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Kostoglou K, Bello-Robles F, Brassard P, Chacon M, Claassen JA, Czosnyka M, Elting JW, Hu K, Labrecque L, Liu J, Marmarelis VZ, Payne SJ, Shin DC, Simpson D, Smirl J, Panerai RB, Mitsis GD. Time-domain methods for quantifying dynamic cerebral blood flow autoregulation: Review and recommendations. A white paper from the Cerebrovascular Research Network (CARNet). J Cereb Blood Flow Metab 2024:271678X241249276. [PMID: 38688529 DOI: 10.1177/0271678x241249276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Cerebral Autoregulation (CA) is an important physiological mechanism stabilizing cerebral blood flow (CBF) in response to changes in cerebral perfusion pressure (CPP). By maintaining an adequate, relatively constant supply of blood flow, CA plays a critical role in brain function. Quantifying CA under different physiological and pathological states is crucial for understanding its implications. This knowledge may serve as a foundation for informed clinical decision-making, particularly in cases where CA may become impaired. The quantification of CA functionality typically involves constructing models that capture the relationship between CPP (or arterial blood pressure) and experimental measures of CBF. Besides describing normal CA function, these models provide a means to detect possible deviations from the latter. In this context, a recent white paper from the Cerebrovascular Research Network focused on Transfer Function Analysis (TFA), which obtains frequency domain estimates of dynamic CA. In the present paper, we consider the use of time-domain techniques as an alternative approach. Due to their increased flexibility, time-domain methods enable the mitigation of measurement/physiological noise and the incorporation of nonlinearities and time variations in CA dynamics. Here, we provide practical recommendations and guidelines to support researchers and clinicians in effectively utilizing these techniques to study CA.
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Affiliation(s)
- Kyriaki Kostoglou
- Department of Electrical and Computer Engineering, McGill University, Montreal, QC, Canada
- Institute of Neural Engineering, Graz University of Technology, Graz, Austria
| | - Felipe Bello-Robles
- Departamento de Ingeniería Informática, Universidad de Santiago de Chile, Santiago, Chile
| | - Patrice Brassard
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec, QC, Canada
- Research Center of the Institut universitaire de cardiologie et de pneumologie de Québec, Quebec, QC, Canada
| | - Max Chacon
- Departamento de Ingeniería Informática, Universidad de Santiago de Chile, Santiago, Chile
| | - Jurgen Ahr Claassen
- Department of Geriatrics, Radboud University Medical Center, Research Institute for Medical Innovation and Donders Institute, Nijmegen, The Netherlands
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM), Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Marek Czosnyka
- Department of Clinical Neurosciences, Neurosurgery Department, University of Cambridge, Cambridge, UK
| | - Jan-Willem Elting
- Department of Neurology and Clinical Neurophysiology, University Medical Center Groningen, Groningen, The Netherlands
| | - Kun Hu
- Medical Biodynamics Program, Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
- Division of Sleep Medicine, Harvard Medical School, Boston, MA, USA
| | - Lawrence Labrecque
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec, QC, Canada
- Research Center of the Institut universitaire de cardiologie et de pneumologie de Québec, Quebec, QC, Canada
| | - Jia Liu
- Laboratory for Engineering and Scientific Computing, Institute of Advanced Computing and Digital Engineering, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Vasilis Z Marmarelis
- Department Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA
| | - Stephen J Payne
- Institute of Applied Mechanics, National Taiwan University, Taipei, Taiwan
| | - Dae Cheol Shin
- Department Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA
| | - David Simpson
- Institute of Sound and Vibration Research, University of Southampton, Southampton, UK
| | - Jonathan Smirl
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Ronney B Panerai
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM), Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
- NIHR Leicester Biomedical Research Centre, British Heart Foundation, Glenfield Hospital, Leicester, UK
| | - Georgios D Mitsis
- Department of Bioengineering, McGill University, Montreal, QC, Canada
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Daher A, Payne S. The conducted vascular response as a mediator of hypercapnic cerebrovascular reactivity: A modelling study. Comput Biol Med 2024; 170:107985. [PMID: 38245966 DOI: 10.1016/j.compbiomed.2024.107985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 12/29/2023] [Accepted: 01/13/2024] [Indexed: 01/23/2024]
Abstract
It is well established that the cerebral blood flow (CBF) shows exquisite sensitivity to changes in the arterial blood partial pressure of CO2 ( [Formula: see text] ), which is reflected by an index termed cerebrovascular reactivity. In response to elevations in [Formula: see text] (hypercapnia), the vessels of the cerebral microvasculature dilate, thereby decreasing the vascular resistance and increasing CBF. Due to the challenges of access, scale and complexity encountered when studying the microvasculature, however, the mechanisms behind cerebrovascular reactivity are not fully understood. Experiments have previously established that the cholinergic release of the Acetylcholine (ACh) neurotransmitter in the cortex is a prerequisite for the hypercapnic response. It is also known that ACh functions as an endothelial-dependent agonist, in which the local administration of ACh elicits local hyperpolarization in the vascular wall; this hyperpolarization signal is then propagated upstream the vascular network through the endothelial layer and is coupled to a vasodilatory response in the vascular smooth muscle (VSM) layer in what is known as the conducted vascular response (CVR). Finally, experimental data indicate that the hypercapnic response is more strongly correlated with the CO2 levels in the tissue than in the arterioles. Accordingly, we hypothesize that the CVR, evoked by increases in local tissue CO2 levels and a subsequent local release of ACh, is responsible for the CBF increase observed in response to elevations in [Formula: see text] . By constructing physiologically grounded dynamic models of CBF and control in the cerebral vasculature, ones that integrate the available knowledge and experimental data, we build a new model of the series of signalling events and pathways underpinning the hypercapnic response, and use the model to provide compelling evidence that corroborates the aforementioned hypothesis. If the CVR indeed acts as a mediator of the hypercapnic response, the proposed mechanism would provide an important addition to our understanding of the repertoire of metabolic feedback mechanisms possessed by the brain and would motivate further in-vivo investigation. We also model the interaction of the hypercapnic response with dynamic cerebral autoregulation (dCA), the collection of mechanisms that the brain possesses to maintain near constant CBF despite perturbations in pressure, and show how the dCA mechanisms, which otherwise tend to be overlooked when analysing experimental results of cerebrovascular reactivity, could play a significant role in shaping the CBF response to elevations in [Formula: see text] . Such in-silico models can be used in tandem with in-vivo experiments to expand our understanding of cerebrovascular diseases, which continue to be among the leading causes of morbidity and mortality in humans.
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Affiliation(s)
- Ali Daher
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, United Kingdom.
| | - Stephen Payne
- Institute of Applied Mechanics, National Taiwan University, Taiwan
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3
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Sayin ES, Duffin J, Stumpo V, Bellomo J, Piccirelli M, Poublanc J, Wijeya V, Para A, Pangalu A, Bink A, Nemeth B, Kulcsar Z, Mikulis DJ, Fisher JA, Sobczyk O, Fierstra J. Assessing Perfusion in Steno-Occlusive Cerebrovascular Disease Using Transient Hypoxia-Induced Deoxyhemoglobin as a Dynamic Susceptibility Contrast Agent. AJNR Am J Neuroradiol 2023; 45:37-43. [PMID: 38164571 PMCID: PMC10756578 DOI: 10.3174/ajnr.a8068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Accepted: 11/01/2023] [Indexed: 01/03/2024]
Abstract
BACKGROUND AND PURPOSE Resting brain tissue perfusion in cerebral steno-occlusive vascular disease can be assessed by MR imaging using gadolinium-based susceptibility contrast agents. Recently, transient hypoxia-induced deoxyhemoglobin has been investigated as a noninvasive MR imaging contrast agent. Here we present a comparison of resting perfusion metrics using transient hypoxia-induced deoxyhemoglobin and gadolinium-based contrast agents in patients with known cerebrovascular steno-occlusive disease. MATERIALS AND METHODS Twelve patients with steno-occlusive disease underwent DSC MR imaging using a standard bolus of gadolinium-based contrast agent compared with transient hypoxia-induced deoxyhemoglobin generated in the lungs using an automated gas blender. A conventional multi-slice 2D gradient echo sequence was used to acquire the perfusion data and analyzed using a standard tracer kinetic model. MTT, relative CBF, and relative CBV maps were generated and compared between contrast agents. RESULTS The spatial distributions of the perfusion metrics generated with both contrast agents were consistent. Perfusion metrics in GM and WM were not statistically different except for WM MTT. CONCLUSIONS Cerebral perfusion metrics generated with noninvasive transient hypoxia-induced changes in deoxyhemoglobin are very similar to those generated using a gadolinium-based contrast agent in patients with cerebrovascular steno-occlusive disease.
