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Clarkson JM, McKeegan DEF, Sparrey J, Marchesi F, Leach MC, Martin JE. Determining Candidate Hypobaric Hypoxia Profiles for Humane Killing of Laboratory Mice. Front Vet Sci 2022; 9:834478. [PMID: 35400097 PMCID: PMC8988232 DOI: 10.3389/fvets.2022.834478] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 02/17/2022] [Indexed: 01/28/2023] Open
Abstract
Millions of mice are used annually in scientific research and must be humanely killed. Despite significant welfare concerns, carbon dioxide exposure remains the most common killing method, primarily because there is no practical and humane alternative. We explored whether hypobaric hypoxia via gradual decompression could induce a non-recovery state in anesthetized male C57BL/6 and Balb/c laboratory mice. We aimed to determine if this was possible in a feasible timescale with minimal pathological consequences, as a proof-of-principle step. Systematic evaluation of two decompression rates (75, 150 ms−1) and three profile shapes (accelerated, linear, gradual) in a factorial design revealed that hypobaric hypoxia effectively induced a non-recovery state in anesthetized laboratory mice, irrespective of decompression rate and shape. Mice took longer to reach a non-recovery state with the 75 ms−1 decompression rate (75 ms−1: 257 ± 8.96 vs. 150 ms−1: 214 ± 7.26 s), with longer latencies in gradual and linear shaped profiles. Accelerated shaped profiles were least susceptible to meaningful refinement via rate. The only pathological changes of concern were moderate middle ear congestion and hemorrhage. These findings suggest that hypobaric hypoxia has potential, and subsequent work will evaluate the welfare consequences of gradual decompression in conscious mice, to identify decompression profiles that minimize welfare harms associated with ear barotrauma.
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Affiliation(s)
- Jasmine M. Clarkson
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- *Correspondence: Jasmine M. Clarkson
| | - Dorothy E. F. McKeegan
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | | | - Francesco Marchesi
- School of Veterinary Medicine, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Matthew C. Leach
- School for Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Jessica E. Martin
- The Royal (Dick) School of Veterinary Studies, The Roslin Institute, The University of Edinburgh, Edinburgh, United Kingdom
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2
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Cobb AB, Levett DZH, Mitchell K, Aveling W, Hurlbut D, Gilbert-Kawai E, Hennis PJ, Mythen MG, Grocott MPW, Martin DS. Physiological responses during ascent to high altitude and the incidence of acute mountain sickness. Physiol Rep 2021; 9:e14809. [PMID: 33904650 PMCID: PMC8077104 DOI: 10.14814/phy2.14809] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 02/25/2021] [Accepted: 03/02/2021] [Indexed: 11/24/2022] Open
Abstract
Acute mountain sickness (AMS) occurs when there is failure of acclimatisation to high altitude. The aim of this study was to describe the relationship between physiological variables and the incidence of AMS during ascent to 5300 m. A total of 332 lowland‐dwelling volunteers followed an identical ascent profile on staggered treks. Self‐reported symptoms of AMS were recorded daily using the Lake Louise score (mild 3–4; moderate‐severe ≥5), alongside measurements of physiological variables (heart rate, respiratory rate (RR), peripheral oxygen saturation (SpO2) and blood pressure) before and after a standardised Xtreme Everest Step‐Test (XEST). The overall occurrence of AMS among participants was 73.5% (23.2% mild, 50.3% moderate–severe). There was no difference in gender, age, previous AMS, weight or body mass index between participants who developed AMS and those who did not. Participants who had not previously ascended >5000 m were more likely to get moderate‐to‐severe AMS. Participants who suffered moderate‐to‐severe AMS had a lower resting SpO2 at 3500 m (88.5 vs. 89.6%, p = 0.02), while participants who suffered mild or moderate‐to‐severe AMS had a lower end‐exercise SpO2 at 3500 m (82.2 vs. 83.8%, p = 0.027; 81.5 vs. 83.8%, p < 0.001 respectively). Participants who experienced mild AMS had lower end‐exercise RR at 3500 m (19.2 vs. 21.3, p = 0.017). In a multi‐variable regression model, only lower end‐exercise SpO2 (OR 0.870, p < 0.001) and no previous exposure to altitude >5000 m (OR 2.740, p‐value 0.003) predicted the development of moderate‐to‐severe AMS. The Xtreme Everest Step‐Test offers a simple, reproducible field test to help predict AMS, albeit with relatively limited predictive precision.
