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Watanabe K, Koch Esteves N, Gibson OR, Akiyama K, Watanabe S, González-Alonso J. Heat-related changes in the velocity and kinetic energy of flowing blood influence the human heart's output during hyperthermia. J Physiol 2024; 602:2227-2251. [PMID: 38690610 DOI: 10.1113/jp285760] [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: 10/03/2023] [Accepted: 04/03/2024] [Indexed: 05/02/2024] Open
Abstract
Passive whole-body hyperthermia increases limb blood flow and cardiac output (Q ̇ $\dot Q$ ), but the interplay between peripheral and central thermo-haemodynamic mechanisms remains unclear. Here we tested the hypothesis that local hyperthermia-induced alterations in peripheral blood flow and blood kinetic energy modulate flow to the heart andQ ̇ $\dot Q$ . Body temperatures, regional (leg, arm, head) and systemic haemodynamics, and left ventricular (LV) volumes and functions were assessed in eight healthy males during: (1) 3 h control (normothermic condition); (2) 3 h of single-leg heating; (3) 3 h of two-leg heating; and (4) 2.5 h of whole-body heating. Leg, forearm, and extracranial blood flow increased in close association with local rises in temperature while brain perfusion remained unchanged. Increases in blood velocity with small to no changes in the conduit artery diameter underpinned the augmented limb and extracranial perfusion. In all heating conditions,Q ̇ $\dot Q$ increased in association with proportional elevations in systemic vascular conductance, related to enhanced blood flow, blood velocity, vascular conductance and kinetic energy in the limbs and head (all R2 ≥ 0.803; P < 0.001), but not in the brain. LV systolic (end-systolic elastance and twist) and diastolic functional profiles (untwisting rate), pulmonary ventilation and systemic aerobic metabolism were only altered in whole-body heating. These findings substantiate the idea that local hyperthermia-induced selective alterations in peripheral blood flow modulate the magnitude of flow to the heart andQ ̇ $\dot Q$ through changes in blood velocity and kinetic energy. Localised heat-activated events in the peripheral circulation therefore affect the human heart's output. KEY POINTS: Local and whole-body hyperthermia increases limb and systemic perfusion, but the underlying peripheral and central heat-sensitive mechanisms are not fully established. Here we investigated the regional (leg, arm and head) and systemic haemodynamics (cardiac output:Q ̇ $\dot Q$ ) during passive single-leg, two-leg and whole-body hyperthermia to determine the contribution of peripheral and central thermosensitive factors in the control of human circulation. Single-leg, two-leg, and whole-body hyperthermia induced graded increases in leg blood flow andQ ̇ $\dot Q$ . Brain blood flow, however, remained unchanged in all conditions. Ventilation, extracranial blood flow and cardiac systolic and diastolic functions only increased during whole-body hyperthermia. The augmentedQ ̇ $\dot Q$ with hyperthermia was tightly related to increased limb and head blood velocity, flow and kinetic energy. The findings indicate that local thermosensitive mechanisms modulate regional blood velocity, flow and kinetic energy, thereby controlling the magnitude of flow to the heart and thus the coupling of peripheral and central circulation during hyperthermia.
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Affiliation(s)
- Kazuhito Watanabe
- Division of Sport, Health and Exercise Sciences, Department of Life Sciences, Brunel University London, Uxbridge, UK
- Faculty of Education and Human Studies, Akita University, Akita, Japan
| | - Nuno Koch Esteves
- Division of Sport, Health and Exercise Sciences, Department of Life Sciences, Brunel University London, Uxbridge, UK
- Research Centre, University College of Osteopathy, London, UK
| | - Oliver R Gibson
- Division of Sport, Health and Exercise Sciences, Department of Life Sciences, Brunel University London, Uxbridge, UK
- Centre for Physical Activity in Health and Disease, Brunel University London, Uxbridge, UK
| | - Koichi Akiyama
- Department of Anesthesiology, Kindai University Hospital, Osaka, Japan
| | - Sumie Watanabe
- Division of Sport, Health and Exercise Sciences, Department of Life Sciences, Brunel University London, Uxbridge, UK
- Faculty of Education and Human Studies, Akita University, Akita, Japan
| | - José González-Alonso
- Division of Sport, Health and Exercise Sciences, Department of Life Sciences, Brunel University London, Uxbridge, UK
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Worley ML, Reed EL, Klaes N, Schlader ZJ, Johnson BD. Cool head-out water immersion does not alter cerebrovascular reactivity to hypercapnia despite elevated middle cerebral artery blood velocity: A pilot study. PLoS One 2024; 19:e0298587. [PMID: 38478550 PMCID: PMC10936844 DOI: 10.1371/journal.pone.0298587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 01/28/2024] [Indexed: 03/24/2024] Open
Abstract
Episodic increases in cerebral blood flow (CBF) are thought to contribute to improved cerebrovascular function and health. Head-out water immersion (HOWI) may be a useful modality to increase CBF secondary to the hydrostatic pressure placed on the body. However, it is unclear whether water temperatures common to the general public elicit similar cerebrovascular responses. We tested the hypothesis that mean middle cerebral artery blood velocity (MCAvmean) and cerebrovascular reactivity to CO2 (CVRCO2) would be higher during an acute bout of thermoneutral (TN; 35°C) vs. cool (COOL; 25°C) HOWI. Ten healthy participants (age: 23±3 y; 4 women) completed two randomized HOWI visits. Right MCAvmean, end-tidal CO2 (PETCO2) mean arterial pressure (MAP), and MCA conductance (MCAvmean/MAP) were continuously recorded. CVRCO2 was assessed using a stepped hypercapnia protocol before (PRE), at 30 minutes of HOWI (HOWI), immediately after HOWI (POST-1), and 45 minutes after HOWI (POST-2). Absolute values are reported as mean ± SD. MCAvmean, PETCO2, MAP, and CVRCO2 were not different between conditions at any timepoint (all P≥0.17). In COOL, MCAvmean increased from PRE (61±9 cm/s) during HOWI (68±11 cm/s), at POST-1 (69±11 cm/s), and POST-2 (72±8 cm/s) (all P<0.01), and in TN from PRE to POST-1 (66±13 vs. 71±14 cm/s; P = 0.05). PETCO2 did not change over time in either condition. In COOL, MAP increased from PRE (85±5 mmHg) during HOWI (101±4 mmHg), at POST-1 (97±7 mmHg), and POST-2 (96±9 mmHg), and in TN from PRE (88±5 mmHg) at HOWI (98±7 mmHg) and POST-1 (99±8 mmHg) (all P<0.01). In COOL, CVRCO2 increased from PRE to HOWI (1.66±0.55 vs. 1.92±0.52 cm/s/mmHg; P = 0.04). MCA conductance was not different between or within conditions. These data indicate that 30 minutes of cool HOWI augments MCAvmean and that the increase in MCAvmean persists beyond cool HOWI. However, cool HOWI does not alter CVRCO2 in healthy young adults.
