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Burma JS, Roy MA, Kennedy CM, Labrecque L, Brassard P, Smirl JD. A systematic review, meta-analysis and meta-regression amalgamating the driven approaches used to quantify dynamic cerebral autoregulation. J Cereb Blood Flow Metab 2024; 44:1271-1297. [PMID: 38635887 DOI: 10.1177/0271678x241235878] [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] [Indexed: 04/20/2024]
Abstract
Numerous driven techniques have been utilized to assess dynamic cerebral autoregulation (dCA) in healthy and clinical populations. The current review aimed to amalgamate this literature and provide recommendations to create greater standardization for future research. The PubMed database was searched with inclusion criteria consisting of original research articles using driven dCA assessments in humans. Risk of bias were completed using Scottish Intercollegiate Guidelines Network and Methodological Index for Non-Randomized Studies. Meta-analyses were conducted for coherence, phase, and gain metrics at 0.05 and 0.10 Hz using deep-breathing, oscillatory lower body negative pressure (OLBNP), sit-to-stand maneuvers, and squat-stand maneuvers. A total of 113 studies were included, with 40 of these incorporating clinical populations. A total of 4126 participants were identified, with younger adults (18-40 years) being the most studied population. The most common techniques were squat-stands (n = 43), deep-breathing (n = 25), OLBNP (n = 20), and sit-to-stands (n = 16). Pooled coherence point estimates were: OLBNP 0.70 (95%CI:0.59-0.82), sit-to-stands 0.87 (95%CI:0.79-0.95), and squat-stands 0.98 (95%CI:0.98-0.99) at 0.05 Hz; and deep-breathing 0.90 (95%CI:0.81-0.99); OLBNP 0.67 (95%CI:0.44-0.90); and squat-stands 0.99 (95%CI:0.99-0.99) at 0.10 Hz. This review summarizes clinical findings, discusses the pros/cons of the 11 unique driven techniques included, and provides recommendations for future investigations into the unique physiological intricacies of dCA.
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Affiliation(s)
- Joel S Burma
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada
- Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Canada
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
- Integrated Concussion Research Program, University of Calgary, Calgary, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Canada
- Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Canada
| | - Marc-Antoine Roy
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, Canada
| | - Courtney M Kennedy
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada
- Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Canada
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
- Integrated Concussion Research Program, University of Calgary, Calgary, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Canada
- Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Canada
| | - Lawrence Labrecque
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, Canada
| | - Patrice Brassard
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, Canada
| | - Jonathan D Smirl
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada
- Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Canada
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
- Integrated Concussion Research Program, University of Calgary, Calgary, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Canada
- Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Canada
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Guo F, Wang C, Tao G, Ma H, Zhang J, Wang Y. A longitudinal study on the impact of high-altitude hypoxia on perceptual processes. Psychophysiology 2024; 61:e14548. [PMID: 38385977 DOI: 10.1111/psyp.14548] [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: 05/22/2023] [Revised: 02/05/2024] [Accepted: 02/07/2024] [Indexed: 02/23/2024]
Abstract
This study aimed to explore the neural mechanisms underlying high-altitude (HA) adaptation and deadaptation in perceptual processes in lowlanders. Eighteen healthy lowlanders were administered a facial S1-S2 matching task that included incomplete face (S1) and complete face (S2) photographs combined with ERP technology. Participants were tested at four time points: shortly before they departed the HA (Test 1), twenty-five days after entering the HA (Test 2), and one week (Test 3) and one month (Test 4) after returning to the lowlands. Compared with those at sea level (SL), shorter reaction times (RTs), shorter latencies of P1 and N170, and larger amplitudes of complete face N170 were found in HAs. After returning to SL, compared with that of HA, the amplitude of the incomplete face P1 was smaller after one week, and the complete face was smaller after one month. The right hemisphere N170 amplitude was greater after entering HA and one week after returning to SL than at baseline, but it returned to baseline after one month. Taken together, the current findings suggest that HA adaptation increases visual cortex excitation to accelerate perceptual processing. More mental resources are recruited during the configural encoding stage of complete faces after HA exposure. The perceptual processes affected by HA exposure are reversible after returning to SL, but the low-level processing stage differs between incomplete and complete faces due to neural compensation mechanisms. The configural encoding stage in the right hemisphere is affected by HA exposure and requires more than one week but less than one month to recover to baseline.
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Affiliation(s)
- Fumei Guo
- CAS Key Laboratory of Mental Health, Institute of Psychology, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Changming Wang
- Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, National Center for Neurological Disorders, Beijing, China
| | - Getong Tao
- CAS Key Laboratory of Mental Health, Institute of Psychology, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Hailin Ma
- Plateau Brain Science Research Center, Tibet University/South China Normal University, Guangzhou/Tibet, China
| | - Jiaxing Zhang
- Institute of Brain Diseases and Cognition, School of Medicine, Xiamen University, Xiamen, China
| | - Yan Wang
- CAS Key Laboratory of Mental Health, Institute of Psychology, Beijing, China
- Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
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Liu Y, Yuan F, Peng Z, Zhan Y, Lin J, Zhang R, Zhang J. Decrease in Cerebral Blood Flow after Reoxygenation Is Associated with Neurological Syndrome Sequelae and Blood Pressure. Brain Sci 2023; 13:1600. [PMID: 38002559 PMCID: PMC10669967 DOI: 10.3390/brainsci13111600] [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: 09/28/2023] [Revised: 10/30/2023] [Accepted: 11/06/2023] [Indexed: 11/26/2023] Open
Abstract
Changes in cerebral blood flow (CBF) and regulation of cerebral circulation occur at high altitude (HA). However, the changes in CBF and their associations with neurological syndrome sequelae and blood pressure after subjects return to the lowlands remain unclear. In this study, the subjects were 23 college students who were teaching at an altitude of 4300 m for 30 days. These subjects were studied before reaching the HA (Test 1), one week after returning to the lowlands (Test 2), and three months after returning to the lowlands (Test 3). Symptom scores for de-acclimatization syndrome were evaluated. Changes in CBF were measured using the magnetic resonance imaging arterial spin labeling (ASL) technique. Additionally, the velocity of CBF in the cerebral arteries was measured using a transcranial doppler (TCD). In Test 2 vs. Test 1, the peak systolic velocity and mean velocity in the basilar artery were significantly decreased. CBF exhibited significant decreases in the left putamen/cerebellum crus1/vermis and right thalamus/inferior temporal gyrus, while significant increases were observed in the left postcentral gyrus/precuneus and right middle cingulate gyrus/superior frontal gyrus. In Test 3 vs. Test 1, the basilar artery velocity returned to the baseline level, while CBF continued to decrease. The mean global CBF showed a decreasing trend from Test 1 to Test 3. Furthermore, the mean global CBF had a negative correlation with the systolic pressure, pulse pressure, and mean arterial pressure. The decrease in CBF after reoxygenation may underlie the neurological symptoms in subjects returning to the lowlands. Increased blood pressure could serve as a predictor of a decrease in CBF.
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Affiliation(s)
- Yanqiu Liu
- Institute of Brain Diseases and Cognition, School of Medicine, Xiamen University, Xiamen 361102, China
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Xiamen University, Xiamen 361102, China
| | - Fengjuan Yuan
- Institute of Brain Diseases and Cognition, School of Medicine, Xiamen University, Xiamen 361102, China
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Xiamen University, Xiamen 361102, China
| | - Zhongwei Peng
- Department of Neurology, Zhongshan Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen 361004, China
| | - Yadong Zhan
- Institute of Brain Diseases and Cognition, School of Medicine, Xiamen University, Xiamen 361102, China
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Xiamen University, Xiamen 361102, China
| | - Jianzhong Lin
- Department of Radiology, Zhongshan Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen 361004, China
| | - Ran Zhang
- Institute of Brain Diseases and Cognition, School of Medicine, Xiamen University, Xiamen 361102, China
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Xiamen University, Xiamen 361102, China
| | - Jiaxing Zhang
- Institute of Brain Diseases and Cognition, School of Medicine, Xiamen University, Xiamen 361102, China
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Xiamen University, Xiamen 361102, China
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Xu Z, Li Q, Shen X. AZU1 (HBP/CAP37) and PRKCG (PKC-gamma) may be candidate genes affecting the severity of acute mountain sickness. BMC Med Genomics 2023; 16:28. [PMID: 36803152 PMCID: PMC9940399 DOI: 10.1186/s12920-023-01457-3] [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: 10/14/2022] [Accepted: 02/13/2023] [Indexed: 02/22/2023] Open
Abstract
BACKGROUND Acute Mountain Sickness (AMS) is one of the diseases that predispose to sudden ascent to high altitudes above 2500 m. Among the many studies on the occurrence and development of AMS, there are few studies on the severity of AMS. Some unidentified phenotypes or genes that determine the severity of AMS may be vital to elucidating the mechanisms of AMS. This study aims to explore the underlying genes or phenotypes associated with AMS severity and to provide evidence for a better understanding of the mechanisms of AMS. METHODS GSE103927 dataset was downloaded from the Gene Expression Omnibus database, and a total of 19 subjects were enrolled in the study. Subjects were divided into a moderate to severe AMS (MS-AMS, 9 subjects) group and a no or mild AMS (NM-AMS, 10 subjects) group based on the Lake Louise score (LLS). Various bioinformatics analyses were used to compare the differences between the two groups. Another dataset, Real-time quantitative PCR (RT-qPCR), and another grouping method were used to validate the analysis results. RESULT No statistically significant differences in phenotypic and clinical data existed between the MS-AMS and NM-AMS groups. Eight differential expression genes are associated with LLS, and their biological functions are related regulating of the apoptotic process and programmed cell death. The ROC curves showed that AZU1 and PRKCG had a better predictive performance for MS-AMS. AZU1 and PRKCG were significantly associated with the severity of AMS. The expression of AZU1 and PRKCG were significantly higher in the MS-AMS group compared to the NM-AMS group. The hypoxic environment promotes the expression of AZU1 and PRKCG. The results of these analyses were validated by an alternative grouping method and RT-qPCR results. AZU1 and PRKCG were enriched in the Neutrophil extracellular trap formation pathway, suggesting the importance of this pathway in influencing the severity of AMS. CONCLUSION AZU1 and PRKCG may be key genes influencing the severity of acute mountain sickness, and can be used as good diagnostic or predictive indicators of the severity of AMS. Our study provides a new perspective to explore the molecular mechanism of AMS.
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Affiliation(s)
- Zhichao Xu
- grid.263826.b0000 0004 1761 0489Key Laboratory of Environmental Medicine Engineering, Ministry of Education, School of Public Health, Southeast University, Nanjing, Jiangsu Province China ,grid.263826.b0000 0004 1761 0489Department of Epidemiology and Health Statistics, School of Public Health, Southeast University, Nanjing, Jiangsu Province China
| | - Qiong Li
- grid.263826.b0000 0004 1761 0489Key Laboratory of Environmental Medicine Engineering, Ministry of Education, School of Public Health, Southeast University, Nanjing, Jiangsu Province China ,grid.263826.b0000 0004 1761 0489Department of Epidemiology and Health Statistics, School of Public Health, Southeast University, Nanjing, Jiangsu Province China
| | - Xiaobing Shen
- Key Laboratory of Environmental Medicine Engineering, Ministry of Education, School of Public Health, Southeast University, Nanjing, Jiangsu Province, China. .,Department of Epidemiology and Health Statistics, School of Public Health, Southeast University, Nanjing, Jiangsu Province, China.
