1
|
Isakovich R, Cates VC, Pentz BA, Bird JD, Vanden Berg ER, de Freitas EM, Nysten CE, Leacy JK, O'Halloran KD, Brutsaert TD, Sherpa MT, Day TA. Using modified Fenn diagrams to assess ventilatory acclimatization during ascent to high altitude: Effect of acetazolamide. Exp Physiol 2024; 109:1080-1098. [PMID: 38747161 PMCID: PMC11215491 DOI: 10.1113/ep091748] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Accepted: 03/12/2024] [Indexed: 07/02/2024]
Abstract
High altitude (HA) ascent imposes systemic hypoxia and associated risk of acute mountain sickness. Acute hypoxia elicits a hypoxic ventilatory response (HVR), which is augmented with chronic HA exposure (i.e., ventilatory acclimatization; VA). However, laboratory-based HVR tests lack portability and feasibility in field studies. As an alternative, we aimed to characterize area under the curve (AUC) calculations on Fenn diagrams, modified by plotting portable measurements of end-tidal carbon dioxide (P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) against peripheral oxygen saturation (S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) to characterize and quantify VA during incremental ascent to HA (n = 46). Secondarily, these participants were compared with a separate group following the identical ascent profile whilst self-administering a prophylactic oral dose of acetazolamide (Az; 125 mg BID; n = 20) during ascent. First, morningP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ andS p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$ measurements were collected on 46 acetazolamide-free (NAz) lowland participants during an incremental ascent over 10 days to 5160 m in the Nepal Himalaya. AUC was calculated from individually constructed Fenn diagrams, with a trichotomized split on ranked values characterizing the smallest, medium, and largest magnitudes of AUC, representing high (n = 15), moderate (n = 16), and low (n = 15) degrees of acclimatization. After characterizing the range of response magnitudes, we further demonstrated that AUC magnitudes were significantly smaller in the Az group compared to the NAz group (P = 0.0021), suggesting improved VA. These results suggest that calculating AUC on modified Fenn diagrams has utility in assessing VA in large groups of trekkers during incremental ascent to HA, due to the associated portability and congruency with known physiology, although this novel analytical method requires further validation in controlled experiments. HIGHLIGHTS: What is the central question of this study? What are the characteristics of a novel methodological approach to assess ventilatory acclimatization (VA) with incremental ascent to high altitude (HA)? What is the main finding and its importance? Area under the curve (AUC) magnitudes calculated from modified Fenn diagrams were significantly smaller in trekkers taking an oral prophylactic dose of acetazolamide compared to an acetazolamide-free group, suggesting improved VA. During incremental HA ascent, quantifying AUC using modified Fenn diagrams is feasible to assess VA in large groups of trekkers with ascent, although this novel analytical method requires further validation in controlled experiments.
Collapse
Affiliation(s)
- Rodion Isakovich
- Department of Biology, Faculty of Science and TechnologyMount Royal UniversityCalgaryAlbertaCanada
| | - Valerie C. Cates
- Department of Biology, Faculty of Science and TechnologyMount Royal UniversityCalgaryAlbertaCanada
| | - Brandon A. Pentz
- Department of Biology, Faculty of Science and TechnologyMount Royal UniversityCalgaryAlbertaCanada
| | - Jordan D. Bird
- Department of Biology, Faculty of Science and TechnologyMount Royal UniversityCalgaryAlbertaCanada
| | - Emily R. Vanden Berg
- Department of Biology, Faculty of Science and TechnologyMount Royal UniversityCalgaryAlbertaCanada
| | - Emily M. de Freitas
- Department of Biology, Faculty of Science and TechnologyMount Royal UniversityCalgaryAlbertaCanada
| | - Cassandra E. Nysten
- Department of Biology, Faculty of Science and TechnologyMount Royal UniversityCalgaryAlbertaCanada
| | - Jack K. Leacy
- Department of Biology, Faculty of Science and TechnologyMount Royal UniversityCalgaryAlbertaCanada
- Department of Physiology, School of Medicine, College of Medicine & HealthUniversity Cork CollegeCorkIreland
| | - Ken D. O'Halloran
- Department of Physiology, School of Medicine, College of Medicine & HealthUniversity Cork CollegeCorkIreland
| | | | | | - Trevor A. Day
- Department of Biology, Faculty of Science and TechnologyMount Royal UniversityCalgaryAlbertaCanada
| |
Collapse
|
2
|
Liu G, Li Y, Liao N, Shang X, Xu F, Yin D, Shao D, Jiang C, Shi J. Energy metabolic mechanisms for high altitude sickness: Downregulation of glycolysis and upregulation of the lactic acid/amino acid-pyruvate-TCA pathways and fatty acid oxidation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 894:164998. [PMID: 37353011 DOI: 10.1016/j.scitotenv.2023.164998] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 06/16/2023] [Accepted: 06/17/2023] [Indexed: 06/25/2023]
Abstract
Hypobaric hypoxia is often associated with the plateau environment and can lead to altitude sickness or death. The underlying cause is a lack of oxygen, which limits energy metabolism and leads to a compensatory stress response. Although glycolysis is commonly accepted as the primary energy source during clinical hypoxia, our preliminary experiments suggest that hypobaric hypoxia may depress glycolysis. To provide a more comprehensive understanding of energy metabolism under short-term hypobaric hypoxia, we exposed mice to a simulated altitude of 5000 m for 6 or 12 h. After the exposure, we collected blood and liver tissues to quantify the substrates, enzymes, and metabolites involved in glycolysis, lactic acid metabolism, the tricarboxylic acid cycle (TCA), and fatty acid β-oxidation. We also performed transcriptome and enzymatic activity analyses of the liver. Our results show that 6 h of hypoxic exposure significantly increased blood glucose, decreased lactic acid and triglyceride concentrations, and altered liver enzyme activities of mice exposed to hypoxia. The key enzymes in the glycolytic, TCA, and fatty acid β-oxidation pathways were primarily affected. Specifically, the activities of key glycolytic enzymes, such as glucokinase, decreased significantly, while the activities of enzymes in the TCA cycle, such as isocitrate dehydrogenase, increased significantly. Lactate dehydrogenase, pyruvate carboxylase, and alanine aminotransferase were upregulated. These changes were partially restored when the exposure time was extended to 12 h, except for further downregulation of phosphofructokinase and glucokinase. This study demonstrates that acute high altitude hypoxia upregulated the lactic acid/amino acid-pyruvate-TCA pathways and fatty acid oxidation, but downregulated glycolysis in the liver of mice. The results obtained in this study provide a theoretical framework for understanding the mechanisms underlying the pathogenesis of high-altitude sickness in humans. Additionally, these findings have potential implications for the development of prevention and treatment strategies for altitude sickness.
Collapse
Affiliation(s)
- Guanwen Liu
- School of Life Sciences, Northwestern Polytechnical University, 127 Youyi West Road, Xi'an, Shaanxi Province 710072, China.
| | - Yinghui Li
- School of Life Sciences, Northwestern Polytechnical University, 127 Youyi West Road, Xi'an, Shaanxi Province 710072, China
| | - Ning Liao
- School of Life Sciences, Northwestern Polytechnical University, 127 Youyi West Road, Xi'an, Shaanxi Province 710072, China.
| | - Xinzhe Shang
- School of Life Sciences, Northwestern Polytechnical University, 127 Youyi West Road, Xi'an, Shaanxi Province 710072, China
| | - Fengqin Xu
- School of Life Sciences, Northwestern Polytechnical University, 127 Youyi West Road, Xi'an, Shaanxi Province 710072, China
| | - Dachuan Yin
- School of Life Sciences, Northwestern Polytechnical University, 127 Youyi West Road, Xi'an, Shaanxi Province 710072, China.
| | - Dongyan Shao
- School of Life Sciences, Northwestern Polytechnical University, 127 Youyi West Road, Xi'an, Shaanxi Province 710072, China.
| | - Chunmei Jiang
- School of Life Sciences, Northwestern Polytechnical University, 127 Youyi West Road, Xi'an, Shaanxi Province 710072, China.
| | - Junling Shi
- School of Life Sciences, Northwestern Polytechnical University, 127 Youyi West Road, Xi'an, Shaanxi Province 710072, China.
| |
Collapse
|
3
|
Mulser L, Moreau D. Effect of Acute Cardiovascular Exercise on Cerebral Blood Flow: A Systematic Review. Brain Res 2023; 1809:148355. [PMID: 37003561 DOI: 10.1016/j.brainres.2023.148355] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/14/2023] [Accepted: 03/21/2023] [Indexed: 04/03/2023]
Abstract
A single bout of cardiovascular exercise can have a cascade of physiological effects, including increased blood flow to the brain. This effect has been documented across multiple modalities, yet studies have reported mixed findings. Here, we systematically review evidence for the acute effect of cardiovascular exercise on cerebral blood flow across a range of neuroimaging techniques and exercise characteristics. Based on 52 studies and a combined sample size of 1,174 individuals, our results indicate that the acute effect of cardiovascular exercise on cerebral blood flow generally follows an inverted U-shaped relationship, whereby blood flow increases early on but eventually decreases as exercise continues. However, we also find that this effect is not uniform across studies, instead varying across a number of key variables including exercise characteristics, brain regions, and neuroimaging modalities. As the most comprehensive synthesis on the topic to date, this systematic review sheds light on the determinants of exercise-induced change in cerebral blood flow, a necessary step toward personalized interventions targeting brain health across a range of populations.
Collapse
Affiliation(s)
- Lisa Mulser
- School of Psychology The University of Auckland
| | - David Moreau
- School of Psychology and Centre for Brain Research The University of Auckland.
| |
Collapse
|
4
|
Zhong Z, Dong H, Wu Y, Zhou S, Li H, Huang P, Tian H, Li X, Xiao H, Yang T, Xiong K, Zhang G, Tang Z, Li Y, Fan X, Yuan C, Ning J, Li Y, Xie J, Li P. Remote ischemic preconditioning enhances aerobic performance by accelerating regional oxygenation and improving cardiac function during acute hypobaric hypoxia exposure. Front Physiol 2022; 13:950086. [PMID: 36160840 PMCID: PMC9500473 DOI: 10.3389/fphys.2022.950086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Accepted: 08/08/2022] [Indexed: 12/02/2022] Open
Abstract
Remote ischemic preconditioning (RIPC) may improve exercise performance. However, the influence of RIPC on aerobic performance and underlying physiological mechanisms during hypobaric hypoxia (HH) exposure remains relatively uncertain. Here, we systematically evaluated the potential performance benefits and underlying mechanisms of RIPC during HH exposure. Seventy-nine healthy participants were randomly assigned to receive sham intervention or RIPC (4 × 5 min occlusion 180 mm Hg/reperfusion 0 mm Hg, bilaterally on the upper arms) for 8 consecutive days in phases 1 (24 participants) and phase 2 (55 participants). In the phases 1, we measured the change in maximal oxygen uptake capacity (VO2max) and muscle oxygenation (SmO2) on the leg during a graded exercise test. We also measured regional cerebral oxygenation (rSO2) on the forehead. These measures and physiological variables, such as cardiovascular hemodynamic parameters and heart rate variability index, were used to evaluate the intervention effect of RIPC on the changes in bodily functions caused by HH exposure. In the phase 2, plasma protein mass spectrometry was then performed after RIPC intervention, and the results were further evaluated using ELISA tests to assess possible mechanisms. The results suggested that RIPC intervention improved VO2max (11.29%) and accelerated both the maximum (18.13%) and minimum (53%) values of SmO2 and rSO2 (6.88%) compared to sham intervention in hypobaric hypoxia exposure. Cardiovascular hemodynamic parameters (SV, SVRI, PPV% and SpMet%) and the heart rate variability index (Mean RR, Mean HR, RMSSD, pNN50, Lfnu, Hfnu, SD1, SD2/SD1, ApEn, SampEn, DFA1and DFA2) were evaluated. Protein sequence analysis showed 42 unregulated and six downregulated proteins in the plasma of the RIPC group compared to the sham group after HH exposure. Three proteins, thymosin β4 (Tβ4), heat shock protein-70 (HSP70), and heat shock protein-90 (HSP90), were significantly altered in the plasma of the RIPC group before and after HH exposure. Our data demonstrated that in acute HH exposure, RIPC mitigates the decline in VO2max and regional oxygenation, as well as physiological variables, such as cardiovascular hemodynamic parameters and the heart rate variability index, by influencing plasma Tβ4, HSP70, and HSP90. These data suggest that RIPC may be beneficial for acute HH exposure.
