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Furian M, Ulliel-Roche M, Howe CA, Zerizer F, Marillier M, Bernard AC, Hancco I, Champigneulle B, Baillieul S, Stauffer E, Pichon AP, Doutreleau S, Verges S, Brugniaux JV. Cerebral homeostasis and orthostatic responses in residents of the highest city in the world. Sci Rep 2024; 14:17732. [PMID: 39085313 PMCID: PMC11291767 DOI: 10.1038/s41598-024-68389-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 07/23/2024] [Indexed: 08/02/2024] Open
Abstract
Permanent residence at high-altitude and chronic mountain sickness (CMS) may alter the cerebrovascular homeostasis and orthostatic responses. Healthy male participants living at sea-level (LL; n = 15), 3800 m (HL3800m; n = 13) and 5100 m (HL5100m; n = 17), respectively, and CMS highlanders living at 5100 m (n = 31) were recruited. Middle cerebral artery mean blood flow velocity (MCAv), cerebral oxygen delivery (CDO2), mean blood pressure (MAP), heart rate variability and spontaneuous cardiac baroreflex sensitivity (cBRS) were assessed while sitting, initial 30 s and after 3 min of standing. Cerebral autoregulation index (ARI) was estimated (ΔMCAv%baseline)/ΔMAP%baseline) in response to the orthostatic challenge. Altitude and CMS were associated with hypoxemia and elevated hemoglobin concentration. While sitting, MCAv and LFpower negatively correlated with altitude but were not affected by CMS. CDO2 remained preserved. BRS was comparable across all altitudes, but lower with CMS. Within initial 30 s of standing, altitude and CMS correlated with a lesser ΔMAP while ARI remained unaffected. After 3 min standing, MCAv, CDO2 and cBRS remained preserved across altitudes. The LF/HF ratio increased in HL5100m compared to LL and HL3800m from sitting to standing. In contrary, CMS showed blunted autonomic nervous activation in responses to standing. Despite altitude- and CMS-associated hypoxemia, erythrocytosis and impaired blood pressure regulation (CMS only), cerebral homeostasis remained overall preserved.
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Affiliation(s)
- M Furian
- HP2 Laboratory, Université Grenoble Alpes, Inserm (U1300), CHU Grenoble Alpes, 38000, Grenoble, France.
- Swiss University of Traditional Chinese Medicine, Bad Zurzach, Switzerland.
| | - M Ulliel-Roche
- HP2 Laboratory, Université Grenoble Alpes, Inserm (U1300), CHU Grenoble Alpes, 38000, Grenoble, France
| | - C A Howe
- Center for Heart, Lung, and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - F Zerizer
- HP2 Laboratory, Université Grenoble Alpes, Inserm (U1300), CHU Grenoble Alpes, 38000, Grenoble, France
| | - M Marillier
- HP2 Laboratory, Université Grenoble Alpes, Inserm (U1300), CHU Grenoble Alpes, 38000, Grenoble, France
| | - A C Bernard
- HP2 Laboratory, Université Grenoble Alpes, Inserm (U1300), CHU Grenoble Alpes, 38000, Grenoble, France
| | - I Hancco
- HP2 Laboratory, Université Grenoble Alpes, Inserm (U1300), CHU Grenoble Alpes, 38000, Grenoble, France
| | - B Champigneulle
- HP2 Laboratory, Université Grenoble Alpes, Inserm (U1300), CHU Grenoble Alpes, 38000, Grenoble, France
| | - S Baillieul
- HP2 Laboratory, Université Grenoble Alpes, Inserm (U1300), CHU Grenoble Alpes, 38000, Grenoble, France
| | - E Stauffer
- Laboratoire Interuniversitaire de Biologie de la Motricité (LIBM) EA7424, Team « Vascular Biology and Red Blood Cell », Université Claude Bernard Lyon 1, Université de Lyon, Lyon, France
| | - A P Pichon
- Laboratory Mobility, aging & exercise (MOVE, EA6314), Faculty of Sport Sciences, University of Poitiers, Poitiers, France
| | - S Doutreleau
- HP2 Laboratory, Université Grenoble Alpes, Inserm (U1300), CHU Grenoble Alpes, 38000, Grenoble, France
| | - S Verges
- HP2 Laboratory, Université Grenoble Alpes, Inserm (U1300), CHU Grenoble Alpes, 38000, Grenoble, France
| | - J V Brugniaux
- HP2 Laboratory, Université Grenoble Alpes, Inserm (U1300), CHU Grenoble Alpes, 38000, Grenoble, France
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Ramchandani R, Florica IT, Zhou Z, Alemi A, Baranchuk A. Review of Athletic Guidelines for High-Altitude Training and Acclimatization. High Alt Med Biol 2024; 25:113-121. [PMID: 38207236 DOI: 10.1089/ham.2023.0042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2024] Open
Abstract
Ramchandani, Rashi, Ioana Tereza Florica, Zier Zhou, Aziz Alemi, and Adrian Baranchuk. Review of athletic guidelines for high-altitude training and acclimatization. High Alt Med Biol. 00:000-000, 2024. Introduction: Exposure to high altitude results in hypobaric hypoxia with physiological acclimatization changes that are thought to influence athletic performance. This review summarizes existing literature regarding implications of high-altitude training and altitude-related guidelines from major governing bodies of sports. Methods: A nonsystematic review was performed using PubMed and OVID Medline to identify articles regarding altitude training and guidelines from international governing bodies of various sports. Sports inherently involving training or competing at high altitude were excluded. Results: Important physiological compensatory mechanisms to high-altitude environments include elevations in blood pressure, heart rate, red blood cell mass, tidal volume, and respiratory rate. These responses can have varying effects on athletic performance. Governing sport bodies have limited and differing regulations for training and competition at high altitudes with recommended acclimatization periods ranging from 3 days to 3 weeks. Discussion: Physiological changes in response to high terrestrial altitude exposure can have substantial impacts on athletic performance. Major sport governing bodies have limited regulations and recommendations regarding altitude training and competition. Existing guidelines are variable and lack substantial evidence to support recommendations. Additional studies are needed to clarify the implications of high-altitude exposure on athletic ability to optimize training and competition.
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Affiliation(s)
- Rashi Ramchandani
- Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Ioana Tereza Florica
- Department of Medicine, Kingston Health Science Center, Queen's University, Kingston, Ontario, Canada
| | - Zier Zhou
- Atherosclerosis, Genomics and Vascular Biology Division, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
| | - Aziz Alemi
- Department of Cardiology, Kingston Health Science Center, Queen's University, Kingston, Ontario, Canada
| | - Adrian Baranchuk
- Department of Medicine, Kingston Health Science Center, Queen's University, Kingston, Ontario, Canada
- Department of Cardiology, Kingston Health Science Center, Queen's University, Kingston, Ontario, Canada
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Champigneulle B, Brugniaux JV, Stauffer E, Doutreleau S, Furian M, Perger E, Pina A, Baillieul S, Deschamps B, Hancco I, Connes P, Robach P, Pichon A, Verges S. Expedition 5300: limits of human adaptations in the highest city in the world. J Physiol 2023. [PMID: 38146929 DOI: 10.1113/jp284550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 12/06/2023] [Indexed: 12/27/2023] Open
Abstract
Exposure to chronic hypobaric hypoxia imposes a significant physiological burden to more than 80 million humans living above 2500 m throughout the world. Among them, 50 000 live in the world's highest city, La Rinconada, located at 5000-5300 m in southern Peru. Expedition 5300 is the first scientific and medical programme led in La Rinconada to investigate the physiological adaptations and altitude-related health issues in this unique population. Dwellers from La Rinconada have very high haemoglobin concentration (20.3 ± 2.4 g/dL; n = 57) and those with chronic mountain sickness (CMS) exhibit even higher concentrations (23.1 ± 1.7 g/dL; n = 150). These values are associated with large total haemoglobin mass and blood volume, without an associated iron deficit. These changes in intravascular volumes lead to a substantial increase in blood viscosity, which is even larger in CMS patients. Despite these large haematological changes, 24 h blood pressure monitoring is essentially normal in La Rinconada, but some results suggest impaired vascular reactivity. Echocardiography revealed large right heart dilatation and high pulmonary arterial pressure as well as left ventricle concentric remodelling and grade I diastolic dysfunction. These changes in heart dimension and function tend to be more severe in highlanders with CMS. Polygraphy evaluations revealed a large reduction in nocturnal pulse oxygen saturation (median SpO2 = 79%), which is even more severe in CMS patients who also tended to show a higher oxygen desaturation index. The population of La Rinconada offers a unique opportunity to investigate the human responses to chronic severe hypoxia, at an altitude that is probably close to the maximum altitude human beings can permanently tolerate without presenting major health issues.
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Affiliation(s)
- Benoit Champigneulle
- Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, HP2 laboratory, Grenoble, France
| | - Julien V Brugniaux
- Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, HP2 laboratory, Grenoble, France
| | - Emeric Stauffer
- Interuniversity Laboratory of Human Movement Biology (LIBM, EA7424), "Red Blood cell and Vascular Biology" Team, Univ Lyon - University Claude Bernard Lyon 1, Villeurbanne, France
| | - Stéphane Doutreleau
- Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, HP2 laboratory, Grenoble, France
| | - Michael Furian
- Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, HP2 laboratory, Grenoble, France
| | - Elisa Perger
- Istituto Auxologico Italiano, IRCCS, Sleep Disorders Center & Department of Cardiovascular, Neural and Metabolic Sciences, San Luca Hospital, Milan, Italy
| | - Alessandra Pina
- Istituto Auxologico Italiano, IRCCS, Sleep Disorders Center & Department of Cardiovascular, Neural and Metabolic Sciences, San Luca Hospital, Milan, Italy
| | - Sébastien Baillieul
- Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, HP2 laboratory, Grenoble, France
| | - Blandine Deschamps
- Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, HP2 laboratory, Grenoble, France
| | - Ivan Hancco
- Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, HP2 laboratory, Grenoble, France
| | - Philippe Connes
- Interuniversity Laboratory of Human Movement Biology (LIBM, EA7424), "Red Blood cell and Vascular Biology" Team, Univ Lyon - University Claude Bernard Lyon 1, Villeurbanne, France
| | - Paul Robach
- Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, HP2 laboratory, Grenoble, France
- National School for Mountain Sports, Site of the National School for Skiing and Mountaineering (ENSA), Chamonix, France
| | - Aurélien Pichon
- Laboratory Mobility, Aging & Exercise (MOVE, EA6314), Faculty of Sport Sciences, University of Poitiers, Poitiers, France
| | - Samuel Verges
- Univ. Grenoble Alpes, Inserm, CHU Grenoble Alpes, HP2 laboratory, Grenoble, France
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Bader TJ, Leacy JK, Keough JRG, Ciorogariu‐Ivan A, Donald JR, Marullo AL, O’Halloran KD, Jendzjowsky NG, Wilson RJA, Day TA. The effects of acute incremental hypocapnia on the magnitude of neurovascular coupling in healthy participants. Physiol Rep 2021; 9:e14952. [PMID: 34350726 PMCID: PMC8339533 DOI: 10.14814/phy2.14952] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Accepted: 04/17/2021] [Indexed: 12/03/2022] Open
Abstract
The high metabolic demand of cerebral tissue requires that local perfusion is tightly coupled with local metabolic rate (neurovascular coupling; NVC). During chronic altitude exposure, where individuals are exposed to the antagonistic cerebrovascular effects of hypoxia and hypocapnia, pH is maintained through renal compensation and NVC remains stable. However, the potential independent effect of acute hypocapnia and respiratory alkalosis on NVC remains to be determined. We hypothesized that acute steady-state hypocapnia via voluntary hyperventilation would attenuate the magnitude of NVC. We recruited 17 healthy participants and insonated the posterior cerebral artery (PCA) with transcranial Doppler ultrasound. NVC was elicited using a standardized strobe light stimulus (6 Hz; 5 × 30 s on/off) where absolute delta responses from baseline (BL) in peak, mean, and total area under the curve (tAUC) were quantified. From a BL end-tidal (PET )CO2 level of 36.7 ± 3.2 Torr, participants were coached to hyperventilate to reach steady-state hypocapnic steps of Δ-5 Torr (31.6 ± 3.9) and Δ-10 Torr (26.0 ± 4.0; p < 0.001), which were maintained during the presentation of the visual stimuli. We observed a small but significant reduction in NVC peak (ΔPCAv) from BL during controlled hypocapnia at both Δ-5 (-1.58 cm/s) and Δ-10 (-1.37 cm/s), but no significant decrease in mean or tAUC NVC response was observed. These data demonstrate that acute respiratory alkalosis attenuates peak NVC magnitude at Δ-5 and Δ-10 Torr PET CO2 , equally. Although peak NVC magnitude was mildly attenuated, our data illustrate that mean and tAUC NVC are remarkably stable during acute respiratory alkalosis, suggesting multiple mechanisms underlying NVC.
