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Taylor JL, Barnes JN, Johnson BD. The Utility of High Intensity Interval Training to Improve Cognitive Aging in Heart Disease Patients. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:16926. [PMID: 36554807 PMCID: PMC9778921 DOI: 10.3390/ijerph192416926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/06/2022] [Accepted: 12/13/2022] [Indexed: 06/17/2023]
Abstract
Adults with cardiovascular disease and heart failure are at higher risk of cognitive decline. Cerebral hypoperfusion appears to be a significant contributor, which can result from vascular dysfunction and impairment of cerebral blood flow regulation. In contrast, higher cardiorespiratory fitness shows protection against brain atrophy, reductions in cerebral blood flow, and cognitive decline. Given that high intensity interval training (HIIT) has been shown to be a potent stimulus for improving cardiorespiratory fitness and peripheral vascular function, its utility for improving cognitive aging is an important area of research. This article will review the physiology related to cerebral blood flow regulation and cognitive decline in adults with cardiovascular disease and heart failure, and how HIIT may provide a more optimal stimulus for improving cognitive aging in this population.
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Affiliation(s)
- Jenna L. Taylor
- Human Integrative and Environmental Physiology Laboratory, Mayo Clinic, Rochester, MN 55902, USA
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN 55902, USA
| | - Jill N. Barnes
- Bruno Balke Biodynamics Laboratory, Department of Kinesiology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Bruce D. Johnson
- Human Integrative and Environmental Physiology Laboratory, Mayo Clinic, Rochester, MN 55902, USA
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN 55902, USA
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2
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Li C, Shah KA, Powell K, Wu YC, Chaung W, Sonti AN, White TG, Doobay M, Yang WL, Wang P, Becker LB, Narayan RK. CBF oscillations induced by trigeminal nerve stimulation protect the pericontusional penumbra in traumatic brain injury complicated by hemorrhagic shock. Sci Rep 2021; 11:19652. [PMID: 34608241 PMCID: PMC8490389 DOI: 10.1038/s41598-021-99234-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 09/16/2021] [Indexed: 02/08/2023] Open
Abstract
Traumatic peri-contusional penumbra represents crucial targets for therapeutic interventions after traumatic brain injury (TBI). Current resuscitative approaches may not adequately alleviate impaired cerebral microcirculation and, hence, compromise oxygen delivery to peri-contusional areas. Low-frequency oscillations in cerebral blood flow (CBF) may improve cerebral oxygenation in the setting of oxygen deprivation. However, no method has been reported to induce controllable oscillations in CBF and it hasn't been applied as a therapeutic strategy. Electrical stimulation of the trigeminal nerve (TNS) plays a pivotal role in modulating cerebrovascular tone and cerebral perfusion. We hypothesized that TNS can modulate CBF at the targeted frequency band via the trigemino-cerebrovascular network, and TNS-induced CBF oscillations would improve cerebral oxygenation in peri-contusional areas. In a rat model of TBI complicated by hemorrhagic shock, TNS-induced CBF oscillations conferred significant preservation of peri-contusional tissues leading to reduced lesion volume, attenuated hypoxic injury and neuroinflammation, increased eNOS expression, improved neurological recovery and better 10-day survival rate, despite not significantly increasing CBF as compared with those in immediate and delayed resuscitation animals. Our findings indicate that low-frequency CBF oscillations enhance cerebral oxygenation in peri-contusional areas, and play a more significant protective role than improvements in non-oscillatory cerebral perfusion or volume expansion alone.
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Affiliation(s)
- Chunyan Li
- Translational Brain Research Laboratory, The Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY, 11030, USA. .,Department of Neurosurgery, Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY, USA.
| | - Kevin A Shah
- Translational Brain Research Laboratory, The Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY, 11030, USA.,Department of Neurosurgery, Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY, USA
| | - Keren Powell
- Translational Brain Research Laboratory, The Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY, 11030, USA
| | - Yi-Chen Wu
- Translational Brain Research Laboratory, The Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY, 11030, USA
| | - Wayne Chaung
- Center for Immunology and Inflammation, The Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | - Anup N Sonti
- Translational Brain Research Laboratory, The Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY, 11030, USA.,Department of Neurosurgery, Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY, USA
| | - Timothy G White
- Translational Brain Research Laboratory, The Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY, 11030, USA.,Department of Neurosurgery, Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY, USA
| | - Mohini Doobay
- Translational Brain Research Laboratory, The Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY, 11030, USA
| | - Weng-Lang Yang
- Department of Radiation Oncology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Ping Wang
- Center for Immunology and Inflammation, The Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | - Lance B Becker
- Department of Emergency Medicine, Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY, USA
| | - Raj K Narayan
- Translational Brain Research Laboratory, The Feinstein Institutes for Medical Research, 350 Community Drive, Manhasset, NY, 11030, USA.,Department of Neurosurgery, Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY, USA
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3
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Claassen JAHR, Thijssen DHJ, Panerai RB, Faraci FM. Regulation of cerebral blood flow in humans: physiology and clinical implications of autoregulation. Physiol Rev 2021; 101:1487-1559. [PMID: 33769101 PMCID: PMC8576366 DOI: 10.1152/physrev.00022.2020] [Citation(s) in RCA: 295] [Impact Index Per Article: 98.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Brain function critically depends on a close matching between metabolic demands, appropriate delivery of oxygen and nutrients, and removal of cellular waste. This matching requires continuous regulation of cerebral blood flow (CBF), which can be categorized into four broad topics: 1) autoregulation, which describes the response of the cerebrovasculature to changes in perfusion pressure; 2) vascular reactivity to vasoactive stimuli [including carbon dioxide (CO2)]; 3) neurovascular coupling (NVC), i.e., the CBF response to local changes in neural activity (often standardized cognitive stimuli in humans); and 4) endothelium-dependent responses. This review focuses primarily on autoregulation and its clinical implications. To place autoregulation in a more precise context, and to better understand integrated approaches in the cerebral circulation, we also briefly address reactivity to CO2 and NVC. In addition to our focus on effects of perfusion pressure (or blood pressure), we describe the impact of select stimuli on regulation of CBF (i.e., arterial blood gases, cerebral metabolism, neural mechanisms, and specific vascular cells), the interrelationships between these stimuli, and implications for regulation of CBF at the level of large arteries and the microcirculation. We review clinical implications of autoregulation in aging, hypertension, stroke, mild cognitive impairment, anesthesia, and dementias. Finally, we discuss autoregulation in the context of common daily physiological challenges, including changes in posture (e.g., orthostatic hypotension, syncope) and physical activity.
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Affiliation(s)
- Jurgen A H R Claassen
- Department of Geriatrics, Radboud University Medical Center, Donders Institute for Brain, Cognition, and Behaviour, Nijmegen, The Netherlands
| | - Dick H J Thijssen
- Department of Physiology, Radboud Institute for Health Sciences, Nijmegen, The Netherlands
- Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom
| | - Ronney B Panerai
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
- >National Institute for Health Research Leicester Biomedical Research Centre, University of Leicester, Leicester, United Kingdom
| | - Frank M Faraci
- Departments of Internal Medicine, Neuroscience, and Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa
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4
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Lie SL, Hisdal J, Høiseth LØ. Cerebral blood flow velocity during simultaneous changes in mean arterial pressure and cardiac output in healthy volunteers. Eur J Appl Physiol 2021; 121:2207-2217. [PMID: 33890157 PMCID: PMC8260418 DOI: 10.1007/s00421-021-04693-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Accepted: 04/15/2021] [Indexed: 02/03/2023]
Abstract
Purpose Cerebral blood flow (CBF) needs to be precisely controlled to maintain brain functions. While previously believed to be autoregulated and near constant over a wide blood pressure range, CBF is now understood as more pressure passive. However, there are still questions regarding the integrated nature of CBF regulation and more specifically the role of cardiac output. Our aim was, therefore, to explore the effects of MAP and cardiac output on CBF in a combined model of reduced preload and increased afterload. Method 16 healthy volunteers were exposed to combinations of different levels of simultaneous lower body negative pressure and isometric hand grip. We measured blood velocity in the middle cerebral artery (MCAV) and internal carotid artery (ICAV) by Doppler ultrasound, and cerebral oxygen saturation (ScO2) by near-infrared spectroscopy, as surrogates for CBF. The effect of changes in MAP and cardiac output on CBF was estimated with mixed multiple regression. Result Both MAP and cardiac output had independent effects on MCAV, ICAV and ScO2. For ICAV and ScO2 there was also a statistically significant interaction effect between MAP and cardiac output. The estimated effect of a change of 10 mmHg in MAP on MCAV was 3.11 cm/s (95% CI 2.51–3.71, P < 0.001), and the effect of a change of 1 L/min in cardiac output was 3.41 cm/s (95% CI 2.82–4.00, P < 0.001). Conclusion The present study indicates that during reductions in cardiac output, both MAP and cardiac output have independent effects on CBF. Supplementary Information The online version contains supplementary material available at 10.1007/s00421-021-04693-6.
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Affiliation(s)
- Sole Lindvåg Lie
- Faculty of Medicine, University of Oslo, Oslo, Norway. .,Section of Vascular Investigations, Department of Vascular Surgery, Oslo University Hospital, 0424, Oslo, Norway.
| | - Jonny Hisdal
- Faculty of Medicine, University of Oslo, Oslo, Norway.,Section of Vascular Investigations, Department of Vascular Surgery, Oslo University Hospital, 0424, Oslo, Norway
| | - Lars Øivind Høiseth
- Department of Anesthesiology, Division of Emergencies and Critical Care, Oslo University Hospital, Oslo, Norway
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5
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Mohammadyari P, Gadda G, Taibi A. Modelling physiology of haemodynamic adaptation in short-term microgravity exposure and orthostatic stress on Earth. Sci Rep 2021; 11:4672. [PMID: 33633331 PMCID: PMC7907254 DOI: 10.1038/s41598-021-84197-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 02/08/2021] [Indexed: 11/09/2022] Open
Abstract
Cardiovascular haemodynamics alters during posture changes and exposure to microgravity. Vascular auto-remodelling observed in subjects living in space environment causes them orthostatic intolerance when they return on Earth. In this study we modelled the human haemodynamics with focus on head and neck exposed to different hydrostatic pressures in supine, upright (head-up tilt), head-down tilt position, and microgravity environment by using a well-developed 1D-0D haemodynamic model. The model consists of two parts that simulates the arterial (1D) and brain-venous (0D) vascular tree. The cardiovascular system is built as a network of hydraulic resistances and capacitances to properly model physiological parameters like total peripheral resistance, and to calculate vascular pressure and the related flow rate at any branch of the tree. The model calculated 30.0 mmHg (30%), 7.1 mmHg (78%), 1.7 mmHg (38%) reduction in mean blood pressure, intracranial pressure and central venous pressure after posture change from supine to upright, respectively. The modelled brain drainage outflow percentage from internal jugular veins is 67% and 26% for supine and upright posture, while for head-down tilt and microgravity is 65% and 72%, respectively. The model confirmed the role of peripheral veins in regional blood redistribution during posture change from supine to upright and microgravity environment as hypothesized in literature. The model is able to reproduce the known haemodynamic effects of hydraulic pressure change and weightlessness. It also provides a virtual laboratory to examine the consequence of a wide range of orthostatic stresses on human haemodynamics.