Collapse
Affiliation(s)
- Zhifeng Zhong
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Huaping Dong
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Yu Wu
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Simin Zhou
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Hong Li
- Department of Anesthesiology, Xinqiao Hospital, Army Medical University (Third Military Medical University), Chongqing, China
| | - Pei Huang
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Huaijun Tian
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Xiaoxu Li
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
| | - Heng Xiao
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Tian Yang
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
| | - Kun Xiong
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
| | - Gang Zhang
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education of China, Army Medical University (Third Military Medical University), Chongqing, China
| | - Zhongwei Tang
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
| | - Yaling Li
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Xueying Fan
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Chao Yuan
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education of China, Army Medical University (Third Military Medical University), Chongqing, China
| | - Jiaolin Ning
- Department of Anesthesiology, First Affiliated Hospital, Army Medical University (Third Military Medical University), Chongqing, China
| | - Yue Li
- Department of Anesthesiology, First Affiliated Hospital, Army Medical University (Third Military Medical University), Chongqing, China
| | - Jiaxin Xie
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
- *Correspondence: Jiaxin Xie, ; Peng Li,
| | - Peng Li
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education of China, Army Medical University (Third Military Medical University), Chongqing, China
- *Correspondence: Jiaxin Xie, ; Peng Li,
| |
Collapse
|
5
|
Megaritis D, Wagner PD, Vogiatzis I. Ergogenic value of oxygen supplementation in chronic obstructive pulmonary disease. Intern Emerg Med 2022; 17:1277-1286. [PMID: 35819698 PMCID: PMC9352614 DOI: 10.1007/s11739-022-03037-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 06/16/2022] [Indexed: 11/05/2022]
Abstract
Patients with COPD exhibit limited exercise endurance time compared to healthy age-matched individuals. Oxygen supplementation is often applied to improve endurance time during pulmonary rehabilitation in patients with COPD and thus a comprehensive understanding of the mechanisms leading to improved endurance is desirable. This review analyses data from two studies by our research group investigating the effect of oxygen supplementation on cerebrovascular, systemic, respiratory and locomotor muscle oxygen availability on the same cohort of individuals with advanced COPD, and the mechanisms associated with improved endurance time in hyperoxia, which was essentially doubled (at the same power output). In hyperoxia at isotime (the time at which patients became exhausted in normoxia) exercise was associated with greater respiratory and locomotor muscle (but not frontal cortex) oxygen delivery (despite lower cardiac output), lower lactate concentration and less tachypnoea. Frontal cortex oxygen saturation was higher, and respiratory drive lower. Hence, improved endurance in hyperoxia appears to be facilitated by several factors: increased oxygen availability to the respiratory and locomotor muscles, less metabolic acidosis, and lower respiratory drive. At exhaustion in both normoxia and hyperoxia, only cardiac output and breathing pattern were not different between conditions. However, minute ventilation in hyperoxia exceeded the critical level of ventilatory constraints (VE/MVV > 75-80%). Lactate remained lower and respiratory and locomotor muscle oxygen delivery greater in hyperoxia, suggesting greater muscle oxygen availability improving muscle function. Taken together, these findings suggest that central haemodynamic and ventilatory limitations and not contracting muscle conditions dictate endurance time in COPD during exercise in hyperoxia.
Collapse
Affiliation(s)
- Dimitrios Megaritis
- grid.42629.3b0000000121965555Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Tyne and Wear, Newcastle upon Tyne, UK
| | - Peter D. Wagner
- grid.42629.3b0000000121965555Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Tyne and Wear, Newcastle upon Tyne, UK
- grid.266100.30000 0001 2107 4242Department of Medicine, University of California, San Diego, CA USA
| | - Ioannis Vogiatzis
- grid.42629.3b0000000121965555Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Tyne and Wear, Newcastle upon Tyne, UK
| |
Collapse
|
6
|
Melo LT, Rodrigues A, Cabral EE, Tanaka T, Goligher EC, Brochard L, Reid WD. Prefrontal cortex activation during incremental inspiratory loading in healthy participants. Respir Physiol Neurobiol 2021; 296:103827. [PMID: 34808586 DOI: 10.1016/j.resp.2021.103827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 10/01/2021] [Accepted: 11/11/2021] [Indexed: 11/28/2022]
Abstract
We aimed to investigate whether changes in prefrontal cortex (PFC) oxyhemoglobin (O2Hb) and deoxyhemoglobin (HHb) associates with inspiratory muscle effort during inspiratory threshold loading (ITL) in healthy participants. Participants performed an incremental ITL. Breathing pattern, partial pressure of end-tidal CO2 (PETCO2), mouth pressure and O2Hb and HHb over the right dorsolateral PFC, sternocleidomastoid (SCM), and diaphragm/intercostals (Dia/IC) were monitored. Fourteen healthy participants (8 men; 29 ± 5 years) completed testing. Dyspnea was higher post- than pre-ITL (5 ± 1 vs. 0 ± 1, respectively; P<0.05). PFC O2Hb increased (P < 0.001) and HHb decreased (P = 0.001) at low loads but remained stable with increasing ITL intensities. PFC total hemoglobin increased at task failure compared to rest. SCM HHb increased throughout increasing intensities. SCM and Dia/IC total hemoglobin increased in the at task failure compared to rest. PETCO2 did not change (P = 0.528). PFC is activated early during the ITL but does not show central fatigue at task failure despite greater dyspnea and an imbalance of SCM oxygen demand and delivery.
Collapse
Affiliation(s)
- Luana T Melo
- Department of Physical Therapy, University of Toronto, Ontario, Canada; Keenan Centre for Biomedical Research, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada
| | - Antenor Rodrigues
- Department of Physical Therapy, University of Toronto, Ontario, Canada; Keenan Centre for Biomedical Research, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada.
| | - Elis Emmanuelle Cabral
- Department of Physical Therapy, University of Toronto, Ontario, Canada; Performance Lab, Pneumocardiovascular and Respiratory Muscles (PneumoCardioVascular Lab/HUOL), Department of Physical Therapy, Federal University of Rio Grande do Norte (UFRN), Rio Grande do Norte, Brazil
| | - Takako Tanaka
- Department of Physical Therapy, University of Toronto, Ontario, Canada; Department of Cardiopulmonary Rehabilitation Science, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Ewan C Goligher
- Division of Respirology, Department of Medicine, University Health Network, Toronto, Canada; Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada; Department of Physiology, University of Toronto, Toronto, Canada
| | - Laurent Brochard
- Keenan Centre for Biomedical Research, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada; Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada; Department of Medicine, University of Toronto, Toronto, Canada
| | - W Darlene Reid
- Department of Physical Therapy, University of Toronto, Ontario, Canada; Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada; KITE, Toronto Rehabilitation Institute, University Health Network, Toronto, Canada
| |
Collapse
|
7
|
Burtscher J, Mallet RT, Burtscher M, Millet GP. Hypoxia and brain aging: Neurodegeneration or neuroprotection? Ageing Res Rev 2021; 68:101343. [PMID: 33862277 DOI: 10.1016/j.arr.2021.101343] [Citation(s) in RCA: 108] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 04/06/2021] [Accepted: 04/09/2021] [Indexed: 12/12/2022]
Abstract
The absolute reliance of the mammalian brain on oxygen to generate ATP renders it acutely vulnerable to hypoxia, whether at high altitude or in clinical settings of anemia or pulmonary disease. Hypoxia is pivotal to the pathogeneses of myriad neurological disorders, including Alzheimer's, Parkinson's and other age-related neurodegenerative diseases. Conversely, reduced environmental oxygen, e.g. sojourns or residing at high altitudes, may impart favorable effects on aging and mortality. Moreover, controlled hypoxia exposure may represent a treatment strategy for age-related neurological disorders. This review discusses evidence of hypoxia's beneficial vs. detrimental impacts on the aging brain and the molecular mechanisms that mediate these divergent effects. It draws upon an extensive literature search on the effects of hypoxia/altitude on brain aging, and detailed analysis of all identified studies directly comparing brain responses to hypoxia in young vs. aged humans or rodents. Special attention is directed toward the risks vs. benefits of hypoxia exposure to the elderly, and potential therapeutic applications of hypoxia for neurodegenerative diseases. Finally, important questions for future research are discussed.
Collapse
Affiliation(s)
- Johannes Burtscher
- Department of Biomedical Sciences, University of Lausanne, CH-1015, Lausanne, Switzerland; Institute of Sport Sciences, University of Lausanne, CH-1015, Lausanne, Switzerland.
| | - Robert T Mallet
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Martin Burtscher
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Grégoire P Millet
- Institute of Sport Sciences, University of Lausanne, CH-1015, Lausanne, Switzerland
| |
Collapse
|
8
|
Mallet RT, Burtscher J, Richalet JP, Millet GP, Burtscher M. Impact of High Altitude on Cardiovascular Health: Current Perspectives. Vasc Health Risk Manag 2021; 17:317-335. [PMID: 34135590 PMCID: PMC8197622 DOI: 10.2147/vhrm.s294121] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 05/12/2021] [Indexed: 12/12/2022] Open
Abstract
Globally, about 400 million people reside at terrestrial altitudes above 1500 m, and more than 100 million lowlanders visit mountainous areas above 2500 m annually. The interactions between the low barometric pressure and partial pressure of O2, climate, individual genetic, lifestyle and socio-economic factors, as well as adaptation and acclimatization processes at high elevations are extremely complex. It is challenging to decipher the effects of these myriad factors on the cardiovascular health in high altitude residents, and even more so in those ascending to high altitudes with or without preexisting diseases. This review aims to interpret epidemiological observations in high-altitude populations; present and discuss cardiovascular responses to acute and subacute high-altitude exposure in general and more specifically in people with preexisting cardiovascular diseases; the relations between cardiovascular pathologies and neurodegenerative diseases at altitude; the effects of high-altitude exercise; and the putative cardioprotective mechanisms of hypobaric hypoxia.
Collapse
Affiliation(s)
- Robert T Mallet
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Johannes Burtscher
- Department of Biomedical Sciences, University of Lausanne, Lausanne, CH-1015, Switzerland
- Institute of Sport Sciences, University of Lausanne, Lausanne, CH-1015, Switzerland
| | - Jean-Paul Richalet
- Laboratoire Hypoxie & Poumon, UMR Inserm U1272, Université Sorbonne Paris Nord 13, Bobigny Cedex, F-93017, France
| | - Gregoire P Millet
- Department of Biomedical Sciences, University of Lausanne, Lausanne, CH-1015, Switzerland
- Institute of Sport Sciences, University of Lausanne, Lausanne, CH-1015, Switzerland
| | - Martin Burtscher
- Department of Sport Science, University of Innsbruck, Innsbruck, A-6020, Austria
- Austrian Society for Alpine and High-Altitude Medicine, Mieming, Austria
| |
Collapse
|
9
|
Furian M, Flueck D, Scheiwiller PM, Mueller-Mottet S, Urner LM, Latshang TD, Ulrich S, Bloch KE. Nocturnal cerebral tissue oxygenation in lowlanders with chronic obstructive pulmonary disease travelling to an altitude of 2,590 m: Data from a randomised trial. J Sleep Res 2021; 30:e13365. [PMID: 33902162 DOI: 10.1111/jsr.13365] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 04/06/2021] [Accepted: 04/07/2021] [Indexed: 11/29/2022]
Abstract
Altitude exposure induces hypoxaemia in patients with chronic obstructive pulmonary disease (COPD), particularly during sleep. The present study tested the hypothesis in patients with COPD staying overnight at high altitude that nocturnal arterial hypoxaemia is associated with impaired cerebral tissue oxygenation (CTO). A total of 35 patients with moderate-to-severe COPD, living at <800 m (mean [SD] age 62.4 [12.3] years, forced expiratory volume in 1 s [FEV1 ] 61 [16]% predicted, awake pulse oximetry ≥92%) underwent continuous overnight monitoring of pulse oximetry (oxygen saturation [SpO2 ]) and near-infrared spectroscopy of prefrontal CTO, respectively, at 490 m and 2,590 m. Regression analysis was used to evaluate whether nocturnal arterial desaturation (COPDDesat , SpO2 <90% for >30% of night-time) at 490 m predicted CTO at 2,590 m when controlling for baseline variables. At 2,590 m, mean nocturnal SpO2 and CTO were decreased versus 490 m, mean change -8.8% (95% confidence interval [CI] -10.0 to -7.6) and -3.6% (95% CI -5.7 to -1.6), difference in change ΔCTO-ΔSpO2 5.2% (95% CI 3.0 to 7.3; p < .001). Moreover, frequent cyclic desaturations (≥4% dips/hr) occurred in SpO2 and CTO, mean change from 490 m 35.3/hr (95% CI 24.9 to 45.7) and 3.4/hr (95% CI 1.4 to 5.3), difference in change ΔCTO-ΔSpO2 -32.8/hr (95% CI -43.8 to -21.8; p < .001). Regression analysis confirmed an association of COPDDesat with lower CTO at 2,590 m (coefficient -7.6%, 95% CI -13.2 to -2.0; p = .007) when controlling for several confounders. We conclude that lowlanders with COPD staying overnight at 2,590 m experience altitude-induced hypoxaemia and periodic breathing in association with sustained and intermittent cerebral deoxygenation. Although less pronounced than the arterial deoxygenation, the altitude-induced cerebral tissue deoxygenation may represent a risk of brain dysfunction, especially in patients with COPD with nocturnal hypoxaemia at low altitude.
Collapse
Affiliation(s)
- Michael Furian
- Pulmonary Division and Sleep Disorders Center, University Hospital of Zurich, Zurich, Switzerland
| | - Deborah Flueck
- Pulmonary Division and Sleep Disorders Center, University Hospital of Zurich, Zurich, Switzerland
| | - Philipp M Scheiwiller
- Pulmonary Division and Sleep Disorders Center, University Hospital of Zurich, Zurich, Switzerland
| | - Séverine Mueller-Mottet
- Pulmonary Division and Sleep Disorders Center, University Hospital of Zurich, Zurich, Switzerland
| | - Lorenz M Urner
- Pulmonary Division and Sleep Disorders Center, University Hospital of Zurich, Zurich, Switzerland
| | - Tsogyal D Latshang
- Pulmonary Division and Sleep Disorders Center, University Hospital of Zurich, Zurich, Switzerland
| | - Silvia Ulrich
- Pulmonary Division and Sleep Disorders Center, University Hospital of Zurich, Zurich, Switzerland
| | - Konrad E Bloch
- Pulmonary Division and Sleep Disorders Center, University Hospital of Zurich, Zurich, Switzerland
| |
Collapse
|
10
|
Triantafyllou GA, Dipla K, Triantafyllou A, Gkaliagkousi E, Douma S. Measurement and Changes in Cerebral Oxygenation and Blood Flow at Rest and During Exercise in Normotensive and Hypertensive Individuals. Curr Hypertens Rep 2020; 22:71. [PMID: 32852614 DOI: 10.1007/s11906-020-01075-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
PURPOSE OF REVIEW Summarize the methods used for measurement of cerebral blood flow and oxygenation; describe the effects of hypertension on cerebral blood flow and oxygenation. RECENT FINDINGS Information regarding the effects of hypertension on cerebrovascular circulation during exercise is very limited, despite a plethora of methods to help with its assessment. In normotensive individuals performing incremental exercise testing, total blood flow to the brain increases. In contrast, the few studies performed in hypertensive patients suggest a smaller increase in cerebral blood flow, despite higher blood pressure levels. Endothelial dysfunction and increased vasoconstrictor concentration, as well as large vessel atherosclerosis and decreased small vessel number, have been proposed as the underlying mechanisms. Hypertension may adversely impact oxygen and blood delivery to the brain, both at rest and during exercise. Future studies should utilize the newer, noninvasive techniques to better characterize the interplay between the brain and exercise in hypertension.