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Affiliation(s)
- Morgan L. Worley
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States of America
| | - Emma L. Reed
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States of America
- Department of Human Physiology, College of Arts and Sciences, University of Oregon, Eugene, OR, United States of America
| | - Nathan Klaes
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States of America
| | - Zachary J. Schlader
- Department of Kinesiology, School of Public Health-Bloomington, Indiana University, Bloomington, IN, United States of America
| | - Blair D. Johnson
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States of America
- Department of Kinesiology, School of Public Health-Bloomington, Indiana University, Bloomington, IN, United States of America
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Moes MI, Elia A, Gennser M, Keramidas ME. Combined effects of mild hypothermia and nitrous-oxide-induced narcosis on manual and cognitive performance. Am J Physiol Regul Integr Comp Physiol 2024; 326:R197-R209. [PMID: 38189165 DOI: 10.1152/ajpregu.00246.2023] [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: 11/08/2023] [Revised: 12/18/2023] [Accepted: 01/02/2024] [Indexed: 01/09/2024]
Abstract
Divers are at enhanced risk of suffering from acute cognitive deterioration because of the low ambient temperatures and the narcotic action of inert gases inspired at high pressures. Yet, the behavioral effects of cold and inert gas narcosis have commonly been assessed in isolation and during short-term provocations. We therefore evaluated the interactive influence of mild hypothermia and narcosis engendered by a subanesthetic dose of nitrous oxide (N2O; a normobaric intervention analog of hyperbaric nitrogen) on cognitive function during prolonged iterative exposure. Fourteen men partook in two ∼12-h sessions (separated by ≥4 days), wherein they performed sequentially three 120-min cold (20°C) water immersions (CWIs), while inhaling, in a single-blinded manner, either normal air or a normoxic gas mixture containing 30% N2O. CWIs were separated by a 120-min rewarming in room-air breathing conditions. Before the first CWI and during each CWI, subjects performed a finger dexterity test, and the Spaceflight Cognitive Assessment Tool for Windows (WinSCAT) test assessing aspects of attention, memory, learning, and visuospatial ability. Rectal and skin temperatures were, on average, reduced by ∼1.2 °C and ∼8 °C, respectively (P < 0.001). Cooling per se impaired (P ≤ 0.01) only short-term memory (∼37%) and learning (∼18%); the impairments were limited to the first CWI. N2O also attenuated (P ≤ 0.02) short-term memory (∼37%) and learning (∼35%), but the reductions occurred in all CWIs. Furthermore, N2O invariably compromised finger dexterity, attention, concentration, working memory, and spatial processing (P < 0.05). The present results demonstrate that inert gas narcosis aggravates, in a persistent manner, basic and higher-order cognitive abilities during protracted cold exposure.
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Affiliation(s)
- Maaike I Moes
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Antonis Elia
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Mikael Gennser
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Michail E Keramidas
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
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Fan H, Meng Y, Zhu L, Fan M, Wang D, Zhao Y. A review of methods for assessment of cognitive function in high-altitude hypoxic environments. Brain Behav 2024; 14:e3418. [PMID: 38409925 PMCID: PMC10897364 DOI: 10.1002/brb3.3418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 01/03/2024] [Accepted: 01/13/2024] [Indexed: 02/28/2024] Open
Abstract
Hypoxic environments like those present at high altitudes may negatively affect brain function. Varying levels of hypoxia, whether acute or chronic, are previously shown to impair cognitive function in humans. Assessment and prevention of such cognitive impairment require detection of cognitive changes and impairment using specific cognitive function assessment tools. This paper summarizes the findings of previous research, outlines the methods for cognitive function assessment used at a high altitude, elaborates the need to develop standardized and systematic cognitive function assessment tools for high-altitude hypoxia environments.
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Affiliation(s)
- Haojie Fan
- Department of PsychologyZhejiang Sci‐Tech UniversityHangzhouChina
- Department of Cognitive and StressBeijing Institute of Basic Medical SciencesBeijingChina
| | - Ying Meng
- Department of PsychologyZhejiang Sci‐Tech UniversityHangzhouChina
- Department of Cognitive and StressBeijing Institute of Basic Medical SciencesBeijingChina
| | - Lingling Zhu
- Department of Cognitive and StressBeijing Institute of Basic Medical SciencesBeijingChina
| | - Ming Fan
- Department of Cognitive and StressBeijing Institute of Basic Medical SciencesBeijingChina
- School of Information Sciences & EngineeringLanzhou UniversityLanzhouChina
| | - Du‐Ming Wang
- Department of PsychologyZhejiang Sci‐Tech UniversityHangzhouChina
| | - Yong‐Qi Zhao
- Department of PsychologyZhejiang Sci‐Tech UniversityHangzhouChina
- Department of Cognitive and StressBeijing Institute of Basic Medical SciencesBeijingChina
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Skinner BD, Lucas RAI, Lucas SJE. Exposure to passive heat and cold stress differentially modulates cerebrovascular-CO 2 responsiveness. J Appl Physiol (1985) 2024; 136:23-32. [PMID: 37969086 DOI: 10.1152/japplphysiol.00494.2023] [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: 07/20/2023] [Revised: 10/30/2023] [Accepted: 11/13/2023] [Indexed: 11/17/2023] Open
Abstract
Heat and cold stress influence cerebral blood flow (CBF) regulatory factors (e.g., arterial CO2 partial pressure). However, it is unclear whether the CBF response to a CO2 stimulus (i.e., cerebrovascular-CO2 responsiveness) is maintained under different thermal conditions. This study aimed to compare cerebrovascular-CO2 responsiveness between normothermia, passive heat, and cold stress conditions. Sixteen participants (8 females; 25 ± 7 yr) completed two experimental sessions (randomized) comprising normothermic and either passive heat or cold stress conditions. Middle and posterior cerebral artery velocity (MCAv, PCAv) were measured during rest, hypercapnia (5% CO2 inhalation), and hypocapnia (voluntary hyperventilation to an end-tidal CO2 of 30 mmHg). The linear slope of the cerebral blood velocity (CBv) response to changing end-tidal CO2 was calculated to measure cerebrovascular-CO2 responsiveness, and cerebrovascular conductance (CVC) was used to examine responsiveness independent of blood pressure. CBv-CVC-CO2 responsiveness to hypocapnia was greater during heat stress compared with cold stress (MCA: +0.05 ± 0.08 cm/s/mmHg/mmHg, P = 0.04; PCA: +0.02 ± 0.02 cm/s/mmHg/mmHg, P = 0.002). CBv-CO2 responsiveness to hypercapnia decreased during heat stress (MCA: -0.67 ± 0.89 cm/s/mmHg, P = 0.02; PCA: -0.64 ± 0.62 cm/s/mmHg; P = 0.01) and increased during cold stress (MCA: +0.98 ± 1.33 cm/s/mmHg, P = 0.03; PCA: +1.00 ± 0.82 cm/s/mmHg; P = 0.01) compared with normothermia. However, CBv-CVC-CO2 responsiveness to hypercapnia was not different between thermal conditions (P > 0.08). Overall, passive heat, but not cold, stress challenges the maintenance of cerebral perfusion. A greater cerebrovascular responsiveness to hypocapnia during heat stress likely reduces an already impaired cerebrovascular reserve capacity and may contribute to adverse events (e.g., syncope).NEW & NOTEWORTHY This study demonstrates that thermoregulatory-driven perfusion pressure changes, from either cold or heat stress, impact cerebrovascular responsiveness to hypercapnia. Compared with cold stress, heat stress poses a greater challenge to the maintenance of cerebral perfusion during hypocapnia, challenging cerebrovascular reserve capacity while increasing cerebrovascular-CO2 responsiveness. This likely exacerbates cerebral hypoperfusion during heat stress since hyperthermia-induced hyperventilation results in hypocapnia. No regional differences in middle and posterior cerebral artery responsiveness were found with thermal stress.