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Affiliation(s)
- Taylor J. Bader
- Department of BiologyFaculty of Science and TechnologyMount Royal UniversityCalgaryABCanada
| | - Jack K. Leacy
- Department of PhysiologySchool of MedicineCollege of Medicine and HealthUniversity College CorkCorkIreland
| | - Joanna R. G. Keough
- Department of BiologyFaculty of Science and TechnologyMount Royal UniversityCalgaryABCanada
| | | | - Joshua R. Donald
- Department of BiologyFaculty of Science and TechnologyMount Royal UniversityCalgaryABCanada
| | - Anthony L. Marullo
- Department of BiologyFaculty of Science and TechnologyMount Royal UniversityCalgaryABCanada
| | - Ken D. O’Halloran
- Department of PhysiologySchool of MedicineCollege of Medicine and HealthUniversity College CorkCorkIreland
| | - Nicholas G. Jendzjowsky
- Division of Respiratory and Critical Care Physiology and MedicineThe Lundquist Institute for Biomedical Innovation at Harbor‐UCLA Medical CenterTorranceCAUSA
| | - Richard J. A. Wilson
- Department of Physiology and PharmacologyHotchkiss Brain InstituteCumming School of MedicineUniversity of CalgaryCalgaryABCanada
| | - Trevor A. Day
- Department of BiologyFaculty of Science and TechnologyMount Royal UniversityCalgaryABCanada
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Shen Y, Yang YQ, Liu C, Yang J, Zhang JH, Jin J, Tan H, Yuan FZY, Ke JB, He CY, Zhang LP, Zhang C, Yu J, Huang L. Association between physiological responses after exercise at low altitude and acute mountain sickness upon ascent is sex-dependent. Mil Med Res 2020; 7:53. [PMID: 33148321 PMCID: PMC7643355 DOI: 10.1186/s40779-020-00283-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2020] [Accepted: 10/20/2020] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND Acute mountain sickness (AMS) is the mildest form of acute altitude illnesses, and consists of non-specific symptoms when unacclimatized persons ascend to elevation of ≥2500 m. Risk factors of AMS include: the altitude, individual susceptibility, ascending rate and degree of pre-acclimatization. In the current study, we examined whether physiological response at low altitude could predict the development of AMS. METHODS A total of 111 healthy adult healthy volunteers participated in this trial; and 99 (67 men and 32 women) completed the entire study protocol. Subjects were asked to complete a 9-min exercise program using a mechanically braked bicycle ergometer at low altitude (500 m). Heart rate, blood pressure (BP) and pulse oxygen saturation (SpO2) were recorded prior to and during the last minute of exercise. The ascent from 500 m to 4100 m was completed in 2 days. AMS was defined as ≥3 points in a 4-item Lake Louise Score, with at least one point from headache wat 6-8 h after the ascent. RESULTS Among the 99 assessable subjects, 47 (23 men and 24 women) developed AMS at 4100 m. In comparison to the subjects without AMS, those who developed AMS had lower proportion of men (48.9% vs. 84.6%, P < 0.001), height (168.4 ± 5.9 vs. 171.3 ± 6.1 cm, P = 0.019), weight (62.0 ± 10.0 vs. 66.7 ± 8.6 kg, P = 0.014) and proportion of smokers (23.4% vs. 51.9%, P = 0.004). Multivariate regression analysis revealed the following independent risks for AMS: female sex (odds ratio (OR) =6.32, P < 0.001), SpO2 change upon exercise at low altitude (OR = 0.63, P = 0.002) and systolic BP change after the ascent (OR = 0.96, P = 0.029). Women had larger reduction in SpO2 after the ascent, higher AMS percentage and absolute AMS score. Larger reduction of SpO2 after exercise was associated with both AMS incidence (P = 0.001) and AMS score (P < 0.001) in men but not in women. CONCLUSIONS Larger SpO2 reduction after exercise at low altitude was an independent risk for AMS upon ascent. Such an association was more robust in men than in women. TRIAL REGISTRATION Chinese Clinical Trial Registration, ChiCTR1900025728 . Registered 6 September 2019.
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Affiliation(s)
- Yang Shen
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China
| | - Yuan-Qi Yang
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China
| | - Chuan Liu
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China
| | - Jie Yang
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China
| | - Ji-Hang Zhang
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China
| | - Jun Jin
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China
| | - Hu Tan
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China
| | - Fang-Zheng-Yuan Yuan
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China
| | - Jing-Bin Ke
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China
| | - Chun-Yan He
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China
| | - Lai-Ping Zhang
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China
| | - Chen Zhang
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China
| | - Jie Yu
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China
| | - Lan Huang
- Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China. .,Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing, 400037, China.
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Association of EPAS1 and PPARA Gene Polymorphisms with High-Altitude Headache in Chinese Han Population. BIOMED RESEARCH INTERNATIONAL 2020; 2020:1593068. [PMID: 32185192 PMCID: PMC7060407 DOI: 10.1155/2020/1593068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 12/09/2019] [Accepted: 12/14/2019] [Indexed: 11/17/2022]
Abstract
Background High-altitude headache (HAH) is the most common complication after high-altitude exposure. Hypoxia-inducible factor- (HIF-) related genes have been confirmed to contribute to high-altitude acclimatization. We aim to investigate a possible association between HIF-related genes and HAH in the Chinese Han population. Methods In total, 580 healthy Chinese Han volunteers were recruited in Chengdu (500 m) and carried to Lhasa (3700 m) by plane in 2 hours. HAH scores and basic physiological parameters were collected within 18-24 hours after the arrival. Thirty-five single nucleotide polymorphisms (SNPs) in HIF-related genes were genotyped, and linkage disequilibrium (LD) was evaluated by Haploview software. The functions of SNPs/haplotypes for HAH were developed by using logistic regression analysis. Results In comparison with wild types, the rs4953354 "G" allele (P=0.013), rs6756667 "A" allele (P=0.013), rs6756667 "A" allele (EPAS1, and rs6520015 "C" allele in PPARA (P=0.013), rs6756667 "A" allele (PPARA (P=0.013), rs6756667 "A" allele (EPAS1, and rs6520015 "C" allele in PPARA (P=0.013), rs6756667 "A" allele (. Conclusions EPAS1 and PPARA polymorphisms were associated with HAH in the Chinese Han population. Our findings pointed out potentially predictive gene markers, provided new insights into understanding pathogenesis, and may further provide prophylaxis and treatment strategies for HAH.EPAS1, and rs6520015 "C" allele in PPARA (.
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Steady-state cerebral blood flow regulation at altitude: interaction between oxygen and carbon dioxide. Eur J Appl Physiol 2019; 119:2529-2544. [DOI: 10.1007/s00421-019-04206-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Accepted: 08/06/2019] [Indexed: 02/07/2023]
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Minhas JS, Panerai RB, Swienton D, Robinson TG. Feasibility of improving cerebral autoregulation in acute intracerebral hemorrhage (BREATHE-ICH) study: Results from an experimental interventional study. Int J Stroke 2019; 15:627-637. [DOI: 10.1177/1747493019873690] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Background Cerebral autoregulation is impaired in a multitude of neurological conditions. Increasingly, clinical studies are correlating the nature of this impairment with prognostic markers. In acute intracerebral hemorrhage, impairment of cerebral autoregulation has been associated with worsening clinical outcomes including poorer Glasgow Coma Score and larger hematoma volume. Hypocapnia has been shown to improve cerebral autoregulation despite concerns over hypoperfusion and consequent ischemic risks, and it is therefore hypothesized that hypocapnia (via hyperventilation) in acute intracerebral hemorrhage may improve cerebral autoregulation and consequently clinical outcome. Aims To assess the feasibility and acceptability of the first cerebral autoregulation-targeted intervention in acute intracerebral hemorrhage utilizing a simple bed-side hyperventilatory maneuver. Methods Twelve patients with acute intracerebral hemorrhage within 48 h of onset were enrolled. The experimental setup measured cerebral blood flow velocity (transcranial Doppler), blood pressure (Finometer), and end-tidal CO2 (EtCO2, capnography) at baseline, and in response to hypocapnia (−5 mmHg below baseline) achieved via a 90-s hyperventilatory maneuver. Cerebral autoregulation was evaluated with transfer function analysis and autoregulatory index calculations. Results We observed tolerance to the protocol in a cohort of mild (National Institutes of Health Scale 4) supratentorial intracerebral hemorrhage patients with small volume hematomas without intraventricular extension. Importantly, a significant difference was noted between ipsilateral autoregulatory index at baseline 4.8 (1.7) and autoregulatory index during hypocapnic intervention 7.0 (0.8) (p = 0.0004), reflecting improved cerebral autoregulation, though a dose-dependent effect of EtCO2 on autoregulatory index was not observed. Conclusions In this small study, there was no observed effect on 14-day death and disability in recruited participants. This is the first report of improvement in cerebral autoregulation in acute intracerebral hemorrhage using a non-invasive interventional maneuver, through induction of hypocapnia via hyperventilation. ClinicalTrials.gov Identifier: NCT03324321 URL: https://clinicaltrials.gov/ct2/show/NCT03324321
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Affiliation(s)
- Jatinder S Minhas
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHIASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Ronney B Panerai
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHIASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
- National Institute for Health Research Leicester Biomedical Research Centre, University of Leicester, Leicester, UK
| | - David Swienton
- Department of Radiology, University Hospitals of Leicester, Leicester, UK
| | - Thompson G Robinson
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHIASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
- National Institute for Health Research Leicester Biomedical Research Centre, University of Leicester, Leicester, UK
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9
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Human Genetic Adaptation to High Altitude: Evidence from the Andes. Genes (Basel) 2019; 10:genes10020150. [PMID: 30781443 PMCID: PMC6410003 DOI: 10.3390/genes10020150] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 01/29/2019] [Accepted: 02/11/2019] [Indexed: 12/31/2022] Open
Abstract
Whether Andean populations are genetically adapted to high altitudes has long been of interest. Initial studies focused on physiological changes in the O₂ transport system that occur with acclimatization in newcomers and their comparison with those of long-resident Andeans. These as well as more recent studies indicate that Andeans have somewhat larger lung volumes, narrower alveolar to arterial O₂ gradients, slightly less hypoxic pulmonary vasoconstrictor response, greater uterine artery blood flow during pregnancy, and increased cardiac O2 utilization, which overall suggests greater efficiency of O₂ transfer and utilization. More recent single nucleotide polymorphism and whole-genome sequencing studies indicate that multiple gene regions have undergone recent positive selection in Andeans. These include genes involved in the regulation of vascular control, metabolic hemostasis, and erythropoiesis. However, fundamental questions remain regarding the functional links between these adaptive genomic signals and the unique physiological attributes of highland Andeans. Well-designed physiological and genome association studies are needed to address such questions. It will be especially important to incorporate the role of epigenetic processes (i.e.; non-sequence-based features of the genome) that are vital for transcriptional responses to hypoxia and are potentially heritable across generations. In short, further exploration of the interaction among genetic, epigenetic, and environmental factors in shaping patterns of adaptation to high altitude promises to improve the understanding of the mechanisms underlying human adaptive potential and clarify its implications for human health.