Collapse
Affiliation(s)
- Georgios A Triantafyllou
- 3rd Department of Internal Medicine, Papageorgiou Hospital, Aristotle University of Thessaloniki, Ring Road Nea Eukarpia, 56403, Thessaloniki, Greece.,Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh Medical Center, 3459 Fifth Avenue, Pittsburgh, PA, 15213, USA
| | - Konstantina Dipla
- Exercise Physiology and Biochemistry Laboratory, Department of Sports Science at Serres, Aristotle University of Thessaloniki, Agios Ioannis, 62122, Serres, Greece
| | - Areti Triantafyllou
- 3rd Department of Internal Medicine, Papageorgiou Hospital, Aristotle University of Thessaloniki, Ring Road Nea Eukarpia, 56403, Thessaloniki, Greece.
| | - Eugenia Gkaliagkousi
- 3rd Department of Internal Medicine, Papageorgiou Hospital, Aristotle University of Thessaloniki, Ring Road Nea Eukarpia, 56403, Thessaloniki, Greece
| | - Stella Douma
- 3rd Department of Internal Medicine, Papageorgiou Hospital, Aristotle University of Thessaloniki, Ring Road Nea Eukarpia, 56403, Thessaloniki, Greece
| |
Collapse
|
11
|
Manferdelli G, Marzorati M, Easton C, Porcelli S. Changes in prefrontal cerebral oxygenation and microvascular blood volume in hypoxia and possible association with acute mountain sickness. Exp Physiol 2020; 106:76-85. [DOI: 10.1113/ep088515] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 07/24/2020] [Indexed: 01/30/2023]
Affiliation(s)
- Giorgio Manferdelli
- Institute of Biomedical Technologies National Research Council Segrate Italy
- School of Health and Exercise Sciences University of the West of Scotland Paisley UK
| | - Mauro Marzorati
- Institute of Biomedical Technologies National Research Council Segrate Italy
| | - Chris Easton
- School of Health and Exercise Sciences University of the West of Scotland Paisley UK
| | - Simone Porcelli
- Institute of Biomedical Technologies National Research Council Segrate Italy
- Department of Molecular Physiology University of Pavia Pavia Italy
| |
Collapse
|
12
|
Ando S, Komiyama T, Sudo M, Higaki Y, Ishida K, Costello JT, Katayama K. The interactive effects of acute exercise and hypoxia on cognitive performance: A narrative review. Scand J Med Sci Sports 2019; 30:384-398. [PMID: 31605635 DOI: 10.1111/sms.13573] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Revised: 09/09/2019] [Accepted: 10/04/2019] [Indexed: 12/13/2022]
Abstract
Acute moderate intensity exercise has been shown to improve cognitive performance. In contrast, hypoxia is believed to impair cognitive performance. The detrimental effects of hypoxia on cognitive performance are primarily dependent on the severity and duration of exposure. In this review, we describe how acute exercise under hypoxia alters cognitive performance, and propose that the combined effects of acute exercise and hypoxia on cognitive performance are mainly determined by interaction among exercise intensity and duration, the severity of hypoxia, and duration of exposure to hypoxia. We discuss the physiological mechanism(s) of the interaction and suggest that alterations in neurotransmitter function, cerebral blood flow, and possibly cerebral metabolism are the primary candidates that determine cognitive performance when acute exercise is combined with hypoxia. Furthermore, acclimatization appears to counteract impaired cognitive performance during prolonged exposure to hypoxia although the precise physiological mechanism(s) responsible for this amelioration remain to be elucidated. This review has implications for sporting, occupational, and recreational activities at terrestrial high altitude where cognitive performance is essential. Further studies are required to understand physiological mechanisms that determine cognitive performance when acute exercise is performed in hypoxia.
Collapse
Affiliation(s)
- Soichi Ando
- Graduate School of Informatics and Engineering, The University of Electro-Communications, Tokyo, Japan
| | - Takaaki Komiyama
- Center for Education in Liberal Arts and Sciences, Osaka University, Osaka, Japan
| | - Mizuki Sudo
- Meiji Yasuda Life Foundation of Health and Welfare, Tokyo, Japan
| | - Yasuki Higaki
- Faculty of Sports Science, Fukuoka University, Fukuoka, Japan
| | - Koji Ishida
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan
| | - Joseph T Costello
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Portsmouth, UK
| | - Keisho Katayama
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan
| |
Collapse
|
13
|
Huang X, Hu Y, Zhao L, Gu B, Zhu R, Li Y, Yang Y, Han T, Yu J, Mu L, Han P, Li C, Zhang W, Hu Y. TRPV4 plays an important role in rat prefrontal cortex changes induced by acute hypoxic exercise. Saudi J Biol Sci 2019; 26:1194-1206. [PMID: 31516349 PMCID: PMC6734159 DOI: 10.1016/j.sjbs.2019.06.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 05/29/2019] [Accepted: 06/02/2019] [Indexed: 11/29/2022] Open
Abstract
OBJECTIVE This study aims to investigate the effects of TRPV4 on acute hypoxic exercise-induced central fatigue, in order to explore the mechanism in central for exercise capacity decline of athletes in the early stage of altitude training. METHODS 120 male Wistar rats were randomly divided into 12 groups: 4 normoxia groups (quiet group, 5-level group, 8-level group, exhausted group), 4 groups at simulated 2500 m altitude (grouping as before), 4 groups at simulated 4500 m altitude (grouping as before), 10 in each group. With incremental load movement, materials were drawn corresponding to the load. Intracellular calcium ion concentration was measured by HE staining, enzyme-linked immunosorbent assay, immunohistochemistry, RT-qPCR, Fluo-4/AM and Fura-2/AM fluorescence staining. RESULTS (1) Hypoxic 2-5 groups showed obvious venous congestion, with symptoms similar to normoxia-8 group; Hypoxic 2-8 groups showed meningeal loosening edema, infra-meningeal venous congestion, with symptoms similar to normoxia-exhausted group and hypoxic 1-exhaused group. (2) For 5,6-EET, regardless of normoxic or hypoxic environment, significant or very significant differences existed between each exercise load group (normoxic - 5 level 20.58 ± 0.66 pg/mL, normoxic - 8 level 23.15 ± 0.46 pg/mL, normoxic - exhausted 26.66 ± 0.71 pg/mL; hypoxic1-5 level 21.72 ± 0.43 pg/mL, hypoxic1-8 level 24.73 ± 0.69 pg/mL, hypoxic 1-exhausted 28.68 ± 0.48 pg/mL; hypoxic2-5 level 22.75 ± 0.20 pg/mL, hypoxic2-8 level 25.62 ± 0.39 pg/mL, hypoxic 2-exhausted 31.03 ± 0.41 pg/mL) and quiet group in the same environment(normoxic-quiet 18.12 ± 0.65 pg/mL, hypoxic 1-quiet 19.94 ± 0.43 pg/mL, hypoxic 2-quiet 21.72 ± 0.50 pg/mL). The 5,6-EET level was significantly or extremely significantly increased in hypoxic 1 environment and hypoxic 2 environment compared with normoxic environment under the same load. (3) With the increase of exercise load, expression of TRPV4 in the rat prefrontal cortex was significantly increased; hypoxic exercise groups showed significantly higher TRPV4 expression than the normoxic group. (4) Calcium ion concentration results showed that in the three environments, 8 level group (normoxic-8 190.93 ± 6.11 nmol/L, hypoxic1-8 208.92 ± 6.20 nmol/L, hypoxic2-8 219.13 ± 4.57 nmol/L) showed very significant higher concentration compared to quiet state in the same environment (normoxic-quiet 107.11 ± 0.49 nmol/L, hypoxic 1-quiet 128.48 ± 1.51 nmol/L, hypoxic 2-quiet 171.71 ± 0.84 nmol/L), and the exhausted group in the same environment (normoxic-exhausted 172.51 ± 3.30 nmol/L, hypoxic 1-exhausted 164.54 ± 6.01 nmol/L, hypoxic 2-exhausted 154.52 ± 1.80 nmol/L) had significant lower concentration than 8-level group; hypoxic2-8 had significant higher concentration than normoxic-8. CONCLUSION Acute hypoxic exercise increases the expression of TRPV4 channel in the prefrontal cortex of the brain. For a lower ambient oxygen concentration, expression of TRPV4 channel is higher, suggesting that TRPV4 channel may be one important mechanism involved in calcium overload in acute hypoxic exercise.
Collapse
Affiliation(s)
- Xing Huang
- School of Kinesiology and Health, Capital University of Physical
Education and Sports, Beijing 100191, China
- School of Sport Science, Beijing Sport University, Beijing 100084,
China
| | - Yanxin Hu
- College of Veterinary Medicine, China Agricultural University, Beijing
100193, China
| | - Li Zhao
- School of Sport Science, Beijing Sport University, Beijing 100084,
China
| | - Boya Gu
- School of Sport Science, Beijing Sport University, Beijing 100084,
China
| | - Rongxin Zhu
- School of Sport Science, Beijing Sport University, Beijing 100084,
China
| | - Yan Li
- School of Sport Science, Beijing Sport University, Beijing 100084,
China
| | - Yun Yang
- School of Kinesiology and Health, Capital University of Physical
Education and Sports, Beijing 100191, China
| | - Tianyu Han
- School of Sport Science, Beijing Sport University, Beijing 100084,
China
| | - Jiabei Yu
- School of Sport Science, Beijing Sport University, Beijing 100084,
China
| | - Lianwei Mu
- School of Sport Science, Beijing Sport University, Beijing 100084,
China
| | - Peng Han
- School of Sport Science, Beijing Sport University, Beijing 100084,
China
| | - Cui Li
- School of Sport Science, Beijing Sport University, Beijing 100084,
China
| | - Weijia Zhang
- School of Sport Science, Beijing Sport University, Beijing 100084,
China
| | - Yang Hu
- School of Sport Science, Beijing Sport University, Beijing 100084,
China
| |
Collapse
|
14
|
Evaluating the methods used for measuring cerebral blood flow at rest and during exercise in humans. Eur J Appl Physiol 2018; 118:1527-1538. [DOI: 10.1007/s00421-018-3887-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 05/09/2018] [Indexed: 10/16/2022]
|
15
|
Willis SJ, Alvarez L, Millet GP, Borrani F. Changes in Muscle and Cerebral Deoxygenation and Perfusion during Repeated Sprints in Hypoxia to Exhaustion. Front Physiol 2017; 8:846. [PMID: 29163193 PMCID: PMC5671463 DOI: 10.3389/fphys.2017.00846] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 10/10/2017] [Indexed: 01/08/2023] Open
Abstract
During supramaximal exercise, exacerbated at exhaustion and in hypoxia, the circulatory system is challenged to facilitate oxygen delivery to working tissues through cerebral autoregulation which influences fatigue development and muscle performance. The aim of the study was to evaluate the effects of different levels of normobaric hypoxia on the changes in peripheral and cerebral oxygenation and performance during repeated sprints to exhaustion. Eleven recreationally active participants (six men and five women; 26.7 ± 4.2 years, 68.0 ± 14.0 kg, 172 ± 12 cm, 14.1 ± 4.7% body fat) completed three randomized testing visits in conditions of simulated altitude near sea-level (~380 m, FIO2 20.9%), ~2000 m (FIO2 16.5 ± 0.4%), and ~3800 m (FIO2 13.3 ± 0.4%). Each session began with a 12-min warm-up followed by two 10-s sprints and the repeated cycling sprint (10-s sprint: 20-s recovery) test to exhaustion. Measurements included power output, vastus lateralis, and prefrontal deoxygenation [near-infrared spectroscopy, delta (Δ) corresponds to the difference between maximal and minimal values], oxygen uptake, femoral artery blood flow (Doppler ultrasound), hemodynamic variables (transthoracic impedance), blood lactate concentration, and rating of perceived exertion. Performance (total work, kJ; −27.1 ± 25.8% at 2000 m, p < 0.01 and −49.4 ± 19.3% at 3800 m, p < 0.001) and pulse oxygen saturation (−7.5 ± 6.0%, p < 0.05 and −18.4 ± 5.3%, p < 0.001, respectively) decreased with hypoxia, when compared to 400 m. Muscle Δ hemoglobin difference ([Hbdiff]) and Δ tissue saturation index (TSI) were lower (p < 0.01) at 3800 m than at 2000 and 400 m, and lower Δ deoxyhemoglobin resulted at 3800 m compared with 2000 m. There were reduced changes in peripheral [Δ[Hbdiff], ΔTSI, Δ total hemoglobin ([tHb])] and greater changes in cerebral (Δ[Hbdiff], Δ[tHb]) oxygenation throughout the test to exhaustion (p < 0.05). Changes in cerebral deoxygenation were greater at 3800 m than at 2000 and 400 m (p < 0.01). This study confirms that performance in hypoxia is limited by continually decreasing oxygen saturation, even though exercise can be sustained despite maximal peripheral deoxygenation. There may be a cerebral autoregulation of increased perfusion accounting for the decreased arterial oxygen content and allowing for task continuation, as shown by the continued cerebral deoxygenation.
