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Poletto E, Kanthimathinathan HK, Gyorgyi Z. How to perform and interpret a middle cerebral artery transcranial Doppler examination in children at risk of brain injury. Arch Dis Child Educ Pract Ed 2024; 109:98-104. [PMID: 37532292 DOI: 10.1136/archdischild-2023-325747] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/01/2023] [Indexed: 08/04/2023]
Abstract
Transcranial Doppler (TCD) ultrasound is a non-invasive neuromonitoring technique that falls under the umbrella of point-of-care ultrasound. In this article, we provide a primer to encourage clinicians to perform TCD examinations and to aid them with accurately interpreting the scans. We focus on the middle cerebral artery waveforms and use traumatic brain injury as a model for brain insult.
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Affiliation(s)
- Elisa Poletto
- Division of Pediatric Intensive Care Unit, San Bortolo Hospital of Vicenza, Vicenza, Italy
| | | | - Zoltan Gyorgyi
- Paediatric Critical Care Unit, Royal Hospital for Children and Young People, Edinburgh, UK
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Caddy HT, Thomas HJ, Kelsey LJ, Smith KJ, Doyle BJ, Green DJ. Comparison of computational fluid dynamics with transcranial Doppler ultrasound in response to physiological stimuli. Biomech Model Mechanobiol 2024; 23:255-269. [PMID: 37805938 PMCID: PMC10902019 DOI: 10.1007/s10237-023-01772-9] [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: 05/24/2023] [Accepted: 09/05/2023] [Indexed: 10/10/2023]
Abstract
Cerebrovascular haemodynamics are sensitive to multiple physiological stimuli that require synergistic response to maintain adequate perfusion. Understanding haemodynamic changes within cerebral arteries is important to inform how the brain regulates perfusion; however, methods for direct measurement of cerebral haemodynamics in these environments are challenging. The aim of this study was to assess velocity waveform metrics obtained using transcranial Doppler (TCD) with flow-conserving subject-specific three-dimensional (3D) simulations using computational fluid dynamics (CFD). Twelve healthy participants underwent head and neck imaging with 3 T magnetic resonance angiography. Velocity waveforms in the middle cerebral artery were measured with TCD ultrasound, while diameter and velocity were measured using duplex ultrasound in the internal carotid and vertebral arteries to calculate incoming cerebral flow at rest, during hypercapnia and exercise. CFD simulations were developed for each condition, with velocity waveform metrics extracted in the same insonation region as TCD. Exposure to stimuli induced significant changes in cardiorespiratory measures across all participants. Measured absolute TCD velocities were significantly higher than those calculated from CFD (P range < 0.001-0.004), and these data were not correlated across conditions (r range 0.030-0.377, P range 0.227-0.925). However, relative changes in systolic and time-averaged velocity from resting levels exhibited significant positive correlations when the distinct techniques were compared (r range 0.577-0.770, P range 0.003-0.049). Our data indicate that while absolute measures of cerebral velocity differ between TCD and 3D CFD simulation, physiological changes from resting levels in systolic and time-averaged velocity are significantly correlated between techniques.
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Affiliation(s)
- Harrison T Caddy
- Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, Australia and the UWA Centre for Medical Research, The University of Western Australia, Perth, Australia
- School of Human Sciences (Exercise and Sport Sciences), The University of Western Australia, Perth, Australia
| | - Hannah J Thomas
- School of Human Sciences (Exercise and Sport Sciences), The University of Western Australia, Perth, Australia
| | - Lachlan J Kelsey
- Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, Australia and the UWA Centre for Medical Research, The University of Western Australia, Perth, Australia
- School of Engineering, The University of Western Australia, Perth, Australia
| | - Kurt J Smith
- School of Human Sciences (Exercise and Sport Sciences), The University of Western Australia, Perth, Australia
- Cerebrovascular Health, Exercise, and Environmental Research Sciences Laboratory, University of Victoria, Victoria, Canada
| | - Barry J Doyle
- Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, Australia and the UWA Centre for Medical Research, The University of Western Australia, Perth, Australia.
- School of Engineering, The University of Western Australia, Perth, Australia.
| | - Daniel J Green
- School of Human Sciences (Exercise and Sport Sciences), The University of Western Australia, Perth, Australia
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Manferdelli G, Narang BJ, Bourdillon N, Giardini G, Debevec T, Millet GP. Impaired cerebrovascular CO 2 reactivity at high altitude in prematurely born adults. J Physiol 2023. [PMID: 38116893 DOI: 10.1113/jp285048] [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: 05/19/2023] [Accepted: 11/30/2023] [Indexed: 12/21/2023] Open
Abstract
Premature birth impairs cardiac and ventilatory responses to both hypoxia and hypercapnia, but little is known about cerebrovascular responses. Both at sea level and after 2 days at high altitude (3375 m), 16 young preterm-born (gestational age, 29 ± 1 weeks) and 15 age-matched term-born (40 ± 0 weeks) adults were exposed to two consecutive 4 min bouts of hyperoxic hypercapnic conditions (3% CO2 -97% O2 ; 6% CO2 -94% O2 ), followed by two periods of voluntary hyperventilation-induced hypocapnia. We measured middle cerebral artery blood velocity, end-tidal CO2 , pulmonary ventilation, beat-by-beat mean arterial pressure and arterialized capillary blood gases. Baseline middle cerebral artery blood velocity increased at high altitude compared with sea level in term-born (+24 ± 39%, P = 0.036), but not in preterm-born (-4 ± 27%, P = 0.278) adults. The end-tidal CO2 , pulmonary ventilation and mean arterial pressure were similar between groups at sea level and high altitude. Hypocapnic cerebrovascular reactivity was higher at high altitude compared with sea level in term-born adults (+173 ± 326%, P = 0.026) but not in preterm-born adults (-21 ± 107%, P = 0.572). Hypercapnic reactivity was altered at altitude only in preterm-born adults (+125 ± 144%, P < 0.001). Collectively, at high altitude, term-born participants showed higher hypocapnic (P = 0.012) and lower hypercapnic (P = 0.020) CO2 reactivity compared with their preterm-born peers. In conclusion, exposure to high altitude revealed different cerebrovascular responses in preterm- compared with term-born adults, despite similar ventilatory responses. These findings suggest a blunted cerebrovascular response at high altitude in preterm-born adults, which might predispose these individuals to an increased risk of high-altitude illnesses. KEY POINTS: Cerebral haemodynamics and cerebrovascular reactivity in normoxia are known to be similar between term-born and prematurely born adults. In contrast, acute exposure to high altitude unveiled different cerebrovascular responses to hypoxia, hypercapnia and hypocapnia. In particular, cerebral vasodilatation was impaired in prematurely born adults, leading to an exaggerated cerebral vasoconstriction. Cardiovascular and ventilatory responses to both hypo- and hypercapnia at sea level and at high altitude were similar between control subjects and prematurely born adults. Other mechanisms might therefore underlie the observed blunted cerebral vasodilatory responses in preterm-born adults at high altitude.
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Affiliation(s)
| | - Benjamin J Narang
- Department of Automatics, Biocybernetics and Robotics, Jožef Stefan Institute, Ljubljana, Slovenia
- Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia
| | - Nicolas Bourdillon
- Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
| | - Guido Giardini
- Mountain Medicine and Neurology Centre, Valle D'Aosta Regional Hospital, Aosta, Italy
| | - Tadej Debevec
- Department of Automatics, Biocybernetics and Robotics, Jožef Stefan Institute, Ljubljana, Slovenia
- Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia
| | - Grégoire P Millet
- Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
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Martin ZT, Akins JD, Merlau ER, Kolade JO, Al-Daas IO, Cardenas N, Vu JK, Brown KK, Brothers RM. The acute effect of whole-body heat therapy on peripheral and cerebral vascular reactivity in Black and White females. Microvasc Res 2023; 148:104536. [PMID: 37024072 PMCID: PMC10908357 DOI: 10.1016/j.mvr.2023.104536] [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: 01/04/2023] [Revised: 03/17/2023] [Accepted: 04/03/2023] [Indexed: 04/08/2023]
Abstract
Among females in the U.S., Black females suffer the most from cardiovascular disease and stroke. While the reasons for this disparity are multifactorial, vascular dysfunction likely contributes. Chronic whole-body heat therapy (WBHT) improves vascular function, but few studies have examined its acute effect on peripheral or cerebral vascular function, which may help elucidate chronic adaptative mechanisms. Furthermore, no studies have investigated this effect in Black females. We hypothesized that Black females would have lower peripheral and cerebral vascular function relative to White females and that one session of WBHT would mitigate these differences. Eighteen young, healthy Black (n = 9; 21 ± 3 yr; BMI: 24.7 ± 4.5 kg/m2) and White (n = 9; 27 ± 3 yr; BMI: 24.8 ± 4.1 kg/m2) females underwent one 60 min session of WBHT (49 °C water via a tube-lined suit). Pre- and 45 min post-testing measures included post-occlusive forearm reactive hyperemia (peripheral microvascular function, RH), brachial artery flow-mediated dilation (peripheral macrovascular function, FMD), and cerebrovascular reactivity (CVR) to hypercapnia. Prior to WBHT, there were no differences in RH, FMD, or CVR (p > 0.05 for all). WBHT improved peak RH in both groups (main effect of WBHT: 79.6 ± 20.1 cm/s to 95.9 ± 30.0 cm/s; p = 0.004, g = 0.787) but not Δ blood velocity (p > 0.05 for both groups). WBHT improved FMD in both groups (6.2 ± 3.4 % to 8.8 ± 3.7 %; p = 0.016, g = 0.618) but had no effect on CVR in either group (p = 0.077). These data indicate that one session of WBHT acutely improves peripheral micro- and macrovascular but not cerebral vascular function in Black and White females.
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Affiliation(s)
- Zachary T Martin
- Department of Kinesiology, The University of Texas at Arlington, Arlington, TX, USA
| | - John D Akins
- Department of Kinesiology, The University of Texas at Arlington, Arlington, TX, USA
| | - Emily R Merlau
- Department of Kinesiology, The University of Texas at Arlington, Arlington, TX, USA
| | - John O Kolade
- Department of Kinesiology, The University of Texas at Arlington, Arlington, TX, USA
| | - Iman O Al-Daas
- Department of Kinesiology, The University of Texas at Arlington, Arlington, TX, USA
| | - Natalia Cardenas
- Department of Kinesiology, The University of Texas at Arlington, Arlington, TX, USA
| | - Joshua K Vu
- Department of Kinesiology, The University of Texas at Arlington, Arlington, TX, USA
| | - Kyrah K Brown
- Department of Kinesiology, The University of Texas at Arlington, Arlington, TX, USA
| | - R Matthew Brothers
- Department of Kinesiology, The University of Texas at Arlington, Arlington, TX, USA.
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Fico BG, Miller KB, Rivera-Rivera LA, Corkery AT, Pearson AG, Loggie NA, Howery AJ, Rowley HA, Johnson KM, Johnson SC, Wieben O, Barnes JN. Cerebral hemodynamics comparison using transcranial doppler ultrasound and 4D flow MRI. Front Physiol 2023; 14:1198615. [PMID: 37304825 PMCID: PMC10250020 DOI: 10.3389/fphys.2023.1198615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Accepted: 05/09/2023] [Indexed: 06/13/2023] Open
Abstract
Introduction: Age-related changes in cerebral hemodynamics are controversial and discrepancies may be due to experimental techniques. As such, the purpose of this study was to compare cerebral hemodynamics measurements of the middle cerebral artery (MCA) between transcranial Doppler ultrasound (TCD) and four-dimensional flow MRI (4D flow MRI). Methods: Twenty young (25 ± 3 years) and 19 older (62 ± 6 years) participants underwent two randomized study visits to evaluate hemodynamics at baseline (normocapnia) and in response to stepped hypercapnia (4% CO2, and 6% CO2) using TCD and 4D flow MRI. Cerebral hemodynamic measures included MCA velocity, MCA flow, cerebral pulsatility index (PI) and cerebrovascular reactivity to hypercapnia. MCA flow was only assessed using 4D flow MRI. Results: MCA velocity between the TCD and 4D flow MRI methods was positively correlated across the normocapnia and hypercapnia conditions (r = 0.262; p = 0.004). Additionally, cerebral PI was significantly correlated between TCD and 4D flow MRI across the conditions (r = 0.236; p = 0.010). However, there was no significant association between MCA velocity using TCD and MCA flow using 4D flow MRI across the conditions (r = 0.079; p = 0.397). When age-associated differences in cerebrovascular reactivity using conductance were compared using both methodologies, cerebrovascular reactivity was greater in young adults compared to older adults when using 4D flow MRI (2.11 ± 1.68 mL/min/mmHg/mmHg vs. 0.78 ± 1.68 mL/min/mmHg/mmHg; p = 0.019), but not with TCD (0.88 ± 1.01 cm/s/mmHg/mmHg vs. 0.68 ± 0.94 cm/s/mmHg/mmHg; p = 0.513). Conclusion: Our results demonstrated good agreement between the methods at measuring MCA velocity during normocapnia and in response to hypercapnia, but MCA velocity and MCA flow were not related. In addition, measurements using 4D flow MRI revealed effects of aging on cerebral hemodynamics that were not apparent using TCD.