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Affiliation(s)
- Alexandra B Cobb
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, UK
| | - Denny Z H Levett
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, UK.,Anaesthesia and Critical Care Research Unit, University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Perioperative and Critical Care Research Theme, NIHR Biomedical Research Centre, University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Integrative Physiology and Critical Illness Group, School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, 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, UK.,Anaesthesia and Critical Care Research Unit, University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Perioperative and Critical Care Research Theme, NIHR Biomedical Research Centre, University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Integrative Physiology and Critical Illness Group, School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
| | - Wynne Aveling
- Anaesthetic Department, University College London Hospital, London, UK
| | - Daniel Hurlbut
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, UK
| | - 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, UK
| | - Philip J Hennis
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, UK
| | - Monty G Mythen
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, UK
| | - Michael P W Grocott
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, UK.,Anaesthesia and Critical Care Research Unit, University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Perioperative and Critical Care Research Theme, NIHR Biomedical Research Centre, University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Integrative Physiology and Critical Illness Group, School of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
| | - Daniel S Martin
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, UK.,Intensive Care Unit, University Hospitals Plymouth, Plymouth, UK.,Peninsula Medical School, University of Plymouth, Plymouth, UK
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3
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Enhanced flow-motion complexity of skin microvascular perfusion in Sherpas and lowlanders during ascent to high altitude. Sci Rep 2019; 9:14391. [PMID: 31591502 PMCID: PMC6779732 DOI: 10.1038/s41598-019-50774-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 09/13/2019] [Indexed: 12/17/2022] Open
Abstract
An increased and more effective microvascular perfusion is postulated to play a key role in the physiological adaptation of Sherpa highlanders to the hypobaric hypoxia encountered at high altitude. To investigate this, we used Lempel-Ziv complexity (LZC) analysis to explore the spatiotemporal dynamics of the variability of the skin microvascular blood flux (BF) signals measured at the forearm and finger, in 32 lowlanders (LL) and 46 Sherpa highlanders (SH) during the Xtreme Everest 2 expedition. Measurements were made at baseline (BL) (LL: London 35 m; SH: Kathmandu 1300 m) and at Everest base camp (LL and SH: EBC 5,300 m). We found that BF signal content increased with ascent to EBC in both SH and LL. At both altitudes, LZC of the BF signals was significantly higher in SH, and was related to local slow-wave flow-motion activity over multiple spatial and temporal scales. In SH, BF LZC was also positively associated with LZC of the simultaneously measured tissue oxygenation signals. These data provide robust mechanistic information of microvascular network functionality and flexibility during hypoxic exposure on ascent to high altitude. They demonstrate the importance of a sustained heterogeneity of network perfusion, associated with local vaso-control mechanisms, to effective tissue oxygenation during hypobaric hypoxia.
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Bhandari S, Cavalleri GL. Population History and Altitude-Related Adaptation in the Sherpa. Front Physiol 2019; 10:1116. [PMID: 31555147 PMCID: PMC6722185 DOI: 10.3389/fphys.2019.01116] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 08/12/2019] [Indexed: 12/29/2022] Open
Abstract
The first ascent of Mount Everest by Tenzing Norgay and Sir Edmund Hillary in 1953 brought global attention to the Sherpa people and human performance at altitude. The Sherpa inhabit the Khumbu Valley of Nepal, and are descendants of a population that has resided continuously on the Tibetan plateau for the past ∼25,000 to 40,000 years. The long exposure of the Sherpa to an inhospitable environment has driven genetic selection and produced distinct adaptive phenotypes. This review summarizes the population history of the Sherpa and their physiological and genetic adaptation to hypoxia. Genomic studies have identified robust signals of positive selection across EPAS1, EGLN1, and PPARA, that are associated with hemoglobin levels, which likely protect the Sherpa from altitude sickness. However, the biological underpinnings of other adaptive phenotypes such as birth weight and the increased reproductive success of Sherpa women are unknown. Further studies are required to identify additional signatures of selection and refine existing Sherpa-specific adaptive phenotypes to understand how genetic factors have underpinned adaptation in this population. By correlating known and emerging signals of genetic selection with adaptive phenotypes, we can further reveal hypoxia-related biological mechanisms of adaptation. Ultimately this work could provide valuable information regarding treatments of hypoxia-related illnesses including stroke, heart failure, lung disease and cancer.