Collapse
Affiliation(s)
- Sarah J Willis
- Faculty of Biology and Medicine, Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
| | - Laurent Alvarez
- Faculty of Biology and Medicine, Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
| | - Grégoire P Millet
- Faculty of Biology and Medicine, Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
| | - Fabio Borrani
- Faculty of Biology and Medicine, Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
| |
Collapse
|
16
|
Smith KJ, Ainslie PN. Regulation of cerebral blood flow and metabolism during exercise. Exp Physiol 2017; 102:1356-1371. [PMID: 28786150 DOI: 10.1113/ep086249] [Citation(s) in RCA: 193] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Accepted: 07/31/2017] [Indexed: 12/18/2022]
Abstract
NEW FINDINGS What is the topic of this review? The manuscript collectively combines the experimental observations from >100 publications focusing on the regulation of cerebral blood flow and metabolism during exercise from 1945 to the present day. What advances does it highlight? This article highlights the importance of traditional and historical assessments of cerebral blood flow and metabolism during exercise, as well as traditional and new insights into the complex factors involved in the integrative regulation of brain blood flow and metabolism during exercise. The overarching theme is the importance of quantifying cerebral blood flow and metabolism during exercise using techniques that consider multiple volumetric cerebral haemodynamics (i.e. velocity, diameter, shear and flow). Cerebral function in humans is crucially dependent upon continuous oxygen delivery, metabolic nutrients and active regulation of cerebral blood flow (CBF). As a consequence, cerebrovascular function is precisely titrated by multiple physiological mechanisms, characterized by complex integration, synergism and protective redundancy. At rest, adequate CBF is regulated through reflexive responses in the following order of regulatory importance: fluctuating arterial blood gases (in particularly, partial pressure of carbon dioxide), cerebral metabolism, arterial blood pressure, neurogenic activity and cardiac output. Unfortunately, the magnitude that these integrative and synergistic relationships contribute to governing the CBF during exercise remains unclear. Despite some evidence indicating that CBF regulation during exercise is dependent on the changes of blood pressure, neurogenic activity and cardiac output, their role as a primary governor of the CBF response to exercise remains controversial. In contrast, the balance between the partial pressure of carbon dioxide and cerebral metabolism continues to gain empirical support as the primary contributor to the intensity-dependent changes in CBF observed during submaximal, moderate and maximal exercise. The goal of this review is to summarize the fundamental physiology and mechanisms involved in regulation of CBF and metabolism during exercise. The clinical implications of a better understanding of CBF during exercise and new research directions are also outlined.
Collapse
Affiliation(s)
- Kurt J Smith
- Cardiovascular Research Group, School of Sports Science, Exercise and Health, University of Western Australia, Crawley, WA, Australia.,Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| |
Collapse
|
17
|
Abstract
Acute exercise has been demonstrated to improve cognitive function. In contrast, severe hypoxia can impair cognitive function. Hence, cognitive function during exercise under severe hypoxia may be determined by the balance between the beneficial effects of exercise and the detrimental effects of severe hypoxia. However, the physiological factors that determine cognitive function during exercise under hypoxia remain unclear. Here, we examined the combined effects of acute exercise and severe hypoxia on cognitive function and identified physiological factors that determine cognitive function during exercise under severe hypoxia. The participants completed cognitive tasks at rest and during moderate exercise under either normoxic or severe hypoxic conditions. Peripheral oxygen saturation, cerebral oxygenation, and middle cerebral artery velocity were continuously monitored. Cerebral oxygen delivery was calculated as the product of estimated arterial oxygen content and cerebral blood flow. On average, cognitive performance improved during exercise under both normoxia and hypoxia, without sacrificing accuracy. However, under hypoxia, cognitive improvements were attenuated for individuals exhibiting a greater decrease in peripheral oxygen saturation. Cognitive performance was not associated with other physiological parameters. Taken together, the present results suggest that arterial desaturation attenuates cognitive improvements during exercise under hypoxia.
Collapse
|
18
|
Sagoo RS, Hutchinson CE, Wright A, Handford C, Parsons H, Sherwood V, Wayte S, Nagaraja S, Ng'Andwe E, Wilson MH, Imray CH. Magnetic Resonance investigation into the mechanisms involved in the development of high-altitude cerebral edema. J Cereb Blood Flow Metab 2017; 37:319-331. [PMID: 26746867 PMCID: PMC5167111 DOI: 10.1177/0271678x15625350] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 11/08/2015] [Accepted: 11/27/2015] [Indexed: 11/20/2022]
Abstract
Rapid ascent to high altitude commonly results in acute mountain sickness, and on occasion potentially fatal high-altitude cerebral edema. The exact pathophysiological mechanisms behind these syndromes remain to be determined. We report a study in which 12 subjects were exposed to a FiO2 = 0.12 for 22 h and underwent serial magnetic resonance imaging sequences to enable measurement of middle cerebral artery velocity, flow and diameter, and brain parenchymal, cerebrospinal fluid and cerebral venous volumes. Ten subjects completed 22 h and most developed symptoms of acute mountain sickness (mean Lake Louise Score 5.4; p < 0.001 vs. baseline). Cerebral oxygen delivery was maintained by an increase in middle cerebral artery velocity and diameter (first 6 h). There appeared to be venocompression at the level of the small, deep cerebral veins (116 cm3 at 2 h to 97 cm3 at 22 h; p < 0.05). Brain white matter volume increased over the 22-h period (574 ml to 587 ml; p < 0.001) and correlated with cumulative Lake Louise scores at 22 h (p < 0.05). We conclude that cerebral oxygen delivery was maintained by increased arterial inflow and this preceded the development of cerebral edema. Venous outflow restriction appeared to play a contributory role in the formation of cerebral edema, a novel feature that has not been observed previously.
Collapse
Affiliation(s)
- Ravjit S Sagoo
- Department of Imaging, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, West Midlands, UK
| | - Charles E Hutchinson
- Department of Imaging, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, West Midlands, UK.,Warwick Medical School, University of Warwick, Coventry, West Midlands, UK
| | - Alex Wright
- College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Charles Handford
- University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
| | - Helen Parsons
- Division of Health Sciences, Warwick Medical School, University of Warwick, Coventry, West Midlands, UK
| | - Victoria Sherwood
- Department of Medical Physics, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, West Midlands, UK
| | - Sarah Wayte
- Department of Medical Physics, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, West Midlands, UK
| | - Sanjoy Nagaraja
- Department of Imaging, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, West Midlands, UK
| | - Eddie Ng'Andwe
- Department of Imaging, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, West Midlands, UK
| | - Mark H Wilson
- Department of Neurosurgery, Imperial College Healthcare NHS Trust, London, UK
| | - Christopher He Imray
- Warwick Medical School, University of Warwick, Coventry, West Midlands, UK .,Department of Surgery, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, West Midlands, UK.,Coventry University, West Midlands, UK
| | | |
Collapse
|
19
|
Auger H, Bherer L, Boucher É, Hoge R, Lesage F, Dehaes M. Quantification of extra-cerebral and cerebral hemoglobin concentrations during physical exercise using time-domain near infrared spectroscopy. BIOMEDICAL OPTICS EXPRESS 2016; 7:3826-3842. [PMID: 27867696 PMCID: PMC5102543 DOI: 10.1364/boe.7.003826] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 08/23/2016] [Accepted: 08/28/2016] [Indexed: 05/10/2023]
Abstract
Fitness is known to have beneficial effects on brain anatomy and function. However, the understanding of mechanisms underlying immediate and long-term neurophysiological changes due to exercise is currently incomplete due to the lack of tools to investigate brain function during physical activity. In this study, we used time-domain near infrared spectroscopy (TD-NIRS) to quantify and discriminate extra-cerebral and cerebral hemoglobin concentrations and oxygen saturation (SO2) in young adults at rest and during incremental intensity exercise. In extra-cerebral tissue, an increase in deoxy-hemoglobin (HbR) and a decrease in SO2 were observed while only cerebral HbR increased at high intensity exercise. Results in extra-cerebral tissue are consistent with thermoregulatory mechanisms to dissipate excess heat through skin blood flow, while cerebral changes are in agreement with cerebral blood flow (CBF) redistribution mechanisms to meet oxygen demand in activated regions during exercise. No significant difference was observed in oxy- (HbO2) and total hemoglobin (HbT). In addition HbO2, HbR and HbT increased with subject's peak power output (equivalent to the maximum oxygen volume consumption; VO2 peak) supporting previous observations of increased total mass of red blood cells in trained individuals. Our results also revealed known gender differences with higher hemoglobin in men. Our approach in quantifying both extra-cerebral and cerebral absolute hemoglobin during exercise may help to better interpret past and future continuous-wave NIRS studies that are prone to extra-cerebral contamination and allow a better understanding of acute cerebral changes due to physical exercise.
Collapse
Affiliation(s)
- Héloïse Auger
- Institute of Biomedical Engineering, Université de Montréal, Montréal, QC,
Canada
- Centre Hospitalier Universitaire Sainte-Justine, Montréal, QC,
Canada
| | - Louis Bherer
- Institut Universitaire de Gériatrie de Montréal, Montréal, QC,
Canada
- PERFORM Centre, Concordia University, Montréal, QC,
Canada
| | - Étienne Boucher
- Centre Hospitalier Universitaire Sainte-Justine, Montréal, QC,
Canada
| | - Richard Hoge
- Institut Universitaire de Gériatrie de Montréal, Montréal, QC,
Canada
- Department of Neurology and Neurosurgery, McGill University, Montréal, QC,
Canada
| | - Frédéric Lesage
- Institute of Biomedical Engineering, Université de Montréal, Montréal, QC,
Canada
- Department of Electrical Engineering, École Polytechnique de Montréal, Montréal, QC,
Canada
| | - Mathieu Dehaes
- Institute of Biomedical Engineering, Université de Montréal, Montréal, QC,
Canada
- Centre Hospitalier Universitaire Sainte-Justine, Montréal, QC,
Canada
- Department of Radiology, Radio-Oncology and Nuclear Medicine, Université de Montréal, Montréal, QC,
Canada
| |
Collapse
|
20
|
Lefferts WK, Babcock MC, Tiss MJ, Ives SJ, White CN, Brutsaert TD, Heffernan KS. Effect of hypoxia on cerebrovascular and cognitive function during moderate intensity exercise. Physiol Behav 2016; 165:108-18. [PMID: 27402021 DOI: 10.1016/j.physbeh.2016.07.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 07/03/2016] [Accepted: 07/07/2016] [Indexed: 12/25/2022]
Abstract
Exercise in hypoxia places added demands on the brain and cerebrovasculature that can impact cognitive function. The purpose of this study was to investigate the effect of acute hypoxia on cerebrovascular hemodynamics, markers of neuro-steroidal modulation and brain-blood barrier (BBB) integrity, and cognition during exercise. Thirty healthy participants (21±4yrs., BMI 24.0±2.6kg∙m(-2); 15 men) were randomized to both a≈2.5h normoxic (FiO2 20.0%) and hypoxic (FiO2 12.5%) condition on two separate days. After 1.25h, participants underwent 10min of exercise-alone (cycling at 55% HRmax) and 15min of exercise+cognitive testing. Prefrontal cortex (PFC) tissue oxygenation and middle cerebral artery (MCA) mean blood velocity (MnV) were measured using near-infrared spectroscopy and transcranial Doppler respectively at rest, during exercise-alone, and during exercise+cognitive testing. Salivary levels of dehydroepiandosterone [DHEA], DHEA-sulfate [DHEAS]) and neuron specific enolase (NSE) were measured pre and post exercise. Cognition was assessed using standard metrics of accuracy and reaction time (RT), and advanced metrics from drift-diffusion modeling across memory recognition, N-Back and Flanker tasks. MCA MnV increased from rest to exercise (p<0.01) and was unchanged with addition of cognitive testing during exercise in both normoxia and hypoxia. PFC oxygenation increased during exercise (p<0.05) and was further increased with addition of cognitive challenge in normoxia but decreased during exercise in hypoxia (p<0.05) with further reductions occurring with addition of cognitive tasks (p<0.05). DHEA and NSE increased and decreased post-exercise, respectively, in both normoxia and hypoxia (p<0.01). Accuracy on cognitive tasks was similar in normoxia compared to hypoxia, while RT was slower in hypoxia vs normoxia across memory recognition (p<0.01) and Flanker tasks (p=0.04). Drift-diffusion modeling suggested changes in memory RT were due to increases in caution (p<0.01). Overall cognitive performance is maintained during exercise in hypoxia concomitant with slower RT in select cognitive tasks and reduced oxygenation in the PFC. These changes were accompanied by slight increases in neuro-steroidal modulation but appear independent of changes in NSE, a biomarker of BBB integrity. Maintained accuracy and select increases in RT during hypoxic exercise may be related behavioral changes in caution.
Collapse
|
21
|
Ainslie PN, Hoiland RL, Bailey DM. Lessons from the laboratory; integrated regulation of cerebral blood flow during hypoxia. Exp Physiol 2016; 101:1160-1166. [PMID: 27058994 DOI: 10.1113/ep085671] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 03/30/2016] [Indexed: 11/08/2022]
Abstract
What is the topic of this review? What is the mechanism underlying the control of human cerebral blood flow in hypoxia and what are the consequences? What advances does it highlight? Although appropriate elevations in cerebral blood flow occur in acute and chronic hypoxia, neuronal processes are more sensitive to even small hypoxic insults; hence, they can result in maladaptive consequences despite maintenance of global oxygen delivery. Exposure to acute or chronic hypoxaemia in otherwise healthy humans results in compensatory increases in cerebral blood flow (CBF) at rest and during exercise, referred to as hypoxic cerebral vasodilatation. These elevations in CBF offset the reduction in arterial oxygen content and maintain cerebral O2 delivery, conforming to the conservation of mass principle. In this review, we discuss the fundamental principles that contribute to the defence of cerebral O2 delivery and the corresponding implications for metabolism. We critically address to what extent the increase in CBF reflects an adaptive or indeed maladaptive physiological response. The molecular mechanisms of CBF regulation in hypoxia are also briefly discussed and future directions proposed.