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Affiliation(s)
- Bethany D Skinner
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Rebekah A I Lucas
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Samuel J E Lucas
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom
- Centre for Human Brain Health, University of Birmingham, Birmingham, United Kingdom
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Wallace PJ, Hartley GL, Nowlan JG, Ljubanovich J, Sieh N, Taber MJ, Gagnon DD, Cheung SS. Endurance capacity impairment in cold air ranging from skin cooling to mild hypothermia. J Appl Physiol (1985) 2024; 136:58-69. [PMID: 37942528 DOI: 10.1152/japplphysiol.00663.2023] [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: 09/14/2023] [Revised: 10/20/2023] [Accepted: 11/06/2023] [Indexed: 11/10/2023] Open
Abstract
We tested the effects of cold air (0°C) exposure on endurance capacity to different levels of cold strain ranging from skin cooling to core cooling of Δ-1.0°C. Ten males completed a randomized, crossover, control study consisting of a cycling time to exhaustion (TTE) at 70% of their peak power output following: 1) 30-min of exposure to 22°C thermoneutral air (TN), 2) 30-min exposure to 0°C air leading to a cold shell (CS), 3) 0°C air exposure causing mild hypothermia of -0.5°C from baseline rectal temperature (HYPO-0.5°C), and 4) 0°C air exposure causing mild hypothermia of -1.0°C from baseline rectal temperature (HYPO-1.0°C). The latter three conditions tested TTE in 0°C air. Core temperature and seven-site mean skin temperature at the start of the TTE were: TN (37.0 ± 0.2°C, 31.2 ± 0.8°C), CS (37.1 ± 0.3°C, 25.5 ± 1.4°C), HYPO-0.5°C (36.6 ± 0.4°C, 22.3 ± 2.2°C), HYPO-1.0°C (36.4 ± 0.5°C, 21.4 ± 2.7°C). There was a significant condition effect (P ≤ 0.001) for TTE, which from TN (23.75 ± 13.75 min) to CS (16.22 ± 10.30 min, Δ-30.9 ± 21.5%, P = 0.055), HYPO-0.5°C (8.50 ± 5.23 min, Δ-61.4 ± 19.7%, P ≤ 0.001), and HYPO-1.0°C (6.50 ± 5.60 min, Δ-71.6 ± 16.4%, P ≤ 0.001). Furthermore, participants had a greater endurance capacity in CS compared with HYPO-0.5°C (P = 0.046), and HYPO-1.0°C (P = 0.007), with no differences between HYPO-0.5°C and HYPO-1.0°C (P = 1.00). Endurance capacity impairment at 70% peak power output occurs early in cold exposure with skin cooling, with significantly larger impairments with mild hypothermia up to Δ-1.0°C.NEW & NOTEWORTHY We developed a novel protocol that cooled skin temperature, or skin plus core temperature (Δ-0.5°C or Δ-1.0 °C), to determine a dose-response of cold exposure on endurance capacity at 70% peak power output. Skin cooling significantly impaired exercise tolerance time by ∼31%, whereas core cooling led to a further reduction of 30%-40% with no difference between Δ-0.5°C and Δ-1.0°C. Overall, simply cooling the skin impaired endurance capacity, but this impairment is further magnified by core cooling.
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Affiliation(s)
- Phillip J Wallace
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
| | - Geoffrey L Hartley
- Department of Physical and Health Education, Nipissing University, North Bay, Ontario, Canada
| | - Josh G Nowlan
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
| | - Johnathan Ljubanovich
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
| | - Nina Sieh
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
| | - Michael J Taber
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
- N2M Consulting Inc., St. Catharines, Ontario, Canada
| | - Dominique D Gagnon
- School of Kinesiology and Health Sciences, Laurentian University, Sudbury, Ontario, Canada
- Faculty of Sports and Health Sciences, University of Jyväskylä, Jyväskylä, Finland
- Clinic for Sports and Exercise Medicine, Department of Sports and Exercise Medicine, Faculty of Medicine, University of Helsinki Mäkelänkatu, Helsinki, Finland
| | - Stephen S Cheung
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
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Wallace PJ, Gagnon DD, Hartley GL, Taber MJ, Cheung SS. Effects of skin and mild core cooling on cognitive function in cold air in men. Physiol Rep 2023; 11:e15893. [PMID: 38114071 PMCID: PMC10730300 DOI: 10.14814/phy2.15893] [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: 11/02/2023] [Revised: 11/20/2023] [Accepted: 11/20/2023] [Indexed: 12/21/2023] Open
Abstract
This study tested the effects of skin and core cooling on cognitive function in 0°C cold air. Ten males completed a randomized, repeated measures study consisting of four environmental conditions: (i) 30 min of exposure to 22°C thermoneutral air (TN), (ii) 15 min to 0°C cold air which cooled skin temperature to ~27°C (CS), (iii) 0°C cold air exposure causing mild core cooling of ∆-0.3°C from baseline (C-0.3°C) and (iv) 0°C cold air exposure causing mild core cooling of ∆-0.8°C from baseline (C-0.8°C). Cognitive function (reaction time [ms] and errors made [#]) were tested using a simple reaction test, a two-six item working memory capacity task, and vertical flanker task to assess executive function. There were no condition effects (all p > 0.05) for number of errors made on any task. There were no significant differences in reaction time relative to TN for the vertical flanker and item working memory capacity task. However, simple reaction time was slower in C-0.3°C (297 ± 33 ms) and C-0.8°C (296 ± 41 ms) compared to CS (267 ± 26 ms) but not TN (274 ± 38). Despite small changes in simple reaction time (~30 ms), executive function and working memory was maintained in 0°C cold air with up to ∆-0.8°C reduction in core temperature.