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Affiliation(s)
- Sushil Bhandari
- Department of Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Gianpiero L Cavalleri
- Department of Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin, Ireland
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5
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Anesthetists (and Physicians) at Altitude. Int Anesthesiol Clin 2019. [PMID: 29521789 DOI: 10.1097/aia.0000000000000184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Cumpstey AF, Minnion M, Fernandez BO, Mikus-Lelinska M, Mitchell K, Martin DS, Grocott MPW, Feelisch M. Pushing arterial-venous plasma biomarkers to new heights: A model for personalised redox metabolomics? Redox Biol 2019; 21:101113. [PMID: 30738322 PMCID: PMC6369731 DOI: 10.1016/j.redox.2019.101113] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 01/04/2019] [Accepted: 01/14/2019] [Indexed: 01/24/2023] Open
Abstract
The chemical and functional interactions between Reactive Oxygen (ROS), Nitrogen (RNS) and Sulfur (RSS) species allow organisms to detect and respond to metabolic and environmental stressors, such as exercise and altitude exposure. Whether redox markers and constituents of this ‘Reactive Species Interactome’ (RSI) differ in concentration between arterial and venous blood is unknown. We hypothesised that such measurements may provide useful insight into metabolic/redox regulation at the whole-body level and would be consistent between individuals exposed to identical challenges. An exploratory study was performed during the Xtreme Alps expedition in 2010 in which four healthy individuals (2 male, 2 female) underwent paired arterial and central venous blood sampling before, during and after performance of a constant-work-rate cardiopulmonary exercise test, at sea level and again at 4559 m. Unexpectedly, plasma total free thiol and free cysteine concentrations remained substantially elevated at altitude throughout exercise with minimal arteriovenous gradients. Free sulfide concentrations changed only modestly upon combined altitude/exercise stress, whereas bound sulfide levels were lower at altitude than sea-level. No consistent signal indicative of the expected increased oxidative stress and nitrate→nitrite→NO reduction was observed with 4-hydroxynonenal, isoprostanes, nitrate, nitrite, nitroso species and cylic guanosine monophosphate. However, the observed arteriovenous concentration differences revealed a dynamic pattern of response that was unique to each participant. This novel redox metabolomic approach of obtaining quantifiable ‘metabolic signatures’ to a defined physiological challenge could potentially offer new avenues for personalised medicine. Exercise and high altitude (hypobaric hypoxia) significantly perturb redox balance. The role of thiols and reactive sulfur species in altitude acclimatization remains largely unknown. First measure of arteriovenous gradients of redox markers at altitude. Different individuals exposed to identical stresses display distinct redox response profiles. Redox metabolomics may offer new ways of personalizing medicine.
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Affiliation(s)
- Andrew F Cumpstey
- Critical Care Research Group, Southampton NIHR Biomedical Research Centre, Tremona Road, Southampton SO16 6YD, UK; Anaesthesia and Critical Care Research Unit, University Hospital Southampton NHS Foundation Trust, Tremona Road, Southampton SO16 6YD, UK; Integrative Physiology and Critical Illness Group, Clinical and Experimental Sciences, University of Southampton, Tremona Road, Southampton SO16 6YD, UK
| | - Magdalena Minnion
- Clinical & Experimental Sciences, Faculty of Medicine, NIHR Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Tremona Road, Southampton SO16 6YD, UK
| | - Bernadette O Fernandez
- Clinical & Experimental Sciences, Faculty of Medicine, NIHR Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Tremona Road, Southampton SO16 6YD, UK; Warwick Medical School, Division of Metabolic and Vascular Health, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
| | - Monika Mikus-Lelinska
- Clinical & Experimental Sciences, Faculty of Medicine, NIHR Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Tremona Road, Southampton SO16 6YD, UK
| | - Kay Mitchell
- Critical Care Research Group, Southampton NIHR Biomedical Research Centre, Tremona Road, Southampton SO16 6YD, UK; Anaesthesia and Critical Care Research Unit, University Hospital Southampton NHS Foundation Trust, Tremona Road, Southampton SO16 6YD, UK; Integrative Physiology and Critical Illness Group, Clinical and Experimental Sciences, University of Southampton, Tremona Road, Southampton SO16 6YD, UK
| | - Daniel S Martin
- UCL Centre for Altitude, Space and Extreme Environment (CASE) Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport Exercise & Health, 170 Tottenham Court Road, London W1T 7HA, UK; Intensive Care Unit, Royal Free Hospital, Pond Street, London NW3 2QG, UK
| | - Michael P W Grocott
- Critical Care Research Group, Southampton NIHR Biomedical Research Centre, Tremona Road, Southampton SO16 6YD, UK; Anaesthesia and Critical Care Research Unit, University Hospital Southampton NHS Foundation Trust, Tremona Road, Southampton SO16 6YD, UK; Integrative Physiology and Critical Illness Group, Clinical and Experimental Sciences, University of Southampton, Tremona Road, Southampton SO16 6YD, UK; Department of Anesthesiology, Duke University Medical School, NC, USA
| | - Martin Feelisch
- Integrative Physiology and Critical Illness Group, Clinical and Experimental Sciences, University of Southampton, Tremona Road, Southampton SO16 6YD, UK; Clinical & Experimental Sciences, Faculty of Medicine, NIHR Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Tremona Road, Southampton SO16 6YD, UK; Warwick Medical School, Division of Metabolic and Vascular Health, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK.