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Fabries P, Gomez-Merino D, Sauvet F, Malgoyre A, Koulmann N, Chennaoui M. Sleep loss effects on physiological and cognitive responses to systemic environmental hypoxia. Front Physiol 2022; 13:1046166. [PMID: 36579023 PMCID: PMC9792101 DOI: 10.3389/fphys.2022.1046166] [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: 09/30/2022] [Accepted: 11/29/2022] [Indexed: 12/15/2022] Open
Abstract
In the course of their missions or training, alpinists, but also mountain combat forces and mountain security services, professional miners, aircrew, aircraft and glider pilots and helicopter crews are regularly exposed to altitude without oxygen supplementation. At altitude, humans are exposed to systemic environmental hypoxia induced by the decrease in barometric pressure (<1,013 hPa) which decreases the inspired partial pressure of oxygen (PIO2), while the oxygen fraction is constant (equal to approximately 20.9%). Effects of altitude on humans occur gradually and depend on the duration of exposure and the altitude level. From 1,500 m altitude (response threshold), several adaptive responses offset the effects of hypoxia, involving the respiratory and the cardiovascular systems, and the oxygen transport capacity of the blood. Fatigue and cognitive and sensory disorders are usually observed from 2,500 m (threshold of prolonged hypoxia). Above 3,500 m (the threshold for disorders), the effects are not completely compensated and maladaptive responses occur and individuals develop altitude headache or acute altitude illness [Acute Mountain Sickness (AMS)]. The magnitude of effects varies considerably between different physiological systems and exhibits significant inter-individual variability. In addition to comorbidities, the factors of vulnerability are still little known. They can be constitutive (genetic) or circumstantial (sleep deprivation, fatigue, speed of ascent.). In particular, sleep loss, a condition that is often encountered in real-life settings, could have an impact on the physiological and cognitive responses to hypoxia. In this review, we report the current state of knowledge on the impact of sleep loss on responses to environmental hypoxia in humans, with the aim of identifying possible consequences for AMS risk and cognition, as well as the value of behavioral and non-pharmacological countermeasures.
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Affiliation(s)
- Pierre Fabries
- REF-Aero Department, French Armed Forces Biomedical Research Institute—IRBA, Brétigny-sur-Orge, France,Laboratoire de Biologie de l’Exercice pour la Performance et la Santé (LBEPS), UMR, Université Paris-Saclay, IRBA, Evry-Courcouronnes, France,French Military Health Academy—Ecole du Val-de-Grâce, Place Alphonse Laveran, Paris, France,*Correspondence: Pierre Fabries,
| | - Danielle Gomez-Merino
- REF-Aero Department, French Armed Forces Biomedical Research Institute—IRBA, Brétigny-sur-Orge, France,Vigilance Fatigue Sommeil et Santé Publique (VIFASOM) URP 7330, Université de Paris Cité, Paris, France
| | - Fabien Sauvet
- REF-Aero Department, French Armed Forces Biomedical Research Institute—IRBA, Brétigny-sur-Orge, France,French Military Health Academy—Ecole du Val-de-Grâce, Place Alphonse Laveran, Paris, France,Vigilance Fatigue Sommeil et Santé Publique (VIFASOM) URP 7330, Université de Paris Cité, Paris, France
| | - Alexandra Malgoyre
- REF-Aero Department, French Armed Forces Biomedical Research Institute—IRBA, Brétigny-sur-Orge, France,Laboratoire de Biologie de l’Exercice pour la Performance et la Santé (LBEPS), UMR, Université Paris-Saclay, IRBA, Evry-Courcouronnes, France
| | - Nathalie Koulmann
- Laboratoire de Biologie de l’Exercice pour la Performance et la Santé (LBEPS), UMR, Université Paris-Saclay, IRBA, Evry-Courcouronnes, France,French Military Health Academy—Ecole du Val-de-Grâce, Place Alphonse Laveran, Paris, France
| | - Mounir Chennaoui
- REF-Aero Department, French Armed Forces Biomedical Research Institute—IRBA, Brétigny-sur-Orge, France,Vigilance Fatigue Sommeil et Santé Publique (VIFASOM) URP 7330, Université de Paris Cité, Paris, France
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Kennedy CM, Burma JS, Newel KT, Brassard P, Smirl JD. Time course recovery of cerebral blood velocity metrics post aerobic exercise: A systematic review. J Appl Physiol (1985) 2022; 133:471-489. [PMID: 35708702 DOI: 10.1152/japplphysiol.00630.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Currently, the standard approach for restricting exercise prior to cerebrovascular data collection varies widely between 6-24 hours. This universally employed practice is a conservative approach to safeguard physiological alterations that could potentially confound one's study design. Therefore, the purpose of this systematic review was to amalgamate the literature that examines the extent and duration cerebrovascular function is impacted following aerobic exercise measured via transcranial Doppler ultrasound. Further, an exploratory aim was to scrutinize and discuss common biases/limitations in the previous studies to help guide future investigations. Search strategies were developed and imported into PubMed, SPORTDiscus, and Medline databases. A total of 595 records were screened and 35 articles met the inclusion criteria in this review, which included assessments of basic cerebrovascular metrics (n=35), dynamic cerebral autoregulation (dCA; n=9), neurovascular coupling (NVC; n=2); and/or cerebrovascular reactivity (CVR-CO2; n=1) following acute bouts of aerobic exercise. Across all studies, it was found NVC was impacted for 1-hour, basic cerebrovascular parameters and CVR-CO2 parameters 2-hours, and dCA metrics 6-hours post-exercise. Therefore, future studies can provide participants with these evidence-based time restrictions, regarding the minimum time to abstain from exercise prior to data collection. However, it should be noted, other physiological mechanisms could still be altered (e.g., metabolic, hormonal, and/or autonomic influences), despite cerebrovascular function returning to baseline levels. Thus, future investigations should seek to control for as many physiological influences when employing cerebrovascular assessments, immediately following these time restraints. The main limitations/biases were lack of female participants, cardiorespiratory fitness, and consideration for vessel diameter.
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Affiliation(s)
- Courtney M Kennedy
- Cerebrovascular Concussion Lab, Faculty of Kinesiology, University of Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, AB, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada
| | - Joel S Burma
- Cerebrovascular Concussion Lab, Faculty of Kinesiology, University of Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, AB, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada
| | - Kailey T Newel
- Cerebrovascular Concussion Lab, Faculty of Kinesiology, University of Calgary, Alberta, Canada.,Faculty of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Patrice Brassard
- Department of Kinesiology, Université Laval, Québec, Québec, Canada.,Research center of the Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Québec, Canada
| | - Jonathan David Smirl
- Cerebrovascular Concussion Lab, Faculty of Kinesiology, University of Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, AB, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada
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An acute bout of controlled subconcussive impacts can alter dynamic cerebral autoregulation indices: a preliminary investigation. Eur J Appl Physiol 2022; 122:1059-1070. [PMID: 35171333 DOI: 10.1007/s00421-022-04908-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 02/01/2022] [Indexed: 11/03/2022]
Abstract
OBJECTIVES There is growing concern repetitive head contacts sustained by soccer players may lead to long-term health ramifications. Therefore, this preliminary investigation examined the impact an acute soccer heading bout has on dynamic cerebral autoregulation (dCA) metrics. METHODS In this preliminary investigation, 40 successful soccer headers were performed in 20 min by 7 male elite soccer players (24.1 ± 1.5 years). Soccer balls were launched at 77.5 ± 3.7 km/h from JUGS soccer machine, located 35 m away from participants. Linear and rotational head accelerations impacts were measured using an accelerometer (xPatch). The SCAT3 indexed concussion symptom score and severity before and after: soccer headers, sham (body contact only), and control conditions. Squat-stand maneuvers were performed at 0.05 Hz and 0.10 Hz to quantity dCA through measures of coherence, phase, and gain. RESULTS Cumulative linear and rotational accelerations during soccer headers were 1574 ± 97.9 g and 313,761 ± 23,966 rads/s2, respectively. SCAT3 symptom severity was elevated after the soccer heading bout (pre 3.7 ± 3.6, post 9.4 ± 7.6: p = 0.030) and five of the seven participants reported an increase in concussion-like symptoms (pre: 2.6 ± 3.0, post: 6.7 ± 6.2; p = 0.078). Phase at 0.10 Hz was elevated following soccer heading (p = 0.008). No other dCA metric differed following the three conditions. CONCLUSION These preliminary results indicate an acute bout of soccer heading resulted in alterations to dCA metrics. Therefore, future research with larger sample sizes is warranted to fully comprehend short- and long-term physiological changes related to soccer heading.
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A prospective cohort study about the effect of repeated living high and working higher on cerebral autoregulation in unacclimatized lowlanders. Sci Rep 2022; 12:2472. [PMID: 35169168 PMCID: PMC8847624 DOI: 10.1038/s41598-022-06270-z] [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: 06/14/2021] [Accepted: 01/10/2022] [Indexed: 11/08/2022] Open
Abstract
Cerebral autoregulation (CA) is impaired during acute high-altitude (HA) exposure, however, effects of temporarily living high and working higher on CA require further investigation. In 18 healthy lowlanders (11 women), we hypothesized that the cerebral autoregulation index (ARI) assessed by the percentage change in middle cerebral artery peak blood velocity (Δ%MCAv)/percentage change in mean arterial blood pressure (Δ%MAP) induced by a sit-to-stand maneuver, is (i) reduced on Day1 at 5050 m compared to 520 m, (ii) is improved after 6 days at 5050 m, and (iii) is less impaired during re-exposure to 5050 m after 7 days at 520 m compared to Cycle1. Participants spent 4-8 h/day at 5050 m and slept at 2900 m similar to real-life working shifts. High/low ARI indicate impaired/intact CA, respectively. With the sit-to-stand at 520 m, mean (95% CI) in ΔMAP and ΔMCAv were - 26% (- 41 to - 10) and - 13% (- 19 to - 7), P < 0.001 both comparisons; mean ± SD in ARI was 0.58 ± 2.44Δ%/Δ%, respectively. On Day1 at 5050 m, ARI worsened compared to 520 m (3.29 ± 2.42Δ%/Δ%), P = 0.006 but improved with acclimatization (1.44 ± 2.43Δ%/Δ%, P = 0.039). ARI was less affected during re-exposure to 5050 m (1.22 ± 2.52Δ%/Δ%, P = 0.027 altitude-induced change between sojourns). This study showed that CA (i) is impaired during acute HA exposure, (ii) improves with living high, working higher and (iii) is ameliorated during re-exposure to HA.