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Affiliation(s)
- Brandon G. Fico
- Department of Kinesiology, Bruno Balke Biodynamics Laboratory, University of Wisconsin-Madison, Madison, WI, United States
| | - Kathleen B. Miller
- Department of Kinesiology, Bruno Balke Biodynamics Laboratory, University of Wisconsin-Madison, Madison, WI, United States
| | - Leonardo A. Rivera-Rivera
- Wisconsin Alzheimer’s Disease Research Center, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
| | - Adam T. Corkery
- Department of Kinesiology, Bruno Balke Biodynamics Laboratory, University of Wisconsin-Madison, Madison, WI, United States
| | - Andrew G. Pearson
- Department of Kinesiology, Bruno Balke Biodynamics Laboratory, University of Wisconsin-Madison, Madison, WI, United States
| | - Nicole A. Loggie
- Department of Kinesiology, Bruno Balke Biodynamics Laboratory, University of Wisconsin-Madison, Madison, WI, United States
| | - Anna J. Howery
- Department of Kinesiology, Bruno Balke Biodynamics Laboratory, University of Wisconsin-Madison, Madison, WI, United States
| | - Howard A. Rowley
- Wisconsin Alzheimer’s Disease Research Center, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
- Department of Radiology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
| | - Kevin M. Johnson
- Wisconsin Alzheimer’s Disease Research Center, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
| | - Sterling C. Johnson
- Wisconsin Alzheimer’s Disease Research Center, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
- Geriatric Research Education and Clinical Center, William S. Middleton Memorial Veteran’s Hospital, Madison, WI, United States
| | - Oliver Wieben
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
| | - Jill N. Barnes
- Department of Kinesiology, Bruno Balke Biodynamics Laboratory, University of Wisconsin-Madison, Madison, WI, United States
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Weston ME, Koep JL, Lester AB, Barker AR, Bond B. The acute effect of exercise intensity on peripheral and cerebral vascular function in healthy adults. J Appl Physiol (1985) 2022; 133:461-470. [PMID: 35796612 PMCID: PMC9377787 DOI: 10.1152/japplphysiol.00772.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The acute effect of exercise intensity on cerebrovascular reactivity and whether this mirrors changes in peripheral vascular function have not been investigated. The aim of this study was to explore the acute effect of exercise intensity on cerebrovascular reactivity (CVR) and peripheral vascular function in healthy young adults (n = 10, 6 females, 22.7 ± 3.5 yr). Participants completed four experimental conditions on separate days: high-intensity interval exercise (HIIE) with intervals performed at 75% maximal oxygen uptake (V̇o2max; HIIE1), HIIE with intervals performed at 90% V̇o2max (HIIE2), continuous moderate-intensity exercise (MIE) at 60% V̇o2max and a sedentary control condition (CON). All exercise conditions were completed on a cycle ergometer and matched for time (30 min) and average intensity (60% V̇o2max). Brachial artery flow-mediated dilation (FMD) and CVR of the middle cerebral artery were measured before exercise, and 1- and 3-h after exercise. CVR was assessed using transcranial Doppler ultrasonography to both hypercapnia (6% carbon dioxide breathing) and hypocapnia (hyperventilation). FMD was significantly elevated above baseline 1 and 3 h following both HIIE conditions (P < 0.05), but FMD was unchanged following the MIE and CON trials (P > 0.33). CVR to both hypercapnia and hypocapnia, and when expressed across the end-tidal CO2 range, was unchanged in all conditions, at all time points (all P > 0.14). In conclusion, these novel findings show that the acute increases in peripheral vascular function following HIIE, compared with MIE, were not mirrored by changes in cerebrovascular reactivity, which was unaltered following all exercise conditions in healthy young adults. NEW & NOTEWORTHY This is the first study to identify that acute improvements in peripheral vascular function following high-intensity interval exercise are not mirrored by improvements in cerebrovascular reactivity in healthy young adults. High-intensity interval exercise completed at both 75% and 90% V̇o2max increased brachial artery flow-mediated dilation 1 and 3 h following exercise, compared with continuous moderate-intensity exercise and a sedentary control condition. By contrast, cerebrovascular reactivity was unchanged following all four conditions.
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Affiliation(s)
- Max Edwin Weston
- Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom.,Physiology and Ultrasound Laboratory in Science and Exercise, School of Human Movement and Nutrition Sciences, University of Queensland, Brisbane, Australia
| | - Jodie L Koep
- Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom.,Physiology and Ultrasound Laboratory in Science and Exercise, School of Human Movement and Nutrition Sciences, University of Queensland, Brisbane, Australia
| | - Alice B Lester
- Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Alan R Barker
- Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Bert Bond
- Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
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Effect of a speed ascent to the top of Europe on cognitive function in elite climbers. Eur J Appl Physiol 2022; 122:635-649. [PMID: 34993575 DOI: 10.1007/s00421-021-04855-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Accepted: 11/19/2021] [Indexed: 11/03/2022]
Abstract
PURPOSE The combined effects of acute hypoxia and exercise on cognition remain to be clarified. We investigated the effect of speed climbing to high altitude on reactivity and inhibitory control in elite climbers. METHODS Eleven elite climbers performed a speed ascent of the Mont-Blanc (4810 m) and were evaluated pre- (at 1000 m) and immediately post-ascent (at 3835 m). In both conditions, a Simon task was done at rest (single-task session, ST) and during a low-intensity exercise (dual-task session, DT). Prefrontal cortex (PFC) oxygenation and middle cerebral artery velocity (MCAv) were monitored using near-infrared spectroscopy and transcranial Doppler, respectively, during the cognitive task. Self-perceived mental fatigue and difficulty to perform the cognitive tests were estimated using a visual analog scale. Heart rate and pulse oxygenation (SpO2) were monitored during the speed ascent. RESULTS Elite climbers performed an intense (~ 50% of the time ≥ 80% of maximal heart rate) and prolonged (8h58 ± 6 min) exercise in hypoxia (minimal SpO2 at 4810 m: 78 ± 4%). Reaction time and accuracy during the Simon task were similar pre- and post-ascent (374 ± 28 ms vs. 385 ± 39 ms and 6 ± 4% vs. 5 ± 4%, respectively; p > 0.05), despite a reported higher mental fatigue and difficulty to perform the Simon task post-ascent (all p < 0.05). The magnitude of the Simon effect was unaltered (p > 0.05), suggesting a preserved cognitive control post-ascent. Pattern of PFC oxygenation and MCAv differed between pre- and post-ascent as well as between ST and DT conditions. CONCLUSIONS Cognitive control is not altered in elite climbers after a speed ascent to high-altitude despite substantial cerebral deoxygenation and fatigue perception.
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8
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Koep JL, Weston ME, Barker AR, Bailey TG, Coombes JS, Lester A, Bond B. The within- and between-day reliability of cerebrovascular reactivity using traditional and novel analytical approaches. Exp Physiol 2021; 107:29-41. [PMID: 34806238 DOI: 10.1113/ep090031] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 11/15/2021] [Indexed: 12/14/2022]
Abstract
NEW FINDINGS What is the central question of the study? What is the reliability of middle cerebral artery velocity cerebrovascular reactivity (CVR) when using traditional and novel outcomes, as measured by transcranial Doppler? What is the main finding and its importance? Traditional CVR approaches presented acceptable reproducibility but should be expressed as an absolute CVR. Large within- and between-individual differences in the middle cerebral artery velocity response profile support using a dynamic peak, rather than a set time point, for the most reliable interpretation. The study highlights the utility of novel kinetic CVR outcomes, but due to increased variability in time-based metrics, this analysis requires larger sample sizes than traditional methods. ABSTRACT Cerebrovascular reactivity (CVR) of middle cerebral artery velocity (MCAv) to CO2 is a common method to assess cerebrovascular function. Yet, the approaches used to calculate CVR outcomes vary. The aim of this study was to explore the within- and between-day reliability of traditional CVR outcomes. The second aim was to explore the reliability of novel kinetic-based analyses. Healthy adults (n = 10, 22.3 ± 3.4 years) completed assessments of CVR over 4 min using a fixed fraction of inspired CO2 (6%). This was repeated across four separate visits (between-day), and on one visit measures were repeated 2.5 h later (within-day). No mean biases were present between assessments for traditional CVR metrics, expressed as absolute (cm/s/mmHg) or relative (%/mmHg) outcomes (minute 3, minute 4, peak 1 s, peak 30 s) (between-day: P > 0.14, ηp 2 < 0.20; within-day: P > 0.22, d > 0.27). Absolute, rather than relative, CVR yielded the most reproducible parameters (coefficient of variation: 8.1-13.2% vs. 14-83%, respectively). There were significant differences between CVR outcomes (P < 0.001, ηp 2 > 0.89) dependent on the time point used to determine CVR, as a steady state MCAv response was rarely observed. Furthermore, the MCAv response was not reproducible within an individual (κ = 0.15, P = 0.09). No mean differences were present for novel kinetic outcomes (amplitude, time-delay, time constant) (between-day: P > 0.05, d < 0.33; within-day: P > 0.38, d < 0.25). The results support the need for standardisation and indicate CVR should be defined as a dynamic peak, rather than a set time point for increased reliability. For novel kinetic outcomes variability was greater (CV: 8.7-120.9%) due to the nature of time-based metrics.
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Affiliation(s)
- Jodie L Koep
- Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK.,Physiology and Ultrasound Laboratory in Science and Exercise, School of Human Movement and Nutrition Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Max E Weston
- Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK.,Physiology and Ultrasound Laboratory in Science and Exercise, School of Human Movement and Nutrition Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Alan R Barker
- Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
| | - Tom G Bailey
- Physiology and Ultrasound Laboratory in Science and Exercise, School of Human Movement and Nutrition Sciences, University of Queensland, Brisbane, Queensland, Australia.,School of Nursing Midwifery and Social Work, University of Queensland, Brisbane, Queensland, Australia
| | - Jeff S Coombes
- Physiology and Ultrasound Laboratory in Science and Exercise, School of Human Movement and Nutrition Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Alice Lester
- Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
| | - Bert Bond
- Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
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9
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Carr JMJR, Caldwell HG, Carter H, Smith K, Tymko MM, Green DJ, Ainslie PN, Hoiland RL. The stability of cerebrovascular CO 2 reactivity following attainment of physiological steady-state. Exp Physiol 2021; 106:2542-2555. [PMID: 34730862 DOI: 10.1113/ep089982] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 10/14/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? During a steady-state cerebrovascular CO2 reactivity test, do different data extraction time points change the outcome for cerebrovascular CO2 reactivity? What is the main finding and its importance? Once steady-state end-tidal pressure of CO2 and haemodynamics were achieved, cerebral blood flow was stable, and so cerebrovascular CO2 reactivity values remained unchanged regardless of data extraction length (30 vs. 60 s) and time point (at 2-5 min). ABSTRACT This study assessed cerebrovascular CO2 reactivity (CVR) and examined data extraction time points and durations with the hypotheses that: (1) there would be no difference in CVR values when calculated with cerebral blood flow (CBF) measures at different time points following the attainment of physiological steady-state, (2) once steady-state was achieved there would be no difference in CVR values derived from 60 to 30 s extracted means, and (3) that changes in V ̇ E would not be associated with any changes in CVR. We conducted a single step iso-oxic hypercapnic CVR test using dynamic end-tidal forcing (end-tidal P C O 2 , +9.4 ± 0.7 mmHg), and transcranial Doppler and Duplex ultrasound of middle cerebral artery (MCA) and internal carotid artery (ICA), respectively. From the second minute of hypercapnia onwards, physiological steady-state was apparent, with no subsequent changes in end-tidal P C O 2 , P O 2 or mean arterial pressure. Therefore, CVR measured in the ICA and MCA was stable following the second minute of hypercapnia onwards. Data extraction durations of 30 or 60 s did not give statistically different CVR values. No differences in CVR were detected following the second minute of hypercapnia after accounting for mean arterial pressure via calculated conductance or covariation of mean arterial pressure. These findings demonstrate that, provided the P C O 2 stimulus remains in a steady-state, data extracted from any minute of a CVR test during physiological steady-state conditions produce equivalent CVR values; any change in the CVR value would represent a failure of CVR mechanisms, a change in the magnitude of the stimulus, or measurement error.