Collapse
Affiliation(s)
- Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, British Columbia, Canada.,Neurovascular Research Laboratory, Research Institute of Health and Wellbeing, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, British Columbia, Canada
| | - Damian M Bailey
- Neurovascular Research Laboratory, Research Institute of Health and Wellbeing, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK
| |
Collapse
|
22
|
Cerebral Blood Flow During Treadmill Exercise Is a Marker of Physiological Postconcussion Syndrome in Female Athletes. J Head Trauma Rehabil 2016; 31:215-24. [DOI: 10.1097/htr.0000000000000145] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
23
|
Tempest GD, Eston RG, Parfitt G. A comparison of head motion and prefrontal haemodynamics during upright and recumbent cycling exercise. Clin Physiol Funct Imaging 2016; 37:723-729. [PMID: 27121773 DOI: 10.1111/cpf.12365] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Accepted: 03/03/2016] [Indexed: 11/27/2022]
Abstract
The aim of this observational study was to compare head motion and prefrontal haemodynamics during exercise using three commercial cycling ergometers. Participants (n = 12) completed an incremental exercise test to exhaustion during upright, recumbent and semi-recumbent cycling. Head motion (using accelerometry), physiological data (oxygen uptake, end-tidal carbon dioxide [PET CO2 ] and heart rate) and changes in prefrontal haemodynamics (oxygenation, deoxygenation and blood volume using near infrared spectroscopy [NIRS]) were recorded. Despite no difference in oxygen uptake and heart rate, head motion was higher and PET CO2 was lower during upright cycling at maximal exercise (P<0·05). Analyses of covariance (covariates: head motion P>0·05; PET CO2 , P<0·01) revealed that prefrontal oxygenation was higher during semi-recumbent than recumbent cycling and deoxygenation and blood volume were higher during upright than recumbent and semi-recumbent cycling (respectively; P<0·05). This work highlights the robustness of the utility of NIRS to head motion and describes the potential postural effects upon the prefrontal haemodynamic response during upright and recumbent cycling exercise.
Collapse
Affiliation(s)
- Gavin D Tempest
- Department of Sports Tourism, Physiology and Medicine, National Research Tomsk State University, Tomsk, Russia
| | - Roger G Eston
- Alliance for Research in Exercise, Nutrition and Activity (ARENA), Sansom Institute for Health Research, School of Health Sciences, University of South Australia, Adelaide, South Australia, Australia
| | - Gaynor Parfitt
- Alliance for Research in Exercise, Nutrition and Activity (ARENA), Sansom Institute for Health Research, School of Health Sciences, University of South Australia, Adelaide, South Australia, Australia
| |
Collapse
|
24
|
Exercise Intolerance in Heart Failure: Did We Forget the Brain? Can J Cardiol 2016; 32:475-84. [DOI: 10.1016/j.cjca.2015.12.021] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 12/21/2015] [Accepted: 12/21/2015] [Indexed: 01/15/2023] Open
|
25
|
Keramidas ME, Stavrou NAM, Kounalakis SN, Eiken O, Mekjavic IB. Severe hypoxia during incremental exercise to exhaustion provokes negative post-exercise affects. Physiol Behav 2016; 156:171-6. [PMID: 26802281 DOI: 10.1016/j.physbeh.2016.01.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 11/09/2015] [Accepted: 01/19/2016] [Indexed: 10/22/2022]
Abstract
The post-exercise emotional response is mainly dependent on the intensity of the exercise performed; moderate exercise causes positive feelings, whereas maximal exercise may prompt negative affects. Acute hypoxia impairs peak O2 uptake (V̇O2peak), resulting in a shift to a lower absolute intensity at the point of exhaustion. Hence, the purpose of the study was to examine whether a severe hypoxic stimulus would influence the post-exercise affective state in healthy lowlanders performing an incremental exercise to exhaustion. Thirty-six male lowlanders performed, in a counter-balanced order and separated by a 48-h interval, two incremental exercise trials to exhaustion to determine their V̇O2peak, while they were breathing either room air (AIR; FiO2: 0.21), or a hypoxic gas mixture (HYPO; FiO2: 0.12). Before and immediately after each trial, subjects were requested to complete two questionnaires, based on how they felt at that particular moment: (i) the Profile of Mood States-Short Form, and (ii) the Activation Deactivation Adjective Check List. During the post-exercise phase, they also completed the Multidimensional Fatigue Inventory. V̇O2peak was significantly lower in the HYPO than the AIR trial (~15%; p<0.001). Still, after the HYPO trial, energy, calmness and motivation were markedly impaired, whereas tension, confusion, and perception of physical and general fatigue were exaggerated (p≤0.05). Accordingly, present findings suggest that an incremental exercise to exhaustion performed in severe hypoxia provokes negative post-exercise emotions, induces higher levels of perceived fatigue and decreases motivation; the affective responses coincide with the comparatively lower V̇O2peak than that achieved in normoxic conditions.
Collapse
Affiliation(s)
- Michail E Keramidas
- Department of Environmental Physiology, Swedish Aerospace Physiology Center, School of Technology and Health, Royal Institute of Technology, Stockholm, Sweden; Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia.
| | - Nektarios A M Stavrou
- Exercise and Sport Science Department, ASPETAR Orthopaedic and Sports Medicine Hospital, Doha, Qatar; Faculty of Physical Education and Sport Science, University of Athens, Athens, Greece
| | - Stylianos N Kounalakis
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia
| | - Ola Eiken
- Department of Environmental Physiology, Swedish Aerospace Physiology Center, School of Technology and Health, Royal Institute of Technology, Stockholm, Sweden
| | - Igor B Mekjavic
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia
| |
Collapse
|
26
|
Van Thienen R, Hespel P. Enhanced muscular oxygen extraction in athletes exaggerates hypoxemia during exercise in hypoxia. J Appl Physiol (1985) 2015; 120:351-61. [PMID: 26607244 DOI: 10.1152/japplphysiol.00210.2015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 11/22/2015] [Indexed: 01/11/2023] Open
Abstract
High rate of muscular oxygen utilization facilitates the development of hypoxemia during exercise at altitude. Because endurance training stimulates oxygen extraction capacity, we investigated whether endurance athletes are at higher risk to developing hypoxemia and thereby acute mountain sickness symptoms during exercise at simulated high altitude. Elite athletes (ATL; n = 8) and fit controls (CON; n = 7) cycled for 20 min at 100 W (EX100W), as well as performed an incremental maximal oxygen consumption test (EXMAX) in normobaric hypoxia (0.107 inspired O2 fraction) or normoxia (0.209 inspired O2 fraction). Cardiorespiratory responses, arterial Po2 (PaO2), and oxygenation status in m. vastus lateralis [tissue oxygenation index (TOIM)] and frontal cortex (TOIC) by near-infrared spectroscopy, were measured. Muscle O2 uptake rate was estimated from change in oxyhemoglobin concentration during a 10-min arterial occlusion in m. gastrocnemius. Maximal oxygen consumption in normoxia was 70 ± 2 ml·min(-1·)kg(-1) in ATL vs. 43 ± 2 ml·min(-1·)kg(-1) in CON, and in hypoxia decreased more in ATL (-41%) than in CON (-25%, P < 0.05). Both in normoxia at PaO2 of ∼95 Torr, and in hypoxia at PaO2 of ∼35 Torr, muscle O2 uptake was twofold higher in ATL than in CON (0.12 vs. 0.06 ml·min(-1)·100 g(-1); P < 0.05). During EX100W in hypoxia, PaO2 dropped to lower (P < 0.05) values in ATL (27.6 ± 0.7 Torr) than in CON (33.5 ± 1.0 Torr). During EXMAX, but not during EX100W, TOIM was ∼15% lower in ATL than in CON (P < 0.05). TOIC was similar between the groups at any time. This study shows that maintenance of high muscular oxygen extraction rate at very low circulating PaO2 stimulates the development of hypoxemia during submaximal exercise in hypoxia in endurance-trained individuals. This effect may predispose to premature development of acute mountain sickness symptoms during exercise at altitude.
Collapse
Affiliation(s)
- Ruud Van Thienen
- Exercise Physiology Research Group, Department of Kinesiology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Peter Hespel
- Exercise Physiology Research Group, Department of Kinesiology, Katholieke Universiteit Leuven, Leuven, Belgium
| |
Collapse
|
27
|
Seo Y, Burns K, Fennell C, Kim JH, Gunstad J, Glickman E, McDaniel J. The Influence of Exercise on Cognitive Performance in Normobaric Hypoxia. High Alt Med Biol 2015. [PMID: 26214045 DOI: 10.1089/ham.2015.0027] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Although previous reports indicate that exercise improves cognitive function in normoxia, the influence of exercise on cognitive function in hypoxia is unknown. The purpose of this study was to determine if the impaired cognitive function in hypoxia can be restored by low to moderate intensity exercise. Sixteen young healthy men completed the ANAM versions of the Go/No-Go task (GNT) and Running Memory Continuous Performance Task (RMCPT) in normoxia to serve as baseline (B-Norm) (21% O2). Following 60 minutes of exposure to normobaric hypoxia (B-Hypo) (12.5% O2), these tests were repeated at rest and during cycling exercise at 40% and 60% of adjusted Vo2max. At B-Hypo, the % correct (p≤0.001) and throughput score (p≤0.001) in RMCPT were significantly impaired compared to B-Norm. During exercise at 40% (p=0.023) and 60% (p=0.006) of adjusted Vo2max, the throughput score in RMCPT improved compared to B-Hypo, and there was no significant difference in throughput score between the two exercise intensities. Mean reaction time also improved at both exercise intensities compared to B-Hypo (p≤0.028). Both peripheral oxygen saturation (Spo2) and regional cerebral oxygen saturation (rSo2) significantly decreased during B-Hypo (p≤0.001) and further decreased at 40% (p≤0.05) and 60% (p≤0.039) exercise. There was no significant difference in Spo2 or rSo2 between two exercise intensities. These data indicate that low to moderate exercise (i.e., 40%-60% adjusted Vo2max) may attenuate the risk of impaired cognitive function that occurs in hypoxic conditions.
Collapse
Affiliation(s)
- Yongsuk Seo
- 1 Department of Exercise Physiology, Kent State University , Kent, Ohio
| | - Keith Burns
- 1 Department of Exercise Physiology, Kent State University , Kent, Ohio
| | - Curtis Fennell
- 1 Department of Exercise Physiology, Kent State University , Kent, Ohio
| | - Jung-Hyun Kim
- 2 National Personal Protective Technology Laboratory, National Institute for Occupational Safety and Health , Centers for Disease Control and Prevention, Pittsburgh, Pennsylvania
| | - John Gunstad
- 1 Department of Exercise Physiology, Kent State University , Kent, Ohio
| | - Ellen Glickman
- 1 Department of Exercise Physiology, Kent State University , Kent, Ohio
| | - John McDaniel
- 1 Department of Exercise Physiology, Kent State University , Kent, Ohio.,3 Louis Stokes Cleveland Veterans Affairs Medical Center , Cleveland, Ohio
| |
Collapse
|
28
|
Furian M, Latshang TD, Aeschbacher SS, Ulrich S, Sooronbaev T, Mirrakhimov EM, Aldashev A, Bloch KE. Cerebral oxygenation in highlanders with and without high-altitude pulmonary hypertension. Exp Physiol 2015; 100:905-14. [DOI: 10.1113/ep085200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 05/20/2015] [Indexed: 01/05/2023]
Affiliation(s)
- M. Furian
- Pulmonary Division and Sleep Disorders Center; University Hospital of Zurich; Zurich Switzerland
- Institute of Human Movement Sciences and Sport; Swiss Federal Institute of Technology; Zurich Switzerland
| | - T. D. Latshang
- Pulmonary Division and Sleep Disorders Center; University Hospital of Zurich; Zurich Switzerland
| | - S. S. Aeschbacher
- Pulmonary Division and Sleep Disorders Center; University Hospital of Zurich; Zurich Switzerland
| | - S. Ulrich
- Pulmonary Division and Sleep Disorders Center; University Hospital of Zurich; Zurich Switzerland
| | - T. Sooronbaev
- National Center for Cardiology and Internal Medicine; Bishkek Kyrgyzstan
| | - E. M. Mirrakhimov
- National Center for Cardiology and Internal Medicine; Bishkek Kyrgyzstan
| | - A. Aldashev
- Research Institute for Molecular Biology and Medicine; Bishkek Kyrgyzstan
| | - K. E. Bloch
- Pulmonary Division and Sleep Disorders Center; University Hospital of Zurich; Zurich Switzerland
| |
Collapse
|
29
|
Kim YS, Seifert T, Brassard P, Rasmussen P, Vaag A, Nielsen HB, Secher NH, van Lieshout JJ. Impaired cerebral blood flow and oxygenation during exercise in type 2 diabetic patients. Physiol Rep 2015; 3:3/6/e12430. [PMID: 26109188 PMCID: PMC4510631 DOI: 10.14814/phy2.12430] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Endothelial vascular function and capacity to increase cardiac output during exercise are impaired in patients with type 2 diabetes (T2DM). We tested the hypothesis that the increase in cerebral blood flow (CBF) during exercise is also blunted and, therefore, that cerebral oxygenation becomes affected and perceived exertion increased in T2DM patients. We quantified cerebrovascular besides systemic hemodynamic responses to incremental ergometer cycling exercise in eight male T2DM and seven control subjects. CBF was assessed from the Fick equation and by transcranial Doppler-determined middle cerebral artery blood flow velocity. Cerebral oxygenation and metabolism were evaluated from the arterial-to-venous differences for oxygen, glucose, and lactate. Blood pressure was comparable during exercise between the two groups. However, the partial pressure of arterial carbon dioxide was lower at higher workloads in T2DM patients and their work capacity and increase in cardiac output were only ~80% of that established in the control subjects. CBF and cerebral oxygenation were reduced during exercise in T2DM patients (P < 0.05), and they expressed a higher rating of perceived exertion (P < 0.05). In contrast, CBF increased ~20% during exercise in the control group while the brain uptake of lactate and glucose was similar in the two groups. In conclusion, these results suggest that impaired CBF and oxygenation responses to exercise in T2DM patients may relate to limited ability to increase cardiac output and to reduced vasodilatory capacity and could contribute to their high perceived exertion.