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Affiliation(s)
- Ece Su Sayin
- From the Department of Physiology (E.S.S., J.D., J.A.F.), University of Toronto, Toronto, Ontario, Canada
- Joint Department of Medical Imaging and the Functional Neuroimaging Lab (E.S.S., J.P., V.W., A. Para, D.J.M., O.S.), University Health Network, Toronto, Ontario, Canada
| | - James Duffin
- From the Department of Physiology (E.S.S., J.D., J.A.F.), University of Toronto, Toronto, Ontario, Canada
- Department of Anesthesia and Pain Management (J.D., J.A.F.), University Health Network, University of Toronto, Toronto, Ontario, Canada
| | - Vittorio Stumpo
- Department of Neurosurgery (V.S., J.B. J.F.), University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Jacopo Bellomo
- Department of Neurosurgery (V.S., J.B. J.F.), University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Marco Piccirelli
- Department of Neuroradiology and Clinical Neuroscience Center (M.P., A. Pangalu, A.B., B.N., Z.K.), University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Julien Poublanc
- Joint Department of Medical Imaging and the Functional Neuroimaging Lab (E.S.S., J.P., V.W., A. Para, D.J.M., O.S.), University Health Network, Toronto, Ontario, Canada
| | - Vepeson Wijeya
- Joint Department of Medical Imaging and the Functional Neuroimaging Lab (E.S.S., J.P., V.W., A. Para, D.J.M., O.S.), University Health Network, Toronto, Ontario, Canada
| | - Andrea Para
- Joint Department of Medical Imaging and the Functional Neuroimaging Lab (E.S.S., J.P., V.W., A. Para, D.J.M., O.S.), University Health Network, Toronto, Ontario, Canada
| | - Athina Pangalu
- Department of Neuroradiology and Clinical Neuroscience Center (M.P., A. Pangalu, A.B., B.N., Z.K.), University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Andrea Bink
- Department of Neuroradiology and Clinical Neuroscience Center (M.P., A. Pangalu, A.B., B.N., Z.K.), University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Bence Nemeth
- Department of Neuroradiology and Clinical Neuroscience Center (M.P., A. Pangalu, A.B., B.N., Z.K.), University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Zsolt Kulcsar
- Department of Neuroradiology and Clinical Neuroscience Center (M.P., A. Pangalu, A.B., B.N., Z.K.), University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - David J Mikulis
- Department of Medical Biophysics (D.J.M.), University of Toronto, Toronto, Ontario, Canada
- Joint Department of Medical Imaging and the Functional Neuroimaging Lab (E.S.S., J.P., V.W., A. Para, D.J.M., O.S.), University Health Network, Toronto, Ontario, Canada
| | - Joseph A Fisher
- From the Department of Physiology (E.S.S., J.D., J.A.F.), University of Toronto, Toronto, Ontario, Canada
- Department of Anesthesia and Pain Management (J.D., J.A.F.), University Health Network, University of Toronto, Toronto, Ontario, Canada
| | - Olivia Sobczyk
- Joint Department of Medical Imaging and the Functional Neuroimaging Lab (E.S.S., J.P., V.W., A. Para, D.J.M., O.S.), University Health Network, Toronto, Ontario, Canada
| | - Jorn Fierstra
- Department of Neurosurgery (V.S., J.B. J.F.), University Hospital Zurich, University of Zurich, Zurich, Switzerland
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Fincham GW, Kartar A, Uthaug MV, Anderson B, Hall L, Nagai Y, Critchley H, Colasanti A. High ventilation breathwork practices: An overview of their effects, mechanisms, and considerations for clinical applications. Neurosci Biobehav Rev 2023; 155:105453. [PMID: 37923236 DOI: 10.1016/j.neubiorev.2023.105453] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 10/19/2023] [Accepted: 10/30/2023] [Indexed: 11/07/2023]
Abstract
High Ventilation Breathwork (HVB) refers to practices employing specific volitional manipulation of breathing, with a long history of use to relieve various forms of psychological distress. This paper seeks to offer a consolidative insight into potential clinical application of HVB as a treatment of psychiatric disorders. We thus review the characteristic phenomenological and neurophysiological effects of these practices to inform their mechanism of therapeutic action, safety profiles and future clinical applications. Clinical observations and data from neurophysiological studies indicate that HVB is associated with extraordinary changes in subjective experience, as well as with profound effects on central and autonomic nervous systems functions through modulation of neurometabolic parameters and interoceptive sensory systems. This growing evidence base may guide how the phenomenological effects of HVB can be understood, and potentially harnessed in the context of such volitional perturbation of psychophysiological state. Reports of putative beneficial effects for trauma-related, affective, and somatic disorders invite further research to obtain detailed mechanistic knowledge, and rigorous clinical testing of these potential therapeutic uses.
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Affiliation(s)
- Guy W Fincham
- Brighton & Sussex Medical School, Department of Neuroscience, University of Sussex, UK; University of Sussex, School of Psychology, Brighton, UK.
| | - Amy Kartar
- Brighton & Sussex Medical School, Department of Neuroscience, University of Sussex, UK
| | - Malin V Uthaug
- The Centre for Psychedelic Research, Division of Psychiatry, Imperial College London, UK; Department of Neuropsychology & Psychopharmacology, Faculty of Psychology & Neuroscience, Maastricht University, The Netherlands
| | - Brittany Anderson
- University of Wisconsin School of Medicine & Public Health, Department of Psychiatry, University of Wisconsin-Madison, USA
| | - Lottie Hall
- Brighton & Sussex Medical School, Department of Neuroscience, University of Sussex, UK
| | - Yoko Nagai
- Brighton & Sussex Medical School, Department of Neuroscience, University of Sussex, UK
| | - Hugo Critchley
- Brighton & Sussex Medical School, Department of Neuroscience, University of Sussex, UK
| | - Alessandro Colasanti
- Brighton & Sussex Medical School, Department of Neuroscience, University of Sussex, UK; Sussex Partnership NHS Foundation Trust.
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Akbar AF, Shou BL, Feng CY, Zhao DX, Kim BS, Whitman G, Bush EL, Cho SM. Lower Oxygen Tension and Intracranial Hemorrhage in Veno-venous Extracorporeal Membrane Oxygenation. Lung 2023; 201:315-320. [PMID: 37086285 PMCID: PMC10578342 DOI: 10.1007/s00408-023-00618-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Accepted: 04/11/2023] [Indexed: 04/23/2023]
Abstract
INTRODUCTION AND METHODS We examined the relationship between 24-h pre- and post-cannulation arterial oxygen tension (PaO2) and arterial carbon dioxide tension (PaCO2) and subsequent acute brain injury (ABI) in patients receiving veno-venous extracorporeal membrane oxygenation (VV-ECMO) with granular arterial blood gas (ABG) data and institutional standardized neuromonitoring. RESULTS Eighty-nine patients underwent VV-ECMO (median age = 50, 63% male). Twenty (22%) patients experienced ABI; intracranial hemorrhage (ICH) was the most common diagnosis (n = 14, 16%). Lower post-cannulation PaO2 levels were significantly associated with ICH (66 vs. 81 mmHg, p = 0.007) and a post-cannulation PaO2 level < 70 mmHg was more frequent in these patients (71% vs. 33%, p = 0.007). PaCO2 parameters were not associated with ABI. By multivariable logistic regression, hypoxemia post-cannulation increased the odds of ICH (OR = 5.06, 95% CI:1.41-18.17; p = 0.01). CONCLUSION In summary, lower oxygen tension in the 24-h post-cannulation was associated with ICH development. The precise roles of peri-cannulation ABG changes deserve further investigation, as they may influence the management of VV-ECMO patients.
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Affiliation(s)
- Armaan F Akbar
- Division of Cardiac Surgery, Department of Surgery, Johns Hopkins Hospital, Baltimore, MD, USA
| | - Benjamin L Shou
- Division of Cardiac Surgery, Department of Surgery, Johns Hopkins Hospital, Baltimore, MD, USA
| | - Cheng-Yuan Feng
- Division of Cardiac Surgery, Department of Surgery, Johns Hopkins Hospital, Baltimore, MD, USA
- Division of Neurosciences Critical Care, Department of Neurology, Neurosurgery, Anesthesiology and Critical Care Medicine, Johns Hopkins Hospital, 600 N. Wolfe Street, Phipps, Baltimore, MD, 455, USA
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins Hospital, Baltimore, MD, USA
- Division of General Thoracic Surgery, Department of Surgery, Johns Hopkins Hospital, Baltimore, MD, USA
| | - David X Zhao
- Division of Cardiac Surgery, Department of Surgery, Johns Hopkins Hospital, Baltimore, MD, USA
- Division of Neurosciences Critical Care, Department of Neurology, Neurosurgery, Anesthesiology and Critical Care Medicine, Johns Hopkins Hospital, 600 N. Wolfe Street, Phipps, Baltimore, MD, 455, USA
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins Hospital, Baltimore, MD, USA
- Division of General Thoracic Surgery, Department of Surgery, Johns Hopkins Hospital, Baltimore, MD, USA
| | - Bo Soo Kim
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins Hospital, Baltimore, MD, USA
| | - Glenn Whitman
- Division of Cardiac Surgery, Department of Surgery, Johns Hopkins Hospital, Baltimore, MD, USA
| | - Errol L Bush
- Division of General Thoracic Surgery, Department of Surgery, Johns Hopkins Hospital, Baltimore, MD, USA
| | - Sung-Min Cho
- Division of Neurosciences Critical Care, Department of Neurology, Neurosurgery, Anesthesiology and Critical Care Medicine, Johns Hopkins Hospital, 600 N. Wolfe Street, Phipps, Baltimore, MD, 455, USA.