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Affiliation(s)
- Jay M J R Carr
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, British Columbia, Canada
| | - Hannah G Caldwell
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, British Columbia, Canada
| | - Howard Carter
- Cardiovascular Research Group, School of Human Sciences (Exercise and Sport Science), University of Western Australia, Perth, Australia
| | - Kurt Smith
- Cerebrovascular Health, Exercise, and Environmental Research Sciences Laboratory (CHEERS), School of Exercise Science and Physical Health Education, Faculty of Education, University of Victoria, Victoria, British Columbia, Canada
| | - Michael M Tymko
- Neurovascular Health Laboratory, Faculty of Kinesiology, Sport, & Recreation, University of Alberta, Edmonton, Canada
| | - Daniel J Green
- Cardiovascular Research Group, School of Human Sciences (Exercise and Sport Science), University of Western Australia, Perth, Australia
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, British Columbia, Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan Campus, Kelowna, British Columbia, Canada.,Department of Anesthesiology, Pharmacology and Therapeutics, Vancouver General Hospital, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.,International Collaborations on Repair Discoveries (ICORD), University of British Columbia, Vancouver, British Columbia, Canada
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10
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Keough JRG, Cates VC, Tymko MM, Boulet LM, Jamieson AN, Foster GE, Day TA. Regional differences in cerebrovascular reactivity in response to acute isocapnic hypoxia in healthy humans: Methodological considerations. Respir Physiol Neurobiol 2021; 294:103770. [PMID: 34343693 DOI: 10.1016/j.resp.2021.103770] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 07/15/2021] [Accepted: 07/29/2021] [Indexed: 11/30/2022]
Abstract
The cerebrovasculature responds to blood gas challenges. Regional differences (anterior vs. posterior) in cerebrovascular responses to increases in CO2 have been extensively studied. However, regional cerebrovascular reactivity (CVR) responses to low O2 (hypoxia) are equivocal, likely due to differences in analysis. We assessed the effects of acute isocapnic hypoxia on regional CVR comparing absolute and relative (%-change) responses in the middle cerebral artery (MCA) and posterior cerebral artery (PCA). We instrumented 14 healthy participants with a transcranial Doppler ultrasound (cerebral blood velocity), finometer (beat-by-beat blood pressure), dual gas analyzer (end-tidal CO2 and O2), and utilized a dynamic end-tidal forcing system to elicit a single 5-min bout of isocapnic hypoxia (∼45 Torr PETO2, ∼80 % SpO2). During exposure to acute hypoxia, absolute responses were larger in the anterior compared to posterior cerebral circulation (P < 0.001), but were not different when comparing relative responses (P = 0.45). Consistent reporting of CVR to hypoxia will aid understanding normative responses, particularly in assessing populations with impaired cerebrovascular function.
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Affiliation(s)
- Joanna R G Keough
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Valerie C Cates
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Michael M Tymko
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada; Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada; Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Lindsey M Boulet
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada; Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Alenna N Jamieson
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada
| | - Glen E Foster
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, 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.
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11
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Kaufman CS, Morris JK, Vidoni ED, Burns JM, Billinger SA. Apolipoprotein E4 Moderates the Association Between Vascular Risk Factors and Brain Pathology. Alzheimer Dis Assoc Disord 2021; 35:223-229. [PMID: 33734100 PMCID: PMC8387316 DOI: 10.1097/wad.0000000000000442] [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: 11/06/2020] [Accepted: 01/18/2021] [Indexed: 01/06/2023]
Abstract
BACKGROUND The strongest genetic risk factor for late-onset Alzheimer disease (AD), Apolipoprotein E4 (APOE4), increases cardiovascular disease risk and may also act synergistically with vascular risk factors to contribute to AD pathogenesis. Here, we assess the interaction between APOE4 and vascular risk on cerebrovascular dysfunction and brain pathology. METHODS This is an observational study of cognitively normal older adults, which included positron emission tomography imaging and vascular risk factors. We measured beat-to-beat blood pressure and middle cerebral artery velocity at rest and during moderate-intensity exercise. Cerebrovascular measures included cerebrovascular conductance index and the cerebrovascular response to exercise. RESULTS There was a significant interaction between resting cerebrovascular conductance index and APOE4 carrier status on β-amyloid deposition (P=0.026), with poor conductance in the cerebrovasculature associated with elevated β-amyloid for the APOE4 carriers only. There was a significant interaction between non-high-density lipoprotein cholesterol and APOE4 carrier status (P=0.014), with elevated non-high-density lipoprotein cholesterol predicting a blunted cerebrovascular response to exercise in APOE4 carriers and the opposite relationship in noncarriers. CONCLUSIONS Both cerebral and peripheral vascular risk factors are preferentially associated with brain pathology in APOE4 carriers. These findings provide insight into pathogenic vascular risk mechanisms and target strategies to potentially delay AD onset.
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Affiliation(s)
- Carolyn S. Kaufman
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS, USA
| | - Jill K. Morris
- University of Kansas Alzheimer’s Disease Center, Fairway, KS, USA
- Department of Neurology, University of Kansas Medical Center, Kansas City, KS
| | - Eric D. Vidoni
- University of Kansas Alzheimer’s Disease Center, Fairway, KS, USA
- Department of Neurology, University of Kansas Medical Center, Kansas City, KS
| | - Jeffrey M. Burns
- University of Kansas Alzheimer’s Disease Center, Fairway, KS, USA
- Department of Neurology, University of Kansas Medical Center, Kansas City, KS
| | - Sandra A. Billinger
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS, USA
- Department of Neurology, University of Kansas Medical Center, Kansas City, KS
- Department of Physical Therapy & Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS, USA
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12
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Crassard I, Berthet K, Lavallée P, Houot M, Payen D, Baron JC, Amarenco P, Lukaszewicz AC. Temporary application of lower body positive pressure improves intracranial velocities in symptomatic acute carotid occlusion or tight stenosis: A pilot study. Int J Stroke 2021; 17:308-314. [PMID: 33759644 DOI: 10.1177/17474930211008003] [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: 12/30/2022]
Abstract
BACKGROUND Patients with isolated cervical carotid artery occlusion not eligible to recanalization therapies but with compromised intracranial hemodynamics may be at risk of further clinical events. Apart from lying flat until spontaneous recanalization or adjustment of the collateral circulation hopefully occurs, no specific treatment is currently implemented. Improving collateral flow is an attractive option in this setting. Lower body positive pressure (LBPP) is known to result in rapid venous blood shift from the lower to the upper body part, in turn improving cardiac preload and output, and is routinely used in acute hemorrhagic shock. We report here cerebral blood flow velocities measured during LBPP in this patient population. METHODS This is a retrospective analysis of the clinical, physiological, and transcranial Doppler monitoring data collected during and 15 min after LBPP in 21 consecutive patients (10 females, median age: 54 years) with recently symptomatic isolated carotid occlusion/tight stenosis (unilateral in 18) mostly due to atherosclerosis or dissection. LBPP was applied for 90 min at a median 5 days after symptom onset. RESULTS At baseline, middle-cerebral artery velocities were markedly lower on the symptomatic, as compared to asymptomatic, side. LBPP significantly improved blood flow velocities in both the symptomatic and asymptomatic middle-cerebral artery as well as the basilar artery, which persisted 15 min after discontinuing the procedure. LBPP also resulted in mild but significant increases in mean arterial blood pressure. CONCLUSIONS LBPP improved intracranial hemodynamics downstream recently symptomatic carotid occlusion/tight stenosis as well as in the contralateral and posterior circulations, which persisted after LBPP deflation. Randomized trials should determine if this easy-to-use, noninvasive, nonpharmacologic approach has long-lasting benefits on the intracranial circulation and improves functional outcome.
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Affiliation(s)
| | - Karine Berthet
- Neurology Department, Hôpital Lariboisière, Paris, France.,Neuraltide, iPEPS, Brain and Spine Institute, Paris, France
| | - Philippa Lavallée
- Department of Neurology and Stroke Center, Hôpital Bichat, Paris, France
| | - Marion Houot
- Centre of Excellence for Neurodegenerative Disease (CoEN), Hôpital Salpêtrière, Paris, France.,Institute of Memory and Alzheimer's disease (IM2A), Department of Neurology, Hôpital Salpêtrière, AP-HP, Paris, France.,Clinical Investigation Centre, Institut du Cerveau et de la Moelle épinière (ICM), Hôpital Salpêtrière, Paris, France
| | - Didier Payen
- Université de Paris, UFR de Médecine Sorbonne, Paris, France
| | - Jean-Claude Baron
- Université de Paris, Institute of Psychiatry and Neuroscience of Paris (IPNP), 27102INSERM U1266, Paris, France.,Department of Neurology, GHU Paris Psychiatrie et Neurosciences, Hôpital Sainte-Anne, Paris, France
| | - Pierre Amarenco
- Department of Neurology and Stroke Center, Hôpital Bichat, Paris, France
| | - Anne-Claire Lukaszewicz
- Department of Anesthesiology and Intensive Care, Hôpital Edouard Herriot, Hospices Civils de Lyon, France.,EA 7426 PI3, Université de Lyon-BioMerieux, Lyon, France
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13
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Washio T, Suzuki K, Saito S, Watanabe H, Ando S, Brothers RM, Ogoh S. Effects of acute interval handgrip exercise on cognitive performance. Physiol Behav 2021; 232:113327. [PMID: 33493545 DOI: 10.1016/j.physbeh.2021.113327] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 01/12/2021] [Accepted: 01/19/2021] [Indexed: 12/16/2022]
Abstract
Previous studies have reported that even a single bout of dynamic exercise improves cognitive performance. However, the acute effect of the interval handgrip (HG) exercise protocol, which is effective in reducing resting blood pressure, on cognitive performance is poorly understood. Cognitive performance was assessed in 17 young healthy subjects before and after a resting control (e.g., time control) and the interval HG exercise (Exercise), which consisted of four trials of 2-min HG exercise at 25% of maximum voluntary contraction with 3-min recovery in between each trial. Mean arterial blood pressure (MAP) and middle cerebral artery blood velocity (MCA V) were measured continuously throughout the experiment. Memory recognition and executive function were assessed using memory recognition and Go/No-Go tasks, respectively. During interval HG exercise, MAP and mean MCA V increased from the resting baseline condition (both P < 0.049) and returned to the resting baseline levels during recovery after the interval HG exercise (both P = 1.000). The reaction time and performance accuracy of the memory recognition task did not change in either the time control condition or Exercise condition (P = 0.514 and P = 0.414 respectively). However, the changes in reaction time of Go/No-Go task from the baseline in Exercise condition was significantly shorter than that in time-control condition (P = 0.004) without affecting performance accuracy (P = 0.482). The results of the present study show that an acute interval HG exercise could improve the processing speed in executive function despite no post-exercise improvement in hemodynamic parameters in young healthy subjects. These findings suggest that the interval HG exercise is a useful exercise mode that can be expected to have a positive effect on the processing speed in executive function regardless of cardiovascular adaptation to exercise.
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Affiliation(s)
- Takuro Washio
- Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan; Research Fellow of Japan Society for the Promotion of Science, Tokyo, Japan
| | - Kazuya Suzuki
- Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan
| | - Shotaro Saito
- Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan
| | - Hironori Watanabe
- Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan
| | - Soichi Ando
- Graduate School of Informatics and Engineering, The University of Electro-Communications, Tokyo, Japan
| | - R Matthew Brothers
- Department of Kinesiology, University of Texas at Arlington, Arlington, Texas
| | - Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan.