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Affiliation(s)
- Parvin Mohammadyari
- Department of Physics and Earth Sciences, University of Ferrara, 44122, Ferrara, Italy
| | - Giacomo Gadda
- National Institute for Nuclear Physics (INFN), Section of Ferrara, 44122, Ferrara, Italy.
| | - Angelo Taibi
- Department of Physics and Earth Sciences, University of Ferrara, 44122, Ferrara, Italy
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6
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Kim YS, van der Ster BJP, Brassard P, Secher NH, van Lieshout JJ. Cerebral vs. Cardiovascular Responses to Exercise in Type 2 Diabetic Patients. Front Physiol 2021; 11:583155. [PMID: 33519500 PMCID: PMC7844205 DOI: 10.3389/fphys.2020.583155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 12/23/2020] [Indexed: 12/17/2022] Open
Abstract
The human brain is constantly active and even small limitations to cerebral blood flow (CBF) may be critical for preserving oxygen and substrate supply, e.g., during exercise and hypoxia. Exhaustive exercise evokes a competition for the supply of oxygenated blood between the brain and the working muscles, and inability to increase cardiac output sufficiently during exercise may jeopardize cerebral perfusion of relevance for diabetic patients. The challenge in diabetes care is to optimize metabolic control to slow progression of vascular disease, but likely because of a limited ability to increase cardiac output, these patients perceive aerobic exercise to be more strenuous than healthy subjects and that limits the possibility to apply physical activity as a preventive lifestyle intervention. In this review, we consider the effects of functional activation by exercise on the brain and how it contributes to understanding the control of CBF with the limited exercise tolerance experienced by type 2 diabetic patients. Whether a decline in cerebral oxygenation and thereby reduced neural drive to working muscles plays a role for "central" fatigue during exhaustive exercise is addressed in relation to brain's attenuated vascular response to exercise in type 2 diabetic subjects.
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Affiliation(s)
- Yu-Sok Kim
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Department of Internal Medicine, Medisch Centrum Leeuwarden, Leeuwarden, Netherlands
| | - Björn J. P. van der Ster
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Department of Anesthesiology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Patrice Brassard
- Department of Kinesiology, Faculty of Medicine, Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, QC, Canada
| | - Niels H. Secher
- Department of Anesthesia, The Copenhagen Muscle Research Center, University of Copenhagen, Copenhagen, Denmark
| | - Johannes J. van Lieshout
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, School of Life Sciences, University of Nottingham Medical School, Queen’s Medical Centre, Nottingham, United Kingdom
- Department of Internal Medicine, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
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7
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Samora M, Vianna LC, Carmo JC, Macedo V, Dawes M, Phillips AA, Paton JFR, Fisher JP. Neurovascular coupling is not influenced by lower body negative pressure in humans. Am J Physiol Heart Circ Physiol 2020; 319:H22-H31. [PMID: 32442032 DOI: 10.1152/ajpheart.00076.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cerebral blood flow is tightly coupled with local neuronal activation and metabolism, i.e., neurovascular coupling (NVC). Studies suggest a role of sympathetic nervous system in the regulation of cerebral blood flow. However, this is controversial, and the sympathetic regulation of NVC in humans remains unclear. Since impaired NVC has been identified in several chronic diseases associated with a heightened sympathetic activity, we aimed to determine whether reflex-mediated sympathetic activation via lower body negative pressure (LBNP) attenuates NVC in humans. NVC was assessed using a visual stimulation protocol (5 cycles of 30 s eyes closed and 30 s of reading) in 11 healthy participants (aged 24 ± 3 yr). NVC assessments were made under control conditions and during LBNP at -20 and -40 mmHg. Posterior (PCA) and middle (MCA) cerebral artery mean blood velocity (Vmean) and vertebral artery blood flow (VAflow) were simultaneously determined with cardiorespiratory variables. Under control conditions, the visual stimulation evoked a robust increase in PCAVmean (∆18.0 ± 4.5%), a moderate rise in VAflow (∆9.6 ± 4.3%), and a modest increase in MCAVmean (∆3.0 ± 1.9%). The magnitude of NVC response was not affected by mild-to-moderate LBNP (all P > 0.05 for repeated-measures ANOVA). Given the small change that occurred in partial pressure of end-tidal CO2 during LBNP, this hypocapnia condition was matched via voluntary hyperventilation in absence of LBNP in a subgroup of participants (n = 8). The mild hypocapnia during LBNP did not exert a confounding influence on the NVC response. These findings indicate that the NVC is not influenced by LBNP or mild hypocapnia in humans.NEW & NOTEWORTHY Visual stimulation evoked a robust increase in posterior cerebral artery velocity and a modest increase in vertebral artery blood flow, i.e., neurovascular coupling (NVC), which was unaffected by lower body negative pressure (LBNP) in humans. In addition, although LBNP induced a mild hypocapnia, this degree of hypocapnia in the absence of LBNP failed to modify the NVC response.
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Affiliation(s)
- Milena Samora
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.,NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Distrito Federal, Brazil
| | - Lauro C Vianna
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Distrito Federal, Brazil
| | - Jake C Carmo
- Biomechanics and Biological Signal Processing Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Distrito Federal, Brazil
| | - Victor Macedo
- Biomechanics and Biological Signal Processing Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Distrito Federal, Brazil
| | - Matthew Dawes
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Aaron A Phillips
- Departments of Physiology, Pharmacology, and Clinical Neurosciences, Libin Cardiovascular Institute, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Alberta, Canada
| | - Julian F R Paton
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - James P Fisher
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
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8
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Ogoh S, Tarumi T. Cerebral blood flow regulation and cognitive function: a role of arterial baroreflex function. J Physiol Sci 2019; 69:813-823. [PMID: 31444691 PMCID: PMC10717347 DOI: 10.1007/s12576-019-00704-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 08/13/2019] [Indexed: 10/26/2022]
Abstract
A strict adequate perfusion pressure via arterial baroreflex for the delivery of oxygen to the tissues of the body is well established; however, the importance of baroreflex for cerebral blood flow (CBF) is unclear. On the other hand, there is convincing evidence for arterial baroreflex function playing an important role in maintaining brain homeostasis, e.g., cerebral metabolism, cerebral hemodynamics, and cognitive function. For example, mild cognitive impairment attenuates the sensitivity of baroreflex, and Alzheimer's disease further decreases it. These clinical findings suggest that CBF and cerebral function are affected by systemic blood pressure regulation via the arterial baroreflex. However, dysfunction of arterial baroreflex is likely to affect CBF regulation as well as the underlying neuronal function, but identifying how this is achieved is arduous since neurological diseases affect systemic as well as cerebral circulation independently. Recent insights into the influence of blood pressure regulation via the arterial baroreflex on cerebral function and blood flow regulation may help elucidate this important question. This review summarizes some update findings regarding direct (autonomic regulation) and indirect (systemic blood pressure regulation) contributions of the arterial baroreflex to the maintenance of cerebral vasculature regulation.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama, 350-8585, Japan.
| | - Takashi Tarumi
- Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
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9
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Neumann S, Burchell AE, Rodrigues JC, Lawton CB, Burden D, Underhill M, Kobetić MD, Adams ZH, Brooks JC, Nightingale AK, Paton JFR, Hamilton MC, Hart EC. Cerebral Blood Flow Response to Simulated Hypovolemia in Essential Hypertension: A Magnetic Resonance Imaging Study. Hypertension 2019; 74:1391-1398. [PMID: 31656098 PMCID: PMC7069391 DOI: 10.1161/hypertensionaha.119.13229] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Supplemental Digital Content is available in the text. Hypertension is associated with raised cerebral vascular resistance and cerebrovascular remodeling. It is currently unclear whether the cerebral circulation can maintain cerebral blood flow (CBF) during reductions in cardiac output (CO) in hypertensive patients thereby avoiding hypoperfusion of the brain. We hypothesized that hypertension would impair the ability to effectively regulate CBF during simulated hypovolemia. In the present study, 39 participants (13 normotensive, 13 controlled, and 13 uncontrolled hypertensives; mean age±SD, 55±10 years) underwent lower body negative pressure (LBNP) at −20, −40, and −50 mmHg to decrease central blood volume. Phase-contrast MR angiography was used to measure flow in the basilar and internal carotid arteries, as well as the ascending aorta. CBF and CO decreased during LBNP (P<0.0001). Heart rate increased during LBNP, reaching significance at −50 mmHg (P<0.0001). There was no change in mean arterial pressure during LBNP (P=0.3). All participants showed similar reductions in CBF (P=0.3, between groups) and CO (P=0.7, between groups) during LBNP. There was no difference in resting CBF between the groups (P=0.36). In summary, during reductions in CO induced by hypovolemic stress, mean arterial pressure is maintained but CBF declines indicating that CBF is dependent on CO in middle-aged normotensive and hypertensive volunteers. Hypertension is not associated with impairments in the CBF response to reduced CO.