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Ochi G, Kuwamizu R, Suwabe K, Fukuie T, Hyodo K, Soya H. Cognitive fatigue due to exercise under normobaric hypoxia is related to hypoxemia during exercise. Sci Rep 2022; 12:9835. [PMID: 35764684 PMCID: PMC9240057 DOI: 10.1038/s41598-022-14146-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 05/17/2022] [Indexed: 11/09/2022] Open
Abstract
We previously found that a 10-min bout of moderate-intensity exercise (50% maximal oxygen uptake) under normobaric and hypoxic conditions (fraction of inspired oxygen [[Formula: see text]] = 0.135) reduced executive performance and neural activity in the left dorsolateral prefrontal cortex (DLPFC). To examine whether this cognitive fatigue is due to a decrease in SpO2 during exercise, we compared executive performance and related prefrontal activation between two experimental conditions, in which the participants inhaled normobaric hypoxic gas ([Formula: see text]= 0.135) (hypoxic exercise [HE]) or hypoxic gas adjusted so that SpO2 during exercise remained at the resting level (milder hypoxic exercise [ME]). ME condition showed that reaction time in executive performance decreased (t[13] = 2.228, P < 0.05, d = 0.34, paired t-test) and left DLPFC activity increased (t[13] = -2.376, P < 0.05, d = 0.63, paired t-test) after exercise compared with HE condition. These results showed that the HE-induced reductions in the left DLPFC activity and executive performance were both suppressed in the ME condition, supporting the hypothesis that exercise-induced cognitive fatigue under hypoxic environment is due to hypoxemia during exercise. This may lead to the development of a method of coping with cognitive fatigue due to exercise that causes hypoxemia.
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Affiliation(s)
- Genta Ochi
- Faculty of Health Sciences, Department of Health and Sports, Niigata University of Health and Welfare, Niigata, 950-3198, Japan.,Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Ibaraki, 305-8574, Japan.,Sports Neuroscience Division, Department of Mind, Advanced Research Initiative for Human High Performance (ARIHHP), Faculty of Health and Sport Sciences, University of Tsukuba, Ibaraki, 305-8574, Japan
| | - Ryuta Kuwamizu
- Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Ibaraki, 305-8574, Japan
| | - Kazuya Suwabe
- Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Ibaraki, 305-8574, Japan.,Sports Neuroscience Division, Department of Mind, Advanced Research Initiative for Human High Performance (ARIHHP), Faculty of Health and Sport Sciences, University of Tsukuba, Ibaraki, 305-8574, Japan.,Faculty of Health and Sport Sciences, Ryutsu Keizai University, Ibaraki, 301-8555, Japan
| | - Takemune Fukuie
- Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Ibaraki, 305-8574, Japan
| | - Kazuki Hyodo
- Physical Fitness Research Institute, Meiji Yasuda Life Foundation of Health and Welfare, Tokyo, 192-0001, Japan
| | - Hideaki Soya
- Laboratory of Exercise Biochemistry and Neuroendocrinology, Faculty of Health and Sport Sciences, University of Tsukuba, Ibaraki, 305-8574, Japan. .,Sports Neuroscience Division, Department of Mind, Advanced Research Initiative for Human High Performance (ARIHHP), Faculty of Health and Sport Sciences, University of Tsukuba, Ibaraki, 305-8574, Japan.
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7
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Watanabe H, Saito S, Washio T, Bailey DM, Ogoh S. Acute Gravitational Stress Selectively Impairs Dynamic Cerebrovascular Reactivity in the Anterior Circulation Independent of Changes to the Central Respiratory Chemoreflex. Front Physiol 2022; 12:749255. [PMID: 35069233 PMCID: PMC8770752 DOI: 10.3389/fphys.2021.749255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 12/03/2021] [Indexed: 11/13/2022] Open
Abstract
Cerebrovascular reactivity (CVR) to changes in the partial pressure of arterial carbon dioxide (PaCO2) is an important mechanism that maintains CO2 or pH homeostasis in the brain. To what extent this is influenced by gravitational stress and corresponding implications for the regulation of cerebral blood flow (CBF) remain unclear. The present study examined the onset responses of pulmonary ventilation (V̇E) and anterior middle (MCA) and posterior (PCA) cerebral artery mean blood velocity (Vmean) responses to acute hypercapnia (5% CO2) to infer dynamic changes in the central respiratory chemoreflex and cerebrovascular reactivity (CVR), in supine and 50° head-up tilt (HUT) positions. Each onset response was evaluated using a single-exponential regression model consisting of the response time latency [CO2-response delay (t0)] and time constant (τ). Onset response of V̇E and PCA Vmean to changes in CO2 was unchanged during 50° HUT compared with supine (τ: V̇E, p = 0.707; PCA Vmean, p = 0.071 vs. supine) but the MCA Vmean onset response was faster during supine than during 50° HUT (τ: p = 0.003 vs. supine). These data indicate that gravitational stress selectively impaired dynamic CVR in the anterior cerebral circulation, whereas the posterior circulation was preserved, independent of any changes to the central respiratory chemoreflex. Collectively, our findings highlight the regional heterogeneity underlying CBF regulation that may have translational implications for the microgravity (and hypercapnia) associated with deep-space flight notwithstanding terrestrial orthostatic diseases that have been linked to accelerated cognitive decline and neurodegeneration.
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Affiliation(s)
- Hironori Watanabe
- Department of Biomedical Engineering, Toyo University, Kawagoe, Japan
| | - Shotaro Saito
- Department of Biomedical Engineering, Toyo University, Kawagoe, Japan
| | - Takuro Washio
- Department of Biomedical Engineering, Toyo University, Kawagoe, Japan.,Research Fellow of Japan Society for the Promotion of Science, Tokyo, Japan
| | - Damian Miles Bailey
- Research Fellow of Japan Society for the Promotion of Science, Tokyo, Japan.,Neurovascular Research Laboratory, University of South Wales, Pontypridd, United Kingdom
| | - Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe, Japan.,Neurovascular Research Laboratory, University of South Wales, Pontypridd, United Kingdom
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8
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Change in the optic nerve sheath diameter after deflation of a pneumatic tourniquet: a prospective observational study. Sci Rep 2022; 12:521. [PMID: 35017581 PMCID: PMC8752803 DOI: 10.1038/s41598-021-04457-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 12/17/2021] [Indexed: 11/22/2022] Open
Abstract
Applying a pneumatic tourniquet provides surgeons with a bloodless surgical field. However, application of the tourniquet induces various physiological changes. We evaluated the effect of tourniquet deflation on the intracranial pressure by using ultrasonography to measure the optic nerve sheath diameter (ONSD) in patients undergoing lower limb surgery. The ONSD was measured in 20 patients at five time points: after anesthetic induction (T0) and immediately before (T1), immediately after (T2), 5 min after (T3), and 10 min after tourniquet deflation (T4). Hemodynamic and respiratory variables were recorded. The ONSD showed significant differences at each point (P < 0.001). The ONSDs at T2 and T3 were significantly greater than that at T1 (P = 0.0007 and < 0.0001, respectively). The change in the end-tidal carbon dioxide partial pressure (EtCO2) was similar to the change in the ONSD. The change in the ONSD was significantly correlated with the change in the EtCO2 after tourniquet deflation (r = 0.484, P = 0.030). In conclusion, the ONSD, as an indicator of intracranial pressure, increased after tourniquet deflation in patients undergoing lower limb surgery. This was correlated with an increased EtCO2 and arterial carbon dioxide partial pressure. Trial registration: ClinicalTrials.gov (NCT03782077).
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9
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Bjertnaes LJ, Hauge A, Thoresen M, Walløe L. Prioritized Brain Circulation During Ergometer Cycling with Apnea and Face Immersion in Ice-Cold Water: A Case Report. Int Med Case Rep J 2021; 14:675-681. [PMID: 34602825 PMCID: PMC8478670 DOI: 10.2147/imcrj.s317404] [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: 04/25/2021] [Accepted: 08/26/2021] [Indexed: 11/23/2022] Open
Abstract
Background Successful cardiopulmonary resuscitation after drowning or avalanche is often attributed to hypothermia-induced decrease in metabolism, which adapts the oxygen demand to the amount supplied under cardiac compression. Four decades ago, we speculated if oxygen-sparing mechanisms like those found in marine mammals, may improve cerebral oxygenation during acute airway blockade in humans. We investigated hemodynamic changes during steady state ergometer cycling with intermittent periods of apnea and face immersion (AFI) in ice-cold water. During AFI, heart rate (HR) dropped by 58% whereas average blood velocity (ABV) determined by means of a Doppler ultrasound velocity meter (UNIDOP University of Oslo, Oslo, Norway) fell by 85% in the radial artery and rose by 67% in the vertebral artery. Similar changes occured in radial artery ABV, albeit more slowly, when the test subject only held his breath while cycling. When he breathed via a snorkel during face immersion, HR remained unchanged while radial artery ABV fell transiently and subsequently returned to its pre-immersion level. These findings later were confirmed by other investigators. Moreover, a recent study revealed that the seal even has a system for selective brain cooling during the dive. Conclusion Our research has confirmed prioritized cerebral circulation during AFI in cold water. We hypothesize that these changes may improve brain oxygenation due both to greater blood flow and possibly also to faster brain cooling, as demonstrated in diving seals.