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14
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Kaufman CS, Bai SX, Eickmeyer SM, Billinger SA. Chronic hyperglycemia before acute ischemic stroke impairs the bilateral cerebrovascular response to exercise during the subacute recovery period. Brain Behav 2021; 11:e01990. [PMID: 33295148 PMCID: PMC7882183 DOI: 10.1002/brb3.1990] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 11/17/2020] [Accepted: 11/20/2020] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND AND PURPOSE Chronic hyperglycemia contributes to cerebrovascular dysfunction by damaging blood vessels. Poor glucose control has been tied to impairments in cerebral blood flow, which may be particularly detrimental for people recovering from major cerebrovascular events such as acute ischemic stroke. In this secondary analysis, we explore for the first time the connection between chronic hyperglycemia before acute stroke and the cerebrovascular response (CVR) to exercise 3 and 6 month into the subacute recovery period. METHODS We recorded middle cerebral artery velocity (MCAv) using transcranial Doppler ultrasound bilaterally at rest and during moderate-intensity exercise in stroke patients at 3 (n = 19) and 6 (n = 12) months post-stroke. We calculated CVR as the difference between MCAv during steady-state exercise and resting MCAv. We obtained hemoglobin A1c levels (HbA1c; a measure of blood glucose over the prior 3 months) from the electronic medical record (EMR) and divided participants by HbA1c greater or less than 7%. RESULTS Participants with high HbA1c (>7%) at the time of acute stroke had significantly lower CVR to exercise for both the stroke-affected (p = .009) and non-affected (p = .007) hemispheres at 3 months post-stroke. These differences remained significant at 6 months post-stroke (stroke-affected, p = .008; non-affected, p = .016). CONCLUSIONS Patients with chronic hyperglycemia before acute ischemic stroke demonstrated impaired cerebrovascular function during exercise months into the subacute recovery period. These findings highlight the importance of maintaining tight glucose control to reduce morbidity and improve recovery post-stroke and could have implications for understanding cerebrovascular pathophysiology.
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Affiliation(s)
- Carolyn S Kaufman
- Department of Molecular and Integrative Physiology, University of Kansas, Medical Center, Kansas City, KS, USA.,Department of Physical Therapy and Rehabilitation Science, University of Kansas, Medical Center, Kansas City, KS, USA
| | - Stephen X Bai
- Department of Physical Medicine and Rehabilitation, University of Kansas, Medical Center, Kansas City, KS, USA
| | - Sarah M Eickmeyer
- Department of Physical Medicine and Rehabilitation, University of Kansas, Medical Center, Kansas City, KS, USA
| | - Sandra A Billinger
- Department of Molecular and Integrative Physiology, University of Kansas, Medical Center, Kansas City, KS, USA.,Department of Physical Therapy and Rehabilitation Science, University of Kansas, Medical Center, Kansas City, KS, USA.,Department of Physical Medicine and Rehabilitation, University of Kansas, Medical Center, Kansas City, KS, USA.,Department of Neurology, University of Kansas, Medical Center, Kansas City, KS, USA
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15
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Beishon L, Clough RH, Kadicheeni M, Chithiramohan T, Panerai RB, Haunton VJ, Minhas JS, Robinson TG. Vascular and haemodynamic issues of brain ageing. Pflugers Arch 2021; 473:735-751. [PMID: 33439324 PMCID: PMC8076154 DOI: 10.1007/s00424-020-02508-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 12/14/2020] [Accepted: 12/16/2020] [Indexed: 01/17/2023]
Abstract
The population is ageing worldwide, thus increasing the burden of common age-related disorders to the individual, society and economy. Cerebrovascular diseases (stroke, dementia) contribute a significant proportion of this burden and are associated with high morbidity and mortality. Thus, understanding and promoting healthy vascular brain ageing are becoming an increasing priority for healthcare systems. In this review, we consider the effects of normal ageing on two major physiological processes responsible for vascular brain function: Cerebral autoregulation (CA) and neurovascular coupling (NVC). CA is the process by which the brain regulates cerebral blood flow (CBF) and protects against falls and surges in cerebral perfusion pressure, which risk hypoxic brain injury and pressure damage, respectively. In contrast, NVC is the process by which CBF is matched to cerebral metabolic activity, ensuring adequate local oxygenation and nutrient delivery for increased neuronal activity. Healthy ageing is associated with a number of key physiological adaptations in these processes to mitigate age-related functional and structural declines. Through multiple different paradigms assessing CA in healthy younger and older humans, generating conflicting findings, carbon dioxide studies in CA have provided the greatest understanding of intrinsic vascular anatomical factors that may mediate healthy ageing responses. In NVC, studies have found mixed results, with reduced, equivalent and increased activation of vascular responses to cognitive stimulation. In summary, vascular and haemodynamic changes occur in response to ageing and are important in distinguishing “normal” ageing from disease states and may help to develop effective therapeutic strategies to promote healthy brain ageing.
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Affiliation(s)
- Lucy Beishon
- Department of Cardiovascular Sciences, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester, LE2 7LX, UK.
| | - Rebecca H Clough
- Department of Cardiovascular Sciences, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester, LE2 7LX, UK
| | - Meeriam Kadicheeni
- Department of Cardiovascular Sciences, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester, LE2 7LX, UK
| | - Tamara Chithiramohan
- Department of Cardiovascular Sciences, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester, LE2 7LX, UK
| | - Ronney B Panerai
- Department of Cardiovascular Sciences, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester, LE2 7LX, UK.,NIHR Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, Glenfield Hospital, Leicester, UK
| | - Victoria J Haunton
- Department of Cardiovascular Sciences, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester, LE2 7LX, UK.,NIHR Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, Glenfield Hospital, Leicester, UK
| | - Jatinder S Minhas
- Department of Cardiovascular Sciences, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester, LE2 7LX, UK.,NIHR Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, Glenfield Hospital, Leicester, UK
| | - Thompson G Robinson
- Department of Cardiovascular Sciences, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester, LE2 7LX, UK.,NIHR Leicester Biomedical Research Centre, British Heart Foundation Cardiovascular Research Centre, Glenfield Hospital, Leicester, UK
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16
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Acute intermittent hypercapnic hypoxia and cerebral neurovascular coupling in males and females. Exp Neurol 2020; 334:113441. [DOI: 10.1016/j.expneurol.2020.113441] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 07/10/2020] [Accepted: 08/21/2020] [Indexed: 01/01/2023]
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17
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Hougaard A, Younis S, Iljazi A, Haanes KA, Lindberg U, Vestergaard MB, Amin FM, Sugimoto K, Kruse LS, Ayata C, Ashina M. Cerebrovascular effects of endothelin-1 investigated using high-resolution magnetic resonance imaging in healthy volunteers. J Cereb Blood Flow Metab 2020; 40:1685-1694. [PMID: 31500524 PMCID: PMC7370364 DOI: 10.1177/0271678x19874295] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Endothelin-1 (ET-1) is a highly potent vasoconstrictor peptide released from vascular endothelium. ET-1 plays a major role in cerebrovascular disorders and likely worsens the outcome of acute ischaemic stroke and aneurismal subarachnoid haemorrhage through vasoconstriction and cerebral blood flow (CBF) reduction. Disorders that increase the risk of stroke, including hypertension, diabetes mellitus, and acute myocardial infarction, are associated with increased plasma levels of ET-1. The in vivo human cerebrovascular effects of systemic ET-1 infusion have not previously been investigated. In a two-way crossover, randomized, double-blind design, we used advanced 3 tesla MRI methods to investigate the effects of high-dose intravenous ET-1 on intra- and extracranial artery circumferences, global and regional CBF, and cerebral metabolic rate of oxygen (CMRO2) in 14 healthy volunteers. Following ET-1 infusion, we observed a 14% increase of mean arterial blood pressure, a 5% decrease of middle cerebral artery (MCA) circumference, but no effects on extracerebral arteries and no effects on CBF or CMRO2. Collectively, the findings indicate MCA constriction secondarily to blood pressure increase and not due to a direct vasoconstrictor effect of ET-1. We suggest that, as opposed to ET-1 in the subarachnoid space, intravascular ET-1 does not exert direct cerebrovascular effects in humans.
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Affiliation(s)
- Anders Hougaard
- Department of Neurology, Danish Headache Center, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Samaira Younis
- Department of Neurology, Danish Headache Center, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Afrim Iljazi
- Department of Neurology, Danish Headache Center, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Kristian A Haanes
- Department of Clinical Experimental Research, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Ulrich Lindberg
- Department of Clinical Physiology, Functional Imaging Unit, Nuclear Medicine and PET, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Mark B Vestergaard
- Department of Clinical Physiology, Functional Imaging Unit, Nuclear Medicine and PET, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Faisal M Amin
- Department of Neurology, Danish Headache Center, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Kazutaka Sugimoto
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, USA.,Department of Neurosurgery, Yamaguchi University School of Medicine, Yamaguchi, Japan
| | - Lars S Kruse
- Department of Clinical Experimental Research, Rigshospitalet Glostrup, Glostrup, Denmark.,Department of Biochemistry, Rigshospitalet Glostrup, Glostrup, Denmark
| | - Cenk Ayata
- Stroke Service, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, USA
| | - Messoud Ashina
- Department of Neurology, Danish Headache Center, Rigshospitalet Glostrup, Glostrup, Denmark
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18
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Jarrett CL, Shields KL, Broxterman RM, Hydren JR, Park SH, Gifford JR, Richardson RS. Imaging transcranial Doppler ultrasound to measure middle cerebral artery blood flow: the importance of measuring vessel diameter. Am J Physiol Regul Integr Comp Physiol 2020; 319:R33-R42. [PMID: 32401627 DOI: 10.1152/ajpregu.00025.2020] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cerebral blood flow (CBF) is commonly inferred from blood velocity measurements in the middle cerebral artery (MCA), using nonimaging, transcranial Doppler ultrasound (TCD). However, both blood velocity and vessel diameter are critical components required to accurately determine blood flow, and there is mounting evidence that the MCA is vasoactive. Therefore, the aim of this study was to employ imaging TCD (ITCD), utilizing color flow images and pulse wave velocity, as a novel approach to measure both MCA diameter and blood velocity to accurately quantify changes in MCA blood flow. ITCD was performed at rest in 13 healthy participants (7 men/6 women; 28 ± 5 yr) with pharmaceutically induced vasodilation [nitroglycerin (NTG), 0.8 mg] and without (CON). Measurements were taken for 2 min before and for 5 min following NTG or sham delivery (CON). There was more than a fivefold, significant, fall in MCA blood velocity in response to NTG (∆-4.95 ± 4.6 cm/s) compared to negligible fluctuation in CON (∆-0.88 ± 4.7 cm/s) (P < 0.001). MCA diameter increased significantly in response to NTG (∆0.09 ± 0.04 cm) compared with the basal variation in CON (∆0.00 ± 0.04 cm) (P = 0.018). Interestingly, the product of the NTG-induced fall in MCA blood velocity and increase in diameter was a significant increase in MCA blood flow following NTG (∆144 ± 159 ml/min) compared with CON (∆-5 ± 130 ml/min) (P = 0.005). These juxtaposed findings highlight the importance of measuring both MCA blood velocity and diameter when assessing CBF and document ITCD as a novel approach to achieve this goal.
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Affiliation(s)
- Catherine L Jarrett
- Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah.,Department of Internal Medicine, University of Utah, Salt Lake City, Utah
| | - Katherine L Shields
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah
| | - Ryan M Broxterman
- Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah.,Department of Internal Medicine, University of Utah, Salt Lake City, Utah
| | - Jay R Hydren
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah
| | - Soung Hun Park
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah
| | - Jayson R Gifford
- Department of Exercise Sciences, Brigham Young University, Provo, Utah
| | - Russell S Richardson
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah.,Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah.,Department of Internal Medicine, University of Utah, Salt Lake City, Utah
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19
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Perdomo SJ, Ward J, Liu Y, Vidoni ED, Sisante JF, Kirkendoll K, Burns JM, Billinger SA. Cardiovascular disease risk is associated with middle cerebral artery blood flow velocity in older adults. Cardiopulm Phys Ther J 2020; 31:38-46. [PMID: 33100924 PMCID: PMC7580865 DOI: 10.1097/cpt.0000000000000110] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
PURPOSE The aim of this study was to evaluate the relationship of cardiovascular disease (CVD) on middle cerebral blood flow velocity (MCAv) at rest and during exercise. A secondary aim was to explore the relationship between MCAv and 1) the presence of white matter lesions and 2) cognitive function. METHODS We recruited individuals who were cognitively normal older adults. CVD risk was assessed by the Pooled Cohort atherosclerotic cardiovascular disease (ASCVD) risk score. Transcranial Doppler ultrasound measured middle cerebral artery at rest and during a bout of moderate intensity exercise. We quantified white matter lesions from MRI and cognitive function outcomes included executive function, language, processing speed, and attention. RESULTS Seventy-two participants 70.1 ± 4.7 years of age completed the study protocol. ASCVD risk score was significantly associated with resting and exercise MCAv (p<0.01) but not associated with white matter lesions (p>0.468). We observed a significant association between resting and exercise MCAv and language processing (p=0.010) but not other cognitive domains. CONCLUSION In cognitively normal older adults, higher ASCVD risk score was associated with blunted resting and exercise MCAv and with lower language processing performance. These results highlight the need for CVD risk management to maintain optimal brain health.