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Xing CY, Serrador JM, Knox A, Ren LH, Zhao P, Wang H, Liu J. Cerebral Blood Flow, Oxygen Delivery, and Pulsatility Responses to Oxygen Inhalation at High Altitude: Highlanders vs. Lowlanders. Front Physiol 2019; 10:61. [PMID: 30792663 PMCID: PMC6375252 DOI: 10.3389/fphys.2019.00061] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 01/18/2019] [Indexed: 01/24/2023] Open
Abstract
Objective: To determine whether the acute cerebral hemodynamic responses to oxygen inhalation are impacted by race or acclimation to high altitude. Methods: Three groups of young healthy males, who were Tibetans (highlanders, n = 15) with lifelong exposure to high altitude, and Han Chinese (lowlanders) with five-year (Han-5 yr, n = 15) and three-day (Han-3 d, n = 16) exposures, participated in the study at an altitude of 3658 m. Cerebral blood flow velocity (CBFV) was recorded for three minutes prior to and during pure oxygen inhalation (2 L/min), respectively, using a transcranial color-coded duplex (TCCD) sonography at the middle cerebral artery (MCA). The blood draw and simultaneous monitoring of blood pressure (BP), heart rate (HR), and finger arterial oxygen saturation (SaO2) were also performed. Results: Values are Mean ± SEM. The three groups had similar demographic characteristics and HR responses, with the group differences (P < 0.05) found in hemoglobin concentration (16.9 ± 0.9, 18.4 ± 1.3, and 15.5 ± 1.0 gm/dL), baseline BPs and HR as expected. Both the Tibetans and Han-5yr groups presented blunted BP responses to O2-inhalation when compared to the Han-3d group; more interestingly, the Tibetans showed significantly reduced responses compared with Han-5yr and Han-3d in CBFV, cerebral oxygen delivery (COD), and pulsatility index (PI) as assessed by Δ%CBFV/ΔSaO2 (-1.50 ± 0.25 vs. -2.24 ± 0.25 and -2.23 ± 0.27, P = 0.049 and 0.048), Δ%COD/ΔSaO2 (-0.52 ± 0.27 vs. -1.33 ± 0.26 and -1.38 ± 0.28, P = 0.044 and 0.031), and Δ%PI (7 ± 2 vs. 16 ± 3 and 16 ± 3 %, P = 0.036 and 0.023), respectively. Conclusion: These findings provide evidence on the Tibetans trait of a distinct cerebral hemodynamic regulatory pattern to keep more stable cerebral blood flow (CBF), oxygen delivery, and pulsatility in response to oxygen inhalation as compared with Han Chinese, which is likely due to a genetic adaptation to altitude.
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Affiliation(s)
- Chang-Yang Xing
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Jorge M Serrador
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ, United States
| | - Allan Knox
- Exercise Science Department, California Lutheran University, Thousand Oaks, CA, United States
| | - Li-Hua Ren
- General Hospital of Tibet Military Area Command, Lhasa, China
| | - Ping Zhao
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Hong Wang
- Department of Ultrasound Diagnostics, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| | - Jie Liu
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China.,Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ, United States
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11
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Cramer NP, Korotcov A, Bosomtwi A, Xu X, Holman DR, Whiting K, Jones S, Hoy A, Dardzinski BJ, Galdzicki Z. Neuronal and vascular deficits following chronic adaptation to high altitude. Exp Neurol 2018; 311:293-304. [PMID: 30321497 DOI: 10.1016/j.expneurol.2018.10.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 09/20/2018] [Accepted: 10/10/2018] [Indexed: 02/03/2023]
Abstract
We sought to understand the mechanisms underlying cognitive deficits that are reported to affect non-native subjects following their prolonged stay and/or work at high altitude (HA). We found that mice exposed to a simulated environment of 5000 m exhibit deficits in hippocampal learning and memory accompanied by abnormalities in brain MR imaging. Exposure (1-8 months) to HA led to an increase in brain ventricular volume, a reduction in relative cerebral blood flow and changes in diffusion tensor imaging (DTI) derived parameters within the hippocampus and corpus callosum. Furthermore, neuropathological examination revealed significant expansion of the neurovascular network, microglia activation and demyelination within the corpus callosum. Electrophysiological recordings from the corpus callosum indicated that axonal excitabilities are increased while refractory periods are longer despite a lack of change in action potential conduction velocities of both myelinated and unmyelinated fibers. Next generation RNA-sequencing identified alterations in hippocampal and amygdala transcriptome signaling pathways linked to angiogenesis, neuroinflammation and myelination. Our findings reveal that exposure to hypobaric-hypoxia triggers maladaptive responses inducing cognitive deficits and suggest potential mechanisms underlying the adverse impacts of staying or traveling at high altitude.
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Affiliation(s)
- Nathan P Cramer
- Department of Anatomy, Physiology and Genetics, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States; Center for Neuroscience and Regenerative Medicine, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Alexandru Korotcov
- Center for Neuroscience and Regenerative Medicine, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States; Department of Radiology and Radiological Sciences, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Asamoah Bosomtwi
- Center for Neuroscience and Regenerative Medicine, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States; Department of Radiology and Radiological Sciences, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Xiufen Xu
- Department of Anatomy, Physiology and Genetics, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States; Center for Neuroscience and Regenerative Medicine, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Derek R Holman
- Department of Anatomy, Physiology and Genetics, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States; Molecular & Cell Biology Graduate Program, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, MD, United States
| | - Kathleen Whiting
- Department of Anatomy, Physiology and Genetics, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States; Neuroscience Graduate Program, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Scott Jones
- Center for Neuroscience and Regenerative Medicine, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States; Department of Radiology and Radiological Sciences, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Andrew Hoy
- Center for Neuroscience and Regenerative Medicine, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States; Department of Radiology and Radiological Sciences, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Bernard J Dardzinski
- Center for Neuroscience and Regenerative Medicine, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States; Department of Radiology and Radiological Sciences, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Zygmunt Galdzicki
- Department of Anatomy, Physiology and Genetics, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States; Center for Neuroscience and Regenerative Medicine, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States; Molecular & Cell Biology Graduate Program, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, MD, United States; Neuroscience Graduate Program, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States.
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12
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Moore LG. Measuring high-altitude adaptation. J Appl Physiol (1985) 2017; 123:1371-1385. [PMID: 28860167 DOI: 10.1152/japplphysiol.00321.2017] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 08/15/2017] [Accepted: 08/15/2017] [Indexed: 12/12/2022] Open
Abstract
High altitudes (>8,000 ft or 2,500 m) provide an experiment of nature for measuring adaptation and the physiological processes involved. Studies conducted over the past ~25 years in Andeans, Tibetans, and, less often, Ethiopians show varied but distinct O2 transport traits from those of acclimatized newcomers, providing indirect evidence for genetic adaptation to high altitude. Short-term (acclimatization, developmental) and long-term (genetic) responses to high altitude exhibit a temporal gradient such that, although all influence O2 content, the latter also improve O2 delivery and metabolism. Much has been learned concerning the underlying physiological processes, but additional studies are needed on the regulation of blood flow and O2 utilization. Direct evidence of genetic adaptation comes from single-nucleotide polymorphism (SNP)-based genome scans and whole genome sequencing studies that have identified gene regions acted upon by natural selection. Efforts have begun to understand the connections between the two with Andean studies on the genetic factors raising uterine blood flow, fetal growth, and susceptibility to Chronic Mountain Sickness and Tibetan studies on genes serving to lower hemoglobin and pulmonary arterial pressure. Critical for future studies will be the selection of phenotypes with demonstrable effects on reproductive success, the calculation of actual fitness costs, and greater inclusion of women among the subjects being studied. The well-characterized nature of the O2 transport system, the presence of multiple long-resident populations, and relevance for understanding hypoxic disorders in all persons underscore the importance of understanding how evolutionary adaptation to high altitude has occurred.NEW & NOTEWORTHY Variation in O2 transport characteristics among Andean, Tibetan, and, when available, Ethiopian high-altitude residents supports the existence of genetic adaptations that improve the distribution of blood flow to vital organs and the efficiency of O2 utilization. Genome scans and whole genome sequencing studies implicate a broad range of gene regions. Future studies are needed using phenotypes of clear relevance for reproductive success for determining the mechanisms by which naturally selected genes are acting.
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Affiliation(s)
- Lorna G Moore
- Division of Reproductive Sciences, Department of Obstetrics & Gynecology, University of Colorado Denver-Anschutz Medical Campus, Aurora, Colorado
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13
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Transcranial Doppler in autonomic testing: standards and clinical applications. Clin Auton Res 2017; 28:187-202. [PMID: 28821991 DOI: 10.1007/s10286-017-0454-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 07/13/2017] [Indexed: 02/06/2023]
Abstract
When cerebral blood flow falls below a critical limit, syncope occurs and, if prolonged, ischemia leads to neuronal death. The cerebral circulation has its own complex finely tuned autoregulatory mechanisms to ensure blood supply to the brain can meet the high metabolic demands of the underlying neuronal tissue. This involves the interplay between myogenic and metabolic mechanisms, input from noradrenergic and cholinergic neurons, and the release of vasoactive substrates, including adenosine from astrocytes and nitric oxide from the endothelium. Transcranial Doppler (TCD) is a non-invasive technique that provides real-time measurements of cerebral blood flow velocity. TCD can be very useful in the work-up of a patient with recurrent syncope. Cerebral autoregulatory mechanisms help defend the brain against hypoperfusion when perfusion pressure falls on standing. Syncope occurs when hypotension is severe, and susceptibility increases with hyperventilation, hypocapnia, and cerebral vasoconstriction. Here we review clinical standards for the acquisition and analysis of TCD signals in the autonomic laboratory and the multiple methods available to assess cerebral autoregulation. We also describe the control of cerebral blood flow in autonomic disorders and functional syndromes.