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Affiliation(s)
- Lars J Bjertnaes
- Anesthesia and Critical Care Research Group, Department of Clinical Medicine, Faculty of Health Sciences, UiT The Arctic University of Norway, Tromsø, N-9037, Norway.,Department of Intensive Care Medicine, University Hospital of North Norway, Tromsø, N- 9017, Norway
| | - Anton Hauge
- Division of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, 0317, Norway
| | - Marianne Thoresen
- Division of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, 0317, Norway.,Translational Health Sciences, University of Bristol, Bristol, UK
| | - Lars Walløe
- Division of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, 0317, Norway
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Brain Tissue Oxygen Response as Indicator for Cerebral Lactate Levels in Aneurysmal Subarachnoid Hemorrhage Patients. J Neurosurg Anesthesiol 2020; 34:193-200. [PMID: 32701532 DOI: 10.1097/ana.0000000000000713] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Accepted: 06/05/2020] [Indexed: 11/25/2022]
Abstract
BACKGROUND Early detection of cerebral ischemia and metabolic crisis is crucial in critically ill subarachnoid hemorrhage (SAH) patients. Variable increases in brain tissue oxygen tension (PbtO2) are observed when the fraction of inspired oxygen (FiO2) is increased to 1.0. The aim of this prospective study was to evaluate whether a 3-minute hyperoxic challenge can identify patients at risk for cerebral ischemia detected by cerebral microdialysis. METHODS Twenty consecutive severe SAH patients undergoing continuous cerebral PbtO2 and microdialysis monitoring were included. FiO2 was increased to 1.0 for 3 minutes (the FiO2 challenge) twice a day and PbtO2 responses during the FiO2 challenges were related to cerebral microdialysis-measures, ie, lactate, the lactate-pyruvate ratio, and glycerol. Multivariable linear and logistic regression models were created for each outcome parameter. RESULTS After predefined exclusions, 274 of 400 FiO2 challenges were included in the analysis. Lower absolute increases in PbtO2 ([INCREMENT]PbtO2) during FiO2 challenges were significantly associated with higher cerebral lactate concentration (P<0.001), and patients were at higher risk for ischemic lactate levels >4 mmol/L (odds ratio 0.947; P=0.04). Median (interquartile range) [INCREMENT]PbtO2 was 7.1 (4.6 to 12.17) mm Hg when cerebral lactate was >4 mmol/L and 10.2 (15.76 to 14.24) mm Hg at normal lactate values (≤4 mmol/L). Median [INCREMENT]PbtO2 was significantly lower during hypoxic than during hyperglycolytic lactate elevations (4.6 vs. 10.6 mm Hg, respectively; P<0.001). Lactate-pyruvate ratio and glycerol levels were mainly determined by baseline characteristics. CONCLUSIONS A 3-minute FiO2 challenge is an easy to perform and feasible bedside diagnostic tool in SAH patients. The absolute increase in PbtO2 during the FiO2 challenge might be a useful surrogate marker to estimate cerebral lactate concentrations and might be used to identify patients at risk for impending ischemia.
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11
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Varadarajan JL. Anesthesia for Neurosurgical Procedures. Anesthesiology 2018. [DOI: 10.1007/978-3-319-74766-8_30] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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12
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Dani KA, Moreton FC, Santosh C, Lopez R, Brennan D, Schwarzbauer C, Goutcher C, O'Hare K, Macrae IM, Muir KW. Oxygen challenge magnetic resonance imaging in healthy human volunteers. J Cereb Blood Flow Metab 2017; 37:366-376. [PMID: 26787107 PMCID: PMC5363753 DOI: 10.1177/0271678x15627827] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Revised: 11/12/2015] [Accepted: 11/16/2015] [Indexed: 11/15/2022]
Abstract
Oxygen challenge imaging involves transient hyperoxia applied during deoxyhaemoglobin sensitive (T2*-weighted) magnetic resonance imaging and has the potential to detect changes in brain oxygen extraction. In order to develop optimal practical protocols for oxygen challenge imaging, we investigated the influence of oxygen concentration, cerebral blood flow change, pattern of oxygen administration and field strength on T2*-weighted signal. Eight healthy volunteers underwent multi-parametric magnetic resonance imaging including oxygen challenge imaging and arterial spin labelling using two oxygen concentrations (target FiO2 of 100 and 60%) administered consecutively (two-stage challenge) at both 1.5T and 3T. There was a greater signal increase in grey matter compared to white matter during oxygen challenge (p < 0.002 at 3T, P < 0.0001 at 1.5T) and at FiO2 = 100% compared to FiO2 = 60% in grey matter at both field strengths (p < 0.02) and in white matter at 3T only (p = 0.0314). Differences in the magnitude of signal change between 1.5T and 3T did not reach statistical significance. Reduction of T2*-weighted signal to below baseline, after hyperoxia withdrawal, confounded interpretation of two-stage oxygen challenge imaging. Reductions in cerebral blood flow did not obscure the T2*-weighted signal increases. In conclusion, the optimal protocol for further study should utilise target FiO2 = 100% during a single oxygen challenge. Imaging at both 1.5T and 3T is clinically feasible.
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Affiliation(s)
- Krishna A Dani
- Institute of Neuroscience and Psychology, College of Medical Veterinary and Life Sciences, University of Glasgow, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Fiona C Moreton
- Institute of Neuroscience and Psychology, College of Medical Veterinary and Life Sciences, University of Glasgow, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Celestine Santosh
- Department of Neuroradiology, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Rosario Lopez
- Department of Clinical Physics, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - David Brennan
- Department of Clinical Physics, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Christian Schwarzbauer
- University of Applied Sciences Munich, School of Applied Sciences and Mechatronics, München
| | - Colin Goutcher
- Department of Anaesthetics, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Kevin O'Hare
- Department of Anaesthetics, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - I Mhairi Macrae
- Institute of Neuroscience and Psychology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow
| | - Keith W Muir
- Institute of Neuroscience and Psychology, College of Medical Veterinary and Life Sciences, University of Glasgow, Queen Elizabeth University Hospital Glasgow, Glasgow
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Lemkuil BP, Gierl BT, Patel PM, Pearn ML, Nguyen LC, Minokadeh A, Drummond JC. The Effect of Clevidipine on Cerebral Blood Flow Velocity and Carbon Dioxide Reactivity in Human Volunteers. J Neurosurg Anesthesiol 2016; 28:337-40. [PMID: 26447497 DOI: 10.1097/ana.0000000000000236] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Clevidipine is a short acting, esterase metabolized, calcium channel antagonist administered as a continuous infusion for control of hypertension. Its profile allows for rapid titration and may be uniquely suited to achieving tight hemodynamic targets in neurosurgical and neurocritical care patients. The present study was designed to investigate the effect of clevidipine infusion on cerebral blood flow and cerebral CO2 responsiveness as measured by cerebral blood flow velocity (CBFV) using transcranial Doppler. MATERIALS AND METHODS CBFV was continuously recorded in 5 healthy subjects during the following conditions: baseline 1 (BL1); baseline with hyperventilation (HV1); baseline 2 (BL2); clevidipine infusion to achieve 15% mean arterial pressure (MAP) reduction (C15); clevidipine infusion to achieve 30% MAP reduction (C30); clevidipine infusion to 30% MAP reduction with hyperventilation (HV2). RESULTS The mean CBFV during intermediate (C15) or maximum (C30) dose clevidipine infusion was unchanged compared with baseline (BL2) (F2,8=0.66; P=0.54). Cerebral CO2 reactivity, expressed as %[INCREMENT]CBFV/[INCREMENT]mm Hg CO2, was not significantly different in the presence of maximal-dose clevidipine (HV2) as compared with baseline (HV1) (1.6±0.4 vs. 1.6±0.3%[INCREMENT]CBFV/[INCREMENT]mm Hg CO2, P=0.73). CONCLUSIONS Clevidipine infusion did not significantly increase CBFV nor was cerebral CO2 reactivity reduced during maximal-dose clevidipine infusion. Further systematic investigation of clevidipine in patients with central nervous system pathology seems justified.