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Burma JS, Kennedy CM, Penner LC, Miutz LN, Galea OA, Ainslie PN, Smirl JD. Long-term heart transplant recipients: heart rate-related effects on augmented transfer function coherence during repeated squat-stand maneuvers in males. Am J Physiol Regul Integr Comp Physiol 2021; 321:R925-R937. [PMID: 34730005 DOI: 10.1152/ajpregu.00177.2021] [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: 11/22/2022]
Abstract
Previous research has highlighted that squat-stand maneuvers (SSMs) augment coherence values within the cerebral pressure-flow relationship to ∼0.99. However, it is not fully elucidated if mean arterial pressure (MAP) leads to this physiological entrainment independently, or if heart rate (HR) and/or the partial pressure of carbon dioxide (Pco2) also have contributing influences. A 2:1 control-to-case model was used in the present investigation [participant number (n) = 40; n = 16 age-matched (AM); n = 16 donor control (DM); n = 8 heart transplant recipients (HTRs)]. The latter group was used to mechanistically isolate the extent to which HR influences the cerebral pressure-flow relationship. Participants completed 5 min of squat-stand maneuvers at 0.05 Hz (10 s) and 0.10 Hz (5 s). Linear transfer function analysis (TFA) examined the relationship between different physiological inputs (i.e., MAP, HR, and Pco2) and output [cerebral blood velocity (CBV)] during SSM; and cardiac baroreceptor sensitivity (BRS). Compared with DM, cardiac BRS was reduced in AM (P < 0.001), which was further reduced in HTR (P < 0.045). In addition, during the SSM, HR was elevated in HTR compared with both control groups (P < 0.001), but all groups had near-maximal coherence metrics ≥0.98 at 0.05 Hz and ≥0.99 at 0.10 Hz (P ≥ 0.399). In contrast, the mean HR-CBV/Pco2-CBV relationships ranged from 0.38 (HTR) to 0.81 (DM). Despite near abolishment of BRS and blunted HR following heart transplantation, long-term HTR exhibited near-maximal coherence within the MAP-CBV relationship, comparable with AM and DM. Therefore, these results show that the augmented coherence with SSM is driven by blood pressure, whereas elevations in TFA coherence as a result of HR contribution are likely correlational in nature.
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Affiliation(s)
- Joel S Burma
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada
| | - Courtney M Kennedy
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada
| | - Linden C Penner
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada
| | - Lauren N Miutz
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada
| | - Olivia A Galea
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia, Kelowna, British Columbia, Canada
| | - Jonathan D Smirl
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada.,Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia, Kelowna, British Columbia, Canada
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10
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Barnes SC, Haunton VJ, Beishon L, Llwyd O, Robinson TG, Panerai RB. Extremes of cerebral blood flow during hypercapnic squat-stand maneuvers. Physiol Rep 2021; 9:e15021. [PMID: 34617685 PMCID: PMC8495794 DOI: 10.14814/phy2.15021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 08/04/2021] [Accepted: 08/09/2021] [Indexed: 11/24/2022] Open
Abstract
Squat-stand maneuvers (SSMs) are a popular method of inducing blood pressure (BP) oscillations to reliably assess dynamic cerebral autoregulation (dCA), but their effects on the cerebral circulation remain controversial. We designed a protocol whereby participants would perform SSMs under hypercapnic conditions. Alarmingly high values of cerebral blood flow velocity (CBFV) were recorded, leading to early study termination after the recruitment of a single participant. One healthy subject underwent recordings at rest (5 min sitting, 5 min standing) and during two SSMs (fixed and random frequency). Two sets of recordings were collected; one while breathing room air, one while breathing 5% CO2 . Continuous recordings of bilateral CBFV (transcranial Doppler), heart rate (ECG), BP (Finometer), and end-tidal CO2 (capnography) were collected. Peak values of systolic CBFV were significantly higher during hypercapnia (p < 0.01), and maximal values exceeded 200 cm.s-1 . Estimates of dCA (ARI) during hypercapnia were impaired relative to poikilocapnia (p = 0.03). The phase was significantly reduced under hypercapnic conditions (p = 0.03). Here we report extremely high values of CBFV in response to repeated SSMs during induced hypercapnia, in an otherwise healthy subject. Our findings suggest that protocols performing hypercapnic SSMs are potentially dangerous. We, therefore, urge caution if other research groups plan to undertake similar protocols.
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Affiliation(s)
- Samuel C. Barnes
- Department of Cardiovascular SciencesUniversity of LeicesterLeicesterUK
| | - Victoria J. Haunton
- Department of Cardiovascular SciencesUniversity of LeicesterLeicesterUK
- National Institute for Health Research (NIHR) Leicester Biomedical Research CentreUniversity of LeicesterLeicesterUK
| | - Lucy Beishon
- Department of Cardiovascular SciencesUniversity of LeicesterLeicesterUK
| | - Osian Llwyd
- Department of Cardiovascular SciencesUniversity of LeicesterLeicesterUK
| | - Thompson G. Robinson
- Department of Cardiovascular SciencesUniversity of LeicesterLeicesterUK
- National Institute for Health Research (NIHR) Leicester Biomedical Research CentreUniversity of LeicesterLeicesterUK
| | - Ronney B. Panerai
- Department of Cardiovascular SciencesUniversity of LeicesterLeicesterUK
- National Institute for Health Research (NIHR) Leicester Biomedical Research CentreUniversity of LeicesterLeicesterUK
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11
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Labrecque L, Smirl JD, Brassard P. Utilization of the repeated squat-stand model for studying the directional sensitivity of the cerebral pressure-flow relationship. J Appl Physiol (1985) 2021; 131:927-936. [PMID: 34264130 DOI: 10.1152/japplphysiol.00269.2021] [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] [Indexed: 02/08/2023] Open
Abstract
Hysteresis in the cerebral pressure-flow relationship describes the superior ability of the cerebrovasculature to buffer cerebral blood flow changes when mean arterial pressure (MAP) increases compared with when MAP decreases. This phenomenon can be evaluated by comparing the change in middle cerebral artery mean blood velocity (MCAv) per change in MAP during either acute increases or decreases in MAP induced by repeated squat-stands (RSS). However, no real baseline can be used for this particular protocol as there is no true stable reference point. Herein, we characterized a novel metric using the greatest MAP oscillations induced by RSS without using an independent baseline value and adjusted for time intervals (ΔMCAvT/ΔMAPT). We also examined whether this metric during each RSS transition was comparable between each other over a 5-min period. ΔMCAvT/ΔMAPT was calculated using the minimum to maximum MCAv and MAP for each RSS performed at 0.05 Hz and 0.10 Hz. We compared averaged ΔMCAvT/ΔMAPT during MAP increases and decreases in 74 healthy participants [9 women; 26 (20-74) yr]. ΔMCAvT/ΔMAPT was lower for MAP increases than MAP decreases at 0.10 Hz RSS only (0.91 ± 0.34 vs. 1.01 ± 0.44 cm·s-1/mmHg; P = 0.0013). For both frequency and MAP direction, time during RSS had no effect on ΔMCAvT/ΔMAPT. This novel analytical method supports the use of the RSS model to evaluate the directional sensitivity of the pressure-flow relationship. These results contribute to the importance of considering the direction of MAP changes, depending on the oscillations frequency when evaluating dynamic cerebral autoregulation.NEW & NOTEWORTHY Repeated squat-stand maneuvers are able to examine the directional sensitivity of the cerebral pressure-flow relationship. These maneuvers induce stable physiological cyclic changes where brain blood flow changes with blood pressure increases are buffered more than blood pressure decreases. These results highlight the importance of considering directional blood pressure changes within cerebral autoregulation.
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Affiliation(s)
- Lawrence Labrecque
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec City, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec City, Québec, Canada
| | - Jonathan D Smirl
- Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Concussion Research Laboratory, Faculty of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada
| | - Patrice Brassard
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec City, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec City, Québec, Canada
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12
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Anderson GK, Rosenberg AJ, Barnes HJ, Bird J, Pentz B, Byman BRM, Jendzjowsky N, Wilson RJA, Day TA, Rickards CA. Peaks and valleys: oscillatory cerebral blood flow at high altitude protects cerebral tissue oxygenation. Physiol Meas 2021; 42:10.1088/1361-6579/ac0593. [PMID: 34038879 PMCID: PMC11046575 DOI: 10.1088/1361-6579/ac0593] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 05/26/2021] [Indexed: 01/21/2023]
Abstract
Introduction.Oscillatory patterns in arterial pressure and blood flow (at ∼0.1 Hz) may protect tissue oxygenation during conditions of reduced cerebral perfusion and/or hypoxia. We hypothesized that inducing oscillations in arterial pressure and cerebral blood flow at 0.1 Hz would protect cerebral blood flow and cerebral tissue oxygen saturation during exposure to a combination of simulated hemorrhage and sustained hypobaric hypoxia.Methods.Eight healthy human subjects (4 male, 4 female; 30.1 ± 7.6 year) participated in two experiments at high altitude (White Mountain, California, USA; altitude, 3800 m) following rapid ascent and 5-7 d of acclimatization: (1) static lower body negative pressure (LBNP, control condition) was used to induce central hypovolemia by reducing chamber pressure to -60 mmHg for 10 min(0 Hz), and; (2) oscillatory LBNP where chamber pressure was reduced to -60 mmHg, then oscillated every 5 s between -30 mmHg and -90 mmHg for 10 min(0.1 Hz). Measurements included arterial pressure, internal carotid artery (ICA) blood flow, middle cerebral artery velocity (MCAv), and cerebral tissue oxygen saturation (ScO2).Results.Forced 0.1 Hz oscillations in mean arterial pressure and mean MCAv were accompanied by a protection of ScO2(0.1 Hz: -0.67% ± 1.0%; 0 Hz: -4.07% ± 2.0%;P = 0.01). However, the 0.1 Hz profile did not protect against reductions in ICA blood flow (0.1 Hz: -32.5% ± 4.5%; 0 Hz: -19.9% ± 8.9%;P = 0.24) or mean MCAv (0.1 Hz: -18.5% ± 3.4%; 0 Hz: -15.3% ± 5.4%;P = 0.16).Conclusions.Induced oscillatory arterial pressure and cerebral blood flow led to protection of ScO2during combined simulated hemorrhage and sustained hypoxia. This protection was not associated with the preservation of cerebral blood flow suggesting preservation of ScO2may be due to mechanisms occurring within the microvasculature.