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14
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Tomimatsu T, Pena JP, Longo LD. Fetal Hypercapnia in High-Altitude Acclimatized Sheep: Cerebral Blood Flow and Cerebral Oxygenation. Reprod Sci 2016; 14:51-8. [PMID: 17636216 DOI: 10.1177/1933719106298211] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The authors tested the hypothesis that in the high-altitude acclimatized fetus, hypercapnia has a significantly less effect on cerebral blood flow (CBF) and cerebral oxygenation than that in normoxic sea level controls. In the high-altitude acclimatized fetus (3801 m; maintained from day 30 of gestation to near term; n = 6), by use of a laser Doppler flowmeter with a fluorescent O (2) probe, the authors measured relative CBF (laser Doppler CBF [LD-CBF]), cortical tissue PO(2) (tPO(2)), and sagittal sinus oxyhemoglobin saturation (HbO(2)) in response to 20-minute hypercapnia. They also calculated cerebral O(2)delivery and cerebral fractional O(2) extraction. The authors compared these results to those obtained in near-sea-level control animals (low-altitude group). In response to hypercapnia (arterial PCO(2) = 63+/- 2 torr vs 42+/- 1 torr baseline), high-altitude fetuses showed similar increases in LD-CBF, cortical tPO(2), and sagittal sinus (HbO(2)) as compared with those responses seen in the fetus at low altitude. Nonetheless, these fetuses showed a significantly smaller decrease in cerebral fractional O(2) extraction compared to low-altitude fetuses. In response to hypercapnia in high-altitude, acclimatized, long-term hypoxic fetal sheep, the response of CBF and cerebral oxygenation did not differ significantly from that of low-altitude controls.
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Affiliation(s)
- Takuji Tomimatsu
- Center for Perinatal Biology, Department of Physiology and Obstetrics, School of Medicine, Loma Linda University, Loma Linda, California 92350, USA
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15
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Wei L, Chen Z, Xi Q, Wen C, Ye D, Chen X, Zhu G. Elevated Hemoglobin Concentration Affects Acute Severe Head Trauma After Recovery from Surgery of Neurologic Function in the Tibetan Plateau. World Neurosurg 2016; 86:181-5. [DOI: 10.1016/j.wneu.2015.09.070] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2014] [Revised: 09/09/2015] [Accepted: 09/11/2015] [Indexed: 10/23/2022]
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16
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Tymko MM, Hoiland RL, Kuca T, Boulet LM, Tremblay JC, Pinske BK, Williams AM, Foster GE. Measuring the human ventilatory and cerebral blood flow response to CO2: a technical consideration for the end-tidal-to-arterial gas gradient. J Appl Physiol (1985) 2016; 120:282-96. [DOI: 10.1152/japplphysiol.00787.2015] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 10/19/2015] [Indexed: 11/22/2022] Open
Abstract
Our aim was to quantify the end-tidal-to-arterial gas gradients for O2 (PET-PaO2) and CO2 (Pa-PETCO2) during a CO2 reactivity test to determine their influence on the cerebrovascular (CVR) and ventilatory (HCVR) response in subjects with (PFO+, n = 8) and without (PFO−, n = 7) a patent foramen ovale (PFO). We hypothesized that 1) the Pa-PETCO2 would be greater in hypoxia compared with normoxia, 2) the Pa-PETCO2 would be similar, whereas the PET-PaO2 gradient would be greater in those with a PFO, 3) the HCVR and CVR would be underestimated when plotted against PETCO2 compared with PaCO2, and 4) previously derived prediction algorithms will accurately target PaCO2. PETCO2 was controlled by dynamic end-tidal forcing in steady-state steps of −8, −4, 0, +4, and +8 mmHg from baseline in normoxia and hypoxia. Minute ventilation (V̇E), internal carotid artery blood flow (Q̇ICA), middle cerebral artery blood velocity (MCAv), and temperature corrected end-tidal and arterial blood gases were measured throughout experimentation. HCVR and CVR were calculated using linear regression analysis by indexing V̇E and relative changes in Q̇ICA, and MCAv against PETCO2, predicted PaCO2, and measured PaCO2. The Pa-PETCO2 was similar between hypoxia and normoxia and PFO+ and PFO−. The PET-PaO2 was greater in PFO+ by 2.1 mmHg during normoxia ( P = 0.003). HCVR and CVR plotted against PETCO2 underestimated HCVR and CVR indexed against PaCO2 in normoxia and hypoxia. Our PaCO2 prediction equation modestly improved estimates of HCVR and CVR. In summary, care must be taken when indexing reactivity measures to PETCO2 compared with PaCO2.
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Affiliation(s)
- Michael M. Tymko
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
| | - Ryan L. Hoiland
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
| | - Tomas Kuca
- Department of Anesthesia, Pain and Perioperative Medicine, Department of Critical Care Medicine, Dalhousie University, Halifax, Canada
| | - Lindsey M. Boulet
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
| | - Joshua C. Tremblay
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
| | - Bryenna K. Pinske
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
| | - Alexandra M. Williams
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
| | - Glen E. Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
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Heinonen IHA, Boushel R, Kalliokoski KK. The Circulatory and Metabolic Responses to Hypoxia in Humans - With Special Reference to Adipose Tissue Physiology and Obesity. Front Endocrinol (Lausanne) 2016; 7:116. [PMID: 27621722 PMCID: PMC5002918 DOI: 10.3389/fendo.2016.00116] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 08/10/2016] [Indexed: 01/07/2023] Open
Abstract
Adipose tissue metabolism and circulation play an important role in human health. It is well-known that adipose tissue mass is increased in response to excess caloric intake leading to obesity and further to local hypoxia and inflammatory signaling. Acute exercise increases blood supply to adipose tissue and mobilization of fat stores for energy. However, acute exercise during systemic hypoxia reduces subcutaneous blood flow in healthy young subjects, but the response in overweight or obese subjects remains to be investigated. Emerging evidence also indicates that exercise training during hypoxic exposure may provide additive benefits with respect to many traditional cardiovascular risk factors as compared to exercise performed in normoxia, but unfavorable effects of hypoxia have also been documented. These topics will be covered in this brief review dealing with hypoxia and adipose tissue physiology.
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Affiliation(s)
- Ilkka H. A. Heinonen
- Turku PET Centre, University of Turku, Turku, Finland
- Department of Clinical Physiology and Nuclear Medicine, University of Turku, Turku, Finland
- Division of Experimental Cardiology, Thoraxcenter, Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands
- *Correspondence: Ilkka H. A. Heinonen,
| | - Robert Boushel
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
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Bian SZ, Jin J, Zhang JH, Li QN, Yu J, Yu SY, Chen JF, Yu XJ, Qin J, Huang L. Principal Component Analysis and Risk Factors for Acute Mountain Sickness upon Acute Exposure at 3700 m. PLoS One 2015; 10:e0142375. [PMID: 26554385 PMCID: PMC4640520 DOI: 10.1371/journal.pone.0142375] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 10/21/2015] [Indexed: 02/06/2023] Open
Abstract
OBJECTIVE We aimed to describe the heterogeneity in the clinical presentation of acute mountain sickness (AMS) and to identify its primary risk factors. METHODS The participants (n = 163) received case report form questionnaires, and their heart rate (HR), oxygen saturation (SpO2), echocardiographic and transcranial Doppler variables, ability to perform mental and physical work, mood and psychological factors were assessed within 18 to 22 hours after arriving at 3700 m from sea level (500 m) by plane. First, we examined the differences in all variables between the AMS-positive and the AMS-negative groups. Second, an adjusted regression analysis was performed after correlation and principal component analyses. RESULTS The AMS patients had a higher diastolic vertebral artery velocity (Vd; p = 0.018), a higher HR (p = 0.006) and a lower SpO2. The AMS subjects also experienced poorer sleep quality, as quantified using the Athens Insomnia Scale (AIS). Moreover, the AMS population exhibited more negative mood states, including anxiety, depression, hostility, fatigue and confusion. Five principal components focused on diverse aspects were also found to be significant. Additionally, more advanced age (p = 0.007), a higher HR (p = 0.034), a higher Vd (p = 0.014), a higher AIS score (p = 0.030), a decreased pursuit aiming capacity (p = 0.035) and decreased vigor (p = 0.015) were risk factors for AMS. CONCLUSIONS Mood states play critical roles in the development of AMS. Furthermore, an elevated HR and Vd, advanced age, elevated AIS sores, insufficient vigor and decreased mental work capacity are independent risk factors for AMS.
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Affiliation(s)
- Shi-Zhu Bian
- Institute of Cardiovascular Diseases of PLA; Xinqiao Hospital, Third Military Medical University, Chongqing, China
- Department of Cardiology, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Jun Jin
- Institute of Cardiovascular Diseases of PLA; Xinqiao Hospital, Third Military Medical University, Chongqing, China
- Department of Cardiology, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Ji-Hang Zhang
- Institute of Cardiovascular Diseases of PLA; Xinqiao Hospital, Third Military Medical University, Chongqing, China
- Department of Cardiology, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Qian-Ning Li
- Department of Neurology, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Jie Yu
- Institute of Cardiovascular Diseases of PLA; Xinqiao Hospital, Third Military Medical University, Chongqing, China
- Department of Cardiology, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Shi-Yong Yu
- Institute of Cardiovascular Diseases of PLA; Xinqiao Hospital, Third Military Medical University, Chongqing, China
- Department of Cardiology, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Jian-Fei Chen
- Institute of Cardiovascular Diseases of PLA; Xinqiao Hospital, Third Military Medical University, Chongqing, China
- Department of Cardiology, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Xue-Jun Yu
- Institute of Cardiovascular Diseases of PLA; Xinqiao Hospital, Third Military Medical University, Chongqing, China
- Department of Cardiology, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Jun Qin
- Institute of Cardiovascular Diseases of PLA; Xinqiao Hospital, Third Military Medical University, Chongqing, China
- Department of Cardiology, Xinqiao Hospital, Third Military Medical University, Chongqing, China
| | - Lan Huang
- Institute of Cardiovascular Diseases of PLA; Xinqiao Hospital, Third Military Medical University, Chongqing, China
- Department of Cardiology, Xinqiao Hospital, Third Military Medical University, Chongqing, China
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Wang J, Xu SZ, Zha Y, Bbu CF, Li LJY, Duan YY. Comparative sonographic study of cerebral hemodynamic differences and changes after oxygen therapy in healthy youths of different ethnicities in Tibet. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 2015; 34:1107-1114. [PMID: 26014331 DOI: 10.7863/ultra.34.6.1107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
OBJECTIVES The purpose of this study was to sonographically assess the cerebral hemodynamic differences and changes after oxygen therapy in healthy youths of different ethnicities in Tibet. METHODS Sixty-six healthy young Han visitors and 29 healthy young Tibetan residents were divided into 4 groups. Basic information was collected. Pulsed Doppler sonography was used to record the cerebral hemodynamic parameters for the internal carotid, vertebral, and middle cerebral arteries. The participants were then instructed to inhale oxygen, and basic information and cerebral hemodynamic parameters were recorded at 1, 2, 4, and 8 minutes, respectively. Differences in these parameters between groups were analyzed. RESULTS In comparisons of the flow parameters between sex-matched groups, the mean resistive index values for the internal carotid, vertebral, and middle cerebral arteries in the Han groups were significantly lower than those in the Tibetan groups (P <. 05). The mean peak systolic velocity, end-diastolic velocity, and mean velocity values for the middle cerebral artery in the Han groups were significantly higher than those in the Tibetan groups (P < .05). After oxygen uptake, there were no significant differences in the mean arterial oxygen saturation, heart rate, mean velocity, and resistive index values between the male groups, and similar changes were found for the arterial oxygen saturation and peak systolic velocity values between female groups after 8 minutes of oxygen uptake (P > .05). CONCLUSIONS Sonography is a useful modality for noninvasive and real-time detection of changes in cerebral hemodynamics and can provide reference values for the prevention and treatment of cerebrovascular diseases.