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Affiliation(s)
- Brian P Lemkuil
- *Department of Anesthesiology, University of California †Veterans Affairs Medical Center, San Diego, CA ‡Department of Anesthesiology, University of Pittsburgh, Pittsburgh, PA
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Heart rate response to therapeutic hypothermia in infants with hypoxic-ischaemic encephalopathy. Resuscitation 2016; 106:53-7. [PMID: 27368430 DOI: 10.1016/j.resuscitation.2016.06.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 05/20/2016] [Accepted: 06/17/2016] [Indexed: 01/15/2023]
Abstract
AIM OF THE STUDY Neonatal encephalopathy (NE) of hypoxic-ischaemic origin may cause death or life-long disability which is reduced by therapeutic hypothermia (TH). Our objective was to assess HR response in infants undergoing TH after perinatal asphyxia. METHODS We performed a retrospective case series, from a single-centre tertiary care NICU. We included ninety-two infants with NE of likely hypoxic-ischaemic origin, moderate or severe, treated with TH (n=60) or normothermia (n=32) who had 18 month outcome data and at least 12 HR recordings the first 24h after birth (1998-2010) Bristol, UK. Poor outcome was defined as death or severe disability. Data are reported as medians and 95% confidence intervals (CI). RESULTS TH to 33.5°C decreased HR by 30bpm to 92bpm (95% CI: 88, 96) 12h after birth in infants with NE and good outcome as compared to infants treated at normothermia 118bpm (95% CI: 110, 130). Despite constant low rectal temperature, HR increased gradually during cooling from 36 to 72h to 97bpm (89, 106) approaching the normothermia group, 117bpm (96, 133). During TH, infants with poor outcome had higher HR at 12h after birth (112bpm, 95% CI: 92, 115) as compared to infants with good outcome (p=0.004). Inotropic support increased HR by 17bpm in infants with good outcome and by 22bpm in infants with poor outcome. CONCLUSIONS In NE, TH decreases HR the first day of life. HR remained lower during TH, but increased during the last day of TH. Infants with poor outcome have higher HR.
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15
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Respiratory challenge MRI: Practical aspects. NEUROIMAGE-CLINICAL 2016; 11:667-677. [PMID: 27330967 PMCID: PMC4901170 DOI: 10.1016/j.nicl.2016.05.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Revised: 04/11/2016] [Accepted: 05/03/2016] [Indexed: 11/24/2022]
Abstract
Respiratory challenge MRI is the modification of arterial oxygen (PaO2) and/or carbon dioxide (PaCO2) concentration to induce a change in cerebral function or metabolism which is then measured by MRI. Alterations in arterial gas concentrations can lead to profound changes in cerebral haemodynamics which can be studied using a variety of MRI sequences. Whilst such experiments may provide a wealth of information, conducting them can be complex and challenging. In this paper we review the rationale for respiratory challenge MRI including the effects of oxygen and carbon dioxide on the cerebral circulation. We also discuss the planning, equipment, monitoring and techniques that have been used to undertake these experiments. We finally propose some recommendations in this evolving area for conducting these experiments to enhance data quality and comparison between techniques. Oxygen and carbon dioxide affect cerebral blood flow and metabolism. This can be imaged with various MRI sequences. The practicalities of these techniques are reviewed. Examples of how this has been used to understand disease mechanisms.
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Modeling the role of osmotic forces in the cerebrovascular response to CO2. Med Hypotheses 2015; 85:25-36. [PMID: 25858437 DOI: 10.1016/j.mehy.2015.03.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2014] [Revised: 03/06/2015] [Accepted: 03/12/2015] [Indexed: 12/15/2022]
Abstract
Increases in blood osmolarity have been shown to exert a vasodilatory effect on cerebral and other vasculature, with accompanying increases in blood flow. It has also been shown that, through an influence on blood concentration of the bicarbonate ion and pH, changes in blood levels of CO2 can alter blood osmolarity sufficiently to have an impact on vessel diameter. We propose here that this phenomenon plays a previously unappreciated role in CO2-mediated vasodilation, and present a biophysical model of osmotically driven vasodilation. Our model, which is based on literature data describing CO2-dependent changes in blood osmolarity and hydraulic conductivity (Lp) of the blood-brain barrier, is used to predict the change in cerebral blood flow (CBF) associated with osmotic forces arising from a specific hypercapnic challenge. Modeled changes were then compared with actual CBF changes determined using arterial spin-labeling (ASL) MRI. For changes in the arterial partial pressure of CO2 (PaCO2) of 20 mmHg, our model predicted increases of 80% from baseline CBF with a temporal evolution that was comparable to the measured hemodynamic responses. Our modeling results suggest that osmotic forces could play a significant role in the cerebrovascular response to CO2.
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17
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Lu H, Liu P, Yezhuvath U, Cheng Y, Marshall O, Ge Y. MRI mapping of cerebrovascular reactivity via gas inhalation challenges. J Vis Exp 2014. [PMID: 25549106 PMCID: PMC4396915 DOI: 10.3791/52306] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The brain is a spatially heterogeneous and temporally dynamic organ, with different regions requiring different amount of blood supply at different time. Therefore, the ability of the blood vessels to dilate or constrict, known as Cerebral-Vascular-Reactivity (CVR), represents an important domain of vascular function. An imaging marker representing this dynamic property will provide new information of cerebral vessels under normal and diseased conditions such as stroke, dementia, atherosclerosis, small vessel diseases, brain tumor, traumatic brain injury, and multiple sclerosis. In order to perform this type of measurement in humans, it is necessary to deliver a vasoactive stimulus such as CO2 and/or O2 gas mixture while quantitative brain magnetic resonance images (MRI) are being collected. In this work, we presented a MR compatible gas-delivery system and the associated protocol that allow the delivery of special gas mixtures (e.g., O2, CO2, N2, and their combinations) while the subject is lying inside the MRI scanner. This system is relatively simple, economical, and easy to use, and the experimental protocol allows accurate mapping of CVR in both healthy volunteers and patients with neurological disorders. This approach has the potential to be used in broad clinical applications and in better understanding of brain vascular pathophysiology. In the video, we demonstrate how to set up the system inside an MRI suite and how to perform a complete experiment on a human participant.
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Affiliation(s)
- Hanzhang Lu
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center;
| | - Peiying Liu
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center
| | - Uma Yezhuvath
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center
| | - Yamei Cheng
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center
| | - Olga Marshall
- Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine
| | - Yulin Ge
- Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine
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18
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Transfer function analysis for the assessment of cerebral autoregulation using spontaneous oscillations in blood pressure and cerebral blood flow. Med Eng Phys 2014; 36:563-75. [DOI: 10.1016/j.medengphy.2014.02.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 01/31/2014] [Accepted: 02/03/2014] [Indexed: 12/21/2022]
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19
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Meel-van den Abeelen ASS, Simpson DM, Wang LJY, Slump CH, Zhang R, Tarumi T, Rickards CA, Payne S, Mitsis GD, Kostoglou K, Marmarelis V, Shin D, Tzeng YC, Ainslie PN, Gommer E, Müller M, Dorado AC, Smielewski P, Yelicich B, Puppo C, Liu X, Czosnyka M, Wang CY, Novak V, Panerai RB, Claassen JAHR. Between-centre variability in transfer function analysis, a widely used method for linear quantification of the dynamic pressure-flow relation: the CARNet study. Med Eng Phys 2014; 36:620-7. [PMID: 24725709 DOI: 10.1016/j.medengphy.2014.02.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 01/31/2014] [Accepted: 02/03/2014] [Indexed: 11/16/2022]
Abstract
Transfer function analysis (TFA) is a frequently used method to assess dynamic cerebral autoregulation (CA) using spontaneous oscillations in blood pressure (BP) and cerebral blood flow velocity (CBFV). However, controversies and variations exist in how research groups utilise TFA, causing high variability in interpretation. The objective of this study was to evaluate between-centre variability in TFA outcome metrics. 15 centres analysed the same 70 BP and CBFV datasets from healthy subjects (n=50 rest; n=20 during hypercapnia); 10 additional datasets were computer-generated. Each centre used their in-house TFA methods; however, certain parameters were specified to reduce a priori between-centre variability. Hypercapnia was used to assess discriminatory performance and synthetic data to evaluate effects of parameter settings. Results were analysed using the Mann-Whitney test and logistic regression. A large non-homogeneous variation was found in TFA outcome metrics between the centres. Logistic regression demonstrated that 11 centres were able to distinguish between normal and impaired CA with an AUC>0.85. Further analysis identified TFA settings that are associated with large variation in outcome measures. These results indicate the need for standardisation of TFA settings in order to reduce between-centre variability and to allow accurate comparison between studies. Suggestions on optimal signal processing methods are proposed.