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Affiliation(s)
- Garen K Anderson
- Cerebral and Cardiovascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, United States of America
- Co-first authorship
| | - Alexander J Rosenberg
- Cerebral and Cardiovascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, United States of America
- Co-first authorship
| | - Haley J Barnes
- Cerebral and Cardiovascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, United States of America
| | - Jordan Bird
- Department of Biology, Mount Royal University, Calgary, Alberta, Canada
| | - Brandon Pentz
- Department of Biology, Mount Royal University, Calgary, Alberta, Canada
| | - Britta R M Byman
- Department of Biology, Mount Royal University, Calgary, Alberta, Canada
| | - Nicholas Jendzjowsky
- Institute of Respiratory Medicine & Exercise Physiology, The Lundquist Institute at UCLA Harbor Medical, Torrance, CA, United States of America
| | - Richard J A Wilson
- Hotchkiss Brain Institute and Alberta Children’s Hospital Research Institute; Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Trevor A Day
- Department of Biology, Mount Royal University, Calgary, Alberta, Canada
| | - Caroline A Rickards
- Cerebral and Cardiovascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, United States of America
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13
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Burma JS, Miutz LN, Newel KT, Labrecque L, Drapeau A, Brassard P, Copeland P, Macaulay A, Smirl JD. What recording duration is required to provide physiologically valid and reliable dynamic cerebral autoregulation transfer functional analysis estimates? Physiol Meas 2021; 42. [PMID: 33761474 DOI: 10.1088/1361-6579/abf1af] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 03/24/2021] [Indexed: 12/31/2022]
Abstract
Objective. Currently, a recording of 300 s is recommended to obtain accurate dynamic cerebral autoregulation estimates using transfer function analysis (TFA). Therefore, this investigation sought to explore the concurrent validity and the within- and between-day reliability of TFA estimates derived from shorter recording durations from squat-stand maneuvers.Approach. Retrospective analyses were performed on 70 young, recreationally active or endurance-trained participants (17 females; age: 26 ± 5 years, [range: 20-39 years]; body mass index: 24 ± 3 kg m-2). Participants performed 300 s of squat-stands at frequencies of 0.05 and 0.10 Hz, where shorter recordings of 60, 120, 180, and 240 s were extracted. Continuous transcranial Doppler ultrasound recordings were taken within the middle and posterior cerebral arteries. Coherence, phase, gain, and normalized gain metrics were derived. Bland-Altman plots with 95% limits of agreement (LOA), repeated measures ANOVA's, two-tailed paired t-tests, coefficient of variation, Cronbach's alpha, intraclass correlation coefficients, and linear regressions were conducted.Main results. When examining the concurrent validity across different recording durations, group differences were noted within coherence (F(4155) > 11.6,p < 0.001) but not phase (F(4155) < 0.27,p > 0.611), gain (F(4155) < 0.61,p > 0.440), or normalized gain (F(4155) < 0.85,p > 0.359) parameters. The Bland-Altman 95% LOA measuring the concurrent validity, trended to narrow as recording duration increased (60 s: < ±0.4, 120 s: < ±0.3, 180 s < ±0.3, 240 s: < ±0.1). The validity of the 180 and 240 s recordings further increased when physiological covariates were included within regression models.Significance. Future studies examining autoregulation should seek to have participants perform 300 s of squat-stand maneuvers. However, valid and reliable TFA estimates can be drawn from 240 s or 180 s recordings if physiological covariates are controlled.
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Affiliation(s)
- Joel S Burma
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, AB, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada.,Concussion Research Laboratory, Faculty of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Lauren N Miutz
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, AB, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada
| | - Kailey T Newel
- Faculty of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Lawrence Labrecque
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, Canada
| | - Audrey Drapeau
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, Canada
| | - Patrice Brassard
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, Canada
| | - Paige Copeland
- Concussion Research Laboratory, Faculty of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Alannah Macaulay
- Concussion Research Laboratory, Faculty of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Jonathan D Smirl
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, AB, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada.,Concussion Research Laboratory, Faculty of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
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14
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Labrecque L, Drapeau A, Rahimaly K, Imhoff S, Brassard P. Dynamic cerebral autoregulation and cerebrovascular carbon dioxide reactivity in middle and posterior cerebral arteries in young endurance-trained women. J Appl Physiol (1985) 2021; 130:1724-1735. [PMID: 33955257 DOI: 10.1152/japplphysiol.00963.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The integrated responses regulating cerebral blood flow are understudied in women, particularly in relation to potential regional differences. In this study, we compared dynamic cerebral autoregulation (dCA) and cerebrovascular reactivity to carbon dioxide (CVRco2) in the middle (MCA) and posterior cerebral arteries (PCA) in 11 young endurance-trained women (age, 25 ± 4 yr; maximal oxygen uptake, 48.1 ± 4.1 mL·kg-1·min-1). dCA was characterized using a multimodal approach including a sit-to-stand and a transfer function analysis (TFA) of forced blood pressure oscillations (repeated squat-stands executed at 0.05 Hz and 0.10 Hz). The hyperoxic rebreathing test was utilized to characterize CVRco2. Upon standing, the percent reduction in blood velocity per percent reduction in mean arterial pressure during initial orthostatic stress (0-15 s after sit-to-stand), the onset of the regulatory response, and the rate of regulation did not differ between MCA and PCA (all P > 0.05). There was an ANOVA effect of anatomical location for TFA gain (P < 0.001) and a frequency effect for TFA phase (P < 0.001). However, normalized gain was not different between arteries (P = 0.18). Absolute CVRco2 was not different between MCA and PCA (1.55 ± 0.81 vs. 1.30 ± 0.49 cm·s-1/Torr, P = 0.26). Relative CVRco2 was 39% lower in the MCA (2.16 ± 1.02 vs. 3.00 ± 1.09%/Torr, P < 0.01). These findings indicate that the cerebral pressure-flow relationship appears to be similar between the MCA and the PCA in young endurance-trained women. The absence of regional differences in absolute CVRco2 could be women specific, although a direct comparison with a group of men will be necessary to address that issue.NEW & NOTEWORTHY Herein, we describe responses from two major mechanisms regulating cerebral blood flow with a special attention on regional differences in young endurance-trained women. The novel findings are that dynamic cerebral autoregulation and absolute cerebrovascular reactivity to carbon dioxide appear similar between the middle and posterior cerebral arteries of these young women.
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Affiliation(s)
- Lawrence Labrecque
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Quebec City, Québec, Canada
| | - Audrey Drapeau
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Quebec City, Québec, Canada
| | - Kevan Rahimaly
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Quebec City, Québec, Canada
| | - Sarah Imhoff
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Quebec City, Québec, Canada
| | - Patrice Brassard
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Quebec City, Québec, Canada
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15
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Burma JS, Copeland P, Macaulay A, Khatra O, Wright AD, Smirl JD. Dynamic cerebral autoregulation across the cardiac cycle during 8 hr of recovery from acute exercise. Physiol Rep 2021; 8:e14367. [PMID: 32163235 PMCID: PMC7066871 DOI: 10.14814/phy2.14367] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 12/28/2019] [Accepted: 12/30/2019] [Indexed: 01/02/2023] Open
Abstract
Current protocols examining cerebral autoregulation (CA) parameters require participants to refrain from exercise for 12–24 hr, however there is sparse objective evidence examining the recovery trajectory of these measures following exercise across the cardiac cycle (diastole, mean, and systole). Therefore, this study sought to determine the duration acute exercise impacts CA and the within‐day reproducibility of these measures. Nine participants performed squat–stand maneuvers at 0.05 and 0.10 Hz at baseline before three interventions: 45‐min moderate‐continuous exercise (at 50% heart‐rate reserve), 30‐min high‐intensity intervals (ten, 1‐min at 85% heart‐rate reserve), and a control day (30‐min quiet rest). Squat–stands were repeated at hours zero, one, two, four, six, and eight after each condition. Transcranial doppler ultrasound of the middle cerebral artery (MCA) and the posterior cerebral artery (PCA) was used to characterize CA parameters across the cardiac cycle. At baseline, the systolic CA parameters were different than mean and diastolic components (ps < 0.015), however following both exercise protocols in both frequencies this disappeared until hour four within the MCA (ps > 0.079). In the PCA, phase values were affected only following high‐intensity intervals until hour four (ps > 0.055). Normalized gain in all cardiac cycle domains remained different following both exercise protocols (ps < 0.005) and across the control day (p < .050). All systolic differences returned by hour six across all measures (ps < 0.034). Future CA studies may use squat–stand maneuvers to assess the cerebral pressure–flow relationship 6 hr after exercise. Finally, CA measures under this paradigm appear to have negligible within‐day variation, allowing for reproducible interpretations to be drawn.
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Affiliation(s)
- Joel S Burma
- Concussion Research Laboratory, Faculty of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada.,Sport Injury Prevention Research Center, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
| | - Paige Copeland
- Concussion Research Laboratory, Faculty of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Alannah Macaulay
- Concussion Research Laboratory, Faculty of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Omeet Khatra
- Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Alexander D Wright
- Concussion Research Laboratory, Faculty of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada.,MD/PhD Program, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.,Experimental Medicine Program, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.,Southern Medical Program, University of British Columbia, Kelowna, BC, Canada
| | - Jonathan D Smirl
- Concussion Research Laboratory, Faculty of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada.,Sport Injury Prevention Research Center, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Southern Medical Program, University of British Columbia, Kelowna, BC, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada
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16
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Burma JS, Copeland P, Macaulay A, Khatra O, Smirl JD. Comparison of diurnal variation, anatomical location, and biological sex within spontaneous and driven dynamic cerebral autoregulation measures. Physiol Rep 2020; 8:e14458. [PMID: 32537905 PMCID: PMC7293969 DOI: 10.14814/phy2.14458] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 04/04/2020] [Accepted: 04/10/2020] [Indexed: 01/31/2023] Open
Abstract
Presently, the literature describing the influence of diurnal variation on dynamic cerebral autoregulation (dCA) metrics is sparse. Additionally, there is little data with respect to dCA comparisons between anterior/posterior circulation beds and biological sexes using squat-stand maneuvers. Eight male and eight female participants (n = 16) performed 5 min of spontaneous upright rest and squat-stand maneuvers at 0.05 and 0.10 Hz across seven time points throughout the day. All testing sessions commenced at 8:00 a.m. each day and dCA parameters were quantified across the cardiac cycle (diastole, mean, and systole) using transcranial Doppler ultrasound to insonate cerebral blood velocity within the middle and posterior cerebral arteries (MCA, PCA). No cardiac cycle alternations were seen spontaneous (all p > .207) while a trend was noted in some driven (all p > .051) dCA metrics. Driven dCA produced much lower coefficient of variances (all <21%) compared with spontaneous (all <58%). Moreover, no sex differences were found within driven metrics (all p > .096). Between vessels, PCA absolute gain was reduced within all spontaneous and driven measures (all p < .014) whereas coherence, phase, and normalized gain were unchanged (all p > .099). There appears to be little influence of diurnal variation on dCA measures across the day (8:00 a.m. to 6:00 p.m.). Absolute gain was blunted in the PCA relative to the MCA and consistent with previous literature, driven methods demonstrated vastly improved reproducibility metrics compared to spontaneous methods. Finally, no dCA differences were found between biological sexes, demonstrating that males and females regulate in a harmonious manner, when females are tested within the early follicular phase of the menstrual cycle.