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Affiliation(s)
- Jia Wang
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (J.W., L.J.Y., Y.Y.D.); and Department of Special Examination, Tibet Corps Hospital, Chinese People's Armed Police Forces, Lhasa, China (S.Z.X., Y.Z., C.F.B.)
| | - Shu Zhen Xu
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (J.W., L.J.Y., Y.Y.D.); and Department of Special Examination, Tibet Corps Hospital, Chinese People's Armed Police Forces, Lhasa, China (S.Z.X., Y.Z., C.F.B.).
| | - Yong Zha
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (J.W., L.J.Y., Y.Y.D.); and Department of Special Examination, Tibet Corps Hospital, Chinese People's Armed Police Forces, Lhasa, China (S.Z.X., Y.Z., C.F.B.)
| | - Ciugene F Bbu
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (J.W., L.J.Y., Y.Y.D.); and Department of Special Examination, Tibet Corps Hospital, Chinese People's Armed Police Forces, Lhasa, China (S.Z.X., Y.Z., C.F.B.)
| | - Li Jun Yuan Li
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (J.W., L.J.Y., Y.Y.D.); and Department of Special Examination, Tibet Corps Hospital, Chinese People's Armed Police Forces, Lhasa, China (S.Z.X., Y.Z., C.F.B.)
| | - Yun You Duan
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (J.W., L.J.Y., Y.Y.D.); and Department of Special Examination, Tibet Corps Hospital, Chinese People's Armed Police Forces, Lhasa, China (S.Z.X., Y.Z., C.F.B.)
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Tymko MM, Ainslie PN, MacLeod DB, Willie CK, Foster GE. End tidal-to-arterial CO2 and O2 gas gradients at low- and high-altitude during dynamic end-tidal forcing. Am J Physiol Regul Integr Comp Physiol 2015; 308:R895-906. [DOI: 10.1152/ajpregu.00425.2014] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 03/23/2015] [Indexed: 11/22/2022]
Abstract
We sought to characterize and quantify the performance of a portable dynamic end-tidal forcing (DEF) system in controlling the partial pressure of arterial CO2 (PaCO2) and O2 (PaO2) at low (LA; 344 m) and high altitude (HA; 5,050 m) during an isooxic CO2 test and an isocapnic O2 test, which is commonly used to measure ventilatory and vascular reactivity in humans ( n = 9). The isooxic CO2 tests involved step changes in the partial pressure of end-tidal CO2 (PetCO2) of −10, −5, 0, +5, and +10 mmHg from baseline. The isocapnic O2 test consisted of a 10-min hypoxic step (PetO2 = 47 mmHg) from baseline at LA and a 5-min euoxic step (PetO2 = 100 mmHg) from baseline at HA. At both altitudes, PetO2 and PetCO2 were controlled within narrow limits (<1 mmHg from target) during each protocol. During the isooxic CO2 test at LA, PetCO2 consistently overestimated PaCO2 ( P < 0.01) at both baseline (2.1 ± 0.5 mmHg) and hypercapnia (+5 mmHg: 2.1 ± 0.7 mmHg; +10 mmHg: 1.9 ± 0.5 mmHg). This Pa-PetCO2 gradient was approximately twofold greater at HA ( P < 0.05). At baseline at both altitudes, PetO2 overestimated PaO2 by a similar extent (LA: 6.9 ± 2.1 mmHg; HA: 4.5 ± 0.9 mmHg; both P < 0.001). This overestimation persisted during isocapnic hypoxia at LA (6.9 ± 0.6 mmHg) and during isocapnic euoxia at HA (3.8 ± 1.2 mmHg). Step-wise multiple regression analysis, on the basis of the collected data, revealed that it may be possible to predict an individual's arterial blood gases during DEF. Future research is needed to validate these prediction algorithms and determine the implications of end-tidal-to-arterial gradients in the assessment of ventilatory and/or vascular reactivity.
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Affiliation(s)
- Michael M. Tymko
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
| | - Philip N. Ainslie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
| | - David B. MacLeod
- Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - Chris K. Willie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
| | - Glen E. Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada; and
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Bian SZ, Jin J, Li QN, Yu J, Tang CF, Rao RS, Yu SY, Zhao XH, Qin J, Huang L. Hemodynamic characteristics of high-altitude headache following acute high altitude exposure at 3700 m in young Chinese men. J Headache Pain 2015; 16:527. [PMID: 25968101 PMCID: PMC4431987 DOI: 10.1186/s10194-015-0527-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 05/01/2015] [Indexed: 12/04/2022] Open
Abstract
Background This study aimed to identify the systemic and cerebral hemodynamic characteristics and their roles in high-altitude headache (HAH) among young Chinese men following acute exposure. Methods The subjects (n = 385) were recruited in June and July of 2012. They completed case report form questionnaires, as well as heart rate (HR), blood pressure, echocardiogram and transcranial Doppler examinations at 3700 m following a two-hour plane flight. A subgroup of 129 participants was examined at two altitudes (500 and 3700 m). Results HAH was characterized by increased HR and cardiac output (CO) and lower saturation pulse oxygen (SpO2) (all p < 0.05). The change in tricuspid regurgitation was also different between the HAH positive (HAH+) and HAH negative (HAH-) subjects. Furthermore, the HAH+ subjects exhibited faster mean (Vm), systolic (Vs) and diastolic (Vd) velocities in the basilar artery (BA; all p < 0.05) and a faster Vd ( 25.96 ± 4.97 cm/s vs. 24.76 ± 4.76 cm/s, p = 0.045) in the left vertebral artery (VA). The bilateral VA asymmetry was also significantly different between the two groups. The pulsatility index (PI) and resistance index (RI) of left VA were lower in the HAH subjects (p < 0.05) and were negatively correlated with HAH (p < 0.05). Baseline CO and Vm in left VA (or right MCA in different regressions) were independent predictors for HAH, whereas CO/HR and ΔVd (Vd difference between bilateral VAs) were independent risk factors for HAH at 3700 m. Conclusions HAH was characterized, in part, by increased systemic hemodynamics and posterior cerebral circulation, which was reflected by the BA and left VA velocities, and lower arterial resistance and compliance. Furthermore, baseline CO and Vm in left VA or right MCA at sea level were independent predictors for HAH, whilst bilateral VA asymmetry may contribute to the development of HAH at high altitude. Electronic supplementary material The online version of this article (doi:10.1186/s10194-015-0527-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Shi-Zhu Bian
- Institute of Cardiovascular Diseases, Xinqiao Hospital, Third Military Medical University, 183 Xinqiao Street, Chongqing, 400037, China,
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Alexandre F, Heraud N, Varray A. Is nocturnal desaturation a trigger for neuronal damage in chronic obstructive pulmonary disease? Med Hypotheses 2015; 84:25-30. [DOI: 10.1016/j.mehy.2014.11.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 11/03/2014] [Accepted: 11/09/2014] [Indexed: 01/26/2023]
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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
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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.
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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
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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.
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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.
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Kong FY, Li Q, Liu SX. Poor Sleep Quality Predicts Decreased Cognitive Function Independently of Chronic Mountain Sickness Score in Young Soldiers with Polycythemia Stationed in Tibet. High Alt Med Biol 2011; 12:237-42. [PMID: 21962067 DOI: 10.1089/ham.2010.1079] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Fan-Yi Kong
- Department of Neurology, Kunming General Hospital of PLA, Kunming, Yunnan Province, PR China
| | - Qiang Li
- Department of Neurology, Kunming General Hospital of PLA, Kunming, Yunnan Province, PR China
| | - Shi-Xiang Liu
- Department of Neurology, Kunming General Hospital of PLA, Kunming, Yunnan Province, PR China
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Brain blood flow in Andean and Himalayan high-altitude populations: evidence of different traits for the same environmental constraint. J Cereb Blood Flow Metab 2011; 31:706-14. [PMID: 20736959 PMCID: PMC3049524 DOI: 10.1038/jcbfm.2010.150] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Humans have populated the Tibetan plateau much longer than the Andean Altiplano. It is thought that the difference in length of occupation of these altitudes has led to different responses to the stress of hypoxia. As such, Andean populations have higher hematocrit levels than Himalayans. In contrast, Himalayans have increased circulation to certain organ systems to meet tissue oxygen demand. In this study, we hypothesize that cerebral blood flow (CBF) is higher in Himalayans than in Andeans. Using a MEDLINE and EMBASE search, we included 10 studies that investigated CBF in Andeans and Himalayans between 3,658 and 4,330 m altitude. The CBF values were corrected for differences in hematocrit and arterial oxygen saturation. The data of these studies show a mean hematocrit of 50% in Himalayans and 54.1% in Andeans. Arterial oxygen saturation was 86.9% in Andeans and 88.4% in Himalayans. The CBF in Himalayans was slightly elevated compared with sea-level subjects, and was 24% higher compared with Andeans. After correction for hematorit and arterial oxygen saturation, CBF was ∼20% higher in Himalayans compared with Andeans. Altered brain metabolism in Andeans, and/or increased nitric oxide availability in Himalayans may have a role to explain this difference in brain blood flow.
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Ravensbergen HJC, Sahota IS. Broken sleep: a new chronic intermittent hypoxia model for obstructive sleep apnoea. J Physiol 2010; 587:5303-4. [PMID: 19915213 DOI: 10.1113/jphysiol.2009.180190] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Affiliation(s)
- H J C Ravensbergen
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada.