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7
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Davies T, Gilbert-Kawai E, Wythe S, Meale P, Mythen M, Levett D, Mitchell K, Grocott M, Clough G, Martin D. Sustained vasomotor control of skin microcirculation in Sherpas versus altitude-naive lowlanders: Experimental evidence from Xtreme Everest 2. Exp Physiol 2018; 103:1494-1504. [PMID: 30182473 DOI: 10.1113/ep087236] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 08/21/2018] [Indexed: 12/20/2022]
Abstract
NEW FINDINGS What is the central question of this study? Do Sherpa highlanders, when exposed to graded hypobaric hypoxia, exhibit enhanced vasomotor and neurovascular control to maintain microcirculatory flux, and thus tissue oxygenation, when compared with altitude-naive lowlanders? What is the main finding and its importance? Sherpas, when exposed to hypobaric hypoxia at high altitude, demonstrated superior preservation of their peripheral microcirculatory perfusion, a greater oxygen unloading rate and sustained microvascular reactivity with enhanced vasomotion, when compared with altitude-naive lowlanders. These differences have not been reported previously and may improve our understanding of the multifactorial responses to sustained environmental hypoxia. ABSTRACT Enhanced oxygen delivery, consequent to an increased microvascular perfusion, has been postulated to play a key role in the physiological adaptation of Tibetan highlanders to the hypobaric hypoxia encountered at high altitude. We tested the hypothesis that Sherpas, when exposed to graded hypobaric hypoxia, demonstrate enhanced vasomotor and neurovascular control to maintain microcirculatory flux, and thus tissue oxygenation, when compared with altitude-naive lowlanders. Eighty-three lowlanders [39 men and 44 women, 38.8 (13.1) years old; mean (SD)] and 61 Sherpas [28 men and 33 women, 27.9 (6.9) years old] were studied on ascent to Everest Base Camp over 11 days. Skin blood flux and tissue oxygen saturation were measured simultaneously using combined laser Doppler fluximetry and white light spectroscopy at baseline, 3500 and 5300 m. In both cohorts, ascent resulted in a decline in the sympathetically mediated microvascular constrictor response (P < 0.001), which was more marked in lowlanders than in Sherpas (P < 0.001). The microvascular dilator response evaluated by postocclusive reactive hyperaemia was significantly greater in Sherpas than in lowlanders at all sites (P < 0.002). Spectral analysis of the blood flux signals revealed enhanced myogenic (vasomotion) activity in Sherpas, which was unaffected by ascent to 5300 m. Although skin tissue oxygenation was lower in Sherpas than in lowlanders, the oxygen unloading rate was faster, and deoxyhaemoglobin levels higher, at all altitudes. Together, these data suggest that Sherpas, when exposed to hypobaric hypoxia, demonstrated superior preservation of peripheral microcirculatory perfusion compared with altitude-naive lowlanders. The physiological differences in local microvasculature vasomotor and neurovascular control may play a key role in Sherpa adaptation to high-altitude hypobaric hypoxia by sustaining local perfusion and tissue oxygenation.
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Affiliation(s)
- Thomas Davies
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, UK
| | - 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, UK
| | - Stephen Wythe
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, UK
| | - Paula Meale
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, UK
| | - Monty Mythen
- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, 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, UK.,Faculty of Medicine (CES) and Institute for Life Science, University of Southampton, Southampton, UK.,NIHR Southampton Biomedical Research Centre, University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Centre for Human Integrative Physiology, Faculty of Medicine, University of Southampton, Southampton, 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, 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, UK.,Faculty of Medicine (CES) and Institute for Life Science, University of Southampton, Southampton, UK.,NIHR Southampton Biomedical Research Centre, University Hospital Southampton NHS Foundation Trust, Southampton, UK.,Centre for Human Integrative Physiology, Faculty of Medicine, University of Southampton, Southampton, UK
| | - Geraldine Clough
- Institute of Developmental Sciences, Faculty of Medicine, University of Southampton, Southampton, 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, UK.,Critical Care Unit, Royal Free Hospital, London, UK
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- University College London Centre for Altitude Space and Extreme Environment Medicine, UCLH NIHR Biomedical Research Centre, Institute of Sport and Exercise Health, London, UK
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Lacey JRN, Kidel C, van der Kaaij JM, Brinkman P, Gilbert‐Kawai ET, Grocott MPW, Mythen MG, Martin DS. The Smell of Hypoxia: using an electronic nose at altitude and proof of concept of its role in the prediction and diagnosis of acute mountain sickness. Physiol Rep 2018; 6:e13854. [PMID: 30187693 PMCID: PMC6125242 DOI: 10.14814/phy2.13854] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 08/01/2018] [Accepted: 08/03/2018] [Indexed: 12/17/2022] Open
Abstract
