We hypothesized that ascent to altitude would result in reduced sublingual microcirculatory flow index (MFI) and increased vessel density. Twenty-four subjects were studied using sidestream dark-field imaging, as they ascended to 5300 m; one cohort remained at this altitude (n = 10), while another ascended higher (maximum 8848 m; n = 14). The MFI, vessel density and grid crossings (GX; an alternative density measure) were calculated. Total study length was 71 days; images were recorded at sea level (SL), Namche Bazaar (3500 m), Everest base camp (5300 m), the Western Cwm (6400 m), South Col (7950 m) and departure from Everest base camp (5300 m; 5300 m-b). Peripheral oxygen saturation (SpO2), heart rate and blood pressure were also recorded. Compared with SL, altitude resulted in reduced sublingual MFI in small (<25 microm; P < 0.0001) and medium vessels (26-50 microm; P = 0.006). The greatest reduction in MFI from SL was seen at 5300 m-b; from 2.8 to 2.5 in small vessels and from 2.9 to 2.4 in medium-sized vessels. The density of vessels <25 microm did not change during ascent, but those >25 microm rose from 1.68 (+/- 0.43) mm mm(-2) at SL to 2.27 (+/- 0.57) mm mm(-2) at 5300 m-b (P = 0.005); GX increased at all altitudes (P < 0.001). The reduction in MFI was greater in climbers than in those who remained at 5300 m in small and medium-sized vessels (P = 0.017 and P = 0.002, respectively). At 7950 m, administration of supplemental oxygen resulted in a further reduction of MFI and increase in vessel density. Thus, MFI was reduced whilst GX increased in the sublingual mucosa with prolonged exposure to hypoxia and was exaggerated in those exposed to extreme altitude.
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Affiliation(s)
- Daniel S Martin
- UCL Centre for Altitude, Space and Extreme Environment Medicine, Portex Unit, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK.
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Martin DS, Levett DZH, Grocott MPW, Montgomery HE. Variation in human performance in the hypoxic mountain environment. Exp Physiol 2010; 95:463-70. [DOI: 10.1113/expphysiol.2009.047589] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Murray AJ. Metabolic adaptation of skeletal muscle to high altitude hypoxia: how new technologies could resolve the controversies. Genome Med 2009; 1:117. [PMID: 20090895 PMCID: PMC2808733 DOI: 10.1186/gm117] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In most tissues of the body, cellular ATP production predominantly occurs via mitochondrial oxidative phosphorylation of reduced intermediates, which are in turn derived from substrates such as glucose and fatty acids. In order to maintain ATP homeostasis, and therefore cellular function, the mitochondria require a constant supply of fuels and oxygen. In many disease states, or in healthy individuals at altitude, tissue oxygen levels fall and the cell must meet this hypoxic challenge to maintain energetics and limit oxidative stress. In humans at altitude and patients with respiratory disease, loss of skeletal muscle mitochondrial density is a consistent finding. Recent studies that have used cultured cells and genetic mouse models have elucidated a number of elegant adaptations that allow cells with a diminished mitochondrial population to function effectively in hypoxia. This article reviews these findings alongside studies of hypoxic human skeletal muscle, putting them into the context of whole-body physiology and acclimatization to high-altitude hypoxia. A number of current controversies are highlighted, which may eventually be resolved by a systems physiology approach that considers the time-or tissue-dependent nature of some adaptive responses. Future studies using high-throughput metabolomic, transcriptomic, and proteomic technologies to investigate hypoxic skeletal muscle in humans and animal models could resolve many of these controversies, and a case is therefore made for the integration of resulting data into computational models that account for factors such as duration and extent of hypoxic exposure, subjects' backgrounds, and whether data have been acquired from active or sedentary individuals. An integrated and more quantitative understanding of the body's metabolic response to hypoxia and the conditions under which adaptive processes occur could reveal much about the ways that tissues function in the very many disease states where hypoxia is a critical factor.
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Affiliation(s)
- Andrew J Murray
- Department of Physiology, Development & Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK
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Allen SH, Moore J, Grocott MP. Expedition medicine in the tropics: through heat and sleet. Trans R Soc Trop Med Hyg 2009; 103:1081-4. [DOI: 10.1016/j.trstmh.2009.07.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Accepted: 07/01/2009] [Indexed: 10/20/2022] Open
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Grocott MPW, Martin DS, Levett DZH, McMorrow R, Windsor J, Montgomery HE. Arterial blood gases and oxygen content in climbers on Mount Everest. N Engl J Med 2009; 360:140-9. [PMID: 19129527 DOI: 10.1056/nejmoa0801581] [Citation(s) in RCA: 279] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND The level of environmental hypobaric hypoxia that affects climbers at the summit of Mount Everest (8848 m [29,029 ft]) is close to the limit of tolerance by humans. We performed direct field measurements of arterial blood gases in climbers breathing ambient air on Mount Everest. METHODS We obtained samples of arterial blood from 10 climbers during their ascent to and descent from the summit of Mount Everest. The partial pressures of arterial oxygen (PaO(2)) and carbon dioxide (PaCO(2)), pH, and hemoglobin and lactate concentrations were measured. The arterial oxygen saturation (SaO(2)), bicarbonate concentration, base excess, and alveolar-arterial oxygen difference were calculated. RESULTS PaO(2) fell with increasing altitude, whereas SaO(2) was relatively stable. The hemoglobin concentration increased such that the oxygen content of arterial blood was maintained at or above sea-level values until the climbers reached an elevation of 7100 m (23,294 ft). In four samples taken at 8400 m (27,559 ft)--at which altitude the barometric pressure was 272 mm Hg (36.3 kPa)--the mean PaO(2) in subjects breathing ambient air was 24.6 mm Hg (3.28 kPa), with a range of 19.1 to 29.5 mm Hg (2.55 to 3.93 kPa). The mean PaCO(2) was 13.3 mm Hg (1.77 kPa), with a range of 10.3 to 15.7 mm Hg (1.37 to 2.09 kPa). At 8400 m, the mean arterial oxygen content was 26% lower than it was at 7100 m (145.8 ml per liter as compared with 197.1 ml per liter). The mean calculated alveolar-arterial oxygen difference was 5.4 mm Hg (0.72 kPa). CONCLUSIONS The elevated alveolar-arterial oxygen difference that is seen in subjects who are in conditions of extreme hypoxia may represent a degree of subclinical high-altitude pulmonary edema or a functional limitation in pulmonary diffusion.
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Affiliation(s)
- Michael P W Grocott
- Centre for Altitude, Space, and Extreme Environment Medicine, University College London Institute of Human Health and Performance, London, United Kingdom.
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Abstract
The Caudwell Xtreme Everest (CXE) expedition in the spring of 2007 was a large field-study investigating adaptive responses to hypoxia, and was supported by a grant from the Intensive Care Foundation. This article sets out to explain why the CXE team went to Everest, what they hope to learn, and discusses some of the key studies.
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Affiliation(s)
- Mike Grocott
- Director, Caudwell Xtreme Everest; Senior Lecturer in Intensive Care Medicine, University College London; Honorary Consultant, The Whittington Hospital NHS Trust
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