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Affiliation(s)
- Aisha S S Meel-van den Abeelen
- Radboud University Medical Center, Department of Geriatric Medicine and Donders Institute for Brain, Cognition and Behaviour, The Netherlands
| | - David M Simpson
- Institute of Sound and Vibration Research, University of Southampton, Southampton, UK
| | - Lotte J Y Wang
- Radboud University Medical Center, Department of Geriatric Medicine and Donders Institute for Brain, Cognition and Behaviour, The Netherlands
| | - Cornelis H Slump
- MIRA-Institute for Biomedical Technology and Technical Medicine, Faculty of Science and Technology, University of Twente, The Netherlands
| | - Rong Zhang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital of Dallas and The University of Texas Southwestern Medical Center at Dallas, Dallas, TX, United States
| | - Takashi Tarumi
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital of Dallas and The University of Texas Southwestern Medical Center at Dallas, Dallas, TX, United States
| | - Caroline A Rickards
- Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, TX, United States
| | - Stephen Payne
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Oxford, UK
| | - Georgios D Mitsis
- Department of Electrical and Computer Engineering, University of Cyprus, Cyprus
| | - Kyriaki Kostoglou
- Department of Electrical and Computer Engineering, University of Cyprus, Cyprus
| | - Vasilis Marmarelis
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, United States
| | - Dae Shin
- Biomedical Simulations Resource, University of Southern California, Los Angeles, CA, United States
| | - Yu-Chieh Tzeng
- Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - Philip N Ainslie
- School of Health and Exercise Science, University of British Columbia Okanagan, Kelowna, B.C., Canada
| | - Erik Gommer
- Maastricht University Medical Center, Department of Clinical Neurophysiology, The Netherlands
| | - Martin Müller
- Luzerner Kantonsspital, Zentrum für Neurologie und Neurorehabilitation, Lucerne, Switzerland
| | - Alexander C Dorado
- KU Leuven, Department of Electrical Engineering-ESAT, SCD-SISTA and iMinds Future Health Department, Leuven, Belgium
| | - Peter Smielewski
- Academic Neurosurgical Unit, Cambridge University Hospital Trust, UK
| | - Bernardo Yelicich
- Emergency Department, Clinics Hospital, Universidad de la República, School of Medicine, Montevideo, Uruguay
| | - Corina Puppo
- Emergency Department, Clinics Hospital, Universidad de la República, School of Medicine, Montevideo, Uruguay
| | - Xiuyun Liu
- Academic Neurosurgical Unit, Cambridge University Hospital Trust, UK
| | - Marek Czosnyka
- Academic Neurosurgical Unit, Cambridge University Hospital Trust, UK
| | - Cheng-Yen Wang
- Research Center for Adaptive Data Analysis, National Central University, Taiwan
| | - Vera Novak
- Division of Gerontology, Beth Israel Deaconess Medical Center, Boston, MA, United States
| | - Ronney B Panerai
- Leicester NIHR Biomedical Research Unit in Cardiovascular Sciences, Glenfield Hospital, Leicester, UK
| | - Jurgen A H R Claassen
- Radboud University Medical Center, Department of Geriatric Medicine and Donders Institute for Brain, Cognition and Behaviour, The Netherlands.
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Morbelli S, Arnaldi D. Brain perfusion SPECT provides new insight on neurobiological effects of hyperbaric hyperoxia. Acta Physiol (Oxf) 2013; 209:5-6. [PMID: 23796321 DOI: 10.1111/apha.12141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- S. Morbelli
- Nuclear Medicine Unit; Department of Health Sciences; IRCCS AOU San Martino - IST; University of Genoa; Genoa; Italy
| | - D. Arnaldi
- Clinical Neurophysiology; Department of Neurosciences, Ophthalmology and Genetics; IRCCS AOU San Martino - IST; University of Genoa; Genoa; Italy
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Regan RE, Duffin J, Fisher JA. Instability of the middle cerebral artery blood flow in response to CO2. PLoS One 2013; 8:e70751. [PMID: 23936248 PMCID: PMC3728315 DOI: 10.1371/journal.pone.0070751] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 06/26/2013] [Indexed: 01/09/2023] Open
Abstract
Background The middle cerebral artery supplies long end-artery branches to perfuse the deep white matter and shorter peripheral branches to perfuse cortical and subcortical tissues. A generalized vasodilatory stimulus such as carbon dioxide not only results in an increase in flow to these various tissue beds but also redistribution among them. We employed a fast step increase in carbon dioxide to detect the dynamics of the cerebral blood flow response. Methodology/Principal Findings The study was approved by the Research Ethics Board of the University Health Network at the University of Toronto. We used transcranial ultrasound to measure the time course of middle cerebral artery blood flow velocity in 28 healthy adults. Normoxic, isoxic step increases in arterial carbon dioxide tension of 10 mmHg from both hypocapnic and normocapnic baselines were produced using a new prospective targeting system that enabled a more rapid step change than has been previously achievable. In most of the 28 subjects the responses at both carbon dioxide ranges were characterised by more complex responses than a single exponential rise. Most responses were characterised by a fast initial response which then declined rapidly to a nadir, followed by a slower secondary response, with some showing oscillations before stabilising. Conclusions/Significance A rapid step increase in carbon dioxide tension is capable of inducing instability in the cerebral blood flow control system. These dynamic aspects of the cerebral blood flow responses to rapid changes in carbon dioxide must be taken into account when using transcranial blood flow velocity in a single artery segment to measure cerebrovascular reactivity.
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Affiliation(s)
- Rosemary E. Regan
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - James Duffin
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
- Department of Anaesthesia, University of Toronto, and University Health Network, Toronto, Ontario, Canada
- * E-mail:
| | - Joseph A. Fisher
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
- Department of Anaesthesia, University of Toronto, and University Health Network, Toronto, Ontario, Canada
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Mild Transient Hypercapnia as a Novel Fear Conditioning Stimulus Allowing Re-Exposure during Sleep. PLoS One 2013; 8:e67435. [PMID: 23840700 PMCID: PMC3693948 DOI: 10.1371/journal.pone.0067435] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 05/20/2013] [Indexed: 12/31/2022] Open
Abstract
Introduction Studies suggest that sleep plays a role in traumatic memories and that treatment of sleep disorders may help alleviate symptoms of posttraumatic stress disorder. Fear-conditioning paradigms in rodents are used to investigate causal mechanisms of fear acquisition and the relationship between sleep and posttraumatic behaviors. We developed a novel conditioning stimulus (CS) that evoked fear and was subsequently used to study re-exposure to the CS during sleep. Methods Experiment 1 assessed physiological responses to a conditioned stimulus (mild transient hypercapnia, mtHC; 3.0% CO2; n = 17)+footshock for the purpose of establishing a novel CS in male FVB/J mice. Responses to the novel CS were compared to tone+footshock (n = 18) and control groups of tone alone (n = 17) and mild transient hypercapnia alone (n = 10). A second proof of principle experiment re-exposed animals during sleep to mild transient hypercapnia or air (control) to study sleep processes related to the CS. Results Footshock elicited a response of acute tachycardia (30–40 bpm) and increased plasma epinephrine. When tone predicted footshock it elicited mild hypertension (1–2 mmHg) and a three-fold increase in plasma epinephrine. When mtHC predicted footshock it also induced mild hypertension, but additionally elicited a conditioned bradycardia and a smaller increase in plasma epinephrine. The overall mean 24 hour sleep–wake profile was unaffected immediately after fear conditioning. Discussion Our study demonstrates the efficacy of mtHC as a conditioning stimulus that is perceptible but innocuous (relative to tone) and applicable during sleep. This novel model will allow future studies to explore sleep-dependent mechanisms underlying maladaptive fear responses, as well as elucidate the moderators of the relationship between fear responses and sleep.
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Anxiety, pCO2 and cerebral blood flow. Int J Psychophysiol 2013; 89:72-7. [PMID: 23727628 DOI: 10.1016/j.ijpsycho.2013.05.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2012] [Revised: 05/16/2013] [Accepted: 05/19/2013] [Indexed: 10/26/2022]
Abstract
This study examined the effect of anxiety on cerebral blood flow at different levels of pCO2 in healthy participants (N=29). Three types of breathing were used to manipulate pCO2 in a within-subject threat-of-shock paradigm: spontaneous breathing, CO2-inhalation and hyperventilation resulting in normo-, hyper- and hypocapnia. Transcranial Doppler ultrasonography was used to measure CBF velocity (CBFv) in the right middle cerebral artery, while breathing behavior and end-tidal pCO2 were monitored. During normocapnia, elevated anxiety was clearly associated with increased CBFv. Consistent with the cerebral vasoconstrictive and vasodilating effects of, respectively, hypo- and hypercapnia, we observed a positive linear association between CBFv and pCO2. The slope of this association became steeper with increasing anxiety, indicating that anxiety enhances the sensitivity of CBFv to changes in pCO2. The findings may elucidate conflicting findings in the literature and are relevant for brain imaging relying on regional cerebral blood flow.