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Affiliation(s)
- Sandra Neumann
- From the Faculty of Life Sciences, School of Physiology, Pharmacology and Neuroscience (S.N., Z.H.A., J.B., A.K.N., J.P., E.C.H.), University of Bristol, United Kingdom
- Faculty of Health Sciences, Bristol Medical School (S.N., M.K.), University of Bristol, United Kingdom
| | - Amy E. Burchell
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
| | - Jonathan C.L. Rodrigues
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
- Department of Radiology, Royal United Hospitals Bath NHS Foundation Trust, United Kingdom (J.R.)
| | - Christopher B. Lawton
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
| | - Daniel Burden
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
| | - Melissa Underhill
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
| | - Matthew D. Kobetić
- Faculty of Health Sciences, Bristol Medical School (S.N., M.K.), University of Bristol, United Kingdom
| | - Zoe H. Adams
- From the Faculty of Life Sciences, School of Physiology, Pharmacology and Neuroscience (S.N., Z.H.A., J.B., A.K.N., J.P., E.C.H.), University of Bristol, United Kingdom
| | - Jonathan C.W. Brooks
- From the Faculty of Life Sciences, School of Physiology, Pharmacology and Neuroscience (S.N., Z.H.A., J.B., A.K.N., J.P., E.C.H.), University of Bristol, United Kingdom
| | - Angus K. Nightingale
- From the Faculty of Life Sciences, School of Physiology, Pharmacology and Neuroscience (S.N., Z.H.A., J.B., A.K.N., J.P., E.C.H.), University of Bristol, United Kingdom
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
| | - Julian F. R. Paton
- From the Faculty of Life Sciences, School of Physiology, Pharmacology and Neuroscience (S.N., Z.H.A., J.B., A.K.N., J.P., E.C.H.), University of Bristol, United Kingdom
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, New Zealand (J.P.)
| | - Mark C.K. Hamilton
- University Hospitals Bristol NHS Foundation Trust, United Kingdom (A.E.B., J.R., C.B.L., D.B., M.U., A.K.N., M.H.)
| | - Emma C. Hart
- From the Faculty of Life Sciences, School of Physiology, Pharmacology and Neuroscience (S.N., Z.H.A., J.B., A.K.N., J.P., E.C.H.), University of Bristol, United Kingdom
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10
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Whittaker JR, Driver ID, Venzi M, Bright MG, Murphy K. Cerebral Autoregulation Evidenced by Synchronized Low Frequency Oscillations in Blood Pressure and Resting-State fMRI. Front Neurosci 2019; 13:433. [PMID: 31133780 PMCID: PMC6514145 DOI: 10.3389/fnins.2019.00433] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 04/15/2019] [Indexed: 01/23/2023] Open
Abstract
Resting-state functional magnetic resonance imaging (rs-fMRI) is a widely used technique for mapping the brain’s functional architecture, so delineating the main sources of variance comprising the signal is crucial. Low frequency oscillations (LFO) that are not of neural origin, but which are driven by mechanisms related to cerebral autoregulation (CA), are present in the blood-oxygenation-level-dependent (BOLD) signal within the rs-fMRI frequency band. In this study we use a MR compatible device (Caretaker, Biopac) to obtain a non-invasive estimate of beat-to-beat mean arterial pressure (MAP) fluctuations concurrently with rs-fMRI at 3T. Healthy adult subjects (n = 9; 5 male) completed two 20-min rs-fMRI scans. MAP fluctuations were decomposed into different frequency scales using a discrete wavelet transform, and oscillations at approximately 0.1 Hz show a high degree of spatially structured correlations with matched frequency fMRI fluctuations. On average across subjects, MAP fluctuations at this scale of the wavelet decomposition explain ∼2.2% of matched frequency fMRI signal variance. Additionally, a simultaneous multi-slice multi-echo acquisition was used to collect 10-min rs-fMRI at three echo times at 7T in a separate group of healthy adults (n = 5; 5 male). Multiple echo times were used to estimate the R2∗ decay at every time point, and MAP was shown to strongly correlate with this signal, which suggests a purely BOLD (i.e., blood flow related) origin. This study demonstrates that there is a significant component of the BOLD signal that has a systemic physiological origin, and highlights the fact that not all localized BOLD signal changes necessarily reflect blood flow supporting local neural activity. Instead, these data show that a proportion of BOLD signal fluctuations in rs-fMRI are due to localized control of blood flow that is independent of local neural activity, most likely reflecting more general systemic autoregulatory processes. Thus, fMRI is a promising tool for studying flow changes associated with cerebral autoregulation with high spatial resolution.
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Affiliation(s)
- Joseph R Whittaker
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Physics and Astronomy, Cardiff University, Cardiff, United Kingdom
| | - Ian D Driver
- CUBRIC, School of Psychology, Cardiff University, Cardiff, United Kingdom
| | - Marcello Venzi
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Physics and Astronomy, Cardiff University, Cardiff, United Kingdom
| | - Molly G Bright
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Kevin Murphy
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Physics and Astronomy, Cardiff University, Cardiff, United Kingdom
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Cornwell WK, Tarumi T, Lawley J, Ambardekar AV. CrossTalk opposing view: Blood flow pulsatility in left ventricular assist device patients is not essential to maintain normal brain physiology. J Physiol 2018; 597:357-359. [PMID: 30560586 DOI: 10.1113/jp276730] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Affiliation(s)
- William K Cornwell
- Department of Medicine, Division of Cardiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Takashi Tarumi
- Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
| | - Justin Lawley
- Department of Sports Science, Division of Physiology, University of Innsbruck, Innsbruck, Austria
| | - Amrut V Ambardekar
- Department of Medicine, Division of Cardiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
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12
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Kaur J, Vranish JR, Barbosa TC, Washio T, Young BE, Stephens BY, Brothers RM, Ogoh S, Fadel PJ. Regulation of Regional Cerebral Blood Flow During Graded Reflex-Mediated Sympathetic Activation via Lower Body Negative Pressure. J Appl Physiol (1985) 2018; 125:1779-1786. [PMID: 30188801 PMCID: PMC10392631 DOI: 10.1152/japplphysiol.00623.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The role of the sympathetic nervous system in cerebral blood flow (CBF) regulation remains unclear. Previous studies have primarily measured middle cerebral artery blood velocity to assess CBF. Recently, there has been a transition towards measuring internal carotid artery (ICA) and vertebral artery (VA) blood flow using duplex Doppler ultrasound. Given that the VA supplies autonomic control centers in the brainstem, we hypothesized that graded sympathetic activation via lower body negative pressure (LBNP) would reduce ICA but not VA blood flow. ICA and VA blood flow were measured during two protocols: Protocol-1, low-to-moderate LBNP (-10, -20, -30, -40 Torr) and Protocol-2, moderate-to-high LBNP (-30, -50, -70 Torr). ICA and VA blood flow, diameter, and blood velocity were unaffected up to -40 LBNP. However, -50 and -70 LBNP evoked reductions in ICA and VA blood flow (e.g., -70 LBNP: %∆VA-baseline= -27.6±3.0) that were mediated by decreases in both diameter and velocity (e.g., -70 LBNP: %∆VA-baseline diameter= -7.5±1.9 and %∆VA-baseline velocity= -13.6±1.7), which were comparable between vessels. Since hyperventilation during -70 LBNP reduced PETCO2, this decrease in PETCO2 was matched via voluntary hyperventilation. Reductions in ICA and VA blood flow during hyperventilation alone were significantly smaller than during -70 LBNP and were primarily mediated by decreases in velocity (%∆VA-baseline velocity= -8.6±2.4; %∆VA-baseline diameter= -0.05±0.56). These data demonstrate that both ICA and VA were unaffected by low-to-moderate sympathetic activation, whereas robust reflex-mediated sympatho-excitation caused similar magnitudes of vasoconstriction in both arteries. Thus, contrary to our hypothesis, the ICA was not preferentially vasoconstricted by sympathetic activation.
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Affiliation(s)
- Jasdeep Kaur
- Department of Kinesiology, University of Texas at Arlington, United States
| | - Jennifer R Vranish
- Department of Kinesiology, University of Texas at Arlington, United States
| | - Thales C Barbosa
- Department of Kinesiology, University of Texas at Arlington, United States
| | - Takuro Washio
- Department of Biomedical Engineering, Toyo University
| | | | | | | | - Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Japan
| | - Paul J Fadel
- Department of Kinesiology, University of Texas at Arlington, United States
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13
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Iwamoto E, Bock JM, Casey DP. Blunted shear-mediated dilation of the internal but not common carotid artery in response to lower body negative pressure. J Appl Physiol (1985) 2018; 124:1326-1332. [DOI: 10.1152/japplphysiol.01011.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Shear-mediated dilation in peripheral conduit arteries is blunted with sympathetic nervous system (SNS) activation; however, the effect of SNS activation on shear-mediated dilation in carotid arteries is unknown. We hypothesized that SNS activation reduces shear-mediated dilation in common and internal carotid arteries (CCA and ICA, respectively), and this attenuation is greater in the ICA compared with the CCA. Shear-mediated dilation in the CCA and ICA were measured in nine healthy men (24 ± 1 yr) with and without SNS activation. Shear-mediated dilation was induced by 3 min of hypercapnia (end‐tidal partial pressure of carbon dioxide +10 mmHg from individual baseline); SNS activity was increased with lower body negative pressure (LBNP; −20 mmHg). CCA and ICA measurements were made using Doppler ultrasound during hypercapnia with (LBNP) or without (Control) SNS activation. LBNP trials began with 5 min of LBNP with subjects breathing hypercapnic gas during the final 3 min. Shear-mediated dilation was calculated as the percent rise in peak diameter from baseline diameter. Sympathetic activation attenuated shear-mediated dilation in the ICA (Control vs. LBNP, 5.5 ± 0.7 vs. 1.8 ± 0.4%, P < 0.01), but not in the CCA (5.1 ± 1.2 vs. 4.2 ± 1.0%, P = 0.31). Moreover, absolute reduction in shear-mediated dilation via SNS activation was greater in the ICA than the CCA (−3.6 ± 0.7 vs. −0.9 ± 0.8%, P = 0.02). Our data indicate that shear-mediated dilation is attenuated during LBNP to a greater extent in the ICA compared with the CCA. These results potentially provide insight into the role of SNS activation on cerebral perfusion, as the ICA is a key supplier of blood to the brain. NEW & NOTEWORTHY We explored the effect of acute sympathetic nervous system (SNS) activation on shear-mediated dilation in the common and internal carotid arteries (CCA and ICA, respectively) in young healthy men. Our data demonstrate that hypercapnia-induced vasodilation of the ICA is attenuated during lower body negative pressure to a greater extent than the CCA. These data may provide novel information related to the role of SNS activation on cerebral perfusion in humans.