Electronic nose (e-nose) devices may be used to identify volatile organic compounds (VOCs) in exhaled breath. VOCs generated via metabolic processes are candidate biomarkers of (patho)physiological pathways. We explored the feasibility of using an e-nose to generate human "breathprints" at high altitude. Furthermore, we explored the hypothesis that pathophysiological processes involved in the development of acute mountain sickness (AMS) would manifest as altered VOC profiles. Breath analysis was performed on Sherpa and lowlander trekkers at high altitude (3500 m). The Lake Louise Scoring (LLS) system was used to diagnose AMS. Raw data were reduced by principal component (PC) analysis (PCA). Cross validated linear discriminant analysis (CV-LDA) and receiver-operating characteristic area under curve (ROC-AUC) assessed discriminative function. Breathprints suitable for analysis were obtained from 58% (37/64) of samples. PCA showed significant differences between breathprints from participants with, and without, AMS; CV-LDA showed correct classification of 83.8%, ROC-AUC 0.86; PC 1 correlated with AMS severity. There were significant differences between breathprints of participants who remained AMS negative and those whom later developed AMS (CV-LDA 68.8%, ROC-AUC 0.76). PCA demonstrated discrimination between Sherpas and lowlanders (CV-LDA 89.2%, ROC-AUC 0.936). This study demonstrated the feasibility of breath analysis for VOCs using an e-nose at high altitude. Furthermore, it provided proof-of-concept data supporting e-nose utility as an objective tool in the prediction and diagnosis of AMS. E-nose technology may have substantial utility both in altitude medicine and under other circumstances where (mal)adaptation to hypoxia may be important (e.g., critically ill patients).
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Affiliation(s)
- Jonathan R. N. Lacey
- University College London Centre for Altitude Space and Extreme Environment (CASE) MedicineUCLH NIHR Biomedical Research CentreInstitute of Sport and Exercise HealthLondonUnited Kingdom
| | - Carlos Kidel
- Royal Free London NHS Foundation TrustLondonUnited Kingdom
| | - Jildou M. van der Kaaij
- University College London Centre for Altitude Space and Extreme Environment (CASE) MedicineUCLH NIHR Biomedical Research CentreInstitute of Sport and Exercise HealthLondonUnited Kingdom
| | - Paul Brinkman
- Respiratory MedicineAMC, University of AmsterdamAmsterdamNetherlands
| | - Edward T. Gilbert‐Kawai
- University College London Centre for Altitude Space and Extreme Environment (CASE) MedicineUCLH NIHR Biomedical Research CentreInstitute of Sport and Exercise HealthLondonUnited Kingdom
| | - Michael P. W. Grocott
- University College London Centre for Altitude Space and Extreme Environment (CASE) MedicineUCLH NIHR Biomedical Research CentreInstitute of Sport and Exercise HealthLondonUnited Kingdom
- Anaesthesia and Critical Care Research UnitUniversity Hospital Southampton NHS Foundation TrustSouthamptonUnited Kingdom
- Critical Care Research AreaNIHR Respiratory Biomedical Research UnitUniversity Hospital Southampton NHS Foundation TrustSouthamptonUnited Kingdom
- Integrative Physiology and Critical Illness GroupClinical and Experimental SciencesFaculty of MedicineUniversity of SouthamptonSouthamptonUnited Kingdom
| | - Michael G. Mythen
- University College London Centre for Altitude Space and Extreme Environment (CASE) MedicineUCLH NIHR Biomedical Research CentreInstitute of Sport and Exercise HealthLondonUnited Kingdom
| | - Daniel S. Martin
- University College London Centre for Altitude Space and Extreme Environment (CASE) MedicineUCLH NIHR Biomedical Research CentreInstitute of Sport and Exercise HealthLondonUnited Kingdom
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Raman S, Chentouf L, DeVile C, Peters MJ, Rahman S. Near infrared spectroscopy with a vascular occlusion test as a biomarker in children with mitochondrial and other neuro-genetic disorders. PLoS One 2018; 13:e0199756. [PMID: 29969469 PMCID: PMC6029804 DOI: 10.1371/journal.pone.0199756] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2017] [Accepted: 06/13/2018] [Indexed: 01/09/2023] Open
Abstract
Background Mitochondrial and neurogenetic diseases can present diagnostic challenges. We investigated if near infrared spectroscopy with the vascular occlusion test is able to differentiate between children with mitochondrial disease and children with neurogenetic disease or healthy controls. Methods Prospective observational study conducted in a tertiary children’s hospital. Results Forty-three children with mitochondrial disease (including both genetically confirmed primary mitochondrial disease and cases with biochemical evidence of mitochondrial dysfunction), 19 children with non-mitochondrial neurogenetic disease and 13 healthy controls were recruited. The delta tissue oxygen index (ΔTOI) values showed greater variability amongst children with mitochondrial disease and neurogenetic disease than healthy controls despite the median ΔTOI being similar (median 14.1 and 18.8, t-test, p = 0.16). A low ΔTOI identifies cases with a higher probability of mitochondrial disease or neurogenetic disease compared to healthy controls (positive likelihood ratio: 3.67; 95%CI:1.01–13). A high ΔTOI with the near infrared spectroscopy with vascular occlusion test identifies cases with a lower probability of having a disease (negative likelihood ratio: 0.51; 95%CI:0.36–0.74). Conclusion Near infrared spectroscopy with vascular occlusion test might be able to discriminate children with mitochondrial disease and neurogenetic disease from healthy controls.