Collapse
Affiliation(s)
- Yu-Sok Kim
- Department of Internal Medicine, AMC Center for Heart Failure Research Academic Medical Center University of Amsterdam, Amsterdam, The Netherlands Department of Anatomy, Embryology & Physiology, AMC Center for Heart Failure Research Academic Medical Center University of Amsterdam, Amsterdam, The Netherlands Laboratory for Clinical Cardiovascular Physiology, AMC Center for Heart Failure Research Academic Medical Center University of Amsterdam, Amsterdam, The Netherlands
| | - Thomas Seifert
- Department of Anesthesia, The Copenhagen Muscle Research Center University of Copenhagen, Copenhagen, Denmark
| | - Patrice Brassard
- Department of Anesthesia, The Copenhagen Muscle Research Center University of Copenhagen, Copenhagen, Denmark
| | - Peter Rasmussen
- Department of Anesthesia, The Copenhagen Muscle Research Center University of Copenhagen, Copenhagen, Denmark
| | - Allan Vaag
- Department of Endocrinology, Rigshospitalet University of Copenhagen, Copenhagen, Denmark
| | - Henning B Nielsen
- Department of Anesthesia, The Copenhagen Muscle Research Center University of Copenhagen, Copenhagen, Denmark
| | - Niels H Secher
- Department of Anesthesia, The Copenhagen Muscle Research Center University of Copenhagen, Copenhagen, Denmark
| | - Johannes J van Lieshout
- Department of Internal Medicine, AMC Center for Heart Failure Research Academic Medical Center University of Amsterdam, Amsterdam, The Netherlands Department of Anatomy, Embryology & Physiology, AMC Center for Heart Failure Research Academic Medical Center University of Amsterdam, Amsterdam, The Netherlands Laboratory for Clinical Cardiovascular Physiology, AMC Center for Heart Failure Research Academic Medical Center University of Amsterdam, Amsterdam, The Netherlands MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, School of Life Sciences University of Nottingham Medical School Queen's Medical Centre, Nottingham, UK
| |
Collapse
|
30
|
Avnstorp MB, Rasmussen P, Brassard P, Seifert T, Overgaard M, Krustrup P, Secher NH, Nordsborg NB. Cerebral water and ion balance remains stable when humans are exposed to acute hypoxic exercise. High Alt Med Biol 2015; 16:18-25. [PMID: 25761236 DOI: 10.1089/ham.2014.1075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Intense physical activity increases the prevalence of acute mountain sickness (AMS) that can occur within 10 h after ascent to altitudes above 1500 m and is likely related to development of cerebral edema. This study evaluated whether disturbed cerebral water and ion homeostasis can be detected when intense exercise is carried out in hypoxia and monitored the influence of muscle metabolism for changes in arterial variables. METHODS On two separate days, in random order, 30 min cycling exercise was performed in either hypoxia (10% O2) or normoxia at an intensity that was exhaustive in the hypoxic trial (∼120 W; n=9). RESULTS Exercise in hypoxia affected muscle metabolism, as evidenced by higher (p<0.05) leg lactate release at 7.5 min and a continuous decline in arterial pH (p<0.001) that was not observed in normoxia. Middle cerebral artery flow velocity increased (p<0.01) with exercise under both circumstances. No cerebral net exchange of Na(+) or K(+) was evident. Likewise, no significant net-exchange of water over the brain was demonstrated and the arterial and jugular venous hemoglobin concentrations were similar. CONCLUSION Challenging exercise in hypoxia for 30 min affected muscle metabolism and increased an index of cerebral blood flow, but cerebral net water and ion homeostasis remained stable. Thus, although AMS develops within hours and may be related to exercise-induced disturbance of cerebral ion and water balance, such changes are not detectable when subjects are exposed to acute 30 min maximal exercise in hypoxia.
Collapse
Affiliation(s)
- Magnus B Avnstorp
- 1 Department of Anesthesia, The Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen , Copenhagen, Denmark
| | | | | | | | | | | | | | | |
Collapse
|
31
|
Smith KJ, MacLeod D, Willie CK, Lewis NCS, Hoiland RL, Ikeda K, Tymko MM, Donnelly J, Day TA, MacLeod N, Lucas SJE, Ainslie PN. Influence of high altitude on cerebral blood flow and fuel utilization during exercise and recovery. J Physiol 2014; 592:5507-27. [PMID: 25362150 PMCID: PMC4270509 DOI: 10.1113/jphysiol.2014.281212] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 10/18/2014] [Indexed: 11/08/2022] Open
Abstract
We examined the hypotheses that: (1) during incremental exercise and recovery following 4-6 days at high altitude (HA) global cerebral blood flow (gCBF) increases to preserve cerebral oxygen delivery (CDO2) in excess of that required by an increasing cerebral metabolic rate of oxygen ( CM RO2); (2) the trans-cerebral exchange of oxygen vs. carbohydrates (OCI; carbohydrates = glucose + ½lactate) would be similar during exercise and recovery at HA and sea level (SL). Global CBF, intra-cranial arterial blood velocities, extra-cranial blood flows, and arterial-jugular venous substrate differences were measured during progressive steady-state exercise (20, 40, 60, 80, 100% maximum workload (Wmax)) and through 30 min of recovery. Measurements (n = 8) were made at SL and following partial acclimatization to 5050 m. At HA, absolute Wmax was reduced by ∼50%. During submaximal exercise workloads (20-60% Wmax), despite an elevated absolute gCBF (∼20%, P < 0.05) the relative increases in gCBF were not different at HA and SL. In contrast, gCBF was elevated at HA compared with SL during 80 and 100% Wmax and recovery. Notwithstanding a maintained CDO2 and elevated absolute CM RO2 at HA compared with SL, the relative increase in CM RO2 was similar during 20-80% Wmax but half that of the SL response (i.e. 17 vs. 27%; P < 0.05 vs. SL) at 100% Wmax. The OCI was reduced at HA compared with SL during 20, 40, and 60% Wmax but comparable at 80 and 100% Wmax. At HA, OCI returned almost immediately to baseline values during recovery, whereas at SL it remained below baseline. In conclusion, the elevations in gCBF during exercise and recovery at HA serve to maintain CDO2. Despite adequate CDO2 at HA the brain appears to increase non-oxidative metabolism during exercise and recovery.
Collapse
Affiliation(s)
- K J Smith
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - D MacLeod
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - C K Willie
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - N C S Lewis
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - R L Hoiland
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - K Ikeda
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - M M Tymko
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - J Donnelly
- University of Otago, Dunedin, New Zealand University Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - T A Day
- Department of Biology, Mount Royal Univeristy, Calgary, AB, Canada
| | - N MacLeod
- Carolina Friends School, Durham, NC, USA
| | - S J E Lucas
- University of Otago, Dunedin, New Zealand University of Birmingham, Birmingham, UK
| | - P N Ainslie
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| |
Collapse
|
32
|
Edsell ME, Wimalasena YH, Malein WL, Ashdown KM, Gallagher CA, Imray CH, Wright AD, Myers SD. High-Intensity Intermittent Exercise Increases Pulmonary Interstitial Edema at Altitude But Not at Simulated Altitude. Wilderness Environ Med 2014; 25:409-15. [DOI: 10.1016/j.wem.2014.06.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2014] [Revised: 05/12/2014] [Accepted: 06/23/2014] [Indexed: 10/24/2022]
|
33
|
Bradwell AR, Myers SD, Beazley M, Ashdown K, Harris NG, Bradwell SB, Goodhart J, Imray CH, Wimalasena Y, Edsell ME, Pattinson KT, Wright AD, Harris SJ. Exercise Limitation of Acetazolamide at Altitude (3459 m). Wilderness Environ Med 2014; 25:272-7. [DOI: 10.1016/j.wem.2014.04.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 03/26/2014] [Accepted: 04/04/2014] [Indexed: 10/25/2022]
|
34
|
Affiliation(s)
- Mark H. Wilson
- The Brain Injury Centre—St Mary's Hospital, Imperial College, London, United Kingdom
- Birmingham Medical Research Expeditionary Society, Birmingham, United Kingdom
- The Institute of Pre-Hospital Care, London's Air Ambulance, Barts and the London Medical School, Queen Mary University of London, The Helipad, The Royal London Hospital, Whitechapel, United Kingdom
| | - Alex Wright
- Birmingham Medical Research Expeditionary Society, Birmingham, United Kingdom
| | - Christopher H.E. Imray
- University Hospital Coventry and Warwickshire NHS Trust and Warwick Medical School, Coventry, United Kingdom
| |
Collapse
|
35
|
Imray C, Chan C, Stubbings A, Rhodes H, Patey S, Wilson MH, Bailey DM, Wright AD. Time Course Variations in the Mechanisms by Which Cerebral Oxygen Delivery Is Maintained on Exposure to Hypoxia/Altitude. High Alt Med Biol 2014; 15:21-7. [DOI: 10.1089/ham.2013.1079] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Christopher Imray
- Warwick Medical School, University Hospitals Coventry and Warwickshire NHS Trust, Warwick, United Kingdom
| | - Colin Chan
- Wirral University Teaching Hospital, Wirral, United Kingdom
| | | | - Hannah Rhodes
- Department Paediatric Surgery, Bristol Royal Hospital for Children, Bristol, United Kingdom
| | - Susannah Patey
- Department of Anaesthetics, University Hospital of South Manchester, Wythenshawe, Manchester, United Kingdom
| | - Mark H. Wilson
- Department of Neurosurgery, Imperial College, St Mary's Hospital, Paddington London, United Kingdom
| | - Damian M. Bailey
- Department of Physiology, University of Glamorgan, Pontypridd, Wales, United Kingdom
| | - Alex D. Wright
- Birmingham Medical Research Expeditionary Society, The Medical School, Birmingham University, Edgbaston, Birmingham, United Kingdom
| | | |
Collapse
|
36
|
Rupp T, Esteve F, Bouzat P, Lundby C, Perrey S, Levy P, Robach P, Verges S. Cerebral hemodynamic and ventilatory responses to hypoxia, hypercapnia, and hypocapnia during 5 days at 4,350 m. J Cereb Blood Flow Metab 2014; 34:52-60. [PMID: 24064493 PMCID: PMC3887348 DOI: 10.1038/jcbfm.2013.167] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 07/31/2013] [Accepted: 08/26/2013] [Indexed: 01/18/2023]
Abstract
This study investigated the changes in cerebral near-infrared spectroscopy (NIRS) signals, cerebrovascular and ventilatory responses to hypoxia and CO2 during altitude exposure. At sea level (SL), after 24 hours and 5 days at 4,350 m, 11 healthy subjects were exposed to normoxia, isocapnic hypoxia, hypercapnia, and hypocapnia. The following parameters were measured: prefrontal tissue oxygenation index (TOI), oxy- (HbO2), deoxy- and total hemoglobin (HbTot) concentrations with NIRS, blood velocity in the middle cerebral artery (MCAv) with transcranial Doppler and ventilation. Smaller prefrontal deoxygenation and larger ΔHbTot in response to hypoxia were observed at altitude compared with SL (day 5: ΔHbO2-0.6±1.1 versus -1.8±1.3 μmol/cmper mm Hg and ΔHbTot 1.4±1.3 versus 0.7±1.1 μmol/cm per mm Hg). The hypoxic MCAv and ventilatory responses were enhanced at altitude. Prefrontal oxygenation increased less in response to hypercapnia at altitude compared with SL (day 5: ΔTOI 0.3±0.2 versus 0.5±0.3% mm Hg). The hypercapnic MCAv and ventilatory responses were decreased and increased, respectively, at altitude. Hemodynamic responses to hypocapnia did not change at altitude. Short-term altitude exposure improves cerebral oxygenation in response to hypoxia but decreases it during hypercapnia. Although these changes may be relevant for conditions such as exercise or sleep at altitude, they were not associated with symptoms of acute mountain sickness.
Collapse
Affiliation(s)
- Thomas Rupp
- 1] INSERM U1042, Grenoble, France [2] HP2 laboratory, Joseph Fourier University, Grenoble, France
| | - François Esteve
- 1] U836/team 6, INSERM, Grenoble, France [2] Grenoble Institute of Neurosciences, Joseph Fourier University, Grenoble, France
| | - Pierre Bouzat
- 1] U836/team 6, INSERM, Grenoble, France [2] Grenoble Institute of Neurosciences, Joseph Fourier University, Grenoble, France
| | - Carsten Lundby
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Stéphane Perrey
- Movement To Health (M2H), Montpellier-1 University, Euromov, France
| | - Patrick Levy
- 1] INSERM U1042, Grenoble, France [2] HP2 laboratory, Joseph Fourier University, Grenoble, France
| | - Paul Robach
- 1] INSERM U1042, Grenoble, France [2] HP2 laboratory, Joseph Fourier University, Grenoble, France [3] Ecole Nationale de Ski et d'Alpinisme, Chamonix, France
| | - Samuel Verges
- 1] INSERM U1042, Grenoble, France [2] HP2 laboratory, Joseph Fourier University, Grenoble, France
| |
Collapse
|
37
|
Laughlin MH, Davis MJ, Secher NH, van Lieshout JJ, Arce-Esquivel AA, Simmons GH, Bender SB, Padilla J, Bache RJ, Merkus D, Duncker DJ. Peripheral circulation. Compr Physiol 2013; 2:321-447. [PMID: 23728977 DOI: 10.1002/cphy.c100048] [Citation(s) in RCA: 174] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Blood flow (BF) increases with increasing exercise intensity in skeletal, respiratory, and cardiac muscle. In humans during maximal exercise intensities, 85% to 90% of total cardiac output is distributed to skeletal and cardiac muscle. During exercise BF increases modestly and heterogeneously to brain and decreases in gastrointestinal, reproductive, and renal tissues and shows little to no change in skin. If the duration of exercise is sufficient to increase body/core temperature, skin BF is also increased in humans. Because blood pressure changes little during exercise, changes in distribution of BF with incremental exercise result from changes in vascular conductance. These changes in distribution of BF throughout the body contribute to decreases in mixed venous oxygen content, serve to supply adequate oxygen to the active skeletal muscles, and support metabolism of other tissues while maintaining homeostasis. This review discusses the response of the peripheral circulation of humans to acute and chronic dynamic exercise and mechanisms responsible for these responses. This is accomplished in the context of leading the reader on a tour through the peripheral circulation during dynamic exercise. During this tour, we consider what is known about how each vascular bed controls BF during exercise and how these control mechanisms are modified by chronic physical activity/exercise training. The tour ends by comparing responses of the systemic circulation to those of the pulmonary circulation relative to the effects of exercise on the regional distribution of BF and mechanisms responsible for control of resistance/conductance in the systemic and pulmonary circulations.