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Affiliation(s)
- Erika Iwamoto
- Human Integrative and Cardiovascular Physiology Laboratory, Department of Physical Therapy and Rehabilitation Science, University of Iowa, Iowa City, Iowa
- School of Health Sciences, Sapporo Medical University, Sapporo, Japan
| | - Joshua M. Bock
- Human Integrative and Cardiovascular Physiology Laboratory, Department of Physical Therapy and Rehabilitation Science, University of Iowa, Iowa City, Iowa
| | - Darren P. Casey
- Human Integrative and Cardiovascular Physiology Laboratory, Department of Physical Therapy and Rehabilitation Science, University of Iowa, Iowa City, Iowa
- Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa
- Fraternal Order of Eagles Diabetes Research Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa
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14
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Brassard P, Tymko MM, Ainslie PN. Sympathetic control of the brain circulation: Appreciating the complexities to better understand the controversy. Auton Neurosci 2017; 207:37-47. [DOI: 10.1016/j.autneu.2017.05.003] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 05/03/2017] [Accepted: 05/04/2017] [Indexed: 12/24/2022]
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15
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Malenfant S, Brassard P, Paquette M, Le Blanc O, Chouinard A, Nadeau V, Allan PD, Tzeng YC, Simard S, Bonnet S, Provencher S. Compromised Cerebrovascular Regulation and Cerebral Oxygenation in Pulmonary Arterial Hypertension. J Am Heart Assoc 2017; 6:e006126. [PMID: 29025748 PMCID: PMC5721836 DOI: 10.1161/jaha.117.006126] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 08/28/2017] [Indexed: 12/18/2022]
Abstract
BACKGROUND Functional cerebrovascular regulatory mechanisms are important for maintaining constant cerebral blood flow and oxygen supply in heathy individuals and are altered in heart failure. We aim to examine whether pulmonary arterial hypertension (PAH) is associated with abnormal cerebrovascular regulation and lower cerebral oxygenation and their physiological and clinical consequences. METHODS AND RESULTS Resting mean flow velocity in the middle cerebral artery mean flow velocity in the middle cerebral artery (MCAvmean); transcranial Doppler), cerebral pressure-flow relationship (assessed at rest and during squat-stand maneuvers; analyzed using transfer function analysis), cerebrovascular reactivity to CO2, and central chemoreflex were assessed in 11 patients with PAH and 11 matched healthy controls. Both groups also completed an incremental ramp exercise protocol until exhaustion, during which MCAvmean, mean arterial pressure, cardiac output (photoplethysmography), end-tidal partial pressure of CO2, and cerebral oxygenation (near-infrared spectroscopy) were measured. Patients were characterized by a significant decrease in resting MCAvmean (P<0.01) and higher transfer function gain at rest and during squat-stand maneuvers (both P<0.05). Cerebrovascular reactivity to CO2 was reduced (P=0.03), whereas central chemoreceptor sensitivity was increased in PAH (P<0.01), the latter correlating with increased resting ventilation (R2=0.47; P<0.05) and the exercise ventilation/CO2 production slope (V˙E/V˙CO2 slope; R2=0.62; P<0.05) during exercise for patients. Exercise-induced increases in MCAvmean were limited in PAH (P<0.05). Reduced MCAvmean contributed to impaired cerebral oxygen delivery and oxygenation (both P<0.05), the latter correlating with exercise capacity in patients with PAH (R2=0.52; P=0.01). CONCLUSIONS These findings provide comprehensive evidence for physiologically and clinically relevant impairments in cerebral hemodynamic regulation and oxygenation in PAH.
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Affiliation(s)
- Simon Malenfant
- Pulmonary Hypertension and Vascular Biology Research Group, Université Laval, Quebec City, Canada
- Quebec Heart and Lung Institute Research Center, Université Laval, Quebec City, Canada
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Canada
| | - Patrice Brassard
- Quebec Heart and Lung Institute Research Center, Université Laval, Quebec City, Canada
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Canada
| | - Myriam Paquette
- Quebec Heart and Lung Institute Research Center, Université Laval, Quebec City, Canada
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Canada
| | - Olivier Le Blanc
- Quebec Heart and Lung Institute Research Center, Université Laval, Quebec City, Canada
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Canada
| | - Audrey Chouinard
- Quebec Heart and Lung Institute Research Center, Université Laval, Quebec City, Canada
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Canada
| | - Valérie Nadeau
- Pulmonary Hypertension and Vascular Biology Research Group, Université Laval, Quebec City, Canada
- Quebec Heart and Lung Institute Research Center, Université Laval, Quebec City, Canada
| | - Philip D Allan
- Wellington Medical Technology Group, Center for Translational Physiology, University of Otago, Wellington, New Zealand
| | - Yu-Chieh Tzeng
- Wellington Medical Technology Group, Center for Translational Physiology, University of Otago, Wellington, New Zealand
| | - Sébastien Simard
- Quebec Heart and Lung Institute Research Center, Université Laval, Quebec City, Canada
| | - Sébastien Bonnet
- Pulmonary Hypertension and Vascular Biology Research Group, Université Laval, Quebec City, Canada
- Quebec Heart and Lung Institute Research Center, Université Laval, Quebec City, Canada
- Department of Medicine, Faculty of Medicine, Université Laval, Quebec City, Canada
| | - Steeve Provencher
- Pulmonary Hypertension and Vascular Biology Research Group, Université Laval, Quebec City, Canada
- Quebec Heart and Lung Institute Research Center, Université Laval, Quebec City, Canada
- Department of Medicine, Faculty of Medicine, Université Laval, Quebec City, Canada
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Castro P, Freitas J, Santos R, Panerai R, Azevedo E. Indexes of cerebral autoregulation do not reflect impairment in syncope: insights from head-up tilt test of vasovagal and autonomic failure subjects. Eur J Appl Physiol 2017; 117:1817-1831. [PMID: 28681121 DOI: 10.1007/s00421-017-3674-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 06/26/2017] [Indexed: 12/27/2022]
Abstract
PURPOSE The study of dynamic cerebral autoregulation (CA), which adapts cerebral blood flow to arterial blood pressure (ABP) fluctuations, has been limited in orthostatic intolerance syndromes, mainly due to its stationary prerequisites hardly to meet during maneuvers to provoke syncope itself. New techniques of continuous estimates of CA could overcome this pitfall. We aimed to evaluate CA during head-up tilt test in common conditions causing syncope. METHODS We compared three groups: eight controls; eight patients with autonomic failure due to familial amyloidotic polyneuropathy; eight patients with vasovagal syncope (VVS). ABP and cerebral blood flow velocity (CBFV) were measured with Finometer® and transcranial Doppler. We calculated cerebrovascular resistance index (CVRi), critical closing pressure (CrCP) and resistance area product (RAP), and derived CA continuously from autoregulation index [ARI(t)]. RESULTS With HUTT, AF subjects showed a pronounced decrease in CBFV (-36 ± 17 versus -7 ± 6%, p < 0.0001), ABP (-29 ± 27 versus 7 ± 12%, p < 0.0001) and RAP (-17 ± 23 versus 3 ± 18%, p < 0.0001) but not CVRi (p = 0.110). VVS subjects showed progressive cerebral vasoconstriction prior to syncope, (reduced CBFV 19 ± 15 versus 1 ± 6, p < 0.000; increased RAP 12 ± 18 versus 2 ± 3%, p = 0.024 and CVRi 12 ± 18 versus 2 ± 3%, p = 0.005). ARI(t) increased significantly in AF patients (5.7 ± 1.2 versus 6.9 ± 1.2, p = 0.040) and VVS (5.8 ± 1.2 versus 7.3 ± 1.2, p = 0.015) in response to ABP fall during syncope. CONCLUSIONS Our data suggest that dynamic cerebral autoregulatory response to orthostatic challenge is neither affected by autonomic dysfunction nor in neutrally mediated syncope. This study also emphasizes that RAP + CrCP model is more informative than CVRi, mainly during cerebral vasodilatory response to orthostatic hypotension.
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Affiliation(s)
- Pedro Castro
- Department of Neurology, São João Hospital Center, Faculty of Medicine of University of Porto, Alameda Professor Hernani Monteiro, 4200-319, Porto, Portugal.
| | - João Freitas
- Autonomic Unit, São João Hospital Center, Faculty of Medicine of University of Porto, Porto, Portugal
| | - Rosa Santos
- Department of Neurology, São João Hospital Center, Faculty of Medicine of University of Porto, Alameda Professor Hernani Monteiro, 4200-319, Porto, Portugal
| | - Ronney Panerai
- Department of Cardiovascular Sciences and NIH Biomedical Research Centre, University of Leicester, Leicester, UK
| | - Elsa Azevedo
- Department of Neurology, São João Hospital Center, Faculty of Medicine of University of Porto, Alameda Professor Hernani Monteiro, 4200-319, Porto, Portugal
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Skytioti M, Søvik S, Elstad M. Internal carotid artery blood flow in healthy awake subjects is reduced by simulated hypovolemia and noninvasive mechanical ventilation. Physiol Rep 2016; 4:e12969. [PMID: 27702883 PMCID: PMC5064133 DOI: 10.14814/phy2.12969] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 08/20/2016] [Accepted: 08/22/2016] [Indexed: 02/02/2023] Open
Abstract
Intact cerebral blood flow (CBF) is essential for cerebral metabolism and function, whereas hypoperfusion in relation to hypovolemia and hypocapnia can lead to severe cerebral damage. This study was designed to assess internal carotid artery blood flow (ICA-BF) during simulated hypovolemia and noninvasive positive pressure ventilation (PPV) in young healthy humans. Beat-by-beat blood velocity (ICA and aorta) were measured by Doppler ultrasound during normovolemia and simulated hypovolemia (lower body negative pressure), with or without PPV in 15 awake subjects. Heart rate, plethysmographic finger arterial pressure, respiratory frequency, and end-tidal CO2 (ETCO2) were also recorded. Cardiac index (CI) and ICA-BF were calculated beat-by-beat. Medians and 95% confidence intervals and Wilcoxon signed rank test for paired samples were used to test the difference between conditions. Effects on ICA-BF were modeled by linear mixed-effects regression analysis. During spontaneous breathing, ICA-BF was reduced from normovolemia (247, 202-284 mL/min) to hypovolemia (218, 194-271 mL/min). During combined PPV and hypovolemia, ICA-BF decreased by 15% (200, 152-231 mL/min, P = 0.001). Regression analysis attributed this fall to concurrent reductions in CI (β: 43.2, SE: 17.1, P = 0.013) and ETCO2 (β: 32.8, SE: 9.3, P = 0.001). Mean arterial pressure was maintained and did not contribute to ICA-BF variance. In healthy awake subjects, ICA-BF was significantly reduced during simulated hypovolemia combined with noninvasive PPV Reductions in CI and ETCO2 had additive effects on ICA-BF reduction. In hypovolemic patients, even low-pressure noninvasive ventilation may cause clinically relevant reductions in CBF, despite maintained arterial blood pressure.