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Affiliation(s)
- Sainath Raman
- Paediatric Intensive Care Unit, Great Ormond Street Hospital, London, United Kingdom
- Anaesthesia, Critical Care and Respiratory Unit, Infection, Immunity, and Inflammation Programme, UCL Institute of Child Health, London, United Kingdom
| | - Latifa Chentouf
- Mitochondrial Research Group, UCL Institute of Child Health, London, United Kingdom
- Metabolic Unit, Great Ormond Street Hospital, London, United Kingdom
| | - Catherine DeVile
- Neurology Department, Great Ormond Street Hospital, London, United Kingdom
| | - Mark J. Peters
- Paediatric Intensive Care Unit, Great Ormond Street Hospital, London, United Kingdom
- Anaesthesia, Critical Care and Respiratory Unit, Infection, Immunity, and Inflammation Programme, UCL Institute of Child Health, London, United Kingdom
| | - Shamima Rahman
- Mitochondrial Research Group, UCL Institute of Child Health, London, United Kingdom
- Metabolic Unit, Great Ormond Street Hospital, London, United Kingdom
- * E-mail:
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Abstract
Cardiopulmonary exercise testing (CPET) in hyperoxia and hypoxia has several applications, stemming from characterization of abnormal physiological response profiles associated with exercise intolerance. As altered oxygenation can impact the performance of gas-concentration and flow sensors and pulmonary gas exchange algorithms, integrated CPET system function requires validation under these conditions. Also, as oxygenation status can influence peak [Formula: see text]o2, care should be taken in the selection of work-rate incrementation rates when CPET performance is to be compared with normobaria at sea level. CPET has been used to evaluate the effects of supplemental O2 on exercise intolerance in chronic obstructive pulmonary disease, interstitial pulmonary fibrosis, and cystic fibrosis at sea level. However, identification of those CPET indices likely to be predictive of supplemental O2 outcomes for exercise tolerance at altitude in such patients is lacking. CPET performance with supplemental O2 in respiratory patients residing at high altitudes is also poorly studied. Finally, CPET has the potential to give physiological and clinical information about acute and chronic mountain sickness, high-altitude pulmonary edema, and high-altitude cerebral edema. It may also translate high-altitude acclimatization and adaptive processes in healthy individuals into intensive care medical practice.
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Metabolic adjustment to high-altitude hypoxia: from genetic signals to physiological implications. Biochem Soc Trans 2018; 46:599-607. [PMID: 29678953 DOI: 10.1042/bst20170502] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 03/24/2018] [Accepted: 03/27/2018] [Indexed: 01/04/2023]
Abstract
Ascent to high altitude is associated with physiological responses that counter the stress of hypobaric hypoxia by increasing oxygen delivery and by altering tissue oxygen utilisation via metabolic modulation. At the cellular level, the transcriptional response to hypoxia is mediated by the hypoxia-inducible factor (HIF) pathway and results in promotion of glycolytic capacity and suppression of oxidative metabolism. In Tibetan highlanders, gene variants encoding components of the HIF pathway have undergone selection and are associated with adaptive phenotypic changes, including suppression of erythropoiesis and increased blood lactate levels. In some highland populations, there has also been a selection of variants in PPARA, encoding peroxisome proliferator-activated receptor alpha (PPARα), a transcriptional regulator of fatty acid metabolism. In one such population, the Sherpas, lower muscle PPARA expression is associated with a decreased capacity for fatty acid oxidation, potentially improving the efficiency of oxygen utilisation. In lowlanders ascending to altitude, a similar suppression of fatty acid oxidation occurs, although the underlying molecular mechanism appears to differ along with the consequences. Unlike lowlanders, Sherpas appear to be protected against oxidative stress and the accumulation of intramuscular lipid intermediates at altitude. Moreover, Sherpas are able to defend muscle ATP and phosphocreatine levels in the face of decreased oxygen delivery, possibly due to suppression of ATP demand pathways. The molecular mechanisms allowing Sherpas to successfully live, work and reproduce at altitude may hold the key to novel therapeutic strategies for the treatment of diseases to which hypoxia is a fundamental contributor.