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Affiliation(s)
- Phillip J. Wallace
- Environmental Ergonomics Laboratory, Department of KinesiologyBrock UniversitySt. CatharinesOntarioCanada
| | - Dominique D. Gagnon
- Faculty of Sports and Health SciencesUniversity of JyväskyläJyväskyläFinland
- Clinic for Sports and Exercise Medicine, Department of Sports and Exercise Medicine, Faculty of MedicineUniversity of Helsinki MäkelänkatuHelsinkiFinland
- School of Kinesiology and Health SciencesLaurentian UniversitySudburyOntarioCanada
| | - Geoffrey L. Hartley
- Department of Physical and Health EducationNipissing UniversityNorth BayOntarioCanada
| | - Michael J. Taber
- Environmental Ergonomics Laboratory, Department of KinesiologyBrock UniversitySt. CatharinesOntarioCanada
- NM Consulting Inc.St. CatharinesOntarioCanada
| | - Stephen S. Cheung
- Environmental Ergonomics Laboratory, Department of KinesiologyBrock UniversitySt. CatharinesOntarioCanada
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Bottenheft C, Groen EL, Mol D, Valk PJL, Houben MMJ, Kingma BRM, van Erp JBF. Effects of heat load and hypobaric hypoxia on cognitive performance: a combined stressor approach. ERGONOMICS 2023; 66:2148-2164. [PMID: 36916391 DOI: 10.1080/00140139.2023.2190062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Accepted: 03/05/2023] [Indexed: 06/18/2023]
Abstract
This study investigates how cognitive performance is affected by the combination of two stressors that are operationally relevant for helicopter pilots: heat load and hypobaric hypoxia. Fifteen participants were exposed to (1) no stressors, (2) heat load, (3) hypobaric hypoxia, and (4) combined heat load and hypobaric hypoxia. Hypobaric hypoxia (13,000 ft) was achieved in a hypobaric chamber. Heat load was induced by increasing ambient temperature to ∼28 °C. Cognitive performance was measured using two multitasks, and a vigilance task. Subjective and physiological data (oxygen saturation, heart rate, core- and skin temperature) were also collected. Mainly heat load caused cognitive performance decline. This can be explained by high subjective heat load and increased skin temperature, which takes away cognitive resources from the tasks. Only the arithmetic subtask was sensitive to hypobaric hypoxia, whereby hypobaric hypoxia caused a further performance decline in addition to the decline caused by heat load.Practitioner summary: Little is known about how multiple environmental stressors interact. This study investigates the combined effects of heat load and hypobaric hypoxia on cognitive performance. An additive effect of heat load and hypobaric hypoxia was found on a arithmetic task, which may be attributed to independent underlying mechanisms.
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Affiliation(s)
- Charelle Bottenheft
- Department of Human Performance, Unit Defence, Safety and Security, Netherlands Organisation for Applied Scientific Research (TNO), Soesterberg, Netherlands
- Human Media Interaction, Computer Science, University of Twente, Enschede, Netherlands
| | - Eric L Groen
- Department of Human Performance, Unit Defence, Safety and Security, Netherlands Organisation for Applied Scientific Research (TNO), Soesterberg, Netherlands
| | - Douwe Mol
- Department of Human Performance, Unit Defence, Safety and Security, Netherlands Organisation for Applied Scientific Research (TNO), Soesterberg, Netherlands
| | - Pierre J L Valk
- Department of Human Performance, Unit Defence, Safety and Security, Netherlands Organisation for Applied Scientific Research (TNO), Soesterberg, Netherlands
| | - Mark M J Houben
- Department of Human Performance, Unit Defence, Safety and Security, Netherlands Organisation for Applied Scientific Research (TNO), Soesterberg, Netherlands
| | - Boris R M Kingma
- Department of Human Performance, Unit Defence, Safety and Security, Netherlands Organisation for Applied Scientific Research (TNO), Soesterberg, Netherlands
| | - Jan B F van Erp
- Human Media Interaction, Computer Science, University of Twente, Enschede, Netherlands
- Department of Human Machine Teaming, Unit Defence, Safety and Security, Netherlands Organisation for Applied Scientific Research (TNO), Soesterberg, Netherlands
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Zhang D, Wang W, Li Z, Wang L, Liu D. Deciphering the lncRNA and mRNA profiles of Min pig backfat after acute cold stress. JOURNAL OF APPLIED ANIMAL RESEARCH 2022. [DOI: 10.1080/09712119.2022.2123811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Affiliation(s)
- Dongjie Zhang
- Institute of Animal Husbandry, Heilongjiang Academy of Agricultural Sciences, Harbin, Heilongjiang, P.R. People’s Republic of China
| | - Wentao Wang
- Institute of Animal Husbandry, Heilongjiang Academy of Agricultural Sciences, Harbin, Heilongjiang, P.R. People’s Republic of China
| | - Zhongqiu Li
- Institute of Animal Husbandry, Heilongjiang Academy of Agricultural Sciences, Harbin, Heilongjiang, P.R. People’s Republic of China
| | - Liang Wang
- Institute of Animal Husbandry, Heilongjiang Academy of Agricultural Sciences, Harbin, Heilongjiang, P.R. People’s Republic of China
| | - Di Liu
- Institute of Animal Husbandry, Heilongjiang Academy of Agricultural Sciences, Harbin, Heilongjiang, P.R. People’s Republic of China
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Cognition and Neuropsychological Changes at Altitude-A Systematic Review of Literature. Brain Sci 2022; 12:brainsci12121736. [PMID: 36552195 PMCID: PMC9775937 DOI: 10.3390/brainsci12121736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 12/05/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022] Open
Abstract
High-altitude (HA) exposure affects cognitive functions, but studies have found inconsistent results. The aim of this systematic review was to evaluate the effects of HA exposure on cognitive functions in healthy subjects. A structural overview of the applied neuropsychological tests was provided with a classification of superordinate cognitive domains. A literature search was performed using PubMed up to October 2021 according to PRISMA guidelines. Eligibility criteria included a healthy human cohort exposed to altitude in the field (at minimum 2440 m [8000 ft]) or in a hypoxic environment in a laboratory, and an assessment of cognitive domains. The literature search identified 52 studies (29 of these were field studies; altitude range: 2440 m-8848 m [8000-29,029 ft]). Researchers applied 112 different neuropsychological tests. Attentional capacity, concentration, and executive functions were the most frequently studied. In the laboratory, the ratio of altitude-induced impairments (64.7%) was twice as high compared to results showing no change or improved results (35.3%), but altitudes studied were similar in the chamber compared to field studies. In the field, the opposite results were found (66.4 % no change or improvements, 33.6% impairments). Since better acclimatization can be assumed in the field studies, the findings support the hypothesis that sufficient acclimatization has beneficial effects on cognitive functions at HA. However, it also becomes apparent that research in this area would benefit most if a consensus could be reached on a standardized framework of freely available neurocognitive tests.