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Affiliation(s)
- Joel S. Burma
- Concussion Research LaboratoryFaculty of Health and Exercise ScienceUniversity of British ColumbiaKelownaBCCanada
- Sport Injury Prevention Research CentreFaculty of KinesiologyUniversity of CalgaryCalgaryABCanada
- Human Performance LaboratoryFaculty of KinesiologyUniversity of CalgaryCalgaryABCanada
- Hotchkiss Brain InstituteUniversity of CalgaryCalgaryABCanada
- Integrated Concussion Research ProgramUniversity of CalgaryCalgaryABCanada
| | - Paige Copeland
- Concussion Research LaboratoryFaculty of Health and Exercise ScienceUniversity of British ColumbiaKelownaBCCanada
| | - Alannah Macaulay
- Concussion Research LaboratoryFaculty of Health and Exercise ScienceUniversity of British ColumbiaKelownaBCCanada
| | - Omeet Khatra
- Faculty of MedicineUniversity of British ColumbiaVancouverBCCanada
| | - Jonathan D. Smirl
- Concussion Research LaboratoryFaculty of Health and Exercise ScienceUniversity of British ColumbiaKelownaBCCanada
- Sport Injury Prevention Research CentreFaculty of KinesiologyUniversity of CalgaryCalgaryABCanada
- Human Performance LaboratoryFaculty of KinesiologyUniversity of CalgaryCalgaryABCanada
- Hotchkiss Brain InstituteUniversity of CalgaryCalgaryABCanada
- Integrated Concussion Research ProgramUniversity of CalgaryCalgaryABCanada
- Alberta Children's Hospital Research InstituteUniversity of CalgaryCalgaryABCanada
- Libin Cardiovascular Institute of AlbertaUniversity of CalgaryCalgaryABCanada
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17
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UBC-Nepal expedition: dynamic cerebral autoregulation is attenuated in lowlanders upon ascent to 5050 m. Eur J Appl Physiol 2020; 120:675-686. [DOI: 10.1007/s00421-020-04307-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 01/18/2020] [Indexed: 12/14/2022]
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18
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Hoiland RL, Howe CA, Carter HH, Tremblay JC, Willie CK, Donnelly J, MacLeod DB, Gasho C, Stembridge M, Boulet LM, Niroula S, Ainslie PN. UBC‐Nepal expedition: phenotypical evidence for evolutionary adaptation in the control of cerebral blood flow and oxygen delivery at high altitude. J Physiol 2019; 597:2993-3008. [DOI: 10.1113/jp277596] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 04/09/2019] [Indexed: 01/26/2023] Open
Affiliation(s)
- Ryan L. Hoiland
- Centre for Heart, Lung and Vascular HealthUniversity of British Columbia–Okanagan Campus, School of Health and Exercise Sciences 3333 University Way Kelowna British Columbia Canada V1V 1V7
| | - Connor A. Howe
- Centre for Heart, Lung and Vascular HealthUniversity of British Columbia–Okanagan Campus, School of Health and Exercise Sciences 3333 University Way Kelowna British Columbia Canada V1V 1V7
| | - Howard H. Carter
- Department of Nutrition, Exercise and SportsUniversity of Copenhagen Nørre Allé 51 DK‐2200 Copenhagen Denmark
| | - Joshua C. Tremblay
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health StudiesQueen's University 28 Division Street Kingston Ontario Canada K7L 3N6
| | - Chris K. Willie
- Centre for Heart, Lung and Vascular HealthUniversity of British Columbia–Okanagan Campus, School of Health and Exercise Sciences 3333 University Way Kelowna British Columbia Canada V1V 1V7
| | - Joseph Donnelly
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical NeurosciencesCambridge Biomedical Campus, University of Cambridge Cambridge CB2 0QQ UK
| | - David B. MacLeod
- Human Pharmacology and Physiology Lab, Department of AnesthesiologyDuke University Medical Center Durham NC 27708 USA
| | - Chris Gasho
- VA Loma Linda Healthcare System and Loma Linda University School of Medicine Loma Linda CA USA
| | - Mike Stembridge
- Cardiff Centre for Exercise and HealthCardiff Metropolitan University Cyncoed Road Cardiff CF23 6XD UK
| | - Lindsey M. Boulet
- Centre for Heart, Lung and Vascular HealthUniversity of British Columbia–Okanagan Campus, School of Health and Exercise Sciences 3333 University Way Kelowna British Columbia Canada V1V 1V7
| | | | - Philip N. Ainslie
- Centre for Heart, Lung and Vascular HealthUniversity of British Columbia–Okanagan Campus, School of Health and Exercise Sciences 3333 University Way Kelowna British Columbia Canada V1V 1V7
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19
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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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20
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Bailey DM, Brugniaux JV, Filipponi T, Marley CJ, Stacey B, Soria R, Rimoldi SF, Cerny D, Rexhaj E, Pratali L, Salmòn CS, Murillo Jáuregui C, Villena M, Smirl JD, Ogoh S, Pietri S, Scherrer U, Sartori C. Exaggerated systemic oxidative-inflammatory-nitrosative stress in chronic mountain sickness is associated with cognitive decline and depression. J Physiol 2019; 597:611-629. [PMID: 30397919 PMCID: PMC6332753 DOI: 10.1113/jp276898] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 11/05/2018] [Indexed: 12/15/2022] Open
Abstract
KEY POINTS Chronic mountain sickness (CMS) is a maladaptation syndrome encountered at high altitude (HA) characterised by severe hypoxaemia that carries a higher risk of stroke and migraine and is associated with increased morbidity and mortality. We examined if exaggerated oxidative-inflammatory-nitrosative stress (OXINOS) and corresponding decrease in vascular nitric oxide bioavailability in patients with CMS (CMS+) is associated with impaired cerebrovascular function and adverse neurological outcome. Systemic OXINOS was markedly elevated in CMS+ compared to healthy HA (CMS-) and low-altitude controls. OXINOS was associated with blunted cerebral perfusion and vasoreactivity to hypercapnia, impaired cognition and, in CMS+, symptoms of depression. These findings are the first to suggest that a physiological continuum exists for hypoxaemia-induced systemic OXINOS in HA dwellers that when excessive is associated with accelerated cognitive decline and depression, helping identify those in need of more specialist neurological assessment and targeted support. ABSTRACT Chronic mountain sickness (CMS) is a maladaptation syndrome encountered at high altitude (HA) characterised by severe hypoxaemia that carries a higher risk of stroke and migraine and is associated with increased morbidity and mortality. The present cross-sectional study examined to what extent exaggerated systemic oxidative-inflammatory-nitrosative stress (OXINOS), defined by an increase in free radical formation and corresponding decrease in vascular nitric oxide (NO) bioavailability, is associated with impaired cerebrovascular function, accelerated cognitive decline and depression in CMS. Venous blood was obtained from healthy male lowlanders (80 m, n = 17), and age- and gender-matched HA dwellers born and bred in La Paz, Bolivia (3600 m) with (CMS+, n = 23) and without (CMS-, n = 14) CMS. We sampled blood for oxidative (electron paramagnetic resonance spectroscopy, HPLC), nitrosative (ozone-based chemiluminescence) and inflammatory (fluorescence) biomarkers. We employed transcranial Doppler ultrasound to measure cerebral blood flow (CBF) and reactivity. We utilised psychometric tests and validated questionnaires to assess cognition and depression. Highlanders exhibited elevated systemic OXINOS (P < 0.05 vs. lowlanders) that was especially exaggerated in the more hypoxaemic CMS+ patients (P < 0.05 vs. CMS-). OXINOS was associated with blunted cerebral perfusion and vasoreactivity to hypercapnia, impaired cognition and, in CMS+, symptoms of depression. Collectively, these findings are the first to suggest that a physiological continuum exists for hypoxaemia-induced OXINOS in HA dwellers that when excessive is associated with accelerated cognitive decline and depression, helping identify those in need of specialist neurological assessment and support.
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Affiliation(s)
- Damian M. Bailey
- Neurovascular Research LaboratoryFaculty of Life Sciences and Education, University of South WalesUK
| | - Julien V. Brugniaux
- Neurovascular Research LaboratoryFaculty of Life Sciences and Education, University of South WalesUK
- HP2 Laboratory, INSERM U1042Grenoble Alpes UniversityGrenobleFrance
| | - Teresa Filipponi
- Neurovascular Research LaboratoryFaculty of Life Sciences and Education, University of South WalesUK
| | - Christopher J. Marley
- Neurovascular Research LaboratoryFaculty of Life Sciences and Education, University of South WalesUK
| | - Benjamin Stacey
- Neurovascular Research LaboratoryFaculty of Life Sciences and Education, University of South WalesUK
| | - Rodrigo Soria
- Department of Cardiology and Clinical ResearchUniversity HospitalBernSwitzerland
| | - Stefano F. Rimoldi
- Department of Cardiology and Clinical ResearchUniversity HospitalBernSwitzerland
| | - David Cerny
- Department of Cardiology and Clinical ResearchUniversity HospitalBernSwitzerland
| | - Emrush Rexhaj
- Department of Cardiology and Clinical ResearchUniversity HospitalBernSwitzerland
| | | | | | | | | | - Jonathan D. Smirl
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise ScienceUniversity of British Columbia OkanaganKelownaBritish ColumbiaCanada
| | | | | | - Urs Scherrer
- Department of Cardiology and Clinical ResearchUniversity HospitalBernSwitzerland
- Facultad de Ciencias, Departamento de BiologíaUniversidad de TarapacáAricaChile
| | - Claudio Sartori
- Department of Internal MedicineUniversity HospitalUNIL‐LausanneSwitzerland
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21
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Willie CK, Stembridge M, Hoiland RL, Tymko MM, Tremblay JC, Patrician A, Steinback C, Moore J, Anholm J, Subedi P, Niroula S, McNeil CJ, McManus A, MacLeod DB, Ainslie PN. UBC-Nepal Expedition: An experimental overview of the 2016 University of British Columbia Scientific Expedition to Nepal Himalaya. PLoS One 2018; 13:e0204660. [PMID: 30379823 PMCID: PMC6209169 DOI: 10.1371/journal.pone.0204660] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 09/12/2018] [Indexed: 01/04/2023] Open
Abstract
The University of British Columbia Nepal Expedition took place over several months in the fall of 2016 and was comprised of an international team of 37 researchers. This paper describes the objectives, study characteristics, organization and management of this expedition, and presents novel blood gas data during acclimatization in both lowlanders and Sherpa. An overview and framework for the forthcoming publications is provided. The expedition conducted 17 major studies with two principal goals—to identify physiological differences in: 1) acclimatization; and 2) responses to sustained high-altitude exposure between lowland natives and people of Tibetan descent. We performed observational cohort studies of human responses to progressive hypobaric hypoxia (during ascent), and to sustained exposure to 5050 m over 3 weeks comparing lowlander adults (n = 30) with Sherpa adults (n = 24). Sherpa were tested both with (n = 12) and without (n = 12) descent to Kathmandu. Data collected from lowlander children (n = 30) in Canada were compared with those collected from Sherpa children (n = 57; 3400–3900m). Studies were conducted in Canada (344m) and the following locations in Nepal: Kathmandu (1400m), Namche Bazaar (3440m), Kunde Hospital (3480m), Pheriche (4371m) and the Ev-K2-CNR Research Pyramid Laboratory (5050m). The core studies focused on the mechanisms of cerebral blood flow regulation, the role of iron in cardiopulmonary regulation, pulmonary pressures, intra-ocular pressures, cardiac function, neuromuscular fatigue and function, blood volume regulation, autonomic control, and micro and macro vascular function. A total of 335 study sessions were conducted over three weeks at 5050m. In addition to an overview of this expedition and arterial blood gas data from Sherpa, suggestions for scientists aiming to perform field-based altitude research are also presented. Together, these findings will contribute to our understanding of human acclimatization and adaptation to the stress of residence at high-altitude.