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Affiliation(s)
- Sophy J Perdomo
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS USA
| | - Jaimie Ward
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS USA
| | - Yumei Liu
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS USA
| | - Eric D Vidoni
- University of Kansas Alzheimer’s Disease Center, University of Kansas Medical Center, Fairway, KS USA
| | - Jason F Sisante
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS USA
- Department of Physical Medicine and Rehabilitation, University of Kansas Medical Center, Kansas City, KS USA
| | - Kiersten Kirkendoll
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS USA
| | - Jeffrey M Burns
- University of Kansas Alzheimer’s Disease Center, University of Kansas Medical Center, Fairway, KS USA
| | - Sandra A Billinger
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS USA
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20
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Burley CV, Lucas RAI, Whittaker AC, Mullinger K, Lucas SJE. The CO 2 stimulus duration and steady-state time point used for data extraction alters the cerebrovascular reactivity outcome measure. Exp Physiol 2020; 105:893-903. [PMID: 32083357 DOI: 10.1113/ep087883] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Accepted: 02/19/2020] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Cerebrovascular reactivity (CVR) is a common functional test to assess brain health, and impaired CVR has been associated with all-cause cardiovascular mortality: does the duration of the CO2 stimulus and the time point used for data extraction alter the CVR outcome measure? What is the main finding and its importance? This study demonstrated CVR measures calculated from 1 and 2 min CO2 stimulus durations were significantly higher than CVR calculated from a 4 min CO2 stimulus. CVRs calculated from the first 2 min of the CO2 stimulus were significantly higher than CVR values calculated from the final minute if the duration was ≥4 min. This study highlights the need for consistent methodological approaches. ABSTRACT Cerebrovascular reactivity to carbon dioxide (CVR) is a common functional test to assess brain vascular health, though conflicting age and fitness effects have been reported. Studies have used different CO2 stimulus durations to induce CVR and extracted data from different time points for analysis. Therefore, this study examined whether these differences alter CVR and explain conflicting findings. Eighteen healthy volunteers (24 ± 5 years) inhaled CO2 for four stimulus durations (1, 2, 4 and 5 min) of 5% CO2 (in air) via the open-circuit Douglas bag method, in a randomized order. CVR data were derived from transcranial Doppler (TCD) measures of middle cerebral artery blood velocity (MCAv), with concurrent ventilatory sensitivity to the CO2 stimulus ( V ̇ E , C O 2 ). Repeated measures ANOVAs compared CVR and V ̇ E , C O 2 measures between stimulus durations and steady-state time points. An effect of stimulus duration was observed (P = 0.002, η² = 0.140), with 1 min (P = 0.010) and 2 min (P < 0.001) differing from 4 min, and 2 min differing from 5 min (P = 0.019) durations. V ̇ E , C O 2 sensitivity increased ∼3-fold from 1 min to 4 and 5 min durations (P < 0.001, η² = 0.485). CVRs calculated from different steady-state time points within each stimulus duration were different (P < 0.001, η² = 0.454), specifically for 4 min (P = 0.001) and 5 min (P < 0.001), but not 2 min stimulus durations (P = 0.273). These findings demonstrate that methodological differences alter the CVR measure.
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Affiliation(s)
- Claire V Burley
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.,Centre for Human Brain Health, University of Birmingham, Birmingham, UK
| | - Rebekah A I Lucas
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - Anna C Whittaker
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - Karen Mullinger
- Centre for Human Brain Health, University of Birmingham, Birmingham, UK.,School of Psychology, University of Birmingham, Birmingham, UK.,School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | - Samuel J E Lucas
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.,Centre for Human Brain Health, University of Birmingham, Birmingham, UK.,Department of Physiology, University of Otago, New Zealand
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21
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Kaufman CS, Vidoni ED, Burns JM, Alwatban MR, Billinger SA. Self-Reported Omega-3 Supplement Use Moderates the Association between Age and Exercising Cerebral Blood Flow Velocity in Older Adults. Nutrients 2020; 12:E697. [PMID: 32150983 PMCID: PMC7146423 DOI: 10.3390/nu12030697] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 02/27/2020] [Accepted: 03/02/2020] [Indexed: 12/11/2022] Open
Abstract
Cerebral blood flow (CBF) decreases across the lifespan, and chronic conditions such as dementia and stroke accelerate this decline. Impaired CBF results in reduced delivery of oxygen and nutrients, which can damage the brain over time. Thus, there is a need to identify lifestyle interventions, including diet and exercise, to maintain CBF with aging and in the presence of chronic disease. In the present study, we used transcranial Doppler ultrasound to record middle cerebral artery velocity (MCAv), a surrogate measure of CBF, during moderate-intensity exercise in sedentary, cognitively normal older adults (n = 90). A multiple linear regression model (F(4, 85) = 3.21, p = 0.02) showed that self-reported omega-3 supplement use significantly moderated the association between age and mean exercising MCAv in these individuals (p = 0.01). Older age was associated with lower exercising MCAv in the group not taking omega-3 supplements, while exercising MCAv showed no decline with increasing age in the group who reported omega-3 supplement use. These findings suggest omega-3 supplementation may have an important role in the preservation of CBF with aging.
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Affiliation(s)
- Carolyn S. Kaufman
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA;
| | - Eric D. Vidoni
- University of Kansas Alzheimer’s Disease Center, Fairway, KS 66103, USA; (E.D.V.); (J.M.B.)
| | - Jeffrey M. Burns
- University of Kansas Alzheimer’s Disease Center, Fairway, KS 66103, USA; (E.D.V.); (J.M.B.)
| | - Mohammed R. Alwatban
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, 3901 Rainbow Boulevard, MS 2002, Kansas City, KS 66160, USA;
| | - Sandra A. Billinger
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA;
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, 3901 Rainbow Boulevard, MS 2002, Kansas City, KS 66160, USA;
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22
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Favre ME, Lim V, Falvo MJ, Serrador JM. Cerebrovascular reactivity and cerebral autoregulation are improved in the supine posture compared to upright in healthy men and women. PLoS One 2020; 15:e0229049. [PMID: 32119678 PMCID: PMC7051088 DOI: 10.1371/journal.pone.0229049] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 01/28/2020] [Indexed: 12/04/2022] Open
Abstract
Cerebrovascular reactivity and cerebral autoregulation are two major mechanisms that regulate cerebral blood flow. Both mechanisms are typically assessed in either supine or seated postures, but the effects of body position and sex differences remain unclear. This study examined the effects of body posture (supine vs. seated vs. standing) on cerebrovascular reactivity during hyper and hypocapnia and on cerebral autoregulation during spontaneous and slow-paced breathing in healthy men and women using transcranial Doppler ultrasonography of the middle cerebral artery. Results indicated significantly improved cerebrovascular reactivity in the supine compared with seated and standing postures (supine = 3.45±0.67, seated = 2.72±0.53, standing = 2.91±0.62%/mmHg, P<0.0167). Similarly, cerebral autoregulatory measures showed significant improvement in the supine posture during slow-paced breathing. Transfer function measures of gain significantly decreased and phase significantly increased in the supine posture compared with seated and standing postures (gain: supine = 1.98±0.56, seated = 2.37±0.53, standing = 2.36±0.71%/mmHg; phase: supine = 59.3±21.7, seated = 39.8±12.5, standing = 36.5±9.7°; all P<0.0167). In contrast, body posture had no effect on cerebral autoregulatory measures during spontaneous breathing. Men and women had similar cerebrovascular reactivity and similar cerebral autoregulation during both spontaneous and slow-paced breathing. These data highlight the importance of making comparisons within the same body position to ensure there is not a confounding effect of posture.
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Affiliation(s)
- Michelle E. Favre
- Department of Pharmacology, Physiology and Neuroscience, Rutgers Biomedical and Health Sciences, Newark, New Jersey, United States of America
| | - Valerie Lim
- Department of Pharmacology, Physiology and Neuroscience, Rutgers Biomedical and Health Sciences, Newark, New Jersey, United States of America
| | - Michael J. Falvo
- Department of Pharmacology, Physiology and Neuroscience, Rutgers Biomedical and Health Sciences, Newark, New Jersey, United States of America
- Department of Physical Medicine and Rehabilitation, Rutgers Biomedical and Health Sciences, Newark, New Jersey, United States of America
- Department of Veterans Affairs, War Related Illness and Injury Study Center, East Orange, New Jersey, United States of America
| | - Jorge M. Serrador
- Department of Pharmacology, Physiology and Neuroscience, Rutgers Biomedical and Health Sciences, Newark, New Jersey, United States of America
- Department of Cardiovascular Electronics, National University of Ireland Galway, Galway, Ireland
- * E-mail:
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23
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Tucker WJ, Thomas BP, Puzziferri N, Samuel TJ, Zaha VG, Lingvay I, Almandoz J, Wang J, Gonzales EA, Brothers RM, Nelson MD. Impact of bariatric surgery on cerebral vascular reactivity and cognitive function: a non-randomized pilot study. Pilot Feasibility Stud 2020; 6:21. [PMID: 32082607 PMCID: PMC7017515 DOI: 10.1186/s40814-020-00569-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 02/06/2020] [Indexed: 01/03/2023] Open
Abstract
Background Bariatric surgery is an effective long-term weight loss strategy yielding improvements in neurocognitive function; however, the mechanism(s) responsible for these improvements remains unclear. Here, we assessed the feasibility of using magnetic resonance imaging (MRI) to evaluate whether cerebral vascular reactivity (CVR) is impaired in severely obese bariatric surgery candidates compared with normal weight healthy controls and whether CVR improves following bariatric surgery. We also investigated whether changes in CVR were associated with changes in cognitive function. Methods Bariatric surgery candidates (n = 6) were compared with normal weight healthy controls of a similar age (n = 10) at baseline, and then reassessed 2 weeks and 14 weeks following sleeve gastrectomy bariatric surgery. Young reference controls (n = 7) were also studied at baseline to establish the range of normal for each outcome measure. Microvascular and macrovascular CVR to hypercapnia (5% CO2) were assessed using blood-oxygen-level-dependent (BOLD) MRI, and changes in the middle cerebral artery (MCA) cross-sectional area, respectively. Cognitive function was assessed using a validated neurocognitive software. Results Compliance with the CVR protocol was high. Both macro- and micro-cerebrovascular function were highest in the young reference controls. Cognitive function was lower in obese bariatric surgery candidates compared with normal weight controls, and improved by 17% at 2 weeks and 21% by 14 weeks following bariatric surgery. To our surprise, whole-brain CVR BOLD did not differ between obese bariatric surgery candidates and normal weight controls of similar age (0.184 ± 0.101 vs. 0.192 ± 0.034 %BOLD/mmHgCO2), and did not change after bariatric surgery. In contrast, we observed vasoconstriction of the MCA during hypercapnia in 60% of the obese patients prior to surgery, which appeared to be abolished following bariatric surgery. Improvements in cognitive function were not associated with improvements in either CVR BOLD or MCA vasodilation after bariatric surgery. Conclusions Assessing CVR responses to a hypercapnic challenge with MRI was feasible in severely obese bariatric patients. However, no changes in whole-brain BOLD CVR were observed following bariatric surgery despite improvements in cognitive function. We recommend that future large trials assess CVR responses to cognitive tasks (rather than hypercapnia) to better define the mechanisms responsible for cognitive function improvements following bariatric surgery.