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11
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Oliveira ALMB. Carotid bodies under a 'thermal' perspective: What 'season' is coming? J Physiol 2022; 600:4969-4971. [PMID: 36226699 DOI: 10.1113/jp283758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 10/07/2022] [Indexed: 01/05/2023] Open
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12
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Gibbons TD, Dempsey JA, Thomas KN, Ainslie PN, Wilson LC, Stothers TAM, Campbell HA, Cotter JD. Carotid body hyperexcitability underlies heat-induced hyperventilation in exercising humans. J Appl Physiol (1985) 2022; 133:1394-1406. [PMID: 36302157 DOI: 10.1152/japplphysiol.00435.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Physical activity is the most common source of heat strain for humans. The thermal strain of physical activity causes overbreathing (hyperventilation) and this has adverse physiological repercussions. The mechanisms underlying heat-induced hyperventilation during exercise are unknown, but recent evidence supports a primary role of carotid body hyperexcitability (increased tonic activity and sensitivity) underpinning hyperventilation in passively heated humans. In a repeated-measures crossover design, 12 healthy participants (6 female) completed two low-intensity cycling exercise conditions (25% maximal aerobic power) in randomized order, one with core temperature (TC) kept relatively stable near thermoneutrality, and the other with progressive heat strain to +2°C TC. To provide a complete examination of carotid body function under graded heat strain, carotid body tonic activity was assessed indirectly by transient hyperoxia, and its sensitivity estimated by responses to both isocapnic and poikilocapnic hypoxia. Carotid body tonic activity was increased by 220 ± 110% during cycling alone, and by 400 ± 290% with supplemental thermal strain to +1°C TC, and 600 ± 290% at +2°C TC (interaction, P = 0.0031). During exercise with heat stress at both +1°C and +2°C TC, carotid body suppression by hyperoxia decreased ventilation below the rates observed during exercise without heat stress (P < 0.0147). Carotid body sensitivity was increased by up to 230 ± 190% with exercise alone, and by 290 ± 250% with supplemental heating to +1°C TC and 510 ± 470% at +2°C TC (interaction, P = 0.0012). These data indicate that the carotid body is further activated and sensitized by heat strain during exercise and this largely explains the added drive to breathe.NEW & NOTEWORTHY Physical activity is the most common way humans increase their core temperature, and excess breathing in the heat can limit heat tolerance and performance, and may increase the risk of heat-related injury. Dose-dependent increases in carotid body tonic activity and sensitivity with core heating provide compelling evidence that carotid body hyperexcitability is the primary cause of heat-induced hyperventilation during exercise.
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Affiliation(s)
- Travis D Gibbons
- Centre for Heart, Lung and Vascular Health, University of British Columbia-Okanagan, School of Health and Exercise Science, Kelowna, British Columbia, Canada
| | - Jerome A Dempsey
- John Rankin Laboratory for Pulmonary Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin
| | - Kate N Thomas
- Department of Surgical Sciences, University of Otago, Dunedin, New Zealand
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, University of British Columbia-Okanagan, School of Health and Exercise Science, Kelowna, British Columbia, Canada
| | - Luke C Wilson
- Department of Medicine, University of Otago, Dunedin, New Zealand
| | - Tiarna A M Stothers
- School of Physical Education, Sport & Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Holly A Campbell
- Department of Surgical Sciences, University of Otago, Dunedin, New Zealand
| | - James D Cotter
- School of Physical Education, Sport & Exercise Sciences, University of Otago, Dunedin, New Zealand
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13
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Gibbons TD, Dempsey JA, Thomas KN, Campbell HA, Stothers TAM, Wilson LC, Ainslie PN, Cotter JD. Contribution of the carotid body to thermally mediated hyperventilation in humans. J Physiol 2022; 600:3603-3624. [PMID: 35731687 DOI: 10.1113/jp282918] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Accepted: 06/15/2022] [Indexed: 01/05/2023] Open
Abstract
Humans hyperventilate under heat and cold strain. This hyperventilatory response has detrimental consequences including acid-base dysregulation, dyspnoea, decreased cerebral blood flow and accelerated brain heating. The ventilatory response to hypoxia is exaggerated under whole-body heating and cooling, indicating that altered carotid body function might contribute to thermally mediated hyperventilation. To address whether the carotid body might contribute to heat- and cold-induced hyperventilation, we indirectly measured carotid body tonic activity via hyperoxia, and carotid body sensitivity via hypoxia, under graded heat and cold strain in 13 healthy participants in a repeated-measures design. We hypothesised that carotid body tonic activity and sensitivity would be elevated in a dose-dependent manner under graded heat and cold strain, thereby supporting its role in driving thermally mediated hyperventilation. Carotid body tonic activity was increased in a dose-dependent manner with heating, reaching 175% above baseline (P < 0.0005), and carotid body suppression with hyperoxia removed all of the heat-induced increase in ventilation (P = 0.9297). Core cooling increased carotid body activity by up to 250% (P < 0.0001), but maximal values were reached with mild cooling and thereafter plateaued. Carotid body sensitivity to hypoxia was profoundly increased by up to 180% with heat stress (P = 0.0097), whereas cooling had no detectable effect on hypoxic sensitivity. In summary, cold stress increased carotid body tonic activity and this effect was saturated with mild cooling, whereas heating had clear dose-dependent effects on carotid body tonic activity and sensitivity. These dose-dependent effects with heat strain indicate that the carotid body probably plays a primary role in driving heat-induced hyperventilation. KEY POINTS: Humans over-breathe (hyperventilate) when under heat and cold stress, and though this has detrimental physiological repercussions, the mechanisms underlying this response are unknown. The carotid body, a small organ that is responsible for driving hyperventilation in hypoxia, was assessed under incremental heat and cold strain. The carotid body drive to breathe, as indirectly assessed by transient hyperoxia, increased in a dose-dependent manner with heating, reaching 175% above baseline; cold stress similarly increased the carotid body drive to breathe, but did not show dose-dependency. Carotid body sensitivity, as indirectly assessed by hypoxic ventilatory responses, was profoundly increased by 70-180% with mild and severe heat strain, whereas cooling had no detectable effect. Carotid body hyperactivity and hypersensitivity are two interrelated mechanisms that probably underlie the increased drive to breathe with heat strain, whereas carotid body hyperactivity during mild cooling may play a subsidiary role in cold-induced hyperventilation.
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Affiliation(s)
- Travis D Gibbons
- School of Physical Education, Sport & Exercise Science, University of Otago, Dunedin, Otago, New Zealand.,Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - Jerome A Dempsey
- John Rankin Laboratory for Pulmonary Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
| | - Kate N Thomas
- Department of Surgical Sciences, University of Otago, Dunedin, Otago, New Zealand
| | - Holly A Campbell
- Department of Surgical Sciences, University of Otago, Dunedin, Otago, New Zealand
| | - Tiarna A M Stothers
- School of Physical Education, Sport & Exercise Science, University of Otago, Dunedin, Otago, New Zealand
| | - Luke C Wilson
- Department of Medicine, University of Otago, Dunedin, Otago, New Zealand
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada
| | - James D Cotter
- School of Physical Education, Sport & Exercise Science, University of Otago, Dunedin, Otago, New Zealand
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14
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Gulati T, Hatwar R, Unnikrishnan G, Rubio JE, Reifman J. A 3-D virtual human model for simulating heat and cold stress. J Appl Physiol (1985) 2022; 133:288-310. [PMID: 35736953 PMCID: PMC9359647 DOI: 10.1152/japplphysiol.00089.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In this study, we extended our previously developed anatomically detailed three-dimensional (3-D) thermoregulatory virtual human model for predicting heat stress to allow for predictions of heat and cold stress in one unified model. Starting with the modified Pennes bioheat transfer equation to estimate the spatiotemporal temperature distribution within the body as the underlying modeling structure, we developed a new formulation to characterize the spatial variation of blood temperature between body elements and within the limbs. We also implemented the means to represent heat generated from shivering and skin blood flow that apply to air exposure and water immersion. Then, we performed simulations and validated the model predictions with experimental data from nine studies, representing a wide range of heat- and cold-stress conditions in air and water and physical activities. We observed excellent agreement between model predictions and measured data, with average root mean squared errors of 0.2 °C for core temperature, 0.9 °C for mean skin temperature, and 27 W for heat from shivering. We found that a spatially varying blood temperature profile within the limbs was crucial to accurately predict core body temperature changes during very cold exposures. Our 3-D thermoregulatory virtual human model consistently predicted the body's thermal state accurately for each of the simulated hot and cold environmental conditions and exertional heat stress. As such, it serves as a reliable tool to assess whole-body, localized tissue, and, potentially, organ-specific injury risks, helping develop injury prevention and mitigation strategies in a systematic and expeditious manner.