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Affiliation(s)
- Maria Skytioti
- Division of Physiology, Institute of Basic Medical Sciences University of Oslo, Oslo, Norway
| | - Signe Søvik
- Deptartment of Anaesthesia and Intensive Care, Akershus University Hospital, Lørenskog, Norway
| | - Maja Elstad
- Division of Physiology, Institute of Basic Medical Sciences University of Oslo, Oslo, Norway
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18
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Hilz MJ, Wang R, Marthol H, Liu M, Tillmann A, Riss S, Hauck P, Hösl KM, Wasmeier G, Stemper B, Köhrmann M. Partial pharmacologic blockade shows sympathetic connection between blood pressure and cerebral blood flow velocity fluctuations. J Neurol Sci 2016; 365:181-7. [PMID: 27206903 DOI: 10.1016/j.jns.2016.04.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 03/24/2016] [Accepted: 04/07/2016] [Indexed: 11/18/2022]
Abstract
Cerebral autoregulation (CA) dampens transfer of blood pressure (BP)-fluctuations onto cerebral blood flow velocity (CBFV). Thus, CBFV-oscillations precede BP-oscillations. The phase angle (PA) between sympathetically mediated low-frequency (LF: 0.03-0.15Hz) BP- and CBFV-oscillations is a measure of CA quality. To evaluate whether PA depends on sympathetic modulation, we assessed PA-changes upon sympathetic stimulation with and without pharmacologic sympathetic blockade. In 10 healthy, young men, we monitored mean BP and CBFV before and during 120-second cold pressor stimulation (CPS) of one foot (0°C ice-water). We calculated mean values, standard deviations and sympathetic LF-powers of all signals, and PAs between LF-BP- and LF-CBFV-oscillations. We repeated measurements after ingestion of the adrenoceptor-blocker carvedilol (25mg). We compared parameters before and during CPS, without and after carvedilol (analysis of variance, post-hoc t-tests, significance: p<0.05). Without carvedilol, CPS increased BP, CBFV, BP-LF- and CBFV-LF-powers, and shortened PA. Carvedilol decreased resting BP, CBFV, BP-LF- and CBFV-LF-powers, while PAs remained unchanged. During CPS, BPs, CBFVs, BP-LF- and CBFV-LF-powers were lower, while PAs were longer with than without carvedilol. With carvedilol, CPS no longer shortened resting PA. Sympathetic activation shortens PA. Partial adrenoceptor blockade abolishes this PA-shortening. Thus, PA-measurements provide a subtle marker of sympathetic influences on CA and might refine CA evaluation.
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Affiliation(s)
- Max J Hilz
- Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
| | - Ruihao Wang
- Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
| | - Harald Marthol
- Department of Psychiatry, Addiction, Psychotherapy and Psychosomatics, Klinikum am Europakanal, Am Europakanal 71, 91056 Erlangen, Germany.
| | - Mao Liu
- Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
| | - Alexandra Tillmann
- Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
| | - Stephan Riss
- Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
| | - Paulina Hauck
- Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
| | - Katharina M Hösl
- Department of Psychiatry and Psychotherapy, Paracelsus Medical University Nuremberg, Prof.-Ernst-Nathan-Strasse 1, 90419 Nuremberg, Germany.
| | - Gerald Wasmeier
- Department of Cardiology, Klinik Neustadt a. d. Aisch, Paracelsusstraße 30-36, 91413 Neustadt a. d. Aisch, Germany.
| | - Brigitte Stemper
- Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany; Bayer HealthCare, Bayer Pharma AG, Global Development Specialty Medicine, Müllerstr. 178, Building P300, Room 239, 13353 Berlin, Germany.
| | - Martin Köhrmann
- Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
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Guo ZN, Shao A, Tong LS, Sun W, Liu J, Yang Y. The Role of Nitric Oxide and Sympathetic Control in Cerebral Autoregulation in the Setting of Subarachnoid Hemorrhage and Traumatic Brain Injury. Mol Neurobiol 2015; 53:3606-3615. [DOI: 10.1007/s12035-015-9308-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 06/16/2015] [Indexed: 12/23/2022]
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Castro PM, Santos R, Freitas J, Panerai RB, Azevedo E. Autonomic dysfunction affects dynamic cerebral autoregulation during Valsalva maneuver: comparison between healthy and autonomic dysfunction subjects. J Appl Physiol (1985) 2014; 117:205-13. [PMID: 24925980 DOI: 10.1152/japplphysiol.00893.2013] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The role of autonomic nervous system (ANS) in adapting cerebral blood flow (CBF) to arterial blood pressure (ABP) fluctuations [cerebral autoregulation (CA)] is still controversial. We aimed to study the repercussion of autonomic failure (AF) on dynamic CA during the Valsalva maneuver (VM). Eight AF subjects with familial amyloidotic polineuropahty (FAP) were compared with eight healthy controls. ABP and CBF velocity (CBFV) were measured continuously with Finapres and transcranial Doppler, respectively. Cerebrovascular response was evaluated by cerebrovascular resistance index (CVRi), critical closing pressure (CrCP), and resistance-area product (RAP) changes. Dynamic CA was derived from continuous estimates of autoregulatory index (ARI) [ARI(t)]. During phase II of VM, FAP subjects showed a more pronounced decrease in normalized CBFV (78 ± 19 and 111 ± 16%; P = 0.002), ABP (78 ± 19 and 124 ± 12%; P = 0.0003), and RAP (67 ± 17 and 89 ± 17%; P = 0.019) compared with controls. CrCP and CVRi increased similarly in both groups during strain. ARI(t) showed a biphasic variation in controls with initial increase followed by a decrease during phase II but in FAP this response was blunted (5.4 ± 3.0 and 2.0 ± 2.9; P = 0.033). Our data suggest that dynamic cerebral autoregulatory response is a time-varying phenomena during VM and that it is disturbed by autonomic dysfunction. This study also emphasizes the fact that RAP + CrCP model allowed additional insights into understanding of cerebral hemodynamics, showing a higher vasodilatory response expressed by RAP in AF and an equal CrCP response in both groups during the increased intracranial and intrathoracic pressure, while classical CVRi paradoxically suggests a cerebral vasoconstriction.
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Affiliation(s)
- Pedro M Castro
- Department Neurology, São João Hospital Center, Faculty of Medicine of University of Porto, Porto, Portugal;
| | - Rosa Santos
- Department Neurology, São João Hospital Center, Faculty of Medicine of University of Porto, Porto, Portugal
| | - João Freitas
- Autonomic Unit, São João Hospital Center, Faculty of Medicine of University of Porto, Porto, Portugal; and
| | - Ronney B Panerai
- Department of Cardiovascular Sciences and Biomedical Research Unit, University of Leicester, Leicester, United Kingdom
| | - Elsa Azevedo
- Department Neurology, São João Hospital Center, Faculty of Medicine of University of Porto, Porto, Portugal
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Cerebral vasoreactivity: impact of heat stress and lower body negative pressure. Clin Auton Res 2014; 24:135-41. [PMID: 24706257 DOI: 10.1007/s10286-014-0241-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 03/20/2014] [Indexed: 10/25/2022]
Abstract
OBJECTIVE Cerebrovascular reactivity represents the capacity of the cerebral circulation to raise blood flow in the face of increased demand, and may be reduced in some clinical and physiological conditions. We tested the hypothesis that the hypercapnia-induced increase in cerebral perfusion is attenuated during heat stress (HS) compared to normothermia (NT), and this response is further reduced during the combined challenges of HS and lower body negative pressure (LBNP). METHODS Ten healthy individuals (9 men) undertook rebreathing-induced hypercapnia during NT, HS, and HS + 20 mmHg LBNP (HSLBNP), while cerebral perfusion was indexed from middle cerebral artery blood velocity (MCA V mean). Cerebrovascular responses were calculated from the slope of the change in MCA V mean and cerebral vascular conductance (CVCi) relative to the increase in end tidal carbon dioxide ([Formula: see text]) during rebreathing. RESULTS MCA V mean was similar in HS (55 ± 19 cm s(-1)) and HSLBNP (52 ± 16 cm s(-1)), and both values were reduced relative to NT (66 ± 20 cm s(-1)), yet the rise in MCA V mean per Torr increase in [Formula: see text] during rebreathing was similar in each condition (NT: 2.5 ± 0.6 cm s(-1) Torr(-1); HS: 2.4 ± 0.8 cm s(-1) Torr(-1); HSLBNP: 2.1 ± 1.1 cm s(-1) Torr(-1)). Likewise, the rate of increase in CVCi was not different between conditions (NT: 2.1 ± 0.65 cm s(-1 )mmHg(-1)100 Torr(-1); HS: 2.4 ± 0.8 cm s(-1) mmHg(-1) 100 Torr(-1); HSLBNP: 2.0 ± 1.0 cm s(-1) mmHg(-1) 100 Torr(-1)). INTERPRETATIONS These data indicate that cerebrovascular reactivity is not compromised during whole-body heat stress alone or when combined with mild orthostatic stress relative to normothermic conditions.