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Can Mitochondrial Cytochrome Oxidase Mediate Hypoxic Vasodilation Via Nitric Oxide Metabolism? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 765:231-238. [DOI: 10.1007/978-1-4614-4989-8_32] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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Ogoh S, Sato K, Nakahara H, Okazaki K, Subudhi AW, Miyamoto T. Effect of acute hypoxia on blood flow in vertebral and internal carotid arteries. Exp Physiol 2012; 98:692-8. [PMID: 23143991 DOI: 10.1113/expphysiol.2012.068015] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Hypoxia changes the regional distribution of cerebral blood flow and stimulates the ventilatory chemoreflex, thereby reducing CO2 tension. We examined the effects of both hypoxia and isocapnic hypoxia on acute changes in internal carotid (ICA) and vertebral artery (VA) blood flow. Ten healthy male subjects underwent the following two randomly assigned respiratory interventions after a resting baseline period with room air: (i) hypoxia; and (ii) isocapnic hypoxia with a controlled gas mixture (12% O2; inspiratory mmHg). In the isocapnic hypoxia intervention, subjects were instructed to maintain the rate and depth of breathing to maintain the level of end-tidal partial pressure of CO2 ( ) during the resting baseline period. The ICA and VA blood flow (velocity × cross-sectional area) were measured using Doppler ultrasonography. The was decreased (-6.3 ± 0.9%, P < 0.001) during hypoxia by hyperventilation (minute ventilation +12.9 ± 2.2%, P < 0.001), while was unchanged during isocapnic hypoxia. The ICA blood flow was unchanged (P = 0.429), while VA blood flow increased (+10.3 ± 3.1%, P = 0.010) during hypoxia. In contrast, isocapnic hypoxia increased both ICA (+14.5 ± 1.4%, P < 0.001) and VA blood flows (+10.9 ± 2.4%, P < 0.001). Thus, hypoxic vasodilatation outweighed hypocapnic vasoconstriction in the VA, but not in the ICA. These findings suggest that acute hypoxia elicits an increase in posterior cerebral blood flow, possibly to maintain essential homeostatic functions of the brainstem.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, 2100 Kujirai, Kawagoe-shi, Saitama 350-8585, Japan.
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Sabir H, Jary S, Tooley J, Liu X, Thoresen M. Increased inspired oxygen in the first hours of life is associated with adverse outcome in newborns treated for perinatal asphyxia with therapeutic hypothermia. J Pediatr 2012; 161:409-16. [PMID: 22521111 DOI: 10.1016/j.jpeds.2012.03.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 01/23/2012] [Accepted: 03/05/2012] [Indexed: 01/15/2023]
Abstract
OBJECTIVE To assess whether increased inspired oxygen and/or hypocarbia during the first 6 hours of life are associated with adverse outcome at 18 months in term neonates treated with therapeutic hypothermia. STUDY DESIGN Blood gas values and ventilatory settings were monitored hourly in 61 newborns for 6 hours after birth. We investigated if there was an association between increased inspired oxygen and/or hypocarbia and adverse outcome (death or disability by Bayley Scales of Newborn Development II examination at 18-20 months). RESULTS Hypothermia was started from 3 hours 45 minutes (10 minutes-10 hours) and median lowest Pco(2) level within the first 6 hours of life was 30 mm Hg (16.5-96 mm Hg). The median highest fraction of inspiratory oxygen within the first hour of life was 0.43 (0.21-1.00). The area under the curve fraction of inspiratory oxygen and Pao(2) for hours 1-6 of life was 0.23 (0.21-1.0) and 86 mm Hg (22-197 mm Hg), respectively. We did not find any association between any measures of hypocapnia and adverse outcome (P > .05), but increased inspired oxygen correlated with adverse outcome, even when excluding newborns with initial oxygenation failure (P < .05). CONCLUSION Increased fraction of inspired oxygen within the first 6 hours of life was significantly associated with adverse outcome in newborns treated with therapeutic hypothermia following hypoxic ischemic encephalopathy.
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Affiliation(s)
- Hemmen Sabir
- School of Clinical Sciences, University of Bristol, St Michael's Hospital, Bristol, United Kingdom
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Comparison of pulsed and pseudocontinuous arterial spin-labeling for measuring CO2-induced cerebrovascular reactivity. J Magn Reson Imaging 2012; 36:312-21. [DOI: 10.1002/jmri.23658] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Accepted: 03/07/2012] [Indexed: 11/07/2022] Open
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Loomba RS, Leavitt JA, Cetta F. Headache and papilledema in an adult with cyanotic congenital heart disease: the importance of fundoscopic evaluation rather than phlebotomy. CONGENIT HEART DIS 2011; 7:E14-7. [PMID: 22070674 DOI: 10.1111/j.1747-0803.2011.00586.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Headaches and blurred vision in patients with cyanotic congenital heart disease and secondary erythrocytosis may be attributed to hyperviscosity and traditionally were treated with phlebotomy. In the current era, phlebotomy is rarely performed in these patients except in cases of hemoptysis or hyperviscosity symptoms. We report a case of a patient with a history of complex cyanotic congenital heart disease and secondary erythrocytosis who presented with headache and visual changes. He was found to have bilateral papilledema and increased intracranial pressure. Reduction of intracranial pressure with acetazolamide therapy led to alleviation of headache and visual changes. This demonstrates the need for formal ophthalmologic evaluation of these patients to assess other treatable causes of headache and visual changes before considering phlebotomy.
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Affiliation(s)
- Rohit S Loomba
- Department of Pediatrics, Chicago Medical School, North Chicago, IL, USA
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29
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The physiology behind direct brain oxygen monitors and practical aspects of their use. Childs Nerv Syst 2010; 26:419-30. [PMID: 19937246 DOI: 10.1007/s00381-009-1037-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Indexed: 10/20/2022]
Abstract
INTRODUCTION Secondary neuronal injury is implicated in poor outcome after acute neurological insults. Outcome can be improved with protocol-driven therapy. These therapies have largely been based on monitoring and control of intracranial pressure and the maintenance of an adequate cerebral perfusion pressure. DISCUSSION In recent years, brain tissue oxygen partial pressure (PbtO2) monitoring has emerged as a clinically useful modality and a complement to intracranial pressure monitors. This review examines the physiology of PbtO2 monitors and practical aspects of their use.
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Peltonen JE, Paterson DH, Shoemaker JK, DeLorey DS, duManoir GR, Petrella RJ, Kowalchuk JM. Cerebral and muscle deoxygenation, hypoxic ventilatory chemosensitivity and cerebrovascular responsiveness during incremental exercise. Respir Physiol Neurobiol 2009; 169:24-35. [DOI: 10.1016/j.resp.2009.08.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Revised: 08/26/2009] [Accepted: 08/26/2009] [Indexed: 10/20/2022]
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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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Ogoh S, Ainslie PN, Miyamoto T. Onset responses of ventilation and cerebral blood flow to hypercapnia in humans: rest and exercise. J Appl Physiol (1985) 2009; 106:880-6. [PMID: 19131474 DOI: 10.1152/japplphysiol.91292.2008] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The respiratory and cerebrovascular reactivity to changes in arterial Pco(2) (Pa(CO(2))) is an important mechanism that maintains CO(2) or pH homeostasis in the brain. It remains unclear, however, how cerebrovascular CO(2) reactivity might influence the respiratory chemoreflex. The purpose of the present study was therefore to examine the interaction between onset responses of the respiratory chemoreflex and middle cerebral artery (MCA) mean blood velocity (V(mean)) to hypercapnia (5.0% CO(2)-40% O(2)-balance N(2)) at rest and during dynamic exercise ( approximately 1.0 l/min O(2) consumption). Each onset response was evaluated using a single-exponential regression model consisting of the response time latency [CO(2)-response delay (t(0))] and time constant (tau). At rest, t(0) and tau data indicated that the MCA V(mean) onset response was faster than the ventilatory (Ve) response (P < 0.001). In contrast, during exercise, t(0) of Ve and MCA V(mean) onset responses were decreased. In addition, despite the enhanced Pa(CO(2)) response to CO(2) administration (P = 0.014), tau of MCA V(mean) tended to increase during exercise (P = 0.054), whereas tau of Ve decreased (P = 0.015). These findings indicate that 1) at rest, faster washout of CO(2) via cerebral vasodilation results in a reduced activation of the central chemoreflex and subsequent reduced Ve onset response, and 2) during exercise, despite higher rates of increasing Pa(CO(2)), the lack of change in the onset response of cerebral blood flow and reduced washout of CO(2) may act to augment the Ve onset response.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas 76107, USA.
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Udomphorn Y, Armstead WM, Vavilala MS. Cerebral blood flow and autoregulation after pediatric traumatic brain injury. Pediatr Neurol 2008; 38:225-34. [PMID: 18358399 PMCID: PMC2330089 DOI: 10.1016/j.pediatrneurol.2007.09.012] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Revised: 08/17/2007] [Accepted: 09/26/2007] [Indexed: 11/25/2022]
Abstract
Traumatic brain injury is a global health concern and is the leading cause of traumatic morbidity and mortality in children. Despite a lower overall mortality than in adult traumatic brain injury, the cost to society from the sequelae of pediatric traumatic brain injury is very high. Predictors of poor outcome after traumatic brain injury include altered systemic and cerebral physiology, including altered cerebral hemodynamics. Cerebral autoregulation is often impaired after traumatic brain injury and may adversely impact the outcome. Although altered cerebrovascular hemodynamics early after traumatic brain injury may contribute to disability in children, there is little information regarding changes in cerebral blood flow and cerebral autoregulation after pediatric traumatic brain injury. This review addresses normal pediatric cerebral physiology and cerebrovascular pathophysiology after pediatric traumatic brain injury.