Collapse
Affiliation(s)
- M Harold Laughlin
- Department of Medical Pharmacology and Physiology, and the Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri, USA.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
38
|
Ando S, Hatamoto Y, Sudo M, Kiyonaga A, Tanaka H, Higaki Y. The effects of exercise under hypoxia on cognitive function. PLoS One 2013; 8:e63630. [PMID: 23675496 PMCID: PMC3651238 DOI: 10.1371/journal.pone.0063630] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2012] [Accepted: 04/04/2013] [Indexed: 11/18/2022] Open
Abstract
Increasing evidence suggests that cognitive function improves during a single bout of moderate exercise. In contrast, exercise under hypoxia may compromise the availability of oxygen. Given that brain function and tissue integrity are dependent on a continuous and sufficient oxygen supply, exercise under hypoxia may impair cognitive function. However, it remains unclear how exercise under hypoxia affects cognitive function. The purpose of this study was to examine the effects of exercise under different levels of hypoxia on cognitive function. Twelve participants performed a cognitive task at rest and during exercise at various fractions of inspired oxygen (FIO2: 0.209, 0.18, and 0.15). Exercise intensity corresponded to 60% of peak oxygen uptake under normoxia. The participants performed a Go/No-Go task requiring executive control. Cognitive function was evaluated using the speed of response (reaction time) and response accuracy. We monitored pulse oximetric saturation (SpO2) and cerebral oxygenation to assess oxygen availability. SpO2 and cerebral oxygenation progressively decreased during exercise as the FIO2 level decreased. Nevertheless, the reaction time in the Go-trial significantly decreased during moderate exercise. Hypoxia did not affect reaction time. Neither exercise nor difference in FIO2 level affected response accuracy. An additional experiment indicated that cognitive function was not altered without exercise. These results suggest that the improvement in cognitive function is attributable to exercise, and that hypoxia has no effects on cognitive function at least under the present experimental condition. Exercise-cognition interaction should be further investigated under various environmental and exercise conditions.
Collapse
Affiliation(s)
- Soichi Ando
- Faculty of Sports and Health Science, Fukuoka University, Fukuoka, Japan.
| | | | | | | | | | | |
Collapse
|
39
|
Gavlak JC, Stocks J, Laverty A, Fettes E, Bucks R, Sonnappa S, Cooper J, Grocott MP, Levett DZ, Martin DS, Imray CH, Kirkham FJ. The Young Everest Study: preliminary report of changes in sleep and cerebral blood flow velocity during slow ascent to altitude in unacclimatised children. Arch Dis Child 2013; 98:356-62. [PMID: 23471157 PMCID: PMC3625826 DOI: 10.1136/archdischild-2012-302512] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND Cerebral blood flow velocity (CBFV) and sleep physiology in healthy children exposed to hypoxia and hypocarbia are under-researched. AIM To investigate associations between sleep variables, daytime end-tidal carbon dioxide (EtCO2) and CBFV in children during high-altitude ascent. METHODS Vital signs, overnight cardiorespiratory sleep studies and transcranial Doppler were undertaken in nine children (aged 6-13 years) at low altitude (130 m), and then at moderate (1300 m) and high (3500 m) altitude during a 5-day ascent. RESULTS Daytime (130 m: 98%; 3500 m: 90%, p=0.004) and mean (130 m: 97%, 1300 m: 94%, 3500: 87%, p=0.0005) and minimum (130 m: 92%, 1300 m: 84%, 3500 m: 79%, p=0.0005) overnight pulse oximetry oxyhaemoglobin saturation decreased, and the number of central apnoeas increased at altitude (130 m: 0.2/h, 1300 m: 1.2/h, 3500 m: 3.5/h, p=0.2), correlating inversely with EtCO2 (R(2) 130 m: 0.78; 3500 m: 0.45). Periodic breathing occurred for median (IQR) 0.0 (0; 0.3)% (130 m) and 0.2 (0; 1.2)% (3500 m) of total sleep time. At 3500 m compared with 130 m, there were increases in middle (MCA) (mean (SD) left 29.2 (42.3)%, p=0.053; right 9.9 (12)%, p=0.037) and anterior cerebral (ACA) (left 65.2 (69)%, p=0.024; right 109 (179)%; p=0.025) but not posterior or basilar CBFV. The right MCA CBFV increase at 3500 m was predicted by baseline CBFV and change in daytime SpO2 and EtCO2 at 3500 m (R(2) 0.92); these associations were not seen on the left. CONCLUSIONS This preliminary report suggests that sleep physiology is disturbed in children even with slow ascent to altitude. The regional variations in CBFV and their association with hypoxia and hypocapnia require further investigation.
Collapse
Affiliation(s)
- Johanna C Gavlak
- Department of Paediatric Respiratory Medicine, Great Ormond Street Hospital for Children NHS Trust, Walrus Ward Level 1, Morgan Stanley Clinical Building, Great Ormond Street, London WC1N 3JH, UK.
| | - Janet Stocks
- Portex Respiratory Unit, UCL Institute of Child Health, London, UK
| | - Aidan Laverty
- Department of Paediatric Respiratory Medicine, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Emma Fettes
- Department of Paediatric Respiratory Medicine, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Romola Bucks
- Department of Psychology, University of Western Australia, Perth, Australia
| | - Samatha Sonnappa
- Department of Paediatric Respiratory Medicine, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK,Portex Respiratory Unit, UCL Institute of Child Health, London, UK
| | - Janine Cooper
- Developmental Neuroscience Unit, UCL Institute of Child Health, London, UK
| | - Michael P Grocott
- Centre for Altitude Space and Extreme Environment Medicine, UCL Institute of Child Health, London, UK,Anaesthesia and Critical Care Research Unit, University Hospitals Southampton NHS Foundation Trust, Southampton, UK,Department of Clinical and Experimental Sciences, University of Southampton, Southampton, UK
| | - Denny Z Levett
- Centre for Altitude Space and Extreme Environment Medicine, UCL Institute of Child Health, London, UK
| | - Daniel S Martin
- Centre for Altitude Space and Extreme Environment Medicine, UCL Institute of Child Health, London, UK
| | - Christopher H Imray
- Department of Vascular Surgery, University Hospitals Coventry and Warwickshire NHS Trust, Warwick Medical School, Coventry, UK
| | - Fenella J Kirkham
- Department of Clinical and Experimental Sciences, University of Southampton, Southampton, UK,Neurosciences Units, UCL Institute of Child Health, London, UK,Department of Child Health, University Hospitals Southampton NHS Foundation Trust, Southampton, UK
| |
Collapse
|
40
|
|
41
|
Hypocapnia during hypoxic exercise and its impact on cerebral oxygenation, ventilation and maximal whole body O2 uptake. Respir Physiol Neurobiol 2013; 185:461-7. [DOI: 10.1016/j.resp.2012.08.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Revised: 08/13/2012] [Accepted: 08/16/2012] [Indexed: 12/27/2022]
|
42
|
Rupp T, Jubeau M, Millet GY, Perrey S, Esteve F, Wuyam B, Levy P, Verges S. The effect of hypoxemia and exercise on acute mountain sickness symptoms. J Appl Physiol (1985) 2012; 114:180-5. [PMID: 23154995 DOI: 10.1152/japplphysiol.00769.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Performing exercise during the first hours of hypoxic exposure is thought to exacerbate acute mountain sickness (AMS), but whether this is due to increased hypoxemia or other mechanisms associated with exercise remains unclear. In 12 healthy men, AMS symptoms were assessed during three 11-h experimental sessions: 1) in Hypoxia-exercise, inspiratory O(2) fraction (Fi(O(2))) was 0.12, and subjects performed 4-h cycling at 45% Fi(O(2))-specific maximal power output from the 4th to the 8th hour; 2) in Hypoxia-rest, Fi(O(2)) was continuously adjusted to match the same arterial oxygen saturation as in Hypoxia-exercise, and subjects remained at rest; and 3) in Normoxia-exercise, Fi(O(2)) was 0.21, and subjects cycled as in Hypoxia-exercise at 45% Fi(O(2))-specific maximal power output. AMS scores did not differ significantly between Hypoxia-exercise and Hypoxia-rest, while they were significantly lower in Normoxia-exercise (Lake Louise score: 5.5 ± 2.1, 4.4 ± 2.4, and 2.3 ± 1.5, and cerebral Environmental Symptom Questionnaire: 1.2 ± 0.7, 1.0 ± 1.0, and 0.3 ± 0.4, in Hypoxia-exercise, Hypoxia-rest, and Normoxia-exercise, respectively; P < 0.01). Headache scored by visual analog scale was higher in Hypoxia-exercise and Hypoxia-rest compared with Normoxia-exercise (36 ± 22, 35 ± 25, and 5 ± 6, P < 0.001), while the perception of fatigue was higher in Hypoxia-exercise compared with Hypoxia-rest (60 ± 24, 32 ± 22, and 46 ± 23, in Hypoxia-exercise, Hypoxia-rest, and Normoxia-exercise, respectively; P < 0.01). Despite significant physiological stress during hypoxic exercise and some AMS symptoms induced by normoxic cycling at similar relative workload, exercise does not significantly worsen AMS severity during the first hours of hypoxic exposure at a given arterial oxygen desaturation. Hypoxemia per se appears, therefore, to be the main mechanism underlying AMS, whether or not exercise is performed.
Collapse
|
43
|
Masschelein E, Van Thienen R, Wang X, Van Schepdael A, Thomis M, Hespel P. Dietary nitrate improves muscle but not cerebral oxygenation status during exercise in hypoxia. J Appl Physiol (1985) 2012; 113:736-45. [DOI: 10.1152/japplphysiol.01253.2011] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Exercise tolerance is impaired in hypoxia, and it has recently been shown that dietary nitrate supplementation can reduce the oxygen (O2) cost of muscle contractions. Therefore, we investigated the effect of dietary nitrate supplementation on arterial, muscle, and cerebral oxygenation status, symptoms of acute mountain sickness (AMS), and exercise tolerance at simulated 5,000 m altitude. Fifteen young, healthy volunteers participated in three experimental sessions according to a crossover study design. From 6 days prior to each session, subjects received either beetroot (BR) juice delivering 0.07 mmol nitrate/kg body wt/day or a control drink (CON). One session was in normoxia with CON (NORCON); the two other sessions were in hypoxia (11% O2), with either CON (HYPCON) or BR (HYPBR). Subjects first cycled for 20 min at 45% of peak O2 consumption (VO2peak; EX45%) and thereafter, performed a maximal incremental exercise test (EXmax). Whole-body VO2, arterial O2 saturation (%SpO2) via pulsoximetry, and tissue oxygenation index of both muscle (TOIM) and cerebral (TOIC) tissue by near-infrared spectroscopy were measured. Hypoxia per se substantially reduced VO2peak, %SpO2, TOIM, and TOIC (NORCON vs. HYPCON, P < 0.05). Compared with HYPCON, VO2 at rest and during EX45% was lower in HYPBR ( P < 0.05), whereas %SpO2 was higher ( P < 0.05). TOIM was ∼4-5% higher in HYPBR than in HYPCON both at rest and during EX45% and EXmax ( P < 0.05). TOIC as well as the incidence of AMS symptoms were similar between HYPCON and HYPBR at any time. Hypoxia reduced time to exhaustion in EXmax by 36% ( P < 0.05), but this ergolytic effect was partly negated by BR (+5%, P < 0.05). Short-term dietary nitrate supplementation improves arterial and muscle oxygenation status but not cerebral oxygenation status during exercise in severe hypoxia. This is associated with improved exercise tolerance against the background of a similar incidence of AMS.
Collapse
Affiliation(s)
- Evi Masschelein
- Research Center for Exercise and Health, Department of Biomedical Kinesiology, KU Leuven, Leuven, Belgium; and
| | - Ruud Van Thienen
- Research Center for Exercise and Health, Department of Biomedical Kinesiology, KU Leuven, Leuven, Belgium; and
| | - Xu Wang
- Laboratory for Pharmaceutical Analysis, Faculty of Pharmaceutical Sciences, KU Leuven, Leuven, Belgium
| | - Ann Van Schepdael
- Laboratory for Pharmaceutical Analysis, Faculty of Pharmaceutical Sciences, KU Leuven, Leuven, Belgium
| | - Martine Thomis
- Research Center for Exercise and Health, Department of Biomedical Kinesiology, KU Leuven, Leuven, Belgium; and
| | - Peter Hespel
- Research Center for Exercise and Health, Department of Biomedical Kinesiology, KU Leuven, Leuven, Belgium; and
| |
Collapse
|
44
|
Obisesan TO, Gillum RF, Johnson S, Umar N, Williams D, Bond V, Kwagyan J. Neuroprotection and neurodegeneration in Alzheimer's disease: role of cardiovascular disease risk factors, implications for dementia rates, and prevention with aerobic exercise in african americans. Int J Alzheimers Dis 2012; 2012:568382. [PMID: 22577592 PMCID: PMC3345220 DOI: 10.1155/2012/568382] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 02/09/2012] [Accepted: 02/12/2012] [Indexed: 12/17/2022] Open
Abstract
Prevalence of Alzheimer's disease (AD) will reach epidemic proportions in the United States and worldwide in the coming decades, and with substantially higher rates in African Americans (AAs) than in Whites. Older age, family history, low levels of education, and ɛ4 allele of the apolipoprotein E (APOE) gene are recognized risk factors for the neurodegeneration in AD and related disorders. In AAs, the contributions of APOE gene to AD risk continue to engender a considerable debate. In addition to the established role of cardiovascular disease (CVD) risk in vascular dementia, it is now believed that CVD risk and its endophenotype may directly comediate AD phenotype. Given the pleiotropic effects of APOE on CVD and AD risks, the higher rates of CVD risks in AAs than in Whites, it is likely that CVD risks contribute to the disproportionately higher rates of AD in AAs. Though the advantageous effects of aerobic exercise on cognition is increasingly recognized, this evidence is hardly definitive, and data on AAs is lacking. In this paper, we will discuss the roles of CVD risk factors in the development of AD and related dementias, the susceptibility of these risk factors to physiologic adaptation, and fitness-related improvements in cognitive function. Its relevance to AD prevention in AAs is emphasized.