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Laughlin MH, Davis MJ, Secher NH, van Lieshout JJ, Arce-Esquivel AA, Simmons GH, Bender SB, Padilla J, Bache RJ, Merkus D, Duncker DJ. Peripheral circulation. Compr Physiol 2013; 2:321-447. [PMID: 23728977 DOI: 10.1002/cphy.c100048] [Citation(s) in RCA: 174] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Blood flow (BF) increases with increasing exercise intensity in skeletal, respiratory, and cardiac muscle. In humans during maximal exercise intensities, 85% to 90% of total cardiac output is distributed to skeletal and cardiac muscle. During exercise BF increases modestly and heterogeneously to brain and decreases in gastrointestinal, reproductive, and renal tissues and shows little to no change in skin. If the duration of exercise is sufficient to increase body/core temperature, skin BF is also increased in humans. Because blood pressure changes little during exercise, changes in distribution of BF with incremental exercise result from changes in vascular conductance. These changes in distribution of BF throughout the body contribute to decreases in mixed venous oxygen content, serve to supply adequate oxygen to the active skeletal muscles, and support metabolism of other tissues while maintaining homeostasis. This review discusses the response of the peripheral circulation of humans to acute and chronic dynamic exercise and mechanisms responsible for these responses. This is accomplished in the context of leading the reader on a tour through the peripheral circulation during dynamic exercise. During this tour, we consider what is known about how each vascular bed controls BF during exercise and how these control mechanisms are modified by chronic physical activity/exercise training. The tour ends by comparing responses of the systemic circulation to those of the pulmonary circulation relative to the effects of exercise on the regional distribution of BF and mechanisms responsible for control of resistance/conductance in the systemic and pulmonary circulations.
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Affiliation(s)
- M Harold Laughlin
- Department of Medical Pharmacology and Physiology, and the Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri, USA.
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Lucas SJE, Lewis NCS, Sikken ELG, Thomas KN, Ainslie PN. Slow breathing as a means to improve orthostatic tolerance: a randomized sham-controlled trial. J Appl Physiol (1985) 2013; 115:202-11. [DOI: 10.1152/japplphysiol.00128.2013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Endogenous oscillations in blood pressure (BP) and cerebral blood flow have been associated with improved orthostatic tolerance. Although slow breathing induces such responses, it has not been tested as a therapeutic strategy to improve orthostatic tolerance. With the use of a randomized, crossover sham-controlled design, we tested the hypothesis that breathing at six breaths/min (vs. spontaneous breathing) would improve orthostatic tolerance via inducing oscillations in mean arterial BP (MAP) and cerebral blood flow. Sixteen healthy participants (aged 25 ± 4 yr; mean ± SD) had continuous beat-to-beat measurements of middle cerebral artery blood velocity (MCAv), BP (finometer), heart rate (ECG), and end-tidal carbon dioxide partial pressure during an incremental orthostatic stress test to presyncope by combining head-up tilt with incremental lower-body negative pressure. Tolerance time to presyncope was improved (+15%) with slow breathing compared with spontaneous breathing (29.2 ± 5.4 vs. 33.7 ± 6.0 min; P < 0.01). The improved tolerance was reflected in elevations in low-frequency (LF; 0.07-0.2 Hz) oscillations of MAP and mean MCAv, improved metrics of dynamic cerebrovascular control (increased LF phase and reduced LF gain), and a reduced rate of decline for MCAv (−0.60 ± 0.27 vs. −0.99 ± 0.51 cm·s−1·min−1; P < 0.01) and MAP (−0.50 ± 0.37 vs. −1.03 ± 0.80 mmHg/min; P = 0.01 vs. spontaneous breathing) across time from baseline to presyncope. Our findings show that orthostatic tolerance can be improved within healthy individuals with a simple, nonpharmacological breathing strategy. The mechanisms underlying this improvement are likely mediated via the generation of negative intrathoracic pressure during slow and deep breathing and the related beneficial impact on cerebrovascular and autonomic function.
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Affiliation(s)
- Samuel J. E. Lucas
- Department of Physiology, University of Otago, Dunedin, New Zealand
- School of Physical Education, University of Otago, Dunedin, New Zealand
- School of Sport and Exercise Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Nia C. S. Lewis
- Centre of Heart, Lung and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia, Okanagan Campus, Vancouver, British Columbia, Canada
- Research Institute of Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom; and
| | - Elisabeth L. G. Sikken
- Department of Physiology, University of Otago, Dunedin, New Zealand
- Department of Physiology, Radboud University, Nijmegen Medical Centre, Nijmegen, the Netherlands
| | - Kate N. Thomas
- Department of Physiology, University of Otago, Dunedin, New Zealand
- School of Physical Education, University of Otago, Dunedin, New Zealand
| | - Philip N. Ainslie
- Centre of Heart, Lung and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia, Okanagan Campus, Vancouver, British Columbia, Canada
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Steinback CD, Zubin P, Breskovic T, Bakovic D, Pivac N, Dujic Z. Cerebral oxygenation following epinephrine infusion. J Neurol Sci 2012; 321:23-8. [DOI: 10.1016/j.jns.2012.07.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 07/04/2012] [Accepted: 07/11/2012] [Indexed: 11/16/2022]
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Sato K, Fisher JP, Seifert T, Overgaard M, Secher NH, Ogoh S. Blood flow in internal carotid and vertebral arteries during orthostatic stress. Exp Physiol 2012; 97:1272-80. [DOI: 10.1113/expphysiol.2012.064774] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Hahn GH, Heiring C, Pryds O, Greisen G. Cerebral vascular effects of hypovolemia and dopamine infusions: a study in newborn piglets. Acta Paediatr 2012; 101:736-42. [PMID: 22404282 DOI: 10.1111/j.1651-2227.2012.02666.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM Despite widespread use, effects of volume boluses and dopamine in hypotensive newborn infants remain controversial. We aimed to elucidate if hypovolemia alone impairs cerebral autoregulation (CA) and if dopamine affects cerebral vasculature. METHODS In 12 piglets, cerebral perfusion (laser-Doppler flux) and oxygenation [near-infrared spectroscopy (NIRS)] were examined during dopamine (20-50 μg/kg per minute) and nonpharmacologically induced blood pressure (ABP) changes. Effect on cerebral perfusion and oxygenation was quantified as frequency gain between ABP and laser-Doppler flux (gain-LDF) and NIRS [gain-oxygenation index (OI)], respectively. Gain quantifies change in perfusion or oxygenation per ABP-change. CA was estimated as gain-LDF during nonpharmacologically induced ABP changes, that is, as degree of impairment. Dopamine's cerebrovascular effect was estimated by contrasting gain during dopamine- and nonpharmacologically induced ABP changes. Measurements were conducted during both normovolemia- and haemorrhage-induced hypovolemia. RESULTS Hypovolemia elicited hypotension (p = 0.02) as well as increasing impairment of CA (p = 0.01). However, hypovolemia without hypotension did not affect CA significantly. Dopamine increased perfusion significantly compared to nonpharmacological challenges (mean difference: 1.5%/mmHg, 95% CI: 0.5-2.6, p = 0.007). Oxygenation was, however, similar (mean difference: 0.01 μmol/L per mmHg, 95% CI: -0.03 to 0.05, p = 0.7). CONCLUSION Our findings do not support that hypovolemia alone impairs CA. Furthermore, dopamine seems to increase cerebral perfusion but not oxygenation.
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Affiliation(s)
- Gitte H Hahn
- Department of Neonatology, Copenhagen University Hospital - Rigshospitalet, Denmark.
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Katsogridakis E, Bush G, Fan L, Birch AA, Simpson DM, Allen R, Potter JF, Panerai RB. Random perturbations of arterial blood pressure for the assessment of dynamic cerebral autoregulation. Physiol Meas 2012; 33:103-16. [PMID: 22227772 DOI: 10.1088/0967-3334/33/2/103] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The assessment of cerebral autoregulation (CA) relies mostly on methods that modulate arterial blood pressure (ABP). Despite advances, the gold standard of assessment remains elusive and clinical practicality is limited. We investigate a novel approach of assessing CA, consisting of the intermittent application of thigh cuffs using square wave sequences. Our aim was to increase ABP variability whilst minimizing volunteer discomfort, thus improving assessment acceptability. Two random square wave sequences and two maximum pressure settings (80 and 150 mmHg) were used, corresponding to four manoeuvres that were conducted in random order after a baseline recording. The intermittent application of thigh cuffs resulted in an amplitude dependent increase in ABP (p = 0.001) and cerebral blood flow velocity (CBFV) variability (p = 0.026) compared to baseline. No statistically significant differences in mean heart rate or heart rate variability were observed (p = 0.108 and p = 0.350, respectively), suggesting that no significant sympathetic response was elicited. No significant differences in the CBFV step response were observed, suggesting no distortion of autoregulatory parameters resulted from the use of thigh cuffs. We conclude that pseudorandom binary sequences are an effective and safe alternative for increasing ABP variability. This new approach shows great promise as a tool for the robust assessment of CA.
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Jeong SM, Shibata S, Levine BD, Zhang R. Exercise plus volume loading prevents orthostatic intolerance but not reduction in cerebral blood flow velocity after bed rest. Am J Physiol Heart Circ Physiol 2011; 302:H489-97. [PMID: 22081705 DOI: 10.1152/ajpheart.00427.2011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study tested the hypothesis that reduction in cerebral blood flow (CBF) during orthostatic stress after bed rest can be ameliorated with volume loading, exercise, or both. Transcranial Doppler was used to measure changes in CBF velocity during lower body negative pressure (LBNP) before and after an 18-day bed rest in 33 healthy subjects. Subjects were assigned into four groups with similar age and sex: 1) supine cycling during bed rest (Exercise group; n = 7), 2) volume loading with Dextran infusion after bed rest to restore reduced left ventricular filling pressure (Dextran group; n = 7), 3) exercise combined with volume loading to prevent orthostatic intolerance (Ex-Dex group; n = 7), and 4) a control group (n = 12). LBNP tolerance was measured using a cumulative stress index (CSI). After bed rest, CBF velocity was reduced at a lower level of LBNP in the Control group, and the magnitude of reduction was greater in the Ex-Dex group. However, reduction in orthostatic tolerance was prevented in the Ex-Dex group. Notably, volume loading alone prevented greater reductions in CBF velocity after bed rest, but CSI was reduced still by 25%. Finally, decreases in CBF velocity during LBNP were correlated with reduction in cardiac output under all conditions (r(2) = 0.86; P = < 0.001). Taken together, these findings demonstrate that volume loading alone can ameliorate reductions in CBF during LBNP. However, the lack of associations between changes in CBF velocity and orthostatic tolerance suggests that reductions in CBF during LBNP under steady-state conditions by itself are unlikely to be a primary factor leading to orthostatic intolerance.