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Abstract
The Himalayan Sherpas, a human population of Tibetan descent, are highly adapted to life in the hypobaric hypoxia of high altitude. Mechanisms involving enhanced tissue oxygen delivery in comparison to Lowlander populations have been postulated to play a role in such adaptation. Whether differences in tissue oxygen utilization (i.e., metabolic adaptation) underpin this adaptation is not known, however. We sought to address this issue, applying parallel molecular, biochemical, physiological, and genetic approaches to the study of Sherpas and native Lowlanders, studied before and during exposure to hypobaric hypoxia on a gradual ascent to Mount Everest Base Camp (5,300 m). Compared with Lowlanders, Sherpas demonstrated a lower capacity for fatty acid oxidation in skeletal muscle biopsies, along with enhanced efficiency of oxygen utilization, improved muscle energetics, and protection against oxidative stress. This adaptation appeared to be related, in part, to a putatively advantageous allele for the peroxisome proliferator-activated receptor A (PPARA) gene, which was enriched in the Sherpas compared with the Lowlanders. Our findings suggest that metabolic adaptations underpin human evolution to life at high altitude, and could have an impact upon our understanding of human diseases in which hypoxia is a feature.
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Gilbert-Kawai E, Coppel J, Court J, van der Kaaij J, Vercueil A, Feelisch M, Levett D, Mythen M, Grocott MP, Martin D. Sublingual microcirculatory blood flow and vessel density in Sherpas at high altitude. J Appl Physiol (1985) 2017; 122:1011-1018. [PMID: 28126908 DOI: 10.1152/japplphysiol.00970.2016] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 01/17/2017] [Accepted: 01/23/2017] [Indexed: 01/29/2023] Open
Abstract
Anecdotal reports suggest that Sherpa highlanders demonstrate extraordinary tolerance to hypoxia at high altitude, despite exhibiting lower arterial oxygen content than acclimatized lowlanders. This study tested the hypothesis that Sherpas exposed to hypobaric hypoxia on ascent to 5,300 m develop increased microcirculatory blood flow as a means of maintaining tissue oxygen delivery. Incident dark-field imaging was used to obtain images of the sublingual microcirculation from 64 Sherpas and 69 lowlanders. Serial measurements were obtained from participants undertaking an ascent from baseline testing (35 m or 1,300 m) to Everest base camp (5,300 m) and following subsequent descent in Kathmandu (1,300 m). Microcirculatory flow index and heterogeneity index were used to provide indexes of microcirculatory flow, while capillary density was assessed using small vessel density. Sherpas demonstrated significantly greater microcirculatory blood flow at Everest base camp, but not at baseline testing or on return in Kathmandu, than lowlanders. Additionally, blood flow exhibited greater homogeneity at 5,300 and 1,300 m (descent) in Sherpas than lowlanders. Sublingual small vessel density was not different between the two cohorts at baseline testing or at 1,300 m; however, at 5,300 m, capillary density was up to 30% greater in Sherpas. These data suggest that Sherpas can maintain a significantly greater microcirculatory flow per unit time and flow per unit volume of tissue at high altitude than lowlanders. These findings support the notion that peripheral vascular factors at the microcirculatory level may be important in the process of adaptation to hypoxia.NEW & NOTEWORTHY Sherpa highlanders demonstrate extraordinary tolerance to hypoxia at high altitude, yet the physiological mechanisms underlying this tolerance remain unknown. In our prospective study, conducted on healthy volunteers ascending to Everest base camp (5,300 m), we demonstrated that Sherpas have a higher sublingual microcirculatory blood flow and greater capillary density at high altitude than lowlanders. These findings support the notion that the peripheral microcirculation plays a key role in the process of long-term adaptation to hypoxia.