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Affiliation(s)
- Wesley J Tucker
- 1Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington, Science & Engineering Innovation & Research Building, 701 S. Nedderman Drive, Room 105, Arlington, TX 76019 USA.,2Department of Nutrition & Food Sciences, Texas Woman's University, Houston, TX USA
| | - Binu P Thomas
- 3Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX USA.,4Department of Bioengineering, University of Texas at Arlington, Arlington, TX USA
| | - Nancy Puzziferri
- 5Department of Surgery, Oregon Health & Science University, Portland, OR USA
| | - T Jake Samuel
- 1Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington, Science & Engineering Innovation & Research Building, 701 S. Nedderman Drive, Room 105, Arlington, TX 76019 USA
| | - Vlad G Zaha
- 3Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX USA.,6Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, TX USA
| | - Ildiko Lingvay
- 7Division of Endocrinology, Diabetes, and Metabolism, University of Texas Southwestern Medical Center, Dallas, TX USA
| | - Jaime Almandoz
- 7Division of Endocrinology, Diabetes, and Metabolism, University of Texas Southwestern Medical Center, Dallas, TX USA
| | - Jing Wang
- 8College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, TX USA
| | - Edward A Gonzales
- 1Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington, Science & Engineering Innovation & Research Building, 701 S. Nedderman Drive, Room 105, Arlington, TX 76019 USA.,8College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, TX USA
| | - R Matthew Brothers
- 1Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington, Science & Engineering Innovation & Research Building, 701 S. Nedderman Drive, Room 105, Arlington, TX 76019 USA
| | - Michael D Nelson
- 1Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington, Science & Engineering Innovation & Research Building, 701 S. Nedderman Drive, Room 105, Arlington, TX 76019 USA.,4Department of Bioengineering, University of Texas at Arlington, Arlington, TX USA
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24
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Estimation of pulsatile cerebral arterial blood volume based on transcranial doppler signals. Med Eng Phys 2019; 74:23-32. [DOI: 10.1016/j.medengphy.2019.07.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 06/30/2019] [Accepted: 07/28/2019] [Indexed: 11/20/2022]
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25
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Herrington BA, Thrall SF, Mann LM, Tymko MM, Day TA. The effect of steady-state CO 2 on regional brain blood flow responses to increases in blood pressure via the cold pressor test. Auton Neurosci 2019; 222:102581. [PMID: 31654818 DOI: 10.1016/j.autneu.2019.102581] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 07/08/2019] [Accepted: 08/19/2019] [Indexed: 10/26/2022]
Abstract
The pressure-passive cerebrovasculature is affected by alterations in cerebral perfusion pressure (CPP) and arterial blood gases (e.g., pressure of arterial [Pa]CO2), where acute changes in either stimulus can influence cerebral blood flow (CBF). The effect of superimposed increases in CPP at different levels of steady-state PaCO2 on regional CBF regulation is unclear. In 17 healthy participants, we simultaneously recorded continuous heart rate (electrocardiogram), blood pressure (finometer), pressure of end-tidal CO2 (PETCO2; gas analyzer), and middle (MCA) and posterior (PCA) cerebral artery blood velocity (CBV; transcranial Doppler ultrasound). Three separate CPTs were administered by passive immersion of both feet into 0-1 °C of ice water for 3-min under three randomized and coached steady-state PETCO2 conditions: normocapnia (room air), hypocapnia (-10 Torr; hyperventilation) and hypercapnia (+9 Torr; 5% inspired CO2;). CBV responses were calculated as the absolute difference (∆) between baseline and mean MCAv and PCAv during the 3-min CPT. Both the ∆MCAv and ∆PCAv responses to the CPT were larger under hypercapnic conditions. The absolute ∆MCAv response was larger than the ∆PCAv during the CPT across all three CO2 trials. Cerebrovascular CO2 reactivity (CVR) was larger in the MCA than PCA in both CPT and baseline conditions, but there were no differences in CVR between CPT and baseline conditions. Our data indicate that (a) increases in CO2 increases the CBV responses to a CPT, (b) the anterior cerebrovasculature is more responsive to a CPT-induced increases in MAP, and (c) although unchanged during a CPT, CVR is larger in the anterior cerebral circulation.
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Affiliation(s)
- Brittney A Herrington
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada
| | - Scott F Thrall
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada
| | - Leah M Mann
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada
| | - Michael M Tymko
- Centre for Heart, Lung and Vascular Health, University of British Columbia, British Columbia, Canada
| | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada.
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26
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Miller KB, Howery AJ, Rivera-Rivera LA, Johnson SC, Rowley HA, Wieben O, Barnes JN. Age-Related Reductions in Cerebrovascular Reactivity Using 4D Flow MRI. Front Aging Neurosci 2019; 11:281. [PMID: 31680935 PMCID: PMC6811507 DOI: 10.3389/fnagi.2019.00281] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 10/01/2019] [Indexed: 12/12/2022] Open
Abstract
Cerebrovascular reactivity (CVR), is important for determining future risk of cerebrovascular disease. It is unclear if primary aging is associated with reductions in CVR because previous studies often include participants with vascular risk factors. Additionally, the inconsistency in the literature may be due to the inherent difficulty in quantifying intracranial cerebral blood flow and CVR. To address these limitations, we determined the effect of age on CVR in the large intracranial vessels in adults with low vascular risk using state-of-the-art MRI techniques. We also determined if the effect of age on CVR was sex-specific. Young (n = 20; 25 ± 3 years) and older (n = 19; 61 ± 5 years) healthy, physically active adults participated in the study. CVR was measured in response to hypercapnia using 4D flow MRI, which allows for simultaneous angiographic and quantitative blood flow measurements in the intracranial arteries. Older adults had lower global CVR and CVR in multiple intracranial arteries [right and left internal carotid arteries (ICA), right and left middle cerebral arteries (MCA), and basilar artery (BA)] compared with young adults (p < 0.05 for all). In addition, the MCA dilated significantly in response to hypercapnia in young (p < 0.05), but not older adults. Young men demonstrated higher global CVR and CVR in multiple intracranial arteries (ICAs, MCAs, and BA) compared with young women and older men (p < 0.05 for both); however, CVR did not differ between young women and older women. Our results demonstrate that, using 4D flow MRI, primary aging is associated with lower CVR in adults with low vascular risk. In addition, the effect of age on CVR may be driven by men. The 4D flow MRI technique may provide a promising new alternative to measure cerebrovascular physiology without the limitations of commonly used techniques. Future studies could utilize this MRI technique to examine interventions to maintain CVR with advancing age. This study was registered under clinicaltrials.gov # NCT02840851.
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Affiliation(s)
- Kathleen B Miller
- Bruno Balke Biodynamics Laboratory, Department of Kinesiology, University of Wisconsin-Madison, Madison, WI, United States
| | - Anna J Howery
- Bruno Balke Biodynamics Laboratory, Department of Kinesiology, University of Wisconsin-Madison, Madison, WI, United States
| | - Leonardo A Rivera-Rivera
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
| | - Sterling C Johnson
- Wisconsin Alzheimer's Disease Research Center, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States.,William S. Middleton Memorial Veterans Hospital, Geriatric Research Education and Clinical Center, Madison, WI, United States
| | - Howard A Rowley
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States.,Wisconsin Alzheimer's Disease Research Center, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
| | - Oliver Wieben
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
| | - Jill N Barnes
- Bruno Balke Biodynamics Laboratory, Department of Kinesiology, University of Wisconsin-Madison, Madison, WI, United States
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27
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Fan JL, O'Donnell T, Gray CL, Croft K, Noakes AK, Koch H, Tzeng YC. Dietary nitrate supplementation enhances cerebrovascular CO 2 reactivity in a sex-specific manner. J Appl Physiol (1985) 2019; 127:760-769. [PMID: 31318615 DOI: 10.1152/japplphysiol.01116.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Insufficient nitric oxide (NO) bioavailability plays an important role in endothelial dysfunction, and increased NO has the potential to enhance cerebral blood flow (CBF). Dietary supplementation with sodium nitrate, a precursor of NO, could improve cerebrovascular function, but this has not been investigated. In 17 individuals, we examined the effects of a 7-day supplementation of dietary nitrate (0.1 mmol·kg-1·day -1) on cerebrovascular function using a randomized, single-blinded placebo-controlled crossover design. We hypothesized that 7-day dietary nitrate supplementation increases CBF response to CO2 (cerebrovascular CO2 reactivity) and cerebral autoregulation (CA). We assessed middle cerebral artery blood velocity (MCAv) and blood pressure (BP) at rest and during CO2 breathing. Transfer function analysis was performed on resting beat-to-beat MCAv and BP to determine CA, from which phase, gain, and coherence of the BP-MCAv data were derived. Dietary nitrate elevated plasma nitrate concentration by ~420% (P < 0.001) and lowered gain (d = 1.2, P = 0.025) and phase of the BP-MCAv signal compared with placebo treatment (d = 0.7, P = 0.043), while coherence was unaffected (P = 0.122). Dietary nitrate increased the MCAv-CO2 slope in a sex-specific manner (interaction: P = 0.016). Dietary nitrate increased the MCAv-CO2 slope in men (d = 1.0, P = 0.014 vs. placebo), but had no effect in women (P = 0.919). Our data demonstrate that dietary nitrate greatly increased cerebrovascular CO2 reactivity in healthy individuals, while its effect on CA remains unclear. The selective increase in the MCAv-CO2 slope observed in men indicates a clear sexual dimorphic role of NO in cerebrovascular function.NEW & NOTEWORTHY We found dietary nitrate supplementation improved the brain blood vessels' response to CO2, cerebrovascular CO2 reactivity, without affecting blood pressure in a group of healthy individuals. Meanwhile, the effect of dietary nitrate on the relationship between blood pressure and brain blood flow, cerebral autoregulation, was inconclusive. The improvement in cerebrovascular CO2 reactivity was only observed in the male participants, alluding to a sex difference in the effect of dietary nitrate on brain blood flow control. Our findings indicate that dietary nitrate could be an effective strategy to enhance cerebrovascular CO2 reactivity.
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Affiliation(s)
- Jui-Lin Fan
- Wellington Medical Technology Group, Department of Surgery and Anaesthesia, University of Otago, Wellington, New Zealand.,Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - Terrence O'Donnell
- Wellington Medical Technology Group, Department of Surgery and Anaesthesia, University of Otago, Wellington, New Zealand.,Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - Clint Lee Gray
- Centre for Translational Physiology, University of Otago, Wellington, New Zealand.,Paediatrics and Child Health, University of Otago, Wellington, New Zealand
| | - Kevin Croft
- School of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Western Australia, Perth, Australia
| | - Annabel Kate Noakes
- Wellington Medical Technology Group, Department of Surgery and Anaesthesia, University of Otago, Wellington, New Zealand.,Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - Henrietta Koch
- School of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Western Australia, Perth, Australia
| | - Yu-Chieh Tzeng
- Wellington Medical Technology Group, Department of Surgery and Anaesthesia, University of Otago, Wellington, New Zealand.,Centre for Translational Physiology, University of Otago, Wellington, New Zealand
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28
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Perdomo SJ, Balzer JR, Jakicic JM, Kline CE, Gibbs BB. Acute effects of aerobic exercise duration on blood pressure, pulse wave velocity and cerebral blood flow velocity in middle-aged adults. SPORT SCIENCES FOR HEALTH 2019. [DOI: 10.1007/s11332-019-00566-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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29
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Witte E, Liu Y, Ward JL, Kempf KS, Whitaker A, Vidoni ED, Craig JC, Poole DC, Billinger SA. Exercise intensity and middle cerebral artery dynamics in humans. Respir Physiol Neurobiol 2019; 262:32-39. [PMID: 30710650 PMCID: PMC6393201 DOI: 10.1016/j.resp.2019.01.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 01/11/2019] [Accepted: 01/29/2019] [Indexed: 12/24/2022]
Abstract
Despite its necessity for understanding healthy brain aging, the influence of exercise intensity on cerebrovascular kinetics is currently unknown. We, therefore characterized middle cerebral artery blood flow velocity (MCAv) kinetics associated with two exercise intensities: low and moderate. We hypothesized that increasing exercise intensity would increase the MCAv amplitude response (Amp) and that age and estimated fitness (V̇O2max) would be related to Amp. Baseline (BL) values were collected for 90-seconds followed by a 6-minute exercise bout. Heart rate, end-tidal CO2, mean arterial pressure and MCAv were recorded throughout. MCAv kinetics were described by Amp, time delay (TD) and time constant (τ). Sixty-four adults completed the study. Amp was greater during moderate compared to low exercise intensity (p < 0.001) while no difference was observed in either TD (p = 0.65) or τ (p = 0.47). Amp was negatively associated with age (p < 0.01) and positively correlated with estimated V̇O2max (p < 0.01). Although Amp declines with age, maintaining higher V̇O2max may benefit the cerebrovascular response to exercise.
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Affiliation(s)
- Emily Witte
- University of Kansas Medical Center, Physical Therapy and Rehabilitation Science, MS 2002, 3901 Rainbow Boulevard, Kansas City, KS 66160, United States
| | - Yumei Liu
- University of Kansas Medical Center, Physical Therapy and Rehabilitation Science, MS 2002, 3901 Rainbow Boulevard, Kansas City, KS 66160, United States
| | - Jaimie L Ward
- University of Kansas Medical Center, Physical Therapy and Rehabilitation Science, MS 2002, 3901 Rainbow Boulevard, Kansas City, KS 66160, United States
| | - Katie S Kempf
- University of Kansas Medical Center, Physical Therapy and Rehabilitation Science, MS 2002, 3901 Rainbow Boulevard, Kansas City, KS 66160, United States
| | - Alicen Whitaker
- University of Kansas Medical Center, Physical Therapy and Rehabilitation Science, MS 2002, 3901 Rainbow Boulevard, Kansas City, KS 66160, United States
| | - Eric D Vidoni
- University of Kansas, Alzheimer's Disease Center, KU Clinical Research Center 4350 Shawnee Mission Parkway, MS 6002, Fairway, KS 66205, United States
| | - Jesse C Craig
- Kansas State University, Departments of Kinesiology, 131 Coles Hall, 920 Denison Ave, Manhattan, KS 66506, United States
| | - David C Poole
- Kansas State University, Departments of Kinesiology, 131 Coles Hall, 920 Denison Ave, Manhattan, KS 66506, United States
| | - Sandra A Billinger
- University of Kansas Medical Center, Physical Therapy and Rehabilitation Science, MS 2002, 3901 Rainbow Boulevard, Kansas City, KS 66160, United States.