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Affiliation(s)
- Sung-Moon Jeong
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, and University of Texas Southwestern Medical Center at Dallas, TX 75231, USA
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Rickards CA, Ryan KL, Cooke WH, Convertino VA. Tolerance to central hypovolemia: the influence of oscillations in arterial pressure and cerebral blood velocity. J Appl Physiol (1985) 2011; 111:1048-58. [DOI: 10.1152/japplphysiol.00231.2011] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Higher oscillations of cerebral blood velocity and arterial pressure (AP) induced by breathing with inspiratory resistance are associated with delayed onset of symptoms and increased tolerance to central hypovolemia. We tested the hypothesis that subjects with high tolerance (HT) to central hypovolemia would display higher endogenous oscillations of cerebral blood velocity and AP at presyncope compared with subjects with low tolerance (LT). One-hundred thirty-five subjects were exposed to progressive lower body negative pressure (LBNP) until the presence of presyncopal symptoms. Subjects were classified as HT if they completed at least the −60-mmHg level of LBNP (93 subjects; LBNP time, 1,880 ± 259 s) and LT if they did not complete this level (42 subjects; LBNP time, 1,277 ± 199 s). Middle cerebral artery velocity (MCAv) was measured by transcranial Doppler, and AP was measured at the finger by photoplethysmography. Mean MCAv and mean arterial pressure (MAP) decreased progressively from baseline to presyncope for both LT and HT subjects ( P < 0.001). However, low frequency (0.04–0.15 Hz) oscillations of mean MCAv and MAP were higher at presyncope in HT subjects compared with LT subjects (MCAv: HT, 7.2 ± 0.7 vs. LT, 5.3 ± 0.6 (cm/s)2, P = 0.075; MAP: HT, 15.3 ± 1.4 vs. 7.9 ± 1.2 mmHg2, P < 0.001). Consistent with our previous findings using inspiratory resistance, high oscillations of mean MCAv and MAP are associated with HT to central hypovolemia.
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Affiliation(s)
- Caroline A. Rickards
- Department of Health and Kinesiology, University of Texas at San Antonio, San Antonio; and
| | - Kathy L. Ryan
- US Army Institute of Surgical Research, Fort Sam Houston, Texas
| | - William H. Cooke
- Department of Health and Kinesiology, University of Texas at San Antonio, San Antonio; and
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Gierthmühlen J, Allardt A, Sawade M, Baron R, Wasner G. Dynamic cerebral autoregulation in stroke patients with a central sympathetic deficit. Acta Neurol Scand 2011; 123:332-8. [PMID: 20809903 DOI: 10.1111/j.1600-0404.2010.01424.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To investigate the functional role of the sympathetic innervation on cerebral autoregulation. MATERIALS AND METHODS Seventeen patients with infarction of the dorsolateral medulla oblongata affecting central sympathetic pathways (Wallenberg's syndrome) and 21 healthy controls were included in the study. Cerebral blood flow velocity (CBFV) in the medial cerebral artery was investigated using transcranial Doppler ultrasound during decrease in cerebral perfusion pressure induced by leg-cuff test and tilt table. RESULTS Upon leg-cuff test, changes of cerebral blood flow and mean arterial blood pressure as well as autoregulatory index did not differ between patients or controls. No differences were found in changes of CBFV, mean arterial blood pressure and heart rate between patients or controls during the tilt table test. CONCLUSIONS We suggest that the sympathetic nervous system does not have an influence on cerebral autoregulation after decrease in perfusion pressure under normotonous conditions.
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Affiliation(s)
- J Gierthmühlen
- Department of Neurology, Division ofNeurological Pain Research and Therapy, University Hospital Schleswig-Holstein, Campus Kiel, Germany.
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Abstract
Cerebral blood flow (CBF) increases and dynamic cerebral autoregulation is impaired by acute hypoxia. We hypothesized that progressive hypocapnia with restoration of arterial oxygen content after altitude acclimatization would normalize CBF and dynamic cerebral autoregulation. To test this hypothesis, dynamic cerebral autoregulation was examined by spectral and transfer function analyses between arterial pressure and CBF velocity variabilities in 11 healthy members of the Danish High-Altitude Research Expedition during normoxia and acute hypoxia (10.5% O(2)) at sea level, and after acclimatization (for over 1 month at 5,260 m at Chacaltaya, Bolivia). Arterial pressure and CBF velocity in the middle cerebral artery (transcranial Doppler), were recorded on a beat-by-beat basis. Steady-state CBF velocity increased during acute hypoxia, but normalized after acclimatization with partial restoration of SaO(2) (acute, 78% ± 2%; chronic, 89% ± 1%) and progression of hypocapnia (end-tidal carbon dioxide: acute, 34 ± 2 mm Hg; chronic, 21 ± 1 mm Hg). Coherence (0.40 ± 0.05 Units at normoxia) and transfer function gain (0.77 ± 0.13 cm/s per mm Hg at normoxia) increased, and phase (0.86 ± 0.15 radians at normoxia) decreased significantly in the very-low-frequency range during acute hypoxia (gain, 141% ± 24%; coherence, 136% ± 29%; phase, -25% ± 22%), which persisted after acclimatization (gain, 136% ± 36%; coherence, 131% ± 50%; phase, -42% ± 13%), together indicating impaired dynamic cerebral autoregulation in this frequency range. The similarity between both acute and chronic conditions suggests that dynamic cerebral autoregulation is impaired by hypoxia even after successful acclimatization to an extreme high altitude.
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33
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Zhang P, Huang G, Shi X. Cerebral vasoreactivity during hypercapnia is reset by augmented sympathetic influence. J Appl Physiol (1985) 2010; 110:352-8. [PMID: 21071587 DOI: 10.1152/japplphysiol.00802.2010] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Sympathetic nerve activity influences cerebral blood flow, but it is unknown whether augmented sympathetic nerve activity resets cerebral vasoreactivity to hypercapnia. This study tested the hypothesis that cerebral vasodilation during hypercapnia is restrained by lower-body negative pressure (LBNP)-stimulated sympathoexcitation. Cerebral hemodynamic responses were assessed in nine healthy volunteers [age 25 yr (SD 3)] during rebreathing-induced increases in partial pressure of end-tidal CO(2) (Pet(CO(2))) at rest and during LBNP. Cerebral hemodynamic responses were determined by changes in flow velocity of middle cerebral artery (MCAV) using transcranial Doppler sonography and in regional cerebral tissue oxygenation (ScO(2)) using near-infrared spectroscopy. Pet(CO(2)) values during rebreathing were similarly increased from 41.9 to 56.5 mmHg at rest and from 40.7 to 56.0 mmHg during LBNP of -15 Torr. However, the rates of increases in MCAV and in ScO(2) per unit increase in Pet(CO(2)) (i.e., the slopes of MCAV/Pet(CO(2)) and ScO(2)/Pet(CO(2))) were significantly (P ≤0.05) decreased from 2.62 ± 0.16 cm·s(-1)·mmHg(-1) and 0.89 ± 0.10%/mmHg at rest to 1.68 ± 0.18 cm·s(-1)·mmHg(-1) and 0.63 ± 0.07%/mmHg during LBNP. In conclusion, the sensitivity of cerebral vasoreactivity to hypercapnia, in terms of the rate of increases in MCAV and in ScO(2), is diminished by LBNP-stimulated sympathoexcitation.
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Affiliation(s)
- Peizhen Zhang
- Department of Integrative Physiology, UNT Health Science Center, Fort Worth, TX 76107, USA
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Deegan BM, Devine ER, Geraghty MC, Jones E, Ólaighin G, Serrador JM. The relationship between cardiac output and dynamic cerebral autoregulation in humans. J Appl Physiol (1985) 2010; 109:1424-31. [PMID: 20689094 DOI: 10.1152/japplphysiol.01262.2009] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cerebral autoregulation adjusts cerebrovascular resistance in the face of changing perfusion pressures to maintain relatively constant flow. Results from several studies suggest that cardiac output may also play a role. We tested the hypothesis that cerebral blood flow would autoregulate independent of changes in cardiac output. Transient systemic hypotension was induced by thigh-cuff deflation in 19 healthy volunteers (7 women) in both supine and seated positions. Mean arterial pressure (Finapres), cerebral blood flow (transcranial Doppler) in the anterior (ACA) and middle cerebral artery (MCA), beat-by-beat cardiac output (echocardiography), and end-tidal Pco(2) were measured. Autoregulation was assessed using the autoregulatory index (ARI) defined by Tiecks et al. (Tiecks FP, Lam AM, Aaslid R, Newell DW. Stroke 26: 1014-1019, 1995). Cerebral autoregulation was better in the supine position in both the ACA [supine ARI: 5.0 ± 0.21 (mean ± SE), seated ARI: 3.9 ± 0.4, P = 0.01] and MCA (supine ARI: 5.0 ± 0.2, seated ARI: 3.8 ± 0.3, P = 0.004). In contrast, cardiac output responses were not different between positions and did not correlate with cerebral blood flow ARIs. In addition, women had better autoregulation in the ACA (P = 0.046), but not the MCA, despite having the same cardiac output response. These data demonstrate cardiac output does not appear to affect the dynamic cerebral autoregulatory response to sudden hypotension in healthy controls, regardless of posture. These results also highlight the importance of considering sex when studying cerebral autoregulation.