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Abstract
Chronic Mountain Sickness (CMS) is an important high-altitude (HA) pathology in most mountainous regions of the world. Although its most characteristic sign is excessive erytrocytosis (EE), in the more severe stages of the disease, high-altitude pulmonary hypertension (HAPH), with remodeling of pulmonary arterioles and right ventricular enlargement is commonly found. The degree of ventricular hypertrophy depends on the vasoconstrictor pulmonary response, the intensity of vascular resistance and the level of altitude, and therefore on the degree of hypoxemia. This chapter briefly summarizes the existing data regarding the clinical and pathophysiological features of the cardiopulmonary system in CMS, with emphasis in findings from research in the Andes. The literature shows variability in cardiac output values in CMS, which might be related to the degree of EE. Recent findings have shown that cardiac output (l/min) is lower in CMS when compared with sea-level (SL) dwellers. Mean pulmonary acceleration time (ms) is significantly lower in CMS subjects than in SL and HA natives, and pulmonary vascular resistance index (Wood units) is higher in CMS and HA natives when compared with SL dwellers. Systemic blood pressure has similar values in CMS patients and healthy HA natives, but some differences arise in its control mechanisms. Although CMS individuals have a less effective vasoconstrictor reflex, their tolerance to orthostatic stress is similar to that of healthy HA natives which might be explained in terms of the larger blood volume present in CMS subjects. At present research is directed to design strategies on pharmacological intervention for CMS treatment. Recently, a clinical trial with acetazolamide, in patients with CMS has proven to be effective in increasing mean pulmonary acceleration time and decreasing pulmonary vascular resistance index, which might be indirectly due the reduction of hematocrit.
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Slessarev M, Mardimae A, Preiss D, Vesely A, Balaban DY, Greene R, Duffin J, Fisher JA. Differences in the control of breathing between Andean highlanders and lowlanders after 10 days acclimatization at 3850 m. J Physiol 2010; 588:1607-21. [PMID: 20231143 DOI: 10.1113/jphysiol.2009.186064] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We used Duffin's isoxic hyperoxic ( mmHg) and hypoxic ( mmHg) rebreathing tests to compare the control of breathing in eight (7 male) Andean highlanders and six (4 male) acclimatizing Caucasian lowlanders after 10 days at 3850 m. Compared to lowlanders, highlanders had an increased non-chemoreflex drive to breathe, characterized by higher basal ventilation at both hyperoxia (10.5 +/- 0.7 vs. 4.9 +/- 0.5 l min(1), P = 0.002) and hypoxia (13.8 +/- 1.4 vs. 5.7 +/- 0.9 l min(1), P < 0.001). Highlanders had a single ventilatory sensitivity to CO(2) that was lower than that of the lowlanders (P < 0.001), whose response was characterized by two ventilatory sensitivities (VeS1 and VeS2) separated by a patterning threshold. There was no difference in ventilatory recruitment thresholds (VRTs) between populations (P = 0.209). Hypoxia decreased VRT within both populations (highlanders: 36.4 +/- 1.3 to 31.7 +/- 0.7 mmHg, P < 0.001; lowlanders: 35.3 +/- 1.3 to 28.8 +/- 0.9 mmHg, P < 0.001), but it had no effect on basal ventilation (P = 0.12) or on ventilatory sensitivities in either population (P = 0.684). Within lowlanders, VeS2 was substantially greater than VeS1 at both isoxic tensions (hyperoxic: 9.9 +/- 1.7 vs. 2.8 +/- 0.2, P = 0.005; hypoxic: 13.2 +/- 1.9 vs. 2.8 +/- 0.5, P < 0.001), although hypoxia had no effect on either of the sensitivities (P = 0.192). We conclude that the control of breathing in Andean highlanders is different from that in acclimatizing lowlanders, although there are some similarities. Specifically, acclimatizing lowlanders have relatively lower non-chemoreflex drives to breathe, increased ventilatory sensitivities to CO(2), and an altered pattern of ventilatory response to CO(2) with two ventilatory sensitivities separated by a patterning threshold. Similar to highlanders and unlike lowlanders at sea-level, acclimatizing lowlanders respond to hypobaric hypoxia by decreasing their VRT instead of changing their ventilatory sensitivity to CO(2).
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Affiliation(s)
- Marat Slessarev
- Department of Anesthesia, University Health Network, University of Toronto, Toronto, Canada, M5G 2C4
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Slessarev M, Prisman E, Ito S, Watson RR, Jensen D, Preiss D, Greene R, Norboo T, Stobdan T, Diskit D, Norboo A, Kunzang M, Appenzeller O, Duffin J, Fisher JA. Differences in the control of breathing between Himalayan and sea-level residents. J Physiol 2010; 588:1591-606. [PMID: 20194122 DOI: 10.1113/jphysiol.2009.185504] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We compared the control of breathing of 12 male Himalayan highlanders with that of 21 male sea-level Caucasian lowlanders using isoxic hyperoxic ( = 150 mmHg) and hypoxic ( = 50 mmHg) Duffin's rebreathing tests. Highlanders had lower mean +/- s.e.m. ventilatory sensitivities to CO(2) than lowlanders at both isoxic tensions (hyperoxic: 2.3 +/- 0.3 vs. 4.2 +/- 0.3 l min(1) mmHg(1), P = 0.021; hypoxic: 2.8 +/- 0.3 vs. 7.1 +/- 0.6 l min(1) mmHg(1), P < 0.001), and the usual increase in ventilatory sensitivity to CO(2) induced by hypoxia in lowlanders was absent in highlanders (P = 0.361). Furthermore, the ventilatory recruitment threshold (VRT) CO(2) tensions in highlanders were lower than in lowlanders (hyperoxic: 33.8 +/- 0.9 vs. 48.9 +/- 0.7 mmHg, P < 0.001; hypoxic: 31.2 +/- 1.1 vs. 44.7 +/- 0.7 mmHg, P < 0.001). Both groups had reduced ventilatory recruitment thresholds with hypoxia (P < 0.001) and there were no differences in the sub-threshold ventilations (non-chemoreflex drives to breathe) between lowlanders and highlanders at both isoxic tensions (P = 0.982), with a trend for higher basal ventilation during hypoxia (P = 0.052). We conclude that control of breathing in Himalayan highlanders is distinctly different from that of sea-level lowlanders. Specifically, Himalayan highlanders have decreased central and absent peripheral sensitivities to CO(2). Their response to hypoxia was heterogeneous, with the majority decreasing their VRT indicating either a CO(2)-independent increase in activity of peripheral chemoreceptor or hypoxia-induced increase in [H(+)] at the central chemoreceptor. In some highlanders, the decrease in VRT was accompanied by an increase in sensitivity to CO(2), while in others VRT remained unchanged and their sub-threshold ventilations increased, although these were not statistically significant.
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Affiliation(s)
- M Slessarev
- Department of Anesthesia, University Health Network, University of Toronto, Toronto, Canada
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Hogan AM, Virues-Ortega J, Botti AB, Bucks R, Holloway JW, Rose-Zerilli MJ, Palmer LJ, Webster RJ, Baldeweg T, Kirkham FJ. Development of aptitude at altitude. Dev Sci 2009; 13:533-544. [DOI: 10.1111/j.1467-7687.2009.00909.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Norcliffe-Kaufmann LJ, Kaufmann H, Hainsworth R. Enhanced vascular responses to hypocapnia in neurally mediated syncope. Ann Neurol 2008; 63:288-94. [PMID: 17823939 DOI: 10.1002/ana.21205] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE The susceptibility to suffer neurally mediated syncope and loss of consciousness varies markedly. In addition to vasodilatation and bradycardia, hyperventilation precedes loss of consciousness. The resultant hypocapnia causes cerebral vasoconstriction and peripheral vasodilatation. We postulate that more pronounced cerebral and peripheral vascular responses to reductions in arterial CO(2) levels underlie greater susceptibility to neurally mediated syncope. METHODS We compared vascular responses to CO(2) among 31 patients with histories of recurrent neurally mediated syncope and low orthostatic tolerance and 14 age- and sex-matched control subjects with no history of syncope and normal orthostatic tolerance. Vascular responses to CO(2) were calculated after all subjects had fully recovered and their blood pressures and heart rates were stable. We measured blood flow velocity in the middle cerebral artery (transcranial Doppler) and in the left brachial artery (brachial Doppler), and end-tidal CO(2) during voluntary hyperventilation and hypoventilation (end-tidal CO(2) from 21-45mm Hg), and determined the slopes of the relations. RESULTS Hypocapnia produced a significantly greater reduction in cerebral blood flow velocity and in forearm vascular resistance in patients with neurally mediated syncope than in control subjects. Opposite changes occurred in response to hypercapnia. In all subjects, the changes in cerebral blood flow velocity and forearm vasodilatation were inversely related with orthostatic tolerance. INTERPRETATION Susceptibility to neurally mediated syncope can be explained, at least in part, by enhanced cerebral vasoconstriction and peripheral vasodilatation in response to hypocapnia. This may have therapeutic implications.
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Puri GD, Jayant A, Dorje M, Tashi M. Propofol-fentanyl anaesthesia at high altitude: anaesthetic requirements and haemodynamic variations when compared with anaesthesia at low altitude. Acta Anaesthesiol Scand 2008; 52:427-31. [PMID: 18269393 DOI: 10.1111/j.1399-6576.2007.01561.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND There are few published accounts of anaesthesia delivery at high altitude. Natives at high altitude are known to have altered cardiorespiratory reserve. This study seeks to demonstrate the safety of propofol-fentanyl anaesthesia at high altitude titrated to the bispectral index (BIS) (3505 metres above sea level) in native highlanders. It also shows the differential effects of anaesthesia and surgery on the haemodynamics of such individuals as compared with individuals living at low altitude. METHODS Fifteen consenting adults scheduled to undergo general surgical/orthopaedic procedures under general anaesthesia using fentanyl, and propofol infusions titrated to the BIS along with nitrous oxide in oxygen after intubation, were recruited in the high-altitude arm. Their anaesthesia record was compared with retrospective data from low altitude with respect to anaesthetic requirements, recovery after anaesthesia and the haemodynamic responses to surgical stress. RESULTS The high-altitude dwellers required significantly larger doses of propofol at anaesthetic induction (2.31+/-0.64 vs. 1.41+/-0.24 mg/kg, P<0.0001) and thereafter to maintain designated BIS than their low-altitude counterparts (6.22+/-1.14 vs. 4.61+/-1.29 mg/kg/h, P<0.01). They, however, had uneventful and short recovery times. The high-altitude population also had significantly lower baseline heart rates (72+/-9.83 vs. 88+/-12.1, P<0.04) as also the heart rate responses to noxious stimulation such as direct laryngoscopy or skin incision (P<0.04, P<0.005, respectively). CONCLUSIONS High-altitude dwellers require significantly larger amounts of intravenous anaesthetic propofol. Heart rate at rest as also the heart rate responses to surgical stress were significantly attenuated at high altitude.
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Affiliation(s)
- G D Puri
- Department of Anaesthesia and Intensive Care, PGIMER, Chandigarh, India.