Collapse
Affiliation(s)
- Thomas O. Obisesan
- Division of Geriatrics, Department of Medicine, Howard University Hospital, 2041 Georgia Avenue, NW, Washington, DC 20059, USA
| | - Richard F. Gillum
- Division of Geriatrics, Department of Medicine, Howard University Hospital, 2041 Georgia Avenue, NW, Washington, DC 20059, USA
| | - Stephanie Johnson
- Division of Geriatrics, Department of Medicine, Howard University Hospital, 2041 Georgia Avenue, NW, Washington, DC 20059, USA
| | - Nisser Umar
- Division of Geriatrics, Department of Medicine, Howard University Hospital, 2041 Georgia Avenue, NW, Washington, DC 20059, USA
| | - Deborah Williams
- Division of Cardiology, Department of Medicine, Howard University Hospital, 2041 Georgia Avenue, NW, Washington, DC 20059, USA
| | - Vernon Bond
- Department of Health and Human Performance, Howard University Hospital, 2041 Georgia Avenue, NW, Washington, DC 20059, USA
| | - John Kwagyan
- Howard University Hospital, Georgetown-Howard Universities Center for Clinical and Translational Science, 2041 Georgia Avenue, NW, Washington, DC 20059, USA
| |
Collapse
|
45
|
Verges S, Rupp T, Jubeau M, Wuyam B, Esteve F, Levy P, Perrey S, Millet GY. Cerebral perturbations during exercise in hypoxia. Am J Physiol Regul Integr Comp Physiol 2012; 302:R903-16. [DOI: 10.1152/ajpregu.00555.2011] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Reduction of aerobic exercise performance observed under hypoxic conditions is mainly attributed to altered muscle metabolism due to impaired O2 delivery. It has been recently proposed that hypoxia-induced cerebral perturbations may also contribute to exercise performance limitation. A significant reduction in cerebral oxygenation during whole body exercise has been reported in hypoxia compared with normoxia, while changes in cerebral perfusion may depend on the brain region, the level of arterial oxygenation and hyperventilation induced alterations in arterial CO2. With the use of transcranial magnetic stimulation, inconsistent changes in cortical excitability have been reported in hypoxia, whereas a greater impairment in maximal voluntary activation following a fatiguing exercise has been suggested when arterial O2 content is reduced. Electromyographic recordings during exercise showed an accelerated rise in central motor drive in hypoxia, probably to compensate for greater muscle contractile fatigue. This accelerated development of muscle fatigue in moderate hypoxia may be responsible for increased inhibitory afferent signals to the central nervous system leading to impaired central drive. In severe hypoxia (arterial O2 saturation <70–75%), cerebral hypoxia per se may become an important contributor to impaired performance and reduced motor drive during prolonged exercise. This review examines the effects of acute and chronic reduction in arterial O2 (and CO2) on cerebral blood flow and cerebral oxygenation, neuronal function, and central drive to the muscles. Direct and indirect influences of arterial deoxygenation on central command are separated. Methodological concerns as well as future research avenues are also considered.
Collapse
Affiliation(s)
- Samuel Verges
- INSERM U1042, Grenoble
- HP2 laboratory, Joseph Fourier University, Grenoble
- Exercise Research Unit, Grenoble University Hospital, Grenoble
| | - Thomas Rupp
- INSERM U1042, Grenoble
- HP2 laboratory, Joseph Fourier University, Grenoble
| | | | - Bernard Wuyam
- INSERM U1042, Grenoble
- HP2 laboratory, Joseph Fourier University, Grenoble
- Exercise Research Unit, Grenoble University Hospital, Grenoble
| | - François Esteve
- Exercise Research Unit, Grenoble University Hospital, Grenoble
- INSERM U836/team 6, Grenoble Institute of Neurosciences, Grenoble
| | - Patrick Levy
- INSERM U1042, Grenoble
- HP2 laboratory, Joseph Fourier University, Grenoble
- Exercise Research Unit, Grenoble University Hospital, Grenoble
| | - Stéphane Perrey
- Movement To Health (M2H), Montpellier-1 University, Euromov, Montpellier; and
| | | |
Collapse
|
46
|
Goodall S, González-Alonso J, Ali L, Ross EZ, Romer LM. Supraspinal fatigue after normoxic and hypoxic exercise in humans. J Physiol 2012; 590:2767-82. [PMID: 22473785 PMCID: PMC3424730 DOI: 10.1113/jphysiol.2012.228890] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Inadequate cerebral O2 availability has been proposed to be an important contributing factor to the development of central fatigue during strenuous exercise. Here we tested the hypothesis that supraspinal processes of fatigue would be increased after locomotor exercise in acute hypoxia compared to normoxia, and that such change would be related to reductions in cerebral O2 delivery and tissue oxygenation. Nine endurance-trained cyclists completed three constant-load cycling exercise trials at ∼80% of maximal work rate: (1) to the limit of tolerance in acute hypoxia; (2) for the same duration but in normoxia (control); and (3) to the limit of tolerance in normoxia. Throughout each trial, prefrontal cortex tissue oxygenation and middle cerebral artery blood velocity (MCAV) were assessed using near-infrared spectroscopy and transcranial Doppler sonography, respectively. Cerebral O2 delivery was calculated as the product of arterial O2 content and MCAV. Before and immediately after each trial, twitch responses to supramaximal femoral nerve stimulation and transcranial magnetic stimulation were obtained to assess neuromuscular and cortical function, respectively. Exercise time was reduced by 54% in hypoxia compared to normoxia (3.6 ± 1.3 vs. 8.1 ± 2.9 min; P < 0.001). Cerebral O2 delivery, cerebral oxygenation and maximum O2 uptake were reduced whereas muscle electromyographic activity was increased in hypoxia compared to control (P < 0.05). Maximum voluntary force and potentiated quadriceps twitch force were decreased below baseline after exercise in each trial; the decreases were greater in hypoxia compared to control (P < 0.001), but were not different in the exhaustive trials (P > 0.05). Cortical voluntary activation was also decreased after exercise in all trials, but the decline in hypoxia (Δ18%) was greater than in the normoxic trials (Δ5–9%) (P < 0.05). The reductions in cortical voluntary activation were paralleled by reductions in cerebral O2 delivery. The results suggest that curtailment of exercise performance in acute severe hypoxia is due, in part, to failure of drive from the motor cortex, possibly as a consequence of diminished O2 availability in the brain.
Collapse
Affiliation(s)
- Stuart Goodall
- Centre for Sports Medicine and Human Performance, Brunel University, Uxbridge, UK
| | | | | | | | | |
Collapse
|
47
|
Debevec T, Mekjavic IB. Short intermittent hypoxic exposures augment ventilation but do not alter regional cerebral and muscle oxygenation during hypoxic exercise. Respir Physiol Neurobiol 2012; 181:132-42. [DOI: 10.1016/j.resp.2012.02.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 02/20/2012] [Accepted: 02/23/2012] [Indexed: 11/25/2022]
|
48
|
Millet GY, Muthalib M, Jubeau M, Laursen PB, Nosaka K. Severe hypoxia affects exercise performance independently of afferent feedback and peripheral fatigue. J Appl Physiol (1985) 2012; 112:1335-44. [PMID: 22323647 DOI: 10.1152/japplphysiol.00804.2011] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To test the hypothesis that hypoxia centrally affects performance independently of afferent feedback and peripheral fatigue, we conducted two experiments under complete vascular occlusion of the exercising muscle under different systemic O(2) environmental conditions. In experiment 1, 12 subjects performed repeated submaximal isometric contractions of the elbow flexor to exhaustion (RCTE) with inspired O(2) fraction fixed at 9% (severe hypoxia, SevHyp), 14% (moderate hypoxia, ModHyp), 21% (normoxia, Norm), or 30% (hyperoxia, Hyper). The number of contractions (performance), muscle (biceps brachii), and prefrontal near-infrared spectroscopy (NIRS) parameters and high-frequency paired-pulse (PS100) evoked responses to electrical muscle stimulation were monitored. In experiment 2, 10 subjects performed another RCTE in SevHyp and Norm conditions in which the number of contractions, biceps brachii electromyography responses to electrical nerve stimulation (M wave), and transcranial magnetic stimulation responses (motor-evoked potentials, MEP, and cortical silent period, CSP) were recorded. Performance during RCTE was significantly reduced by 10-15% in SevHyp (arterial O(2) saturation, SpO(2) = ∼75%) compared with ModHyp (SpO(2) = ∼90%) or Norm/Hyper (SpO(2) > 97%). Performance reduction in SevHyp occurred despite similar 1) metabolic (muscle NIRS parameters) and functional (changes in PS100 and M wave) muscle states and 2) MEP and CSP responses, suggesting comparable corticospinal excitability and spinal and cortical inhibition between SevHyp and Norm. It is concluded that, in SevHyp, performance and central drive can be altered independently of afferent feedback and peripheral fatigue. It is concluded that submaximal performance in SevHyp is partly reduced by a mechanism related directly to brain oxygenation.
Collapse
Affiliation(s)
- Guillaume Y Millet
- School of Exercise and Health Sciences, Edith Cowan University, Joondalup, Australia.
| | | | | | | | | |
Collapse
|
49
|
Wilson MH, Edsell MEG, Davagnanam I, Hirani SP, Martin DS, Levett DZH, Thornton JS, Golay X, Strycharczuk L, Newman SP, Montgomery HE, Grocott MPW, Imray CHE. Cerebral artery dilatation maintains cerebral oxygenation at extreme altitude and in acute hypoxia--an ultrasound and MRI study. J Cereb Blood Flow Metab 2011; 31:2019-29. [PMID: 21654697 PMCID: PMC3208157 DOI: 10.1038/jcbfm.2011.81] [Citation(s) in RCA: 168] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Transcranial Doppler is a widely used noninvasive technique for assessing cerebral artery blood flow. All previous high altitude studies assessing cerebral blood flow (CBF) in the field that have used Doppler to measure arterial blood velocity have assumed vessel diameter to not alter. Here, we report two studies that demonstrate this is not the case. First, we report the highest recorded study of CBF (7,950 m on Everest) and demonstrate that above 5,300 m, middle cerebral artery (MCA) diameter increases (n=24 at 5,300 m, 14 at 6,400 m, and 5 at 7,950 m). Mean MCA diameter at sea level was 5.30 mm, at 5,300 m was 5.23 mm, at 6,400 m was 6.66 mm, and at 7,950 m was 9.34 mm (P<0.001 for change between 5,300 and 7,950 m). The dilatation at 7,950 m reversed with oxygen. Second, we confirm this dilatation by demonstrating the same effect (and correlating it with ultrasound) during hypoxia (FiO(2)=12% for 3 hours) in a 3-T magnetic resonance imaging study at sea level (n=7). From these results, we conclude that it cannot be assumed that cerebral artery diameter is constant, especially during alterations of inspired oxygen partial pressure, and that transcranial 2D ultrasound is a technique that can be used at the bedside or in the remote setting to assess MCA caliber.
Collapse
Affiliation(s)
- Mark H Wilson
- Centre for Altitude, Space and Extreme Environment Medicine, Institute of Human Health and Performance, Charterhouse Building, UCL Archway Campus, University College London, London, UK.
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
50
|
Vogiatzis I, Louvaris Z, Habazettl H, Athanasopoulos D, Andrianopoulos V, Cherouveim E, Wagner H, Roussos C, Wagner PD, Zakynthinos S. Frontal cerebral cortex blood flow, oxygen delivery and oxygenation during normoxic and hypoxic exercise in athletes. J Physiol 2011; 589:4027-39. [PMID: 21727220 DOI: 10.1113/jphysiol.2011.210880] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
During maximal hypoxic exercise, a reduction in cerebral oxygen delivery may constitute a signal to the central nervous system to terminate exercise. We investigated whether the rate of increase in frontal cerebral cortex oxygen delivery is limited in hypoxic compared to normoxic exercise. We assessed frontal cerebral cortex blood flow using near-infrared spectroscopy and the light-absorbing tracer indocyanine green dye, as well as frontal cortex oxygen saturation (S(tO2)%) in 11 trained cyclists during graded incremental exercise to the limit of tolerance (maximal work rate, WRmax) in normoxia and acute hypoxia (inspired O2 fraction (F(IO2)), 0.12). In normoxia, frontal cortex blood flow and oxygen delivery increased (P < 0.05) from baseline to sub-maximal exercise, reaching peak values at near-maximal exercise (80% WRmax: 287 ± 9 W; 81 ± 23% and 75 ± 22% increase relative to baseline, respectively), both leveling off thereafter up to WRmax (382 ± 10 W). Frontal cortex S(tO2)% did not change from baseline (66 ± 3%) throughout graded exercise. During hypoxic exercise, frontal cortex blood flow increased (P = 0.016) from baseline to sub-maximal exercise, peaking at 80% WRmax (213 ± 6 W; 60 ± 15% relative increase) before declining towards baseline at WRmax (289 ± 5 W). Despite this, frontal cortex oxygen delivery remained unchanged from baseline throughout graded exercise, being at WRmax lower than at comparable loads (287 ± 9 W) in normoxia (by 58 ± 12%; P = 0.01). Frontal cortex S(tO2)% fell from baseline (58 ± 2%) on light and moderate exercise in parallel with arterial oxygen saturation, but then remained unchanged to exhaustion (47 ± 1%). Thus, during maximal, but not light to moderate, exercise frontal cortex oxygen delivery is limited in hypoxia compared to normoxia. This limitation could potentially constitute the signal to limit maximal exercise capacity in hypoxia.
Collapse
Affiliation(s)
- Ioannis Vogiatzis
- Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, M. Simou, and G.P. Livanos Laboratories, National and Kapodistrian University of Athens, Greece.
| | | | | | | | | | | | | | | | | | | |
Collapse
|