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30
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Favre ME, Serrador JM. Sex differences in cerebral autoregulation are unaffected by menstrual cycle phase in young, healthy women. Am J Physiol Heart Circ Physiol 2019; 316:H920-H933. [DOI: 10.1152/ajpheart.00474.2018] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sex is known to affect the prevalence of conditions such as stroke. However, effects of sex on cerebral blood flow regulation are still not well understood. Critical to this understanding is how fluctuations in hormones across the menstrual cycle affect cerebral autoregulation. We measured autoregulation in the early follicular, late follicular, and midluteal phases during spontaneous and induced blood pressure oscillations in 26 young, healthy individuals (13 women and 13 men, age: 26 ± 4 yr). Men participated three times, ~1–3 wk apart. Beat-by-beat blood pressure, heart rate, end-tidal CO2, and transcranial Doppler ultrasonography of the middle (MCA) and anterior (ACA) cerebral arteries were obtained. We did not find a difference in cerebral autoregulation across the menstrual cycle in women but found significantly improved autoregulation in the MCA and ACA of women compared with men. Women demonstrated significantly lower MCA gain (0.97 ± 0.13 vs. 1.17 ± 0.14%/mmHg, P = 0.001), higher MCA phase (46.1 ± 12.6 vs. 35.8 ± 7.9°, P = 0.019), and higher ACA phase (40.5 ± 10.8 vs 31.5 ± 8.5°, P = 0.040) during repeated squat-to-stand maneuvers. Women also had lower MCA gain (1.50 ± 0.11 vs. 1.72 ± 0.30%/mmHg, P = 0.029) during spontaneous fluctuations in pressure while standing and less of a decrease in MCA flow velocity (−18.7 ± 2.7 vs. −23.2 ± 6.0%, P = 0.014) during sit-to-stand maneuvers. Our results suggest that young women have improved cerebral autoregulation compared with young men regardless of menstrual cycle phase and that autoregulation is relatively robust to acute fluctuations in female sex hormones. NEW & NOTEWORTHY This is the first study to investigate thoroughly the effects of menstrual cycle phase and sex differences in cerebral autoregulation in young, healthy individuals. Cerebral autoregulation was unaffected by menstrual cycle phase during both repeated squat-to-stand and sit-to-stand maneuvers. However, women demonstrated significantly improved cerebral autoregulation in the middle and anterior cerebral arteries, suggesting women were able to maintain cerebral blood flow during changes in blood pressure more efficiently than men.
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Affiliation(s)
- Michelle E. Favre
- Department of Pharmacology, Physiology and Neuroscience; Rutgers Biomedical and Health Sciences, Newark, New Jersey
| | - Jorge M. Serrador
- Department of Pharmacology, Physiology and Neuroscience; Rutgers Biomedical and Health Sciences, Newark, New Jersey
- War-Related Illness and Injury Study Center, Department of Veterans Affairs, East Orange, New Jersey
- Department of Cardiovascular Electronics, National University of Ireland Galway, Galway, Ireland
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31
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Guiney H, Lucas SJE, Cotter JD, Machado L. Investigating links between habitual physical activity, cerebrovascular function, and cognitive control in healthy older adults. Neuropsychologia 2019; 125:62-69. [PMID: 30682349 DOI: 10.1016/j.neuropsychologia.2019.01.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 11/29/2018] [Accepted: 01/22/2019] [Indexed: 12/20/2022]
Abstract
A growing body of evidence indicates regular physical activity benefits older adults' cognitive functioning, particularly when a high level of cognitive control is required. Recent research has pointed to improved cerebrovascular function as one mechanism through which such benefits might arise. This study built on previous research by investigating in 51 healthy older adults aged 60-72 years relationships between habitual physical activity, cerebrovascular function (indicated by resting cerebral blood flow velocity in the middle cerebral artery [n = 42], and its responsiveness to hypercapnia [n = 26] and hypocapnia [n = 25]), and cognitive control (inhibition and switching). Linear regression analyses showed moderate positive associations between physical activity and inhibitory control, but not cerebrovascular function. There were also no significant relationships between the cerebrovascular measures and cognitive control. These results indicate that regular engagement in physical activity is associated with superior inhibitory control in older adulthood, but cerebrovascular function was not found to explain those relationships. Taken together, the current findings reinforce reports of positive links between habitual physical activity and cognition in healthy older adults, but also signal that interrelationships with cerebrovascular function may be more complex than currently indicated by the literature, necessitating further research to elucidate the role cerebrovascular function might play in accounting for physical activity-cognition links in healthy older adults.
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Affiliation(s)
- Hayley Guiney
- Department of Psychology and Brain Health Research Centre, University of Otago, Dunedin, New Zealand; Brain Research New Zealand, Auckland, New Zealand.
| | - Samuel J E Lucas
- Department of Physiology, University of Otago, Dunedin, New Zealand; School of Sport, Exercise, and Rehabilitation Sciences and Centre for Human Brain Health, University of Birmingham, Birmingham, England
| | - James D Cotter
- School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Liana Machado
- Department of Psychology and Brain Health Research Centre, University of Otago, Dunedin, New Zealand; Brain Research New Zealand, Auckland, New Zealand
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32
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Sisante JFV, Vidoni ED, Kirkendoll K, Ward J, Liu Y, Kwapiszeski S, Maletsky R, Burns JM, Billinger SA. Blunted cerebrovascular response is associated with elevated beta-amyloid. J Cereb Blood Flow Metab 2019; 39:89-96. [PMID: 28914134 PMCID: PMC6311677 DOI: 10.1177/0271678x17732449] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The goal of this study was to explore the association of beta-amyloid accumulation and cerebrovascular response (CVR) in cognitively normal older adults. Beta-amyloid accumulation was characterized with [18F] Florbetapir positron emission tomography scans. CVR was calculated as middle cerebral artery blood flow velocity change from rest to moderate intensity exercise. We found that individuals with elevated beta-amyloid aggregation had a blunted CVR ( n = 25, age 70.1 ± 4.8; 3.3 ± 3.7 cm/s) compared to non-elevated individuals ( n = 45, age 72.0 ± 4.9; 7.2 ± 5.0 cm/s, p < 0.001). Further, greater beta-amyloid burden was linearly associated with less CVR across all participants (b = -11.7, p < 0.001). Greater CVR and less beta-amyloid burden were associated with processing speed ( p < 0.05). This study is the first to show that CVR from rest to exercise is blunted across increased global beta-amyloid burden.
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Affiliation(s)
- Jason-Flor V Sisante
- 1 Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS, USA
| | - Eric D Vidoni
- 2 University of Kansas Alzheimer's Disease Center, Fairway, KS, USA
| | - Kiersten Kirkendoll
- 1 Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS, USA
| | - Jaimie Ward
- 1 Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS, USA
| | - Yumei Liu
- 1 Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS, USA
| | - Sarah Kwapiszeski
- 1 Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS, USA
| | | | - Jeffrey M Burns
- 2 University of Kansas Alzheimer's Disease Center, Fairway, KS, USA
| | - Sandra A Billinger
- 1 Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS, USA
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33
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Falvo MJ, Lindheimer JB, Serrador JM. Dynamic cerebral autoregulation is impaired in Veterans with Gulf War Illness: A case-control study. PLoS One 2018; 13:e0205393. [PMID: 30321200 PMCID: PMC6188758 DOI: 10.1371/journal.pone.0205393] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 09/25/2018] [Indexed: 02/03/2023] Open
Abstract
Neurological dysfunction has been reported in Gulf War Illness (GWI), including abnormal cerebral blood flow (CBF) responses to physostigmine challenge. However, it is unclear whether the CBF response to normal physiological challenges and regulation is similarly dysfunctional. The goal of the present study was to evaluate the CBF velocity response to orthostatic stress (i.e., sit-to-stand maneuver) and increased fractional concentration of carbon dioxide. 23 cases of GWI (GWI+) and 9 controls (GWI) volunteered for this study. Primary variables of interest included an index of dynamic autoregulation and cerebrovascular reactivity. Dynamic autoregulation was significantly lower in GWI+ than GWI- both for autoregulatory index (2.99±1.5 vs 4.50±1.5, p = 0.017). In addition, we observed greater decreases in CBF velocity both at the nadir after standing (-18.5±6.0 vs -9.8±4.9%, p = 0.001) and during steady state standing (-5.7±7.1 vs -1.8±3.2%, p = 0.042). In contrast, cerebrovascular reactivity was not different between groups. In our sample of Veterans with GWI, dynamic autoregulation was impaired and consistent with greater cerebral hypoperfusion when standing. This reduced CBF may contribute to cognitive difficulties in these Veterans when upright.
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Affiliation(s)
- Michael J. Falvo
- War Related Illness and Injury Study Center, Department of Veterans Affairs, East Orange, New Jersey, United States of America
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, New Jersey, United States of America
- Department of Physical Medicine and Rehabilitation, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, New Jersey, United States of America
| | - Jacob B. Lindheimer
- William S. Middleton Memorial Veterans Hospital, Department of Veterans Affairs, Madison, Wisconsin, United States of America
- Department of Kinesiology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Jorge M. Serrador
- War Related Illness and Injury Study Center, Department of Veterans Affairs, East Orange, New Jersey, United States of America
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, New Jersey, United States of America
- Department of Cardiovascular Electronics, National University of Ireland Galway, Galway, Connacht, IRE
- * E-mail:
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Stembridge M, Hoiland RL, Bain AR, Barak OF, Drvis I, MacLeod DB, MacLeod DM, Madden D, Batinic T, O'Donoghue P, Shave R, Dujic Z, Ainslie PN. Influence of lung volume on the interaction between cardiac output and cerebrovascular regulation during extreme apnoea. Exp Physiol 2018; 102:1288-1299. [PMID: 28762565 DOI: 10.1113/ep086429] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 07/20/2017] [Indexed: 12/12/2022]
Abstract
NEW FINDINGS What is the central question of this study? Does the reduction in cardiac output observed during extreme voluntary apnoea, secondary to high lung volume, result in a reduction in cerebral blood flow, perfusion pressure and oxygen delivery in a group of elite free divers? What is the main finding and its importance? High lung volumes reduce cardiac output and ventricular filling during extreme apnoea, but changes in cerebral blood flow are observed only transiently during the early stages of apnoea. This reveals that whilst cardiac output is important in regulating cerebral haemodynamics, the role of mean arterial pressure in restoring cerebral perfusion pressure is of greater significance to the regulation of cerebral blood flow. We investigated the role of lung volume-induced changes in cardiac output (Q̇) on cerebrovascular regulation during prolonged apnoea. Fifteen elite apnoea divers (one female; 185 ± 7 cm, 82 ± 12 kg, 29 ± 7 years old) attended the laboratory on two separate occasions and completed maximal breath-holds at total lung capacity (TLC) and functional residual capacity (FRC) to elicit disparate cardiovascular responses. Mean arterial pressure (MAP), internal jugular venous pressure and arterial blood gases were measured via cannulation. Global cerebral blood flow was quantified by ultrasound and cardiac output was quantified by via photoplethysmography. At FRC, stroke volume and Q̇ did not change from baseline (P > 0.05). In contrast, during the TLC trial stroke volume and Q̇ were decreased until 80 and 40% of apnoea, respectively (P < 0.05). During the TLC trial, global cerebral blood flow was significantly lower at 20%, but subsequently increased so that cerebral oxygen delivery was comparable to that during the FRC trial. Internal jugular venous pressure was significantly higher throughout the TLC trial in comparison to FRC. The MAP increased progressively in both trials but to a greater extent at TLC, resulting in a comparable cerebral perfusion pressure between trials by the end of apnoea. In summary, although lung volume has a profound effect on Q̇ during prolonged breath-holding, these changes do not translate to the cerebrovasculature owing to the greater sensitivity of cerebral blood flow to arterial blood gases and MAP; regulatory mechanisms that facilitate the maintenance of cerebral oxygen delivery.