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Affiliation(s)
- Christopher K. Willie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | - Michael Stembridge
- Cardiff Centre for Exercise and Health, Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Ryan L. Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | - Michael M. Tymko
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | - Joshua C. Tremblay
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen’s University, Kingston, Ontario, Canada
| | - Alexander Patrician
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | | | - Jonathan Moore
- Bangor University, School of Sport, Health & Exercise Sciences, Gwynedd, Wales, United Kingdom
| | - James Anholm
- Pulmonary/Critical Care Section, VA Loma Linda Healthcare System, Loma Linda, California, United States of America
| | - Prajan Subedi
- Paloma Medical Group, San Juan Capistrano, California, United States of America
| | | | - Chris J. McNeil
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | - Ali McManus
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | - David B. MacLeod
- Human Pharmacology & Physiology Lab, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Philip N. Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
- * E-mail:
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22
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Panerai RB, Barnes SC, Nath M, Ball N, Robinson TG, Haunton VJ. Directional sensitivity of dynamic cerebral autoregulation in squat-stand maneuvers. Am J Physiol Regul Integr Comp Physiol 2018; 315:R730-R740. [DOI: 10.1152/ajpregu.00010.2018] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Dynamic cerebral autoregulation (CA), the transient response of cerebral blood flow (CBF) to rapid changes in arterial blood pressure (BP), is usually modeled as a linear mechanism. We tested the hypothesis that dynamic CA can display nonlinear behavior resulting from differential efficiency dependent on the direction of BP changes. Cerebral blood velocity (CBV) (transcranial Doppler), heart rate (HR) (three-lead ECG), continuous BP (Finometer), and end-tidal CO2 (capnograph) were measured in 10 healthy young subjects during 15 squat-stand maneuvers (SSM) with a frequency of 0.05 Hz. The protocol was repeated with a median (interquartile range) of 44 (35–64) days apart. Dynamic CA was assessed with the autoregulation index (ARI) obtained from CBV step responses estimated with an autoregressive moving-average model. Mean BP, HR, and CBV were different (all P < 0.001) between squat and stand, regardless of visits. ARI showed a strong interaction ( P < 0.001) of SSM with the progression of transients; in general, the mean ARI was higher for the squat phase compared with standing. The changes in ARI were partially explained by concomitant changes in CBV ( P = 0.023) and pulse pressure ( P < 0.001), but there was no evidence that ARI differed between visits ( P = 0.277). These results demonstrate that dynamic CA is dependent on the direction of BP change, but further work is needed to confirm if this finding can be generalized to other physiological conditions and also to assess its dependency on age, sex and pathology.
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Affiliation(s)
- Ronney B. Panerai
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
- National Institute for Health Research, Leicester Biomedical Research Centre, University of Leicester, Leicester, United Kingdom
| | - Sam C. Barnes
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
| | - Mintu Nath
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
- National Institute for Health Research, Leicester Biomedical Research Centre, University of Leicester, Leicester, United Kingdom
| | - Naomi Ball
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
| | - Thompson G. Robinson
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
- National Institute for Health Research, Leicester Biomedical Research Centre, University of Leicester, Leicester, United Kingdom
| | - Victoria J. Haunton
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
- National Institute for Health Research, Leicester Biomedical Research Centre, University of Leicester, Leicester, United Kingdom
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23
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Labrecque L, Rahimaly K, Imhoff S, Paquette M, Le Blanc O, Malenfant S, Lucas SJE, Bailey DM, Smirl JD, Brassard P. Diminished dynamic cerebral autoregulatory capacity with forced oscillations in mean arterial pressure with elevated cardiorespiratory fitness. Physiol Rep 2018; 5:5/21/e13486. [PMID: 29122957 PMCID: PMC5688778 DOI: 10.14814/phy2.13486] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 10/07/2017] [Indexed: 12/12/2022] Open
Abstract
The effect that cardiorespiratory fitness has on the dynamic cerebral autoregulatory capacity during changes in mean arterial pressure (MAP) remains equivocal. Using a multiple‐metrics approach, challenging MAP across the spectrum of physiological extremes (i.e., spontaneous through forced MAP oscillations), we characterized dynamic cerebral autoregulatory capacity in 19 male endurance athletes and eight controls via three methods: (1) onset of regulation (i.e., time delay before an increase in middle cerebral artery (MCA) conductance [MCA blood velocity (MCAv)/MAP] and rate of regulation, after transient hypotension induced by sit‐to‐stand, and transfer function analysis (TFA) of MAP and MCAv responses during (2) spontaneous and (3) forced oscillations (5‐min of squat‐stand maneuvers performed at 0.05 and 0.10 Hz). Reductions in MAP and mean MCAv (MCAVmean) during initial orthostatic stress (0‐30 sec after sit‐to‐stand) and the prevalence of orthostatic hypotension were also determined. Onset of regulation was delayed after sit‐to‐stand in athletes (3.1 ± 1.7 vs. 1.5 ± 1.0 sec; P = 0.03), but rate of regulation was not different between groups (0.24 ± 0.05 vs. 0.21 ± 0.09 sec−1; P = 0.82). While both groups had comparable TFA metrics during spontaneous oscillations, athletes had higher TFA gain during 0.10 Hz squat‐stand versus recreational controls (P = 0.01). Reductions in MAP (P = 0.15) and MCAVmean (P = 0.11) during orthostatic stress and the prevalence of initial orthostatic hypotension (P = 0.65) were comparable between groups. These results indicate an intact ability of the cerebral vasculature to react to spontaneous oscillations but an attenuated capability to counter rapid and large changes in MAP in individuals with elevated cardiorespiratory fitness.
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Affiliation(s)
- Lawrence Labrecque
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada.,Research center of the Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada
| | - Kevan Rahimaly
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada.,Research center of the Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada
| | - Sarah Imhoff
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada.,Research center of the Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada
| | - Myriam Paquette
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada.,Research center of the Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada
| | - Olivier Le Blanc
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada.,Research center of the Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada
| | - Simon Malenfant
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada.,Research center of the Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada
| | - Samuel J E Lucas
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom.,Department of Physiology, University of Otago, Dunedin, New Zealand
| | - Damian M Bailey
- Neurovascular Research Laboratory Faculty of Life Sciences and Education University of South Wales, South Wales, United Kingdom.,Faculty of Medicine, Reichwald Health Sciences Centre University of British Columbia-Okanagan, Kelowna British Columbia, Canada
| | - Jonathan D Smirl
- Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Patrice Brassard
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada .,Research center of the Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada
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24
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Smirl JD, Wright AD, Ainslie PN, Tzeng YC, van Donkelaar P. Differential Systolic and Diastolic Regulation of the Cerebral Pressure-Flow Relationship During Squat-Stand Manoeuvres. ACTA NEUROCHIRURGICA SUPPLEMENT 2018; 126:263-268. [DOI: 10.1007/978-3-319-65798-1_52] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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25
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Barnes SC, Ball N, Haunton VJ, Robinson TG, Panerai RB. The cerebrocardiovascular response to periodic squat-stand maneuvers in healthy subjects: a time-domain analysis. Am J Physiol Heart Circ Physiol 2017; 313:H1240-H1248. [DOI: 10.1152/ajpheart.00331.2017] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Squat-stand maneuvers (SSMs) have been used to improve the coherence of transfer function analysis (TFA) estimates during the assessment of dynamic cerebral autoregulation (dCA). There is a need to understand the influence of peripheral changes resulting from SSMs on cerebral blood flow, which might confound estimates of dCA. Healthy subjects ( n = 29) underwent recordings at rest (5-min standing) and 15 SSMs (0.05 Hz). Heart rate (three-lead ECG), end-tidal CO2 (capnography), blood pressure (Finometer), cerebral blood velocity (CBV; transcranial Doppler, middle cerebral artery), and the angle of the thigh (tilt sensor) were measured continuously. The response of CBV to SSMs was decomposed into the relative contributions of mean arterial pressure (MAP), resistance-area product (RAP), and critical closing pressure (CrCP). Upon squatting, a rise in MAP (83.6 ± 21.1% contribution) was followed by increased CBV. A dCA response could be detected, determined by adjustments in RAP and CrCP (left hemisphere) with peak contributions of 24.8 ± 12.7% and 27.4 ± 22.8%, respectively, at different times during SSMs. No interhemispheric differences were detected. During standing, the contributions of MAP, RAP, and CrCP changed considerably. In conclusion, the changes of CBV subcomponents during repeated SSMs indicate a complex response of CBV to SSMs that can only be partially explained by myogenic mechanisms. More work is needed to clarify the potential contribution of other cofactors, such as breath-to-breath changes in Pco2, heart rate, stroke volume, and the neurogenic component of dCA. NEW & NOTEWORTHY Here, we describe the different contributions to the cerebral blood flow response after squat-stand maneuvers. Furthermore, we demonstrate the complex interaction of peripheral and cerebral parameters for the first time. Moreover, we show that the cerebral blood velocity response to squatting is likely to include a significant metabolic component.
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Affiliation(s)
- Sam C. Barnes
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
| | - Naomi Ball
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
| | - Victoria Joanna Haunton
- National Institute for Health Research, Leicester Biomedical Research Centre, University of Leicester, Leicester, United Kingdom
| | - Thompson G. Robinson
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
- National Institute for Health Research, Leicester Biomedical Research Centre, University of Leicester, Leicester, United Kingdom
| | - Ronney B. Panerai
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
- National Institute for Health Research, Leicester Biomedical Research Centre, University of Leicester, Leicester, United Kingdom
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26
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Barnes SC, Ball N, Panerai RB, Robinson TG, Haunton VJ. Random squat/stand maneuvers: a novel approach for assessment of dynamic cerebral autoregulation? J Appl Physiol (1985) 2017. [DOI: 10.1152/japplphysiol.00316.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Squat/stand maneuvers (SSM) have been used to assess dynamic cerebral autoregulation (dCA), but always at a fixed frequency (FF). This study aimed to assess the use of random-frequency (RF) SSMs as a stimulus for measuring dCA and determine the reproducibility of FF and RFSSMs. Twenty-nine healthy volunteers [19 male, mean age 23.0 (4.9) yr] completed the study; 11 returned for a repeat visit (median 45 days). Heart rate, beat-to-beat blood pressure, middle cerebral artery (MCA) blood flow velocity, end-tidal CO2, and angle of the squat movement were measured. Subjects underwent four recordings: 5 min sitting, 5 min standing, FFSSMs (0.05Hz), and RFSSMs. Subjects were asked to rate the degree of exertion experienced while performing these maneuvers. Twenty-nine subjects completed the protocol; nine data sets were deemed unsuitable for further analysis. Mean ARI of 6.21 (1.04) while standing was significantly greater than during the SSMs ( P < 0.01), with mean (SD) ARI during the FF and RFSSMs being 5.16 (1.43) and 5.37 (1.21), respectively. However, no significant difference was found between the ARI estimates from the two SSMs ( P = 0.856) or for each of the four recordings between the two visits ( P = 0.645). RFSSMs were found to be significantly less tiring than FFSSMs ( P < 0.01). In conclusion, RFSSMs are an effective and noninvasive method of assessing dCA. There is no difference in the ARI estimates in comparison with FFSSMs. Although FFSSMs have been well tolerated previously, RFSSMs are preferred by healthy subjects and thus may be better tolerated by a patient population in a clinical setting. NEW & NOTEWORTHY RFSSMs provided comparable estimates of autoregulatory indices to FFSSMs. Instead of point estimates at the driven frequency, RFSSMs generate a broader power spectrum of changes in arterial blood pressure and cerebral blood flow velocity, allowing direct comparison with spontaneous fluctuations through transfer function analysis. Moreover, random-frequency SSMs are preferred by participants. They are a novel tool by which larger blood pressure oscillations can be elicited for the reliable measurement of dynamic cerebral autoregulation.