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Affiliation(s)
- Edward Gilbert-Kawai
- University College London Centre for Altitude, Space, and Extreme Environment Medicine, University College London Hospitals National Institute for Health Research Biomedical Research Centre, Institute of Sport and Exercise Health, London, United Kingdom;
| | - Jonny Coppel
- University College London Centre for Altitude, Space, and Extreme Environment Medicine, University College London Hospitals National Institute for Health Research Biomedical Research Centre, Institute of Sport and Exercise Health, London, United Kingdom
| | - Jo Court
- University College London Centre for Altitude, Space, and Extreme Environment Medicine, University College London Hospitals National Institute for Health Research Biomedical Research Centre, Institute of Sport and Exercise Health, London, United Kingdom
| | - Jildou van der Kaaij
- University College London Centre for Altitude, Space, and Extreme Environment Medicine, University College London Hospitals National Institute for Health Research Biomedical Research Centre, Institute of Sport and Exercise Health, London, United Kingdom
| | - Andre Vercueil
- University College London Centre for Altitude, Space, and Extreme Environment Medicine, University College London Hospitals National Institute for Health Research Biomedical Research Centre, Institute of Sport and Exercise Health, London, United Kingdom
| | - Martin Feelisch
- University College London Centre for Altitude, Space, and Extreme Environment Medicine, University College London Hospitals National Institute for Health Research Biomedical Research Centre, Institute of Sport and Exercise Health, London, United Kingdom.,Integrative Physiology and Critical Illness Group, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Denny Levett
- University College London Centre for Altitude, Space, and Extreme Environment Medicine, University College London Hospitals National Institute for Health Research Biomedical Research Centre, Institute of Sport and Exercise Health, London, United Kingdom.,Anaesthesia and Critical Care Research Area, National Institute for Health Research Respiratory Biomedical Research Unit, University Hospital Southampton National Health Service Foundation Trust, Southampton, United Kingdom; and.,Integrative Physiology and Critical Illness Group, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Monty Mythen
- University College London Centre for Altitude, Space, and Extreme Environment Medicine, University College London Hospitals National Institute for Health Research Biomedical Research Centre, Institute of Sport and Exercise Health, London, United Kingdom
| | - Michael P Grocott
- University College London Centre for Altitude, Space, and Extreme Environment Medicine, University College London Hospitals National Institute for Health Research Biomedical Research Centre, Institute of Sport and Exercise Health, London, United Kingdom.,Anaesthesia and Critical Care Research Area, National Institute for Health Research Respiratory Biomedical Research Unit, University Hospital Southampton National Health Service Foundation Trust, Southampton, United Kingdom; and.,Integrative Physiology and Critical Illness Group, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Daniel Martin
- University College London Centre for Altitude, Space, and Extreme Environment Medicine, University College London Hospitals National Institute for Health Research Biomedical Research Centre, Institute of Sport and Exercise Health, London, United Kingdom
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Hennis PJ, Mitchell K, Gilbert-Kawai E, Bountziouka V, Wade A, Feelisch M, Grocott MP, Martin DS. Effects of dietary nitrate supplementation on symptoms of acute mountain sickness and basic physiological responses in a group of male adolescents during ascent to Mount Everest Base Camp. Nitric Oxide 2016; 60:24-31. [DOI: 10.1016/j.niox.2016.08.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Revised: 08/28/2016] [Accepted: 08/31/2016] [Indexed: 11/16/2022]
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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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Murray AJ. Energy metabolism and the high-altitude environment. Exp Physiol 2015; 101:23-7. [PMID: 26315373 DOI: 10.1113/ep085317] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2015] [Accepted: 08/20/2015] [Indexed: 01/08/2023]
Abstract
At high altitude the barometric pressure falls, challenging oxygen delivery to the tissues. Thus, whilst hypoxia is not the only physiological stress encountered at high altitude, low arterial P(O2) is a sustained feature, even after allowing adequate time for acclimatization. Cardiac and skeletal muscle energy metabolism is altered in subjects at, or returning from, high altitude. In the heart, energetic reserve falls, as indicated by lower phosphocreatine-to-ATP ratios. The underlying mechanism is unknown, but in the hypoxic rat heart fatty acid oxidation and respiratory capacity are decreased, whilst pyruvate oxidation is also lower after sustained hypoxic exposure. In skeletal muscle, there is not a consensus. With prolonged exposure to extreme high altitude (>5500 m) a loss of muscle mitochondrial density is seen, but this was not observed in a simulated ascent of Everest in hypobaric chambers. At more moderate high altitude, decreased respiratory capacity may occur without changes in mitochondrial volume density, and fat oxidation may be downregulated, although this is not seen in all studies. The underlying mechanisms, including the possible role of hypoxia-signalling pathways, remain to be resolved, particularly in light of confounding factors in the high-altitude environment. In high-altitude-adapted Tibetan natives, however, there is evidence of natural selection centred around the hypoxia-inducible factor pathway, and metabolic features in this population (e.g. low cardiac phosphocreatine-to-ATP ratios, increased cardiac glucose uptake and lower muscle mitochondrial densities) share similarities with those in acclimatized lowlanders, supporting a possible role for the hypoxia-inducible factor pathway in the metabolic response of cardiac and skeletal muscle energy metabolism to high altitude.
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Affiliation(s)
- Andrew J Murray
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
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