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Affiliation(s)
- Tushar Gulati
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Development Command, Fort Detrick, Maryland, United States.,The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland, United States
| | - Rajeev Hatwar
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Development Command, Fort Detrick, Maryland, United States.,The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland, United States
| | - Ginu Unnikrishnan
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Development Command, Fort Detrick, Maryland, United States.,The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland, United States
| | - Jose E Rubio
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Development Command, Fort Detrick, Maryland, United States.,The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland, United States
| | - Jaques Reifman
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, United States Army Medical Research and Development Command, Fort Detrick, Maryland, United States
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15
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Schultz Martins R, Wallace PJ, Steele SW, Scott JS, Taber MJ, Hartley GL, Cheung SS. The Clamping of End-Tidal Carbon Dioxide Does Not Influence Cognitive Function Performance During Moderate Hyperthermia With or Without Skin Temperature Manipulation. Front Psychol 2021; 12:788027. [PMID: 35002880 PMCID: PMC8730541 DOI: 10.3389/fpsyg.2021.788027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 11/26/2021] [Indexed: 11/13/2022] Open
Abstract
Increases in body temperature from heat stress (i.e., hyperthermia) generally impairs cognitive function across a range of domains and complexities, but the relative contribution from skin versus core temperature changes remains unclear. Hyperthermia also elicits a hyperventilatory response that decreases the partial pressure of end-tidal carbon dioxide (PetCO2) and subsequently cerebral blood flow that may influence cognitive function. We studied the role of skin and core temperature along with PetCO2 on cognitive function across a range of domains. Eleven males completed a randomized, single-blinded protocol consisting of poikilocapnia (POIKI, no PetCO2 control) or isocapnia (ISO, PetCO2 maintained at baseline levels) during passive heating using a water-perfused suit (water temperature ~ 49°C) while middle cerebral artery velocity (MCAv) was measured continuously as an index of cerebral blood flow. Cognitive testing was completed at baseline, neutral core-hot skin (37.0 ± 0.2°C-37.4 ± 0.3°C), hot core-hot skin (38.6 ± 0.3°C-38.7 ± 0.2°C), and hot core-cooled skin (38.5 ± 0.3°C-34.7 ± 0.6°C). The cognitive test battery consisted of a detection task (psychomotor processing), 2-back task (working memory), set-shifting and Groton Maze Learning Task (executive function). At hot core-hot skin, poikilocapnia led to significant (both p < 0.05) decreases in PetCO2 (∆−21%) and MCAv (∆−26%) from baseline, while isocapnia clamped PetCO2 (∆ + 4% from baseline) leading to a significantly (p = 0.023) higher MCAv (∆−18% from baseline) compared to poikilocapnia. There were no significant differences in errors made on any task (all p > 0.05) irrespective of skin temperature or PetCO2 manipulation. We conclude that neither skin temperature nor PetCO2 maintenance significantly alter cognitive function during passive hyperthermia.
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Affiliation(s)
- Ricardo Schultz Martins
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada
| | - Phillip J. Wallace
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada
| | - Scott W. Steele
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada
| | - Jake S. Scott
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada
| | - Michael J. Taber
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada
- NM Consulting Inc., St. Catharines, ON, Canada
| | - Geoffrey L. Hartley
- Department of Physical and Health Education, Nipissing University, North Bay, ON, Canada
| | - Stephen S. Cheung
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada
- *Correspondence: Stephen S. Cheung,
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16
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Larson EA, Ely BR, Brunt VE, Francisco MA, Harris SM, Halliwill JR, Minson CT. Brachial and carotid hemodynamic response to hot water immersion in men and women. Am J Physiol Regul Integr Comp Physiol 2021; 321:R823-R832. [PMID: 34643115 DOI: 10.1152/ajpregu.00110.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This study sought to compare the brachial and carotid hemodynamic response to hot water immersion (HWI) between healthy young men and women. Ten women (W) and 11 men (M) (24 ± 4 yr) completed a 60-min HWI session immersed to the level of the sternum in 40°C water. Brachial and carotid artery hemodynamics (Doppler ultrasound) were measured at baseline (seated rest) and every 15 min throughout HWI. Within the brachial artery, total shear rate was elevated to a greater extent in women [+479 (+364, +594) s-1] than in men [+292 (+222, +361) s-1] during HWI (P = 0.005). As shear rate is inversely proportional to blood vessel diameter and directly proportional to blood flow velocity, the sex difference in brachial shear response to HWI was the result of a smaller brachial diameter among women at baseline (P < 0.0001) and throughout HWI (main effect of sex, P < 0.0001) and a greater increase in brachial velocity seen in women [+48 (+36, +61) cm/s] compared with men [+35 (+27, +43) cm/s] with HWI (P = 0.047) which allowed for a similar increase in brachial blood flow between sexes [M: +369 (+287, +451) mL/min, W: +364 (+243, +486) mL/min, P = 0.943]. In contrast, no differences were seen between sexes in carotid total shear rate, flow, velocity, or diameter at baseline or throughout HWI. These data indicate the presence of an artery-specific sex difference in the hemodynamic response to a single bout of HWI.
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Affiliation(s)
- Emily A Larson
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - Brett R Ely
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - Vienna E Brunt
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | | | - Sarianne M Harris
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - John R Halliwill
- Department of Human Physiology, University of Oregon, Eugene, Oregon
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17
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Coombs GB, Akins JD, Patik JC, Vizcardo-Galindo GA, Figueroa-Mujica R, Tymko MM, Stacey BS, Iannetelli A, Bailey DM, Villafuerte FC, Ainslie PN, Brothers RM. Global Reach 2018: Nitric oxide-mediated cutaneous vasodilation is reduced in chronic, but not acute, hypoxia independently of enzymatic superoxide formation. Free Radic Biol Med 2021; 172:451-458. [PMID: 34129928 DOI: 10.1016/j.freeradbiomed.2021.06.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 05/23/2021] [Accepted: 06/06/2021] [Indexed: 01/15/2023]
Abstract
We tested the hypotheses that 1) cutaneous microvascular function is impaired by acute normobaric and chronic hypobaric hypoxia and 2) that the superoxide free radical (via NADPH oxidase or xanthine oxidase) contributes to this impairment via nitric oxide (NO) scavenging. Local heating-induced cutaneous hyperemia (39 °C) was measured in the forearm of 11 male lowlanders at sea level (SL) and following 14-18 days at high altitude (HA; 4340 m in Cerro de Pasco, Peru), and compared to 11 highlanders residing permanently at this elevation. Cutaneous vascular conductance (CVC; laser-Doppler flux/mean arterial pressure) was not different during 39 °C [control site: 73 (19) vs. 71 (18)%max; P = 0.68] between normoxia and acute normobaric hypoxia (FIO2 = 0.125; equivalent to HA), respectively. At HA, CVC was reduced during 39 °C in lowlanders compared to SL [control site: 54 (14) vs. 73 (19)%max; P < 0.01] and was lower in Andean highlanders compared to lowlanders at HA [control site: 50 (24) vs. 54 (14)%max; P = 0.02]. The NO contribution to vasodilation during 39 °C (i.e., effect of NO synthase inhibition) was reduced in lowlanders at HA compared to SL [control site: 41 (11) vs 49 (10)%max; P = 0.04] and in Andean highlanders compared to lowlanders at HA [control site: 32 (21) vs. 41 (11)%max; P = 0.01]. Intradermal administration (cutaneous microdialysis) of the superoxide mimetic Tempol, inhibition of xanthine oxidase (via allopurinol), or NADPH oxidase (via apocynin) had no influence on cutaneous endothelium-dependent dilation during any of the conditions (all main effects of drug P > 0.05). These results suggest that time at HA impairs NO-mediated cutaneous vasodilation independent of enzymatic superoxide formation.