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Claydon VE, Gulli G, Slessarev M, Appenzeller O, Zenebe G, Gebremedhin A, Hainsworth R. Cerebrovascular Responses to Hypoxia and Hypocapnia in Ethiopian High Altitude Dwellers. Stroke 2008; 39:336-42. [DOI: 10.1161/strokeaha.107.491498] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background and Purpose—
Cerebrovascular responses to hypoxia and hypocapnia in Peruvian altitude dwellers are impaired. This could contribute to the high incidence of altitude-related illness in Andeans. Ethiopian high altitude dwellers may show a different pattern of adaptation to high altitude. We aimed to examine cerebral reactivity to hypoxia and hypocapnia in healthy Ethiopian high altitude dwellers. Responses were compared with our previous data from Peruvians.
Methods—
We studied 9 Ethiopian men at their permanent residence of 3622 m, and one day after descent to 794 m. We continuously recorded cerebral blood flow velocity (CBFV; transcranial Doppler). End-tidal oxygen (P
ET
o
2
) was decreased from 100 mm Hg to 50 mm Hg with end-tidal carbon dioxide (P
ET
co
2
) clamped at the subject’s resting level. P
ET
co
2
was then manipulated by voluntary hyper- and hypoventilation, with P
ET
o
2
clamped at 100 mm Hg (normoxia) and 50 mm Hg (hypoxia).
Results—
During spontaneous breathing, P
ET
co
2
increased after descent, from 38.2±1.0 mm Hg to 49.8±0.6 mm Hg (
P
<0.001). There was no significant response of CBFV to hypoxia at either high (−0.19±3.1%) or low (1.1±2.9%) altitudes. Cerebrovascular reactivity to normoxic hypocapnia at high and low altitudes was 3.92±0.5%.mm Hg
−1
and 3.09±0.4%.mm Hg
−1
; reactivity to hypoxic hypocapnia was 4.83±0.7%.mm Hg
−1
and 2.82±0.5%.mm Hg
−1
. Responses to hypoxic hypocapnia were significantly smaller at low altitude.
Conclusions—
The cerebral circulation of Ethiopian high altitude dwellers is insensitive to hypoxia, unlike Peruvian high altitude dwellers. Cerebrovascular responses to P
ET
co
2
were greater in Ethiopians than Peruvians, particularly at high altitude. This, coupled with their high P
ET
co
2
levels, would lead to high cerebral blood flows, and may be advantageous for altitude living.
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Affiliation(s)
- Victoria E. Claydon
- From ICORD (V.E.C.), University of British Columbia, Vancouver, Canada; the Institute for Cardiovascular Research (V.E.C., G.G., R.H.), University of Leeds, UK; the Department of Physiology (M.S.), University of Toronto and Department of Anaesthesia, Toronto General Hospital, Ontario, Canada; the New Mexico Health Enhancement and Marathon Clinics (NMHEMC) Research Foundation (O.A.), Albuquerque, NM; the Department of Neurology (G.Z.), Yehuleshet Higher Clinic, University of Addis Ababa, Ethiopia
| | - Giosué Gulli
- From ICORD (V.E.C.), University of British Columbia, Vancouver, Canada; the Institute for Cardiovascular Research (V.E.C., G.G., R.H.), University of Leeds, UK; the Department of Physiology (M.S.), University of Toronto and Department of Anaesthesia, Toronto General Hospital, Ontario, Canada; the New Mexico Health Enhancement and Marathon Clinics (NMHEMC) Research Foundation (O.A.), Albuquerque, NM; the Department of Neurology (G.Z.), Yehuleshet Higher Clinic, University of Addis Ababa, Ethiopia
| | - Marat Slessarev
- From ICORD (V.E.C.), University of British Columbia, Vancouver, Canada; the Institute for Cardiovascular Research (V.E.C., G.G., R.H.), University of Leeds, UK; the Department of Physiology (M.S.), University of Toronto and Department of Anaesthesia, Toronto General Hospital, Ontario, Canada; the New Mexico Health Enhancement and Marathon Clinics (NMHEMC) Research Foundation (O.A.), Albuquerque, NM; the Department of Neurology (G.Z.), Yehuleshet Higher Clinic, University of Addis Ababa, Ethiopia
| | - Otto Appenzeller
- From ICORD (V.E.C.), University of British Columbia, Vancouver, Canada; the Institute for Cardiovascular Research (V.E.C., G.G., R.H.), University of Leeds, UK; the Department of Physiology (M.S.), University of Toronto and Department of Anaesthesia, Toronto General Hospital, Ontario, Canada; the New Mexico Health Enhancement and Marathon Clinics (NMHEMC) Research Foundation (O.A.), Albuquerque, NM; the Department of Neurology (G.Z.), Yehuleshet Higher Clinic, University of Addis Ababa, Ethiopia
| | - Guta Zenebe
- From ICORD (V.E.C.), University of British Columbia, Vancouver, Canada; the Institute for Cardiovascular Research (V.E.C., G.G., R.H.), University of Leeds, UK; the Department of Physiology (M.S.), University of Toronto and Department of Anaesthesia, Toronto General Hospital, Ontario, Canada; the New Mexico Health Enhancement and Marathon Clinics (NMHEMC) Research Foundation (O.A.), Albuquerque, NM; the Department of Neurology (G.Z.), Yehuleshet Higher Clinic, University of Addis Ababa, Ethiopia
| | - Amha Gebremedhin
- From ICORD (V.E.C.), University of British Columbia, Vancouver, Canada; the Institute for Cardiovascular Research (V.E.C., G.G., R.H.), University of Leeds, UK; the Department of Physiology (M.S.), University of Toronto and Department of Anaesthesia, Toronto General Hospital, Ontario, Canada; the New Mexico Health Enhancement and Marathon Clinics (NMHEMC) Research Foundation (O.A.), Albuquerque, NM; the Department of Neurology (G.Z.), Yehuleshet Higher Clinic, University of Addis Ababa, Ethiopia
| | - Roger Hainsworth
- From ICORD (V.E.C.), University of British Columbia, Vancouver, Canada; the Institute for Cardiovascular Research (V.E.C., G.G., R.H.), University of Leeds, UK; the Department of Physiology (M.S.), University of Toronto and Department of Anaesthesia, Toronto General Hospital, Ontario, Canada; the New Mexico Health Enhancement and Marathon Clinics (NMHEMC) Research Foundation (O.A.), Albuquerque, NM; the Department of Neurology (G.Z.), Yehuleshet Higher Clinic, University of Addis Ababa, Ethiopia
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Brugniaux JV, Hodges ANH, Hanly PJ, Poulin MJ. Cerebrovascular responses to altitude. Respir Physiol Neurobiol 2007; 158:212-23. [PMID: 17544954 DOI: 10.1016/j.resp.2007.04.008] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Revised: 04/17/2007] [Accepted: 04/19/2007] [Indexed: 10/23/2022]
Abstract
The regulation of cerebral blood flow (CBF) is a complex process that is altered significantly with altitude exposure. Acute exposure produces a marked increase in CBF, in proportion to the severity of the hypoxia and mitigated by hyperventilation-induced hypocapnia when CO(2) is uncontrolled. A number of mediators contribute to the hypoxia-induced cerebral vasodilation, including adenosine, potassium channels, substance P, prostaglandins, and NO. Upon acclimatization to altitude, CBF returns towards normal sea-level values in subsequent days and weeks, mediated by a progressive increase in PO2, first through hyperventilation followed by erythropoiesis. With long-term altitude exposure, a number of mechanisms play a role in regulating CBF, including acid-base balance, hematological modifications, and angiogenesis. Finally, several cerebrovascular disorders are associated with altitude exposure. Existing gaps in our knowledge of CBF and altitude, and areas of future investigation include effects of longer exposures, intermittent hypoxia, and gender differences in the CBF responses to altitude.
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Affiliation(s)
- Julien V Brugniaux
- Department of Physiology & Biophysics, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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37
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Iwasaki KI, Ogawa Y, Shibata S, Aoki K. Acute exposure to normobaric mild hypoxia alters dynamic relationships between blood pressure and cerebral blood flow at very low frequency. J Cereb Blood Flow Metab 2007; 27:776-84. [PMID: 16926845 DOI: 10.1038/sj.jcbfm.9600384] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Acute hypoxia directly causes cerebral arteriole vasodilation and also stimulates peripheral chemoreceptors to change autonomic neural activity. These changes may alter cerebral vascular modulation. We therefore hypothesized that dynamic cerebral autoregulation would be altered during acute exposure to hypoxia. Fifteen healthy men were examined under normoxic (21%) and hypoxic conditions. Oxygen concentrations were decreased in stepwise fashion to 19%, 17%, and 15%, for 10 mins at each level. Mean blood pressure (MBP) in the radial artery was measured via tonometry, and cerebral blood flow velocity (CBFV) in the middle cerebral artery was measured by transcranial Doppler ultrasonography. Dynamic cerebral autoregulation was assessed by spectral and transfer function analysis of beat-by-beat changes in MBP and CBFV. Arterial oxygen saturation decreased significantly during hypoxia, while end-tidal CO2 and respiratory rate were unchanged, as was steady-state CBFV. With 15% O2, very-low-frequency power of MBP and CBFV variability increased significantly by 185% and 282%, respectively. Moreover, transfer function coherence (21% O2, 0.46+/-0.04; 15% O2, 0.64+/-0.04; P=0.028) and gain (21% O2, 0.61+/-0.05 cm/secs/mm Hg; 15% O2, 0.86+/-0.08 cm/secs/mm Hg; P=0.035) in the very-low-frequency range increased significantly by 53% and 48% with 15% O2, respectively. However, these indices were unchanged in low- and high-frequency ranges. Acute hypoxia thus increases arterial pressure oscillations and dependence of cerebral blood flow (CBF) fluctuations on blood pressure oscillations, resulting in apparent increases in CBF fluctuations in the very-low-frequency range. Hypoxia may thus impair dynamic cerebral autoregulation in this range. However, these changes were significant only with hypoxia at 15% O2, suggesting a possible threshold for such changes.
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Affiliation(s)
- Ken-ichi Iwasaki
- Department of Hygiene and Space Medicine, Nihon University School of Medicine, Tokyo, Japan.