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Affiliation(s)
- B M Deegan
- School of Engineering and Informatics, National University of Ireland Galway, Galway, Ireland
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Formes K, Zhang P, Tierney N, Schaller F, Shi X. Chronic physical activity mitigates cerebral hypoperfusion during central hypovolemia in elderly humans. Am J Physiol Heart Circ Physiol 2009; 298:H1029-37. [PMID: 20044443 DOI: 10.1152/ajpheart.00662.2009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study sought to test the hypothesis that orthostasis-induced cerebral hypoperfusion would be less severe in physically active elderly humans (ACT group) than in sedentary elderly humans (SED group). The peak O(2) uptake of 10 SED (67.1 +/- 1.4 yr) and 9 ACT (68.0 +/- 1.1 yr) volunteers was determined by a graded cycling exercise test (22.1 +/- 1.2 vs 35.8 +/- 1.3 ml.min(-1).kg(-1), P < 0.01). Baseline mean arterial pressure (MAP; tonometry) and middle cerebral arterial blood flow velocity (V(MCA); transcranial Doppler) were similar between the groups (SED vs. ACT group: 91 +/- 3 vs. 87 +/- 3 mmHg and 54.9 +/- 2.3 vs. 57.8 +/- 3.2 cm/s, respectively), whereas heart rate was higher and stroke volume (bioimpedance) was smaller in the SED group than in the ACT group. Central hypovolemia during graded lower body negative pressure (LBNP) was larger (P < 0.01) in the ACT group than in the SED group. However, the slope of V(MCA)/LBNP was smaller (P < 0.05) in the ACT group (0.159 +/- 0.016 cm/s/Torr) than in the SED group (0.211 +/- 0.008 cm/s/Torr). During LBNP, the SED group had a greater augmentation of cerebral vasomotor tone (P < 0.05) and hypocapnia (P < 0.001) compared with the ACT group. Baseline MAP variability and V(MCA) variability were significantly smaller in the SED group than in the ACT group, i.e., 0.49 +/- 0.07 vs. 1.04 +/- 0.16 (mmHg)(2) and 1.06 +/- 0.19 vs. 4.24 +/- 1.59 (cm/s)(2), respectively. However, transfer function gain, coherence, and phase between MAP and V(MCA) signals (Welch spectral estimator) from 0.08-0.18 Hz were not different between SED (1.41 +/- 0.18 cm.s(-1).mmHg(-1), 0.63 +/- 0.06 units, and 38.03 +/- 6.57 degrees ) and ACT (1.65 +/- 0.44 cm.s(-1).mmHg(-1), 0.56 +/- 0.05 units, and 48.55 +/- 11.84 degrees ) groups. We conclude that a physically active lifestyle improves the intrinsic mechanism of cerebral autoregulation and helps mitigate cerebral hypoperfusion during central hypovolemia in healthy elderly adults.
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Affiliation(s)
- Kevin Formes
- Dept. of Integrative Physiology, Univ. of North Texas Health Science Center, Fort Worth, 76107, USA
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Panerai RB. Transcranial Doppler for evaluation of cerebral autoregulation. Clin Auton Res 2009; 19:197-211. [PMID: 19370374 DOI: 10.1007/s10286-009-0011-8] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Accepted: 03/13/2009] [Indexed: 12/14/2022]
Abstract
Transcranial Doppler ultrasound (TCD) can measure cerebral blood flow velocity in the main intracranial vessels non-invasively and with high accuracy. Combined with the availability of non-invasive devices for continuous measurement of arterial blood pressure, the relatively low cost, ease-of-use, and excellent temporal resolution of TCD have stimulated the development of new techniques to assess cerebral autoregulation in the laboratory or bedside using a dynamic approach, instead of the more classical 'static' method. Clinical applications have shown consistent results in certain conditions such as severe head injury and carotid artery disease. Studies in syncopal patients revealed a more complex pattern due to aetiological non-homogeneity and methodological limitations mainly due to inadequate sample-size. Different analytical models to quantify autoregulatory performance have also contributed to the diversity of results in the literature. The review concludes with specific recommendations for areas where further validation and research are needed to improve the reliability and usefulness of TCD in clinical practice.
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Affiliation(s)
- Ronney B Panerai
- Medical Physics Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, UK.
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Keller CJ, Cash SS, Narayanan S, Wang C, Kuzniecky R, Carlson C, Devinsky O, Thesen T, Doyle W, Sassaroli A, Boas DA, Ulbert I, Halgren E. Intracranial microprobe for evaluating neuro-hemodynamic coupling in unanesthetized human neocortex. J Neurosci Methods 2009; 179:208-18. [PMID: 19428529 DOI: 10.1016/j.jneumeth.2009.01.036] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2008] [Revised: 01/27/2009] [Accepted: 01/29/2009] [Indexed: 10/21/2022]
Abstract
Measurement of the blood-oxygen-level dependent (BOLD) response with fMRI has revolutionized cognitive neuroscience and is increasingly important in clinical care. The BOLD response reflects changes in deoxy-hemoglobin concentration, blood volume, and blood flow. These hemodynamic changes ultimately result from neuronal firing and synaptic activity, but the linkage between these domains is complex, poorly understood, and may differ across species, cortical areas, diseases, and cognitive states. We describe here a technique that can measure neural and hemodynamic changes simultaneously from cortical microdomains in waking humans. We utilize a "laminar optode," a linear array of microelectrodes for electrophysiological measures paired with a micro-optical device for hemodynamic measurements. Optical measurements include laser Doppler to estimate cerebral blood flow as well as point spectroscopy to estimate oxy- and deoxy-hemoglobin concentrations. The microelectrode array records local field potential gradients (PG) and multi-unit activity (MUA) at 24 locations spanning the cortical depth, permitting estimation of population trans-membrane current flows (Current Source Density, CSD) and population cell firing in each cortical lamina. Comparison of the laminar CSD/MUA profile with the origins and terminations of cortical circuits allows activity in specific neuronal circuits to be inferred and then directly compared to hemodynamics. Access is obtained in epileptic patients during diagnostic evaluation for surgical therapy. Validation tests with relatively well-understood manipulations (EKG, breath-holding, cortical electrical stimulation) demonstrate the expected responses. This device can provide a new and robust means for obtaining detailed, quantitative data for defining neurovascular coupling in awake humans.
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Affiliation(s)
- Corey J Keller
- Department of Neurology, Massachusetts General Hospital, Boston, MA, USA.
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Ainslie PN, Duffin J. Integration of cerebrovascular CO2 reactivity and chemoreflex control of breathing: mechanisms of regulation, measurement, and interpretation. Am J Physiol Regul Integr Comp Physiol 2009; 296:R1473-95. [PMID: 19211719 DOI: 10.1152/ajpregu.91008.2008] [Citation(s) in RCA: 394] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cerebral blood flow (CBF) and its distribution are highly sensitive to changes in the partial pressure of arterial CO(2) (Pa(CO(2))). This physiological response, termed cerebrovascular CO(2) reactivity, is a vital homeostatic function that helps regulate and maintain central pH and, therefore, affects the respiratory central chemoreceptor stimulus. CBF increases with hypercapnia to wash out CO(2) from brain tissue, thereby attenuating the rise in central Pco(2), whereas hypocapnia causes cerebral vasoconstriction, which reduces CBF and attenuates the fall of brain tissue Pco(2). Cerebrovascular reactivity and ventilatory response to Pa(CO(2)) are therefore tightly linked, so that the regulation of CBF has an important role in stabilizing breathing during fluctuating levels of chemical stimuli. Indeed, recent reports indicate that cerebrovascular responsiveness to CO(2), primarily via its effects at the level of the central chemoreceptors, is an important determinant of eupneic and hypercapnic ventilatory responsiveness in otherwise healthy humans during wakefulness, sleep, and exercise and at high altitude. In particular, reductions in cerebrovascular responsiveness to CO(2) that provoke an increase in the gain of the chemoreflex control of breathing may underpin breathing instability during central sleep apnea in patients with congestive heart failure and on ascent to high altitude. In this review, we summarize the major factors that regulate CBF to emphasize the integrated mechanisms, in addition to Pa(CO(2)), that control CBF. We discuss in detail the assessment and interpretation of cerebrovascular reactivity to CO(2). Next, we provide a detailed update on the integration of the role of cerebrovascular CO(2) reactivity and CBF in regulation of chemoreflex control of breathing in health and disease. Finally, we describe the use of a newly developed steady-state modeling approach to examine the effects of changes in CBF on the chemoreflex control of breathing and suggest avenues for future research.
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Affiliation(s)
- Philip N Ainslie
- Department of Physiology, University of Otago, Dunedin, New Zealand.
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Levine BD, Zhang R. Comments on Point:Counterpoint: Sympathetic activity does/does not influence cerebral blood flow. J Appl Physiol (1985) 2008; 105:1373. [DOI: 10.1152/japplphysiol.zdg-8199.pcpcomm.2008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Rebuttal from Strandgaard and Sigurdsson. J Appl Physiol (1985) 2008. [DOI: 10.1152/japplphysiol.90597.2008c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Strandgaard S, Sigurdsson ST. Last Word on Point:Counterpoint: Sympathetic nervous activity does/does not influence cerebral blood flow. J Appl Physiol (1985) 2008; 105:1375. [DOI: 10.1152/japplphysiol.91088.2008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Strandgaard S, Sigurdsson ST. Counterpoint: Sympathetic nerve activity does not influence cerebral blood flow. J Appl Physiol (1985) 2008; 105:1366-7; discussion 1367-8. [DOI: 10.1152/japplphysiol.90597.2008a] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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van Lieshout JJ, Secher NH. Point:Counterpoint: Sympathetic activity does/does not influence cerebral blood flow. Point: Sympathetic activity does influence cerebral blood flow. J Appl Physiol (1985) 2008; 105:1364-6. [PMID: 18583376 DOI: 10.1152/japplphysiol.90597.2008] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Johannes J van Lieshout
- Department of Internal Medicine, Medium Care Unit, AMC Center for Heart Failure Research, Academic Medical Center, University of Amerstdam, The Netherlands.
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Jeon HY, Joung KW, Choi JM, Kim YK, Shin JW, Leem JG, Han SM. The Effects of Superior Cervical Sympathetic Ganglion Block on the Acute Phase Injury and Long Term Protection against Focal Cerebral Ischemia/Reperfusion Injury in Rats. Korean J Pain 2008. [DOI: 10.3344/kjp.2008.21.2.119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- Hae Young Jeon
- Department of Anesthesiology and Pain Medicine, University of Ulsan College of Medicine, Seoul, Korea
| | - Kyoung Woon Joung
- Department of Anesthesiology and Pain Medicine, University of Ulsan College of Medicine, Seoul, Korea
| | - Jae Moon Choi
- Department of Anesthesiology and Pain Medicine, University of Ulsan College of Medicine, Seoul, Korea
| | - Yoo Kyung Kim
- Department of Anesthesiology and Pain Medicine, University of Ulsan College of Medicine, Seoul, Korea
| | - Jin Woo Shin
- Department of Anesthesiology and Pain Medicine, University of Ulsan College of Medicine, Seoul, Korea
| | - Jeong Gill Leem
- Department of Anesthesiology and Pain Medicine, University of Ulsan College of Medicine, Seoul, Korea
| | - Sung Min Han
- Department of Anesthesiology and Pain Medicine, University of Ulsan College of Medicine, Seoul, Korea
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