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Affiliation(s)
- Geoff B Coombs
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, BC, Canada; School of Kinesiology, University of Western Ontario, London, ON, Canada
| | - John D Akins
- Department of Kinesiology, University of Texas at Arlington, Arlington, TX, USA
| | - Jordan C Patik
- Department of Kinesiology, University of Texas at Arlington, Arlington, TX, USA; Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA
| | - Gustavo A Vizcardo-Galindo
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, BC, Canada; Departamento de Ciencias Biológicas y Fisiológicas, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Romulo Figueroa-Mujica
- Departamento de Ciencias Biológicas y Fisiológicas, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Michael M Tymko
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, BC, Canada; Neurovascular Health Laboratory, Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, AB, Canada
| | - Benjamin S Stacey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, United Kingdom
| | - Angelo Iannetelli
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, United Kingdom
| | - Damian M Bailey
- Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, United Kingdom
| | - Francisco C Villafuerte
- Departamento de Ciencias Biológicas y Fisiológicas, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - R Matthew Brothers
- Department of Kinesiology, University of Texas at Arlington, Arlington, TX, USA.
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18
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Costello JT, Wilkes M, Tipton MJ. From pigeon holes to descending spirals: a paradigm of physiology, cognitive performance and behaviour in extreme environments. Exp Physiol 2021; 106:1863-1864. [PMID: 34288179 DOI: 10.1113/ep089938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 07/16/2021] [Indexed: 11/08/2022]
Affiliation(s)
- Joseph T Costello
- Extreme Environments Laboratory, School of Sport, Health and Exercise Science, University of Portsmouth, Portsmouth, UK
| | - Matthew Wilkes
- Extreme Environments Laboratory, School of Sport, Health and Exercise Science, University of Portsmouth, Portsmouth, UK.,Current Health Ltd, Edinburgh, UK
| | - Michael J Tipton
- Extreme Environments Laboratory, School of Sport, Health and Exercise Science, University of Portsmouth, Portsmouth, UK
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19
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Gibbons TD, Ainslie PN, Thomas KN, Wilson LC, Akerman AP, Donnelly J, Campbell HA, Cotter JD. Influence of the mode of heating on cerebral blood flow, non-invasive intracranial pressure and thermal tolerance in humans. J Physiol 2021; 599:1977-1996. [PMID: 33586133 DOI: 10.1113/jp280970] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 02/01/2021] [Indexed: 12/22/2022] Open
Abstract
KEY POINTS The human brain is particularly vulnerable to heat stress; this manifests as impaired cognition, orthostatic tolerance, work capacity and eventually, brain death. The brain's limitation in the heat is often ascribed to inadequate cerebral blood flow (CBF), but elevated intracranial pressure is commonly observed in mammalian models of heat stroke and can on its own cause functional impairment. The CBF response to incremental heat strain was dependent on the mode of heating, decreasing by 30% when exposed passively to hot, humid air (sauna), while remaining unchanged or increasing with passive hot-water immersion (spa) and exercising in a hot environment. Non-invasive intracranial pressure estimates (nICP) were increased universally by 18% at volitional thermal tolerance across all modes of heat stress, and therefore may play a contributing role in eliciting thermal tolerance. The sauna, more so than the spa or exercise, poses a greater challenge to the brain under mild to severe heating due to lower blood flow but similarly increased nICP. ABSTRACT The human brain is particularly vulnerable to heat stress; this manifests as impaired cognitive function, orthostatic tolerance, work capacity, and eventually, brain death. This vulnerability is often ascribed to inadequate cerebral blood flow (CBF); however, elevated intracranial pressure (ICP) is also observed in mammalian models of heat stroke. We investigated the changes in CBF with incremental heat strain under three fundamentally different modes of heating, and assessed whether heating per se increased ICP. Fourteen fit participants (seven female) were heated to thermal tolerance or 40°C core temperature (Tc ; oesophageal) via passive hot-water immersion (spa), passive hot, humid air exposure (sauna), cycling exercise, and cycling exercise with CO2 inhalation to prevent heat-induced hypocapnia. CBF was measured with duplex ultrasound at each 0.5°C increment in Tc and ICP was estimated non-invasively (nICP) from optic nerve sheath diameter at thermal tolerance. At thermal tolerance, CBF was decreased by 30% in the sauna (P < 0.001), but was unchanged in the spa or with exercise (P ≥ 0.140). CBF increased by 17% when end-tidal P C O 2 was clamped at eupnoeic pressure (P < 0.001). On the contrary, nICP increased universally by 18% with all modes of heating (P < 0.001). The maximum Tc was achieved with passive heating, and preventing hypocapnia during exercise did not improve exercise or thermal tolerance (P ≥ 0.146). Therefore, the regulation of CBF is dramatically different depending on the mode and dose of heating, whereas nICP responses are not. The sauna, more so than the spa or exercise, poses a greater challenge to the brain under equivalent heat strain.