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Affiliation(s)
- Sam C. Barnes
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom; and
| | - Naomi Ball
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom; and
| | - Ronney B. Panerai
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom; and
- National Institute for Health Research, Biomedical Research Unit in Cardiovascular Sciences, Clinical Sciences Wing, Glenfield Hospital, Leicester, United Kingdom
| | - Thompson G. Robinson
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom; and
- National Institute for Health Research, Biomedical Research Unit in Cardiovascular Sciences, Clinical Sciences Wing, Glenfield Hospital, Leicester, United Kingdom
| | - Victoria J. Haunton
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom; and
- National Institute for Health Research, Biomedical Research Unit in Cardiovascular Sciences, Clinical Sciences Wing, Glenfield Hospital, Leicester, United Kingdom
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27
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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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Boulet LM, Lovering AT, Tymko MM, Day TA, Stembridge M, Nguyen TA, Ainslie PN, Foster GE. Reduced blood flow through intrapulmonary arteriovenous anastomoses during exercise in lowlanders acclimatizing to high altitude. Exp Physiol 2017; 102:670-683. [PMID: 28370674 DOI: 10.1113/ep086182] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 03/27/2017] [Indexed: 12/13/2022]
Abstract
NEW FINDINGS What is the central question of this study? The aim was to determine, using the technique of agitated saline contrast echocardiography, whether exercise after 4-7 days at 5050 m would affect blood flow through intrapulmonary arteriovenous anastomoses (Q̇IPAVA) compared with exercise at sea level. What is the main finding and its importance? Despite a significant increase in both cardiac output and pulmonary pressure during exercise at high altitude, there is very little Q̇IPAVA at rest or during exercise after 4-7 days of acclimatization. Mathematical modelling suggests that bubble instability at high altitude is an unlikely explanation for the reduced Q̇IPAVA. Blood flow through intrapulmonary arteriovenous anastomoses (Q̇IPAVA) is elevated during exercise at sea level (SL) and at rest in acute normobaric hypoxia. After high altitude (HA) acclimatization, resting Q̇IPAVA is similar to that at SL, but it is unknown whether this is true during exercise at HA. We reasoned that exercise at HA (5050 m) would exacerbate Q̇IPAVA as a result of heightened pulmonary arterial pressure. Using a supine cycle ergometer, seven healthy adults free from intracardiac shunts underwent an incremental exercise test at SL [25, 50 and 75% of SL peak oxygen consumption (V̇O2 peak )] and at HA (25 and 50% of SL V̇O2 peak ). Echocardiography was used to determine cardiac output (Q̇) and pulmonary artery systolic pressure (PASP), and agitated saline contrast was used to determine Q̇IPAVA (bubble score; 0-5). The principal findings were as follows: (i) Q̇ was similar at SL rest (3.9 ± 0.47 l min-1 ) compared with HA rest (4.5 ± 0.49 l min-1 ; P = 0.382), but increased from rest during both SL and HA exercise (P < 0.001); (ii) PASP increased from SL rest (19.2 ± 0.7 mmHg) to HA rest (33.7 ± 2.8 mmHg; P = 0.001) and, compared with SL, PASP was further elevated during HA exercise (P = 0.003); (iii) Q̇IPAVA was increased from SL rest (0) to HA rest (median = 1; P = 0.04) and increased from resting values during SL exercise (P < 0.05), but was unchanged during HA exercise (P = 0.91), despite significant increases in Q̇ and PASP. Theoretical modelling of microbubble dissolution suggests that the lack of Q̇IPAVA in response to exercise at HA is unlikely to be caused by saline contrast instability.
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Affiliation(s)
- Lindsey M Boulet
- Centre for Heart, Lung & Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, OR, USA
| | - Michael M Tymko
- Centre for Heart, Lung & Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada
| | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Mike Stembridge
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, UK
| | - Trang Anh Nguyen
- Centre for Heart, Lung & Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada.,Department of Biomedical Engineering, International University, Vietnam National University, Ho Chi Minh City, Vietnam
| | - Philip N Ainslie
- Centre for Heart, Lung & Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada
| | - Glen E Foster
- Centre for Heart, Lung & Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, British Columbia, Canada
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Bailey DM, Ogoh S. Heterogeneous regulation of cerebral blood flow in hypoxia; implications for dynamic cerebral autoregulation and susceptibility to acute mountain sickness. Exp Physiol 2017; 102:383. [DOI: 10.1113/ep086144] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Damian Miles Bailey
- Neurovascular Research laboratory, Faculty of Life Sciences and Education; University of South Wales; UK
- Faculty of Medicine; University of British Columbia; Kelowna BC Canada
| | - Shigehiko Ogoh
- Department of Biomedical Engineering; Toyo University; Kawagoe Saitama Japan
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30
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Liu W, Liu J, Lou X, Zheng D, Wu B, Wang DJJ, Ma L. A longitudinal study of cerebral blood flow under hypoxia at high altitude using 3D pseudo-continuous arterial spin labeling. Sci Rep 2017; 7:43246. [PMID: 28240265 PMCID: PMC5327438 DOI: 10.1038/srep43246] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 01/20/2017] [Indexed: 12/14/2022] Open
Abstract
Changes in cerebral blood flow (CBF) may occur with acute exposure to high altitude; however, the CBF of the brain parenchyma has not been studied to date. In this study, identical magnetic resonance scans using arterial spin labeling (ASL) were performed to study the haemodynamic changes at both sea level and high altitude. We found that with acute exposure to high altitude, the CBF in acute mountain sickness (AMS) subjects was higher (P < 0.05), while the CBF of non-AMS subjects was lower (P > 0.05) compared with those at sea level. Moreover, magnetic resonance angiography in both AMS and non-AMS subjects showed a significant increase in the cross-sectional areas of the internal carotid, basilar, and middle cerebral arteries on the first day at high altitude. These findings support that AMS may be related to increased CBF rather than vasodilation; these results contradict most previous studies that reported no relationship between CBF changes and the occurrence of AMS. This discrepancy may be attributed to the use of ASL for CBF measurement at both sea level and high altitude in this study, which has substantial advantages over transcranial Doppler for the assessment of CBF.
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Affiliation(s)
- Wenjia Liu
- Department of Radiology, Chinese PLA General Hospital, Beijing, China
| | - Jie Liu
- Department of Radiology, Tibet Military General Hospital, Lhasa, Tibet, China
| | - Xin Lou
- Department of Radiology, Chinese PLA General Hospital, Beijing, China.,Department of Neurology, University of California, Los Angeles, CA, USA
| | - Dandan Zheng
- GE Healthcare, MR Research China, Beijing, China
| | - Bing Wu
- GE Healthcare, MR Research China, Beijing, China
| | - Danny J J Wang
- Department of Neurology, University of California, Los Angeles, CA, USA
| | - Lin Ma
- Department of Radiology, Chinese PLA General Hospital, Beijing, China
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Foster GE, Davies-Thompson J, Dominelli PB, Heran MKS, Donnelly J, duManoir GR, Ainslie PN, Rauscher A, Sheel AW. Changes in cerebral vascular reactivity and structure following prolonged exposure to high altitude in humans. Physiol Rep 2015; 3:3/12/e12647. [PMID: 26660556 PMCID: PMC4760444 DOI: 10.14814/phy2.12647] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Although high‐altitude exposure can lead to neurocognitive impairment, even upon return to sea level, it remains unclear the extent to which brain volume and regional cerebral vascular reactivity (CVR) are altered following high‐altitude exposure. The purpose of this study was to simultaneously determine the effect of 3 weeks at 5050 m on: (1) structural brain alterations; and (2) regional CVR after returning to sea level for 1 week. Healthy human volunteers (n = 6) underwent baseline and follow‐up structural and functional magnetic resonance imaging (MRI) at rest and during a CVR protocol (end‐tidal PCO2 reduced by −10, −5 and increased by +5, +10, and +15 mmHg from baseline). CVR maps (% mmHg−1) were generated using BOLD MRI and brain volumes were estimated. Following return to sea level, whole‐brain volume and gray matter volume was reduced by 0.4 ± 0.3% (P < 0.01) and 2.6 ± 1.0% (P < 0.001), respectively; white matter was unchanged. Global gray matter CVR and white matter CVR were unchanged following return to sea level, but CVR was selectively increased (P < 0.05) in the brainstem (+30 ± 12%), hippocampus (+12 ± 3%), and thalamus (+10 ± 3%). These changes were the result of improvement and/or reversal of negative CVR to positive CVR in these regions. Three weeks of high‐altitude exposure is reflected in loss of gray matter volume and improvements in negative CVR.
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Affiliation(s)
- Glen E Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada School of Kinesiology, University of British Columbia, Vancouver, Canada
| | - Jodie Davies-Thompson
- Department of Ophthalmology and Visual Sciences, Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Paolo B Dominelli
- School of Kinesiology, University of British Columbia, Vancouver, Canada
| | - Manraj K S Heran
- Diagnostic and Therapeutic Neuroradiology, Vancouver General Hospital University of British Columbia, Vancouver, Canada
| | - Joseph Donnelly
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Gregory R duManoir
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | - Alexander Rauscher
- Department of Radiology, UBC MRI Research Centre University of British Columbia, Vancouver, Canada
| | - A William Sheel
- School of Kinesiology, University of British Columbia, Vancouver, Canada
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32
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Smirl JD, Hoffman K, Tzeng YC, Hansen A, Ainslie PN. Relationship between blood pressure and cerebral blood flow during supine cycling: influence of aging. J Appl Physiol (1985) 2015; 120:552-63. [PMID: 26586907 DOI: 10.1152/japplphysiol.00667.2015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 11/13/2015] [Indexed: 11/22/2022] Open
Abstract
The cerebral pressure-flow relationship can be quantified as a high-pass filter, where slow oscillations are buffered (<0.20 Hz) and faster oscillations are passed through relatively unimpeded. During moderate intensity exercise, previous studies have reported paradoxical transfer function analysis (TFA) findings (altered phase or intact gain). This study aimed to determine whether these previous findings accurately represent this relationship. Both younger (20-30 yr; n = 10) and older (62-72 yr; n = 9) adults were examined. To enhance the signal-to-noise ratio, large oscillations in blood pressure (via oscillatory lower body negative pressure; OLBNP) were induced during steady-state moderate intensity supine exercise (∼45-50% of heart rate reserve). Beat-to-beat blood pressure, cerebral blood velocity, and end-tidal Pco2 were monitored. Very low frequency (0.02-0.07 Hz) and low frequency (0.07-0.20 Hz) range spontaneous data were quantified. Driven OLBNP point estimates were sampled at 0.05 and 0.10 Hz. The OLBNP maneuvers augmented coherence to >0.97 at 0.05 Hz and >0.98 at 0.10 Hz in both age groups. The OLBNP protocol conclusively revealed the cerebrovascular system functions as a high-pass filter during exercise throughout aging. It was also discovered that the older adults had elevations (+71%) in normalized gain (+0.46 ± 0.36%/%: 0.05 Hz) and reductions (-34%) in phase (-0.24 ± 0.22 radian: 0.10 Hz). There were also age-related phase differences between resting and exercise conditions. It is speculated that these age-related changes in the TFA metrics are mediated by alterations in vasoactive factors, sympathetic tone, or the mechanical buffering of the compliance vessels.