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38
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Gulli G, Claydon VE, Slessarev M, Zenebe G, Gebremedhin A, Rivera-Ch M, Appenzeller O, Hainsworth R. Autonomic regulation during orthostatic stress in highlanders: comparison with sea-level residents. Exp Physiol 2007; 92:427-35. [PMID: 17138623 DOI: 10.1113/expphysiol.2006.035519] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This report is a comparison of orthostatic tolerance and autonomic function in three groups of high-altitude dwellers: Andeans with and without chronic mountain sickness (CMS) and healthy Ethiopians. Results are compared with those from healthy sea-level residents. The aim was to determine whether different high-altitude populations adapted differently to the prevailing hypobaric hypoxia. Orthostatic tolerance was assessed using a test involving head-up tilt (HUT) and graded lower body suction. This was performed at the subjects' resident altitude. Blood pressure (Portapres) and R-R interval (ECG) were recorded during the test, and spectral and cross-spectral analyses of heart period and systolic blood pressure time series were performed using data obtained both while supine and during HUT. The transfer function gain in the low-frequency range (LF, approximately 0.1 Hz) at the point of maximal coherence was used as a measure of cardiac baroreflex sensitivity (BRS). As previously reported, Peruvians displayed an unusually good orthostatic tolerance, while Ethiopians showed an orthostatic tolerance comparable to that of healthy sea-level residents. There were no significant differences between groups in the supine values of the spectral analysis results. Head-up tilt induced the expected changes in Ethiopians (an increase in the LF components and a decrease in the respiratory components) but not in Andeans. Cross-spectral analysis showed abnormal results from all groups of high-altitude dwellers. These results indicate that Ethiopians, but not Peruvians, behave similarly to sea-level residents in terms of orthostatic tolerance and autonomic responses to orthostatic stress, as assessed from spectral analyses, and this indicates good adaptation to their environment. However, in all the high-altitude groups the results of cross-spectral analysis were atypical, suggesting some degree of impairment in baroreflex function.
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Affiliation(s)
- Giosué Gulli
- Institute for Cardiovascular Research, University of Leeds, Leeds, UK.
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39
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Ainslie PN, Barach A, Murrell C, Hamlin M, Hellemans J, Ogoh S. Alterations in cerebral autoregulation and cerebral blood flow velocity during acute hypoxia: rest and exercise. Am J Physiol Heart Circ Physiol 2007; 292:H976-83. [PMID: 17012355 DOI: 10.1152/ajpheart.00639.2006] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We examined the relationship between changes in cardiorespiratory and cerebrovascular function in 14 healthy volunteers with and without hypoxia [arterial O2 saturation (SaO2) ∼80%] at rest and during 60–70% maximal oxygen uptake steady-state cycling exercise. During all procedures, ventilation, end-tidal gases, heart rate (HR), arterial blood pressure (BP; Finometer) cardiac output (Modelflow), muscle and cerebral oxygenation (near-infrared spectroscopy), and middle cerebral artery blood flow velocity (MCAV; transcranial Doppler ultrasound) were measured continuously. The effect of hypoxia on dynamic cerebral autoregulation was assessed with transfer function gain and phase shift in mean BP and MCAV. At rest, hypoxia resulted in increases in ventilation, progressive hypocapnia, and general sympathoexcitation (i.e., elevated HR and cardiac output); these responses were more marked during hypoxic exercise ( P < 0.05 vs. rest) and were also reflected in elevation of the slopes of the linear regressions of ventilation, HR, and cardiac output with SaO2 ( P < 0.05 vs. rest). MCAV was maintained during hypoxic exercise, despite marked hypocapnia (44.1 ± 2.9 to 36.3 ± 4.2 Torr; P < 0.05). Conversely, hypoxia both at rest and during exercise decreased cerebral oxygenation compared with muscle. The low-frequency phase between MCAV and mean BP was lowered during hypoxic exercise, indicating impairment in cerebral autoregulation. These data indicate that increases in cerebral neurogenic activity and/or sympathoexcitation during hypoxic exercise can potentially outbalance the hypocapnia-induced lowering of MCAV. Despite maintaining MCAV, such hypoxic exercise can potentially compromise cerebral autoregulation and oxygenation.
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Affiliation(s)
- Philip N Ainslie
- Department of Physiology, University of Otago, Dunedin, New Zealand.
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40
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Hainsworth R, Drinkhill MJ, Rivera-Chira M. The autonomic nervous system at high altitude. Clin Auton Res 2007; 17:13-9. [PMID: 17264976 PMCID: PMC1797062 DOI: 10.1007/s10286-006-0395-7] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2007] [Accepted: 01/03/2007] [Indexed: 11/27/2022]
Abstract
The effects of hypobaric hypoxia in visitors depend not only on the actual elevation but also on the rate of ascent. Sympathetic activity increases and there are increases in blood pressure and heart rate. Pulmonary vasoconstriction leads to pulmonary hypertension, particularly during exercise. The sympathetic excitation results from hypoxia, partly through chemoreceptor reflexes and partly through altered baroreceptor function. High pulmonary arterial pressures may also cause reflex systemic vasoconstriction. Most permanent high altitude dwellers show excellent adaptation although there are differences between populations in the extent of the ventilatory drive and the erythropoiesis. Some altitude dwellers, particularly Andeans, may develop chronic mountain sickness, the most prominent characteristic of which being excessive polycythaemia. Excessive hypoxia due to peripheral chemoreceptor dysfunction has been suggested as a cause. The hyperviscous blood leads to pulmonary hypertension, symptoms of cerebral hypoperfusion, and eventually right heart failure and death.
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Affiliation(s)
- Roger Hainsworth
- Institute for Cardiovascular Research, University of Leeds, Leeds, UK.
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41
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Moore JP, Claydon VE, Norcliffe LJ, Rivera-Ch MC, Lèon-Velarde F, Appenzeller O, Hainsworth R. Carotid baroreflex regulation of vascular resistance in high-altitude Andean natives with and without chronic mountain sickness. Exp Physiol 2006; 91:907-13. [PMID: 16763007 DOI: 10.1113/expphysiol.2005.033084] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We investigated carotid baroreflex control of vascular resistance in two groups of high-altitude natives: healthy subjects (HA) and a group with chronic mountain sickness (CMS), a maladaptation condition characterized by high haematocrit values and symptoms attributable to chronic hypoxia. Eleven HA controls and 11 CMS patients underwent baroreflex testing, using the neck collar method in which the pressure distending the carotid baroreceptors was changed by applying pressures of -40 to +60 mmHg to the chamber. Responses of forearm vascular resistance were assessed from changes in the quotient of blood pressure divided by brachial artery blood velocity. Stimulus-response curves were defined at high altitude (4338 m) and within 1 day of descent to sea level. We applied a sigmoid function or third-order polynomial to the curves and determined the maximal slope (equivalent to peak gain) and the corresponding carotid pressure (equivalent to 'set point'). The results showed that the peak gains of the reflex were similar in both groups and at both locations. The 'set point' of the reflex, however, was significantly higher in the CMS patients compared to HA controls, indicating that the reflex operates over higher pressures in the patients (94.4 +/- 3.0 versus 79.6 +/- 4.1 mmHg; P < 0.01). This, however, was seen only when subjects were studied at altitude; after descent to sea level the curve reset to a lower pressure with no significant difference between HA and CMS subjects. These results indicate that carotid baroreceptor control of vascular resistance may be abnormal in CMS patients but that descent to sea level rapidly normalizes it. We speculate that this may be explained by CMS patients having greater vasoconstrictor activity at altitude owing to greater hypoxic stimulation of chemoreceptors.
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42
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Abstract
SUMMARYNatural or artificial selection that favors higher values of a particular trait within a given population should engender an evolutionary response that increases the mean value of the trait. For this prediction to hold, the phenotypic variance of the trait must be caused in part by additive effects of alleles segregating in the population, and also the trait must not be too strongly genetically correlated with other traits that are under selection. Another prediction, rarely discussed in the literature, is that directional selection should favor alleles that increase phenotypic plasticity in the direction of selection, where phenotypic plasticity is defined as the ability of one genotype to produce more than one phenotype when exposed to different environments. This prediction has received relatively little empirical attention. Nonetheless, many laboratory experiments impose selection regimes that could allow for the evolution of enhanced plasticity (e.g. desiccation trials with Drosophila that last for several hours or days). We review one example that involved culturing of Drosophila on lemon for multiple generations and then tested for enhanced plasticity of detoxifying enzymes. We also review an example with vertebrates that involves selective breeding for high voluntary activity levels in house mice, targeting wheel-running behavior on days 5+6 of a 6-day wheel exposure. This selection regime allows for the possibility of wheel running itself or subordinate traits that support such running to increase in plasticity over days 1–4 of wheel access. Indeed, some traits, such as the concentration of the glucose transporter GLUT4 in gastrocnemius muscle, do show enhanced plasticity in the selected lines over a 5–6 day period. In several experiments we have housed mice from both the Selected (S) and Control (C) lines with or without wheel access for several weeks to test for differences in plasticity (training effects). A variety of patterns were observed, including no training effects in either S or C mice, similar changes in both the S and C lines, greater changes in the S lines but in the same direction in the C lines, and even opposite directions of change in the S and C lines. For some of the traits that show a greater training effect in the S lines, but in the same direction as in C lines, the greater effect can be explained statistically by the greater wheel running exhibited by S lines (`more pain, more gain'). For others, however, the differences seem to reflect inherently greater plasticity in the S lines (i.e. for a given amount of stimulus, such as wheel running/day, individuals in the S lines show a greater response as compared with individuals in the C lines). We suggest that any selection experiment in which the selective event is more than instantaneous should explore whether plasticity in the appropriate (adaptive) direction has increased as a component of the response to selection.
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Affiliation(s)
- Theodore Garland
- Department of Biology, University of California, Riverside, Riverside, CA 92521, USA.
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Appenzeller O, Claydon VE, Gulli G, Qualls C, Slessarev M, Zenebe G, Gebremedhin A, Hainsworth R. Cerebral vasodilatation to exogenous NO is a measure of fitness for life at altitude. Stroke 2006; 37:1754-8. [PMID: 16763189 DOI: 10.1161/01.str.0000226973.97858.0b] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Andean highlanders, unlike Ethiopians, develop chronic mountain sickness (CMS), a maladaptation to their native land. Ambient hypoxia induces NO-mediated vasodilatation. Fitness for life at altitude might be revealed by cerebrovascular responses to NO. METHODS Nine altitude-native men were examined at 3622 and 794 m in Ethiopia and compared with 9 altitude-native Andean men tested at 4338 and 150 m in Peru. We assessed CMS scores, hematocrits, end-tidal pressure of carbon dioxide (P(ET)co2), oxygen saturations, and cerebral blood flow velocity (CBV). We evaluated fitness for life at altitude from the cerebrovascular response to an exogenous NO donor. RESULTS At high altitude, CMS scores and hematocrits were higher in Andeans, and they had lower oxygen saturations. Ethiopians had higher P(ET)co2 at all study sites. At low altitude, saturations were similar in both groups. Responsiveness of the cerebral circulation to NO was minimal in Ethiopians at low altitude, whereas Andeans had a large response. In contrast, at high altitude, Ethiopians showed large responses, and Peruvians had minimal responses. CONCLUSIONS By our measure, high altitude-native Peruvians were well-adapted lowlanders, whereas Ethiopian highlanders were well adapted to altitude life. Environmental pressures were sufficient for human adaptation to chronic hypoxia in Africa but not South America. The mechanisms underlying these differences are unknown, although studies of neurovascular diseases suggest that this may be related to a NO receptor polymorphism.
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Affiliation(s)
- Otto Appenzeller
- Department of Neurology, New Mexico Health Enhancement and Marathon Clinics (NMHEMC) Research Foundation, Albuquerque, NM 87122-1424, USA.
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44
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Severinghaus JW. Sightings. High Alt Med Biol 2005. [DOI: 10.1089/ham.2005.6.198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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