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Affiliation(s)
- Travis D Gibbons
- University of Otago, 55/47 Union St. W, Dunedin, Otago, 9016, New Zealand
| | - Philip N Ainslie
- University of British Columbia, Okangan Campus, Kelowna, BC, V1V 1V7, Canada
| | - Kate N Thomas
- University of Otago, 55/47 Union St. W, Dunedin, Otago, 9016, New Zealand
| | - Luke C Wilson
- University of Otago, 55/47 Union St. W, Dunedin, Otago, 9016, New Zealand
| | | | | | - Holly A Campbell
- University of Otago, 55/47 Union St. W, Dunedin, Otago, 9016, New Zealand
| | - Jim D Cotter
- University of Otago, 55/47 Union St. W, Dunedin, Otago, 9016, New Zealand
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20
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Strapazzon G, Putzer G, Dal Cappello T, Falla M, Braun P, Falk M, Glodny B, Pinggera D, Helbok R, Brugger H. Effects of hypothermia, hypoxia, and hypercapnia on brain oxygenation and hemodynamic parameters during simulated avalanche burial: a porcine study. J Appl Physiol (1985) 2020; 130:237-244. [PMID: 33151777 DOI: 10.1152/japplphysiol.00498.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Avalanche patients who are completely buried but still able to breathe are exposed to hypothermia, hypoxia, and hypercapnia (triple H syndrome). Little is known about how these pathological changes affect brain physiology. The study aim was to investigate the effect of hypothermia, hypoxia, and hypercapnia on brain oxygenation and systemic and cerebral hemodynamics. Anesthetized pigs were surface cooled to 28°C. Fraction of inspiratory oxygen ([Formula: see text]) was reduced to 17% and hypercapnia induced. Hemodynamic parameters and blood gas values were monitored. Cerebral measurements included cerebral perfusion pressure (CPP), brain tissue oxygen tension ([Formula: see text]), cerebral venous oxygen saturation ([Formula: see text]), and regional cerebral oxygen saturation (rSo2). Tests were interrupted when hemodynamic instability occurred or 60 min after hypercapnia induction. ANOVA for repeated measures was used to compare values across phases. There was no clinically relevant reduction in cerebral oxygenation ([Formula: see text], [Formula: see text], rSo2) during hypothermia and initial [Formula: see text] reduction. Hypercapnia was associated with an increase in pulmonary resistance followed by a decrease in cardiac output and CPP, resulting in hemodynamic instability and cerebral desaturation (decrease in [Formula: see text], [Formula: see text], rSo2). Hypercapnia may be the main cause of cardiovascular instability, which seems to be the major trigger for a decrease in cerebral oxygenation in triple H syndrome despite severe hypothermia.NEW & NOTEWORTHY Avalanche patients who are completely buried but still able to breathe are exposed to hypothermia, hypoxia, and hypercapnia (triple H syndrome). In a porcine model, there was no clinically relevant reduction in cerebral oxygenation during hypothermia and initial reduction of fraction of inspiratory oxygen ([Formula: see text]), as observed during hypercapnia. Hypercapnia may be the main cause of cardiovascular instability, which seems to be the major trigger for a decrease in cerebral oxygenation in triple H syndrome despite severe hypothermia.
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Affiliation(s)
- Giacomo Strapazzon
- Eurac Research, Institute of Mountain Emergency Medicine, Bolzano, Italy.,Department of Anaesthesiology and Critical Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
| | - Gabriel Putzer
- Department of Anaesthesiology and Critical Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
| | - Tomas Dal Cappello
- Eurac Research, Institute of Mountain Emergency Medicine, Bolzano, Italy
| | - Marika Falla
- Eurac Research, Institute of Mountain Emergency Medicine, Bolzano, Italy.,Centre for Mind/Brain Sciences (CIMeC), University of Trento, Italy
| | - Patrick Braun
- Department of Anaesthesiology and Critical Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
| | - Markus Falk
- Eurac Research, Institute of Mountain Emergency Medicine, Bolzano, Italy
| | - Bernhard Glodny
- Department of Radiology, Medical University of Innsbruck, Innsbruck, Austria
| | - Daniel Pinggera
- Department of Neurosurgery, Medical University of Innsbruck, Innsbruck, Austria
| | - Raimund Helbok
- Neurological Intensive Care Unit, Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
| | - Hermann Brugger
- Eurac Research, Institute of Mountain Emergency Medicine, Bolzano, Italy.,Department of Anaesthesiology and Critical Care Medicine, Medical University of Innsbruck, Innsbruck, Austria
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21
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Knekt P, Järvinen R, Rissanen H, Heliövaara M, Aromaa A. Does sauna bathing protect against dementia? Prev Med Rep 2020; 20:101221. [PMID: 33088678 PMCID: PMC7560162 DOI: 10.1016/j.pmedr.2020.101221] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 09/15/2020] [Accepted: 09/25/2020] [Indexed: 12/29/2022] Open
Abstract
Frequent sauna bathing predicted decreased risk of dementia in a cohort from Finland. Result was independent of several dementia risk factors, and was not modified by sex. Findings support suggested benefits of sauna and passive body heating in the brain.
Repeated heat exposure like sauna bathing is suggested to beneficially affect against dementia development. The epidemiological evidence is, however, scarce. Therefore, we studied the association between heat exposure during sauna bathing (i.e., the frequency of sauna bathing, frequency of heat sessions, length of stay in heat, sauna temperature) and the subsequent risk of dementia. A prospective cohort study was conducted based on 13,994 men and women aged 30–69 and free from dementia diagnosis from the Finnish Mobile Clinic Follow-up Survey. During a follow-up of 39 years, a total of 1805 dementia patients were diagnosed. The sauna bathing data was gathered from a questionnaire. Analyses based on the Cox model included the sauna bathing variables and the potential confounding factors. Sauna bathing frequency was related to a reduced risk of dementia after adjustment for the potential sociodemographic, lifestyle, and metabolic risk factors of dementia considered. The hazard ratio of dementia between individuals sauna bathing 9–12 times per month in comparison with those not sauna bathing or sauna bathing less than four times per month was 0.47 (95% CI = 0.25–0.88) during the first 20 years of follow-up and 0.81 (95% CI = 0.69–0.97) during the whole follow-up. The results are in line with the hypothesis that sauna bathing provides protection against dementia. Further studies are required to verify the suggested benefits of sauna bathing.
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Affiliation(s)
- Paul Knekt
- Finnish Institute for Health and Welfare, Helsinki, Finland
| | | | - Harri Rissanen
- Finnish Institute for Health and Welfare, Helsinki, Finland
| | | | - Arpo Aromaa
- Finnish Institute for Health and Welfare, Helsinki, Finland
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22
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Mugele H, Oliver SJ, Gagnon D, Lawley JS. Integrative crosstalk between hypoxia and the cold: Old data and new opportunities. Exp Physiol 2020; 106:350-358. [DOI: 10.1113/ep088512] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 06/25/2020] [Indexed: 12/20/2022]
Affiliation(s)
- Hendrik Mugele
- Department of Sport Science University of Innsbruck Innsbruck Austria
| | - Samuel J. Oliver
- Extremes Research Group School of Sport, Health and Exercise Sciences Bangor University Wales UK
| | - Daniel Gagnon
- Cardiovascular Prevention and Rehabilitation Centre Montreal Heart Institute Montréal Quebec Canada
- Department of Pharmacology and Physiology Faculty of Medicine Université de Montréal Montréal Quebec Canada
| | - Justin S. Lawley
- Department of Sport Science University of Innsbruck Innsbruck Austria
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23
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Chapman CL, Hess HW, Worley ML. Heterogeneous redistribution of cerebral oxygen delivery to combined thermal and hypoxic exposure. J Physiol 2019; 598:443-445. [PMID: 31856421 DOI: 10.1113/jp279311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Christopher L Chapman
- Center for Research and Education in Special Environments, University at Buffalo, Buffalo, NY, 14214, USA
| | - Hayden W Hess
- Center for Research and Education in Special Environments, University at Buffalo, Buffalo, NY, 14214, USA
| | - Morgan L Worley
- Center for Research and Education in Special Environments, University at Buffalo, Buffalo, NY, 14214, USA
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