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Affiliation(s)
- Jonathan D Smirl
- Centre for Heart, Lung and Vascular Health; School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Canada;
| | - Keegan Hoffman
- Centre for Heart, Lung and Vascular Health; School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Canada
| | - Yu-Chieh Tzeng
- Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - Alex Hansen
- Centre for Heart, Lung and Vascular Health; School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health; School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Canada
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33
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Smirl JD, Hoffman K, Tzeng YC, Hansen A, Ainslie PN. Methodological comparison of active- and passive-driven oscillations in blood pressure; implications for the assessment of cerebral pressure-flow relationships. J Appl Physiol (1985) 2015; 119:487-501. [PMID: 26183476 DOI: 10.1152/japplphysiol.00264.2015] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 07/15/2015] [Indexed: 11/22/2022] Open
Abstract
We examined the between-day reproducibility of active (squat-stand maneuvers)- and passive [oscillatory lower-body negative pressure (OLBNP) maneuvers]-driven oscillations in blood pressure. These relationships were examined in both younger (n = 10; 25 ± 3 yr) and older (n = 9; 66 ± 4 yr) adults. Each testing protocol incorporated rest (5 min), followed by driven maneuvers at 0.05 (5 min) and 0.10 (5 min) Hz to increase blood-pressure variability and improve assessment of the pressure-flow dynamics using linear transfer function analysis. Beat-to-beat blood pressure, middle cerebral artery velocity, and end-tidal partial pressure of CO2 were monitored. The pressure-flow relationship was quantified in the very low (0.02-0.07 Hz) and low (0.07-0.20 Hz) frequencies (LF; spontaneous data) and at 0.05 and 0.10 Hz (driven maneuvers point estimates). Although there were no between-age differences, very few spontaneous and OLBNP transfer function metrics met the criteria for acceptable reproducibility, as reflected in a between-day, within-subject coefficient of variation (CoV) of <20%. Combined CoV data consist of LF coherence (15.1 ± 12.2%), LF gain (15.1 ± 12.2%), and LF normalized gain (18.5 ± 10.9%); OLBNP data consist of 0.05 (12.1 ± 15.%) and 0.10 (4.7 ± 7.8%) Hz coherence. In contrast, the squat-stand maneuvers revealed that all metrics (coherence: 0.6 ± 0.5 and 0.3 ± 0.5%; gain: 17.4 ± 12.3 and 12.7 ± 11.0%; normalized gain: 16.7 ± 10.9 and 15.7 ± 11.0%; and phase: 11.6 ± 10.2 and 17.3 ± 10.8%) at 0.05 and 0.10 Hz, respectively, were considered biologically acceptable for reproducibility. These findings have important implications for the reliable assessment and interpretation of cerebral pressure-flow dynamics in humans.
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Affiliation(s)
- Jonathan D Smirl
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada; and
| | - Keegan Hoffman
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada; and
| | - Yu-Chieh Tzeng
- Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - Alex Hansen
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada; and
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada; and
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Subudhi AW, Grajzel K, Langolf RJ, Roach RC, Panerai RB, Davis JE. Cerebral autoregulation index at high altitude assessed by thigh-cuff and transfer function analysis techniques. Exp Physiol 2015; 100:173-81. [DOI: 10.1113/expphysiol.2014.082479] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Accepted: 11/27/2014] [Indexed: 11/08/2022]
Affiliation(s)
- Andrew W. Subudhi
- Department of Biology; University of Colorado Colorado Springs; Colorado Springs CO USA
- Department of Emergency Medicine; University of Colorado Altitude Research Center; Aurora CO USA
| | - Katalin Grajzel
- Department of Psychology; University of Colorado Colorado Springs; Colorado Springs CO USA
| | - Robert J. Langolf
- Alma College; Department of Integrative Physiology and Health Science; Alma MI USA
| | - Robert C. Roach
- Department of Emergency Medicine; University of Colorado Altitude Research Center; Aurora CO USA
| | - Ronney B. Panerai
- Department of Cardiovascular Sciences and NIHR Biomedical Research Unit; University of Leicester; UK
| | - John E. Davis
- Alma College; Department of Integrative Physiology and Health Science; Alma MI USA
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Smirl JD, Haykowsky MJ, Nelson MD, Tzeng YC, Marsden KR, Jones H, Ainslie PN. Relationship Between Cerebral Blood Flow and Blood Pressure in Long-Term Heart Transplant Recipients. Hypertension 2014; 64:1314-20. [DOI: 10.1161/hypertensionaha.114.04236] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Heart transplant recipients are at an increased risk for cerebral hemorrhage and ischemic stroke; yet, the exact mechanism for this derangement remains unclear. We hypothesized that alterations in cerebrovascular regulation is principally involved. To test this hypothesis, we studied cerebral pressure-flow dynamics in 8 clinically stable male heart transplant recipients (62±8 years of age and 9±7 years post transplant, mean±SD), 9 male age-matched controls (63±8 years), and 10 male donor controls (27±5 years). To increase blood pressure variability and improve assessment of the pressure-flow dynamics, subjects performed squat–stand maneuvers at 0.05 and 0.10 Hz. Beat-to-beat blood pressure, middle cerebral artery velocity, and end-tidal carbon dioxide were continuously measured during 5 minutes of seated rest and throughout the squat–stand maneuvers. Cardiac baroreceptor sensitivity gain and cerebral pressure-flow responses were assessed with linear transfer function analysis. Heart transplant recipients had reductions in R-R interval power and baroreceptor sensitivity low frequency gain (
P
<0.01) compared with both control groups; however, these changes were unrelated to transfer function metrics. Thus, in contrast to our hypothesis, the increased risk of cerebrovascular complication after heart transplantation does not seem to be related to alterations in cerebral pressure-flow dynamics. Future research is, therefore, warranted.
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Affiliation(s)
- Jonathan D. Smirl
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
| | - Mark J. Haykowsky
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
| | - Michael D. Nelson
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
| | - Yu-Chieh Tzeng
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
| | - Katelyn R. Marsden
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
| | - Helen Jones
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
| | - Philip N. Ainslie
- From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular
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MUTHURAJU S, PATI S. Effect of hypobaric hypoxia on cognitive functions and potential therapeutic agents. Malays J Med Sci 2014; 21:41-45. [PMID: 25941462 PMCID: PMC4405810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 10/19/2014] [Indexed: 06/04/2023] Open
Abstract
High altitude (HA), defined as approximately 3000-5000 m, considerably alters physiological and psychological parameters within a few hours. Chronic HA-mediated hypoxia (5000 m) results in permanent neuronal damage to the human brain that persists for one year or longer, even after returning to sea level. At HA, there is a decrease in barometric pressure and a consequential reduction in the partial pressure of oxygen (PO2), an extreme environmental condition to which humans are occasionally exposed. This condition is referred to as hypobaric hypoxia (HBH), which represents the most unfavourable characteristics of HA. HBH causes the disruption of oxygen availability to tissue. However, no review article has explored the impact of HBH on cognitive functions or the potential therapeutic agents for HBH. Therefore, the present review aimed to describe the impact of HBH on both physiological and cognitive functions, specifically learning and memory. Finally, the potential therapeutic agents for the treatment of HBH-induced cognitive impairment are discussed.
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Affiliation(s)
- Sangu MUTHURAJU
- Laboratory of Neuropsychopharmacology, FFCLRP, Universidade de São Paulo, Campus USP, Ribeirão Preto, SP 14049-901, Brazil; Instituto de Neurociencias e Comportamento, Avenida do Café, 2450, Ribeirão Preto, SP 14050-000, Brazil
| | - Soumya PATI
- Departments of Pediatrics-Neurology and Neuroscience, Program in Developmental Biology, Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, 1250 Moursund Street, Room 1250, Houston, TX 77030, USA
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Sightings edited by Erik R. Swenson and Peter Bärtsch. High Alt Med Biol 2014. [DOI: 10.1089/ham.2014.1523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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38
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Smirl JD, Tzeng YC, Monteleone BJ, Ainslie PN. Influence of cerebrovascular resistance on the dynamic relationship between blood pressure and cerebral blood flow in humans. J Appl Physiol (1985) 2014; 116:1614-22. [PMID: 24744385 DOI: 10.1152/japplphysiol.01266.2013] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined the hypothesis that changes in the cerebrovascular resistance index (CVRi), independent of blood pressure (BP), will influence the dynamic relationship between BP and cerebral blood flow in humans. We altered CVRi with (via controlled hyperventilation) and without [via indomethacin (INDO, 1.2 mg/kg)] changes in PaCO2. Sixteen subjects (12 men, 27 ± 7 yr) were tested on two occasions (INDO and hypocapnia) separated by >48 h. Each test incorporated seated rest (5 min), followed by squat-stand maneuvers to increase BP variability and improve assessment of the pressure-flow dynamics using linear transfer function analysis (TFA). Beat-to-beat BP, middle cerebral artery velocity (MCAv), posterior cerebral artery velocity (PCAv), and end-tidal Pco2 were monitored. Dynamic pressure-flow relations were quantified using TFA between BP and MCAv/PCAv in the very low and low frequencies through the driven squat-stand maneuvers at 0.05 and 0.10 Hz. MCAv and PCAv reductions by INDO and hypocapnia were well matched, and CVRi was comparably elevated (P < 0.001). During the squat-stand maneuvers (0.05 and 0.10 Hz), the point estimates of absolute gain were universally reduced, and phase was increased under both conditions. In addition to an absence of regional differences, our findings indicate that alterations in CVRi independent of PaCO2 can alter cerebral pressure-flow dynamics. These findings are consistent with the concept of CVRi being a key factor that should be considered in the correct interpretation of cerebral pressure-flow dynamics as indexed using TFA metrics.
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Affiliation(s)
- J D Smirl
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia Okanagan, Kelowna, British Columbia, Canada;
| | - Y C Tzeng
- Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, Wellington, New Zealand; and
| | - B J Monteleone
- Faculty of Medicine, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - P N Ainslie
- Centre for Heart Lung and Vascular Health, School of Health and Exercise Science, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
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