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Affiliation(s)
- Mike Stembridge
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Ryan L Hoiland
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Anthony R Bain
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Otto F Barak
- School of Medicine, University of Split, Split, Croatia.,Faculty of Medicine, University of Novi Sad, Novi Sad, Serbia
| | - Ivan Drvis
- School of Kinesiology, University of Zagreb, Zagreb, Croatia
| | - David B MacLeod
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | | | - Dennis Madden
- School of Medicine, University of Split, Split, Croatia
| | - Tonci Batinic
- School of Medicine, University of Split, Split, Croatia
| | - Peter O'Donoghue
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Rob Shave
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Zeljko Dujic
- School of Medicine, University of Split, Split, Croatia
| | - Philip N Ainslie
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
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35
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Ward JL, Craig JC, Liu Y, Vidoni ED, Maletsky R, Poole DC, Billinger SA. Effect of healthy aging and sex on middle cerebral artery blood velocity dynamics during moderate-intensity exercise. Am J Physiol Heart Circ Physiol 2018; 315:H492-H501. [PMID: 29775407 PMCID: PMC6172645 DOI: 10.1152/ajpheart.00129.2018] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Blood velocity measured in the middle cerebral artery (MCAV) increases with finite kinetics during moderate-intensity exercise, and the amplitude and dynamics of the response provide invaluable insights into the controlling mechanisms. The MCAV response after exercise onset is well fit to an exponential model in young individuals but remains to be characterized in their older counterparts. The responsiveness of vasomotor control degrades with advancing age, especially in skeletal muscle. We tested the hypothesis that older subjects would evince a slower and reduced MCAV response to exercise. Twenty-nine healthy young (25 ± 1 yr old) and older (69 ± 1 yr old) adults each performed a rapid transition from rest to moderate-intensity exercise on a recumbent stepper. Resting MCAV was lower in older than young subjects (47 ± 2 vs. 64 ± 3 cm/s, P < 0.001), and amplitude from rest to steady-state exercise was lower in older than young subjects (12 ± 2 vs. 18 ± 3 cm/s, P = 0.04), even after subjects were matched for work rate. As hypothesized, the time constant was significantly longer (slower) in the older than young subjects (51 ± 10 vs. 31 ± 4 s, P = 0.03), driven primarily by older women. Neither age-related differences in fitness, end-tidal CO2, nor blood pressure could account for this effect. Thus, MCAV kinetic analyses revealed a marked impairment in the cerebrovascular response to exercise in older individuals. Kinetic analysis offers a novel approach to evaluate the efficacy of therapeutic interventions for improving cerebrovascular function in elderly and patient populations. NEW & NOTEWORTHY Understanding the dynamic cerebrovascular response to exercise has provided insights into sex-related cerebrovascular control mechanisms throughout the aging process. We report novel differences in the kinetics response of cerebrovascular blood velocity after the onset of moderate-intensity exercise. The exponential increase in brain blood flow from rest to exercise revealed that 1) the kinetics profile of the older group was blunted compared with their young counterparts and 2) the older women demonstrated a slowed response.
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Affiliation(s)
- Jaimie L Ward
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center , Kansas City, Kansas
| | - Jesse C Craig
- Department of Kinesiology and Department of Anatomy and Physiology, Kansas State University , Manhattan, Kansas
| | - Yumei Liu
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center , Kansas City, Kansas
| | - Eric D Vidoni
- University of Kansas Alzheimer's Disease Center, Fairway, Kansas
| | | | - David C Poole
- Department of Kinesiology and Department of Anatomy and Physiology, Kansas State University , Manhattan, Kansas
| | - Sandra A Billinger
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center , Kansas City, Kansas
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36
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Uryga A, Kasprowicz M, Calviello L, Diehl RR, Kaczmarska K, Czosnyka M. Assessment of cerebral hemodynamic parameters using pulsatile versus non-pulsatile cerebral blood outflow models. J Clin Monit Comput 2018; 33:85-94. [DOI: 10.1007/s10877-018-0136-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 03/29/2018] [Indexed: 11/28/2022]
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37
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Wright AD, Smirl JD, Bryk K, Fraser S, Jakovac M, van Donkelaar P. Sport-Related Concussion Alters Indices of Dynamic Cerebral Autoregulation. Front Neurol 2018; 9:196. [PMID: 29636724 PMCID: PMC5880892 DOI: 10.3389/fneur.2018.00196] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 03/13/2018] [Indexed: 11/13/2022] Open
Abstract
Sport-related concussion is known to affect a variety of brain functions. However, the impact of this brain injury on cerebral autoregulation (CA) is poorly understood. Thus, the goal of the current study was to determine the acute and cumulative effects of sport-related concussion on indices of dynamic CA. Toward this end, 179 elite, junior-level (age 19.6 ± 1.5 years) contact sport (ice hockey, American football) athletes were recruited for preseason testing, 42 with zero prior concussions and 31 with three or more previous concussions. Eighteen athletes sustained a concussion during that competitive season and completed follow-up testing at 72 h, 2 weeks, and 1 month post injury. Beat-by-beat arterial blood pressure (BP) and middle cerebral artery blood velocity (MCAv) were recorded using finger photoplethysmography and transcranial Doppler ultrasound, respectively. Five minutes of repetitive squat-stand maneuvers induced BP oscillations at 0.05 and 0.10 Hz (20- and 10-s cycles, respectively). The BP-MCAv relationship was quantified using transfer function analysis to estimate Coherence (correlation), Gain (amplitude ratio), and Phase (timing offset). At a group level, repeated-measures ANOVA indicated that 0.10 Hz Phase was significantly reduced following an acute concussion, compared to preseason, by 23% (-0.136 ± 0.033 rads) at 72 h and by 18% (-0.105 ± 0.029 rads) at 2 weeks post injury, indicating impaired autoregulatory functioning; recovery to preseason values occurred by 1 month. Athletes were cleared to return to competition after a median of 14 days (range 7-35), implying that physiologic dysfunction persisted beyond clinical recovery in many cases. When comparing dynamic pressure buffering between athletes with zero prior concussions and those with three or more, no differences were observed. Sustaining an acute sport-related concussion induces transient impairments in the capabilities of the cerebrovascular pressure-buffering system that may persist beyond 2 weeks and may be due to a period of autonomic dysregulation. Athletes with a history of three or more concussions did not exhibit impairments relative to those with zero prior concussions, suggesting recovery of function over time. Findings from this study support the potential need to consider physiological recovery in deciding when patients should return to play following a concussion.
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Affiliation(s)
- Alexander D Wright
- MD/PhD Program, University of British Columbia, Vancouver, BC, Canada.,Southern Medical Program, Reichwald Health Sciences Centre, University of British Columbia Okanagan, Kelowna, BC, Canada.,Experimental Medicine Program, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.,School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Jonathan D Smirl
- School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Kelsey Bryk
- School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Sarah Fraser
- Southern Medical Program, Reichwald Health Sciences Centre, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Michael Jakovac
- Southern Medical Program, Reichwald Health Sciences Centre, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Paul van Donkelaar
- School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, BC, Canada
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38
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Obata Y, Barodka V, Berkowitz DE, Gottschalk A, Hogue CW, Steppan J. Relationship Between the Ambulatory Arterial Stiffness Index and the Lower Limit of Cerebral Autoregulation During Cardiac Surgery. J Am Heart Assoc 2018; 7:JAHA.117.007816. [PMID: 29437601 PMCID: PMC5850197 DOI: 10.1161/jaha.117.007816] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Background Pulse pressure, the ambulatory arterial stiffness index (AASI), and the symmetric AASI are established predictors of adverse cardiovascular outcomes. However, little is known about their relationship to cerebral autoregulation. This study evaluated whether these markers of vascular properties relate to the lower limit of cerebral autoregulation (LLA). Methods and Results The LLA was determined during cardiac surgery with transcranial Doppler ultrasonography in 181 patients. All other variables were calculated from continuous intraoperative readings obtained before cardiopulmonary bypass. The LLA varied directly with the AASI (β=3.12 per 0.1 change in AASI, P<0.001) and to a lesser extent the symmetric AASI (β=2.02 per 0.1 change in symmetric AASI, P≤0.022), while peripheral pulse pressure was not significantly related (β=0.0, P>0.99). Logistic regression revealed that the likelihood of LLA being >65 mm Hg increased by 50% (95% confidence interval, 11%–102%, P=0.008) for every 0.1 increase in the AASI. The AASI was able to predict a LLA above certain thresholds (area under the curve receiver operating characteristic for AASI predicting an LLA >65 mm Hg: 0.60; 95% confidence interval, 0.51%–0.68%, P=0.043). Incorporating additional variables improved the model's predictive ability (area under the curve for AASI predicting a LLA >65 mm Hg: 0.75; 95% confidence interval, 0.68–0.82, P=0.036). Conclusions These data indicate that the LLA is related to the mechanical properties of the vasculature as represented by the AASI. The AASI can be used to predict LLA threshold levels during cardiac surgery. It is now possible to link elevations in the LLA with an increased AASI as determined from readily accessible intraoperative variables.
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Affiliation(s)
- Yurie Obata
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, MD
| | - Viachaslau Barodka
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, MD
| | - Dan E Berkowitz
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, MD.,Department of Biomedical Engineering, Johns Hopkins University Baltimore, MD
| | - Allan Gottschalk
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, MD
| | - Charles W Hogue
- Department of Anesthesiology, Northwestern University Feinberg, Chicago, IL
| | - Jochen Steppan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, MD
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39
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Billinger SA, Craig JC, Kwapiszeski SJ, Sisante JFV, Vidoni ED, Maletsky R, Poole DC. Dynamics of middle cerebral artery blood flow velocity during moderate-intensity exercise. J Appl Physiol (1985) 2017; 122:1125-1133. [PMID: 28280106 DOI: 10.1152/japplphysiol.00995.2016] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 02/21/2017] [Accepted: 03/02/2017] [Indexed: 12/25/2022] Open
Abstract
The dynamic response to a stimulus such as exercise can reveal valuable insights into systems control in health and disease that are not evident from the steady-state perturbation. However, the dynamic response profile and kinetics of cerebrovascular function have not been determined to date. We tested the hypotheses that bilateral middle cerebral artery blood flow mean velocity (MCAV) increases exponentially following the onset of moderate-intensity exercise in 10 healthy young subjects. The MCAV response profiles were well fit to a delay (TD) + exponential (time constant, τ) model with substantial agreement for baseline [left (L): 69, right (R): 64 cm/s, coefficient of variation (CV) 11%], response amplitude (L: 16, R: 13 cm/s, CV 23%), TD (L: 54, R: 52 s, CV 9%), τ (L: 30, R: 30 s, CV 22%), and mean response time (MRT) (L: 83, R: 82 s, CV 8%) between left and right MCAV as supported by the high correlations (e.g., MRT r = 0.82, P < 0.05) and low CVs. Test-retest reliability was high with CVs for the baseline, amplitude, and MRT of 3, 14, and 12%, respectively. These responses contrasted markedly with those of three healthy older subjects in whom the MCAV baseline and exercise response amplitude were far lower and the kinetics slowed. A single older stroke patient showed baseline ipsilateral MCAV that was lower still and devoid of any exercise response whatsoever. We conclude that kinetics analysis of MCAV during exercise has significant potential to unveil novel aspects of cerebrovascular function in health and disease.NEW & NOTEWORTHY Resolution of the dynamic stimulus-response profile provides a greater understanding of the underlying the physiological control processes than steady-state measurements alone. We report a novel method of measuring cerebrovascular blood velocity (MCAv) kinetics under ecologically valid conditions from rest to moderate-intensity exercise. This technique reveals that brain blood flow increases exponentially following the onset of exercise with 1) a strong bilateral coherence in young healthy individuals, and 2) a potential for unique age- and disease-specific profiles.
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Affiliation(s)
- Sandra A Billinger
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, Kansas;
| | - Jesse C Craig
- Department of Kinesiology, Kansas State University, Manhattan, Kansas.,College of Veterinary Medicine, Kansas State University, Manhattan, Kansas; and
| | - Sarah J Kwapiszeski
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, Kansas
| | - Jason-Flor V Sisante
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, Kansas
| | - Eric D Vidoni
- University of Kansas Alzheimer's Disease Center, Fairway, Kansas
| | | | - David C Poole
- Department of Kinesiology, Kansas State University, Manhattan, Kansas.,College of Veterinary Medicine, Kansas State University, Manhattan, Kansas; and
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40
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Hoiland RL, Ainslie PN. Rebuttal from Ryan L. Hoiland and Philip N. Ainslie. J Physiol 2016; 594:4081. [PMID: 27010009 DOI: 10.1113/jp272241] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 02/12/2016] [Indexed: 11/08/2022] Open
Affiliation(s)
- Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, Kelowna, BC, Canada
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