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Affiliation(s)
- Yuthana Udomphorn
- Department of Anesthesiology Harborview Medical Center, University of Washington Seattle, WA
| | - William M. Armstead
- Departments of Anesthesiology and Critical Care and Pharmacology University of Pennsylvania Philadelphia, PA
| | - Monica S. Vavilala
- Department of Anesthesiology Harborview Medical Center, University of Washington Seattle, WA
- Department of Pediatrics Harborview Medical Center, University of Washington Seattle, WA
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Steinback CD, Poulin MJ. Cardiovascular and cerebrovascular responses to acute isocapnic and poikilocapnic hypoxia in humans. J Appl Physiol (1985) 2007; 104:482-9. [PMID: 18263856 DOI: 10.1152/japplphysiol.00553.2007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined the cardiovascular and cerebrovascular responses to acute isocapnic (IH) and poikilocapnic hypoxia (PH) in 10 men (25.7 +/- 4.2 yr, mean +/- SD). Heart rate (HR), mean arterial pressure (MAP), and mean peak middle cerebral artery blood flow velocity (Vp) were measured continuously during two randomized protocols of 20 min of step IH and PH (45 Torr). HR was elevated during both IH (P < 0.01) and PH (P < 0.01), with no differences observed between conditions. MAP was modestly elevated across all time points during IH but only became elevated after 5 min during PH. During IH, Vp was elevated from baseline throughout the exposure with a consistent hypoxic sensitivity of approximately 0.34 cm x s(-1).%desaturation(-1) (P < 0.05). The Vp response to PH was biphasic with an initial decrease from baseline occurring at 79 +/- 23 s, followed by a subsequent elevation, becoming equivalent to the IH response by 10 min. The nadir of the PH response exhibited a hypoxic sensitivity of -0.24 cm x s(-1) x % desaturation(-1). When expressed in relation to end-tidal Pco2, a sensitivity of -1.08 cm x s(-1).Torr(-1) was calculated, similar to previously reported sensitivities to euoxic hypocapnia. Cerebrovascular resistance (CVR) was not changed during IH. During PH, an initial increase in CVR was observed. However, CVR returned to baseline by 20 min of PH. These data show the cerebrovascular response to PH consists of an early hypocapnia-mediated response, followed by a secondary increase, mediated predominantly by hypoxia.
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Affiliation(s)
- Craig D Steinback
- Dept. of Physiology and Biophysics, Faculty of Medicine, Univ. of Calgary, HMRB-212, 3330 Hospital Dr., NW, Calgary, Alberta, Canada T2N 4N1
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Binks AP, Cunningham VJ, Adams L, Banzett RB. Gray matter blood flow change is unevenly distributed during moderate isocapnic hypoxia in humans. J Appl Physiol (1985) 2007; 104:212-7. [PMID: 17991793 DOI: 10.1152/japplphysiol.00069.2007] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hypoxia increases cerebral blood flow (CBF), but it is unknown whether this increase is uniform across all brain regions. We used H(2)(15)O positron emission tomography imaging to measure absolute blood flow in 50 regions of interest across the human brain (n = 5) during normoxia and moderate hypoxia. Pco(2) was kept constant ( approximately 44 Torr) throughout the study to avoid decreases in CBF associated with the hypocapnia that normally occurs with hypoxia. Breathing was controlled by mechanical ventilation. During hypoxia (inspired Po(2) = 70 Torr), mean end-tidal Po(2) fell to 45 +/- 6.3 Torr (means +/- SD). Mean global CBF increased from normoxic levels of 0.39 +/- 0.13 to 0.45 +/- 0.13 ml/g during hypoxia. Increases in regional CBF were not uniform and ranged from 9.9 +/- 8.6% in the occipital lobe to 28.9 +/- 10.3% in the nucleus accumbens. Regions of interest that were better perfused during normoxia generally showed a greater regional CBF response. Phylogenetically older regions of the brain tended to show larger vascular responses to hypoxia than evolutionary younger regions, e.g., the putamen, brain stem, thalamus, caudate nucleus, nucleus accumbens, and pallidum received greater than average increases in blood flow, while cortical regions generally received below average increases. The heterogeneous blood flow distribution during hypoxia may serve to protect regions of the brain with essential homeostatic roles. This may be relevant to conditions such as altitude, breath-hold diving, and obstructive sleep apnea, and may have implications for functional brain imaging studies that involve hypoxia.
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Pandit JJ, Mohan RM, Paterson ND, Poulin MJ. Cerebral blood flow sensitivities to CO2 measured with steady-state and modified rebreathing methods. Respir Physiol Neurobiol 2007; 159:34-44. [PMID: 17586103 DOI: 10.1016/j.resp.2007.05.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Revised: 05/07/2007] [Accepted: 05/09/2007] [Indexed: 10/23/2022]
Abstract
It is well established that the ventilatory response to carbon dioxide (CO(2)) measured by modified rebreathing (Sr(VE)) is closer to that measured by the steady-state method (Ss(VE)) than is the response measured by Read's rebreathing method. It is also known that the value estimated by the steady-state method depends upon the combination of data points used to measure it. The aim of this study was to investigate if these observations were also true for cerebral blood flow (CBF), as measured by steady-state (Ss(CBF)) and modified rebreathing (Sr(CBF)) tests. Six subjects undertook two protocols: (a) steady state: PET(CO2) was held at 1.5 mm Hg above normal (isocapnia) for 10 min, then raised to three levels of hypercapnia, (8 min each; 6.5, 11.5 and 16.5 mm Hg above normal, separated by 4 min isocapnia). End-tidal PO2 was held at 300 mm Hg; (b) modified rebreathing: subjects underwent 6 min of voluntary hyperventilation to PET(CO2) approximately 20 mm Hg, and then rebreathed via a 6l bag filled with 6.5% CO(2) in O(2). We confirmed that the value for Ss(VE) depended upon the combination of data points used to calculate it, and also confirmed that Ss(VE) and Sr(VE) were similar. However, this was not the case with CBF. Estimates of Ss(CBF) were the same, regardless of the data points used in calculation, and Ss(CBF) was 89% greater than Sr(CBF) (P<0.05). We interpret these findings as consistent with the notion that the specific CO(2) stimulus differs for CBF and ventilatory control. The data also indicate that prior hypocapnia in the modified rebreathing protocol may have a persistent effect on both cerebral vessels and central ventilatory control.
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Affiliation(s)
- Jaideep J Pandit
- Nuffield Department of Anaesthetics, John Radcliffe Hospital, Oxford OX3 9DU, UK.
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Slessarev M, Han J, Mardimae A, Prisman E, Preiss D, Volgyesi G, Ansel C, Duffin J, Fisher JA. Prospective targeting and control of end-tidal CO2 and O2 concentrations. J Physiol 2007; 581:1207-19. [PMID: 17446225 PMCID: PMC2170842 DOI: 10.1113/jphysiol.2007.129395] [Citation(s) in RCA: 242] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Current methods of forcing end-tidal PCO2 (PETCO2) and PO2 (PETO2) rely on breath-by-breath adjustment of inspired gas concentrations using feedback loop algorithms. Such servo-control mechanisms are complex because they have to anticipate and compensate for the respiratory response to a given inspiratory gas concentration on a breath-by-breath basis. In this paper, we introduce a low gas flow method to prospectively target and control PETCO2 and PETO2 independent of each other and of minute ventilation in spontaneously breathing humans. We used the method to change PETCO2 from control (40 mmHg for PETCO2 and 100 mmHg for PETO2) to two target PETCO2 values (45 and 50 mmHg) at iso-oxia (100 mmHg), PETO2 to two target values (200 and 300 mmHg) at normocapnia (40 mmHg), and PETCO2 with PETO2 simultaneously to the same targets (45 with 200 mmHg and 50 with 300 mmHg). After each targeted value, PETCO2 and PETO2 were returned to control values. Each state was maintained for 30 s. The average difference between target and measured values for PETCO2 was +/-1 mmHg, and for PETO2 was +/-4 mmHg. PETCO2 varied by +/-1 mmHg and PETO2 by +/-5.6 mmHg (s.d.) over the 30 s stages. This degree of control was obtained despite considerable variability in minute ventilation between subjects (+/-7.6 l min(-1)). We conclude that targeted end-tidal gas concentrations can be attained in spontaneously breathing subjects using this prospective, feed-forward, low gas flow system.
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Affiliation(s)
- Marat Slessarev
- Department of Anaesthesiology, University Health Network, Toronto General Hospital 7EN-242, 200 Elizabeth St, Toronto, Canada, M5G 2C4
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Giardino ND, Friedman SD, Dager SR. Anxiety, respiration, and cerebral blood flow: implications for functional brain imaging. Compr Psychiatry 2007; 48:103-12. [PMID: 17292699 PMCID: PMC1820771 DOI: 10.1016/j.comppsych.2006.11.001] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Accepted: 11/01/2006] [Indexed: 11/25/2022] Open
Abstract
Brain functional imaging methods, such as fMRI, are sensitive to changes in cerebral blood flow (CBF) that are normally associated with changes in regional neural activation. However, other endogenous and exogenous factors can alter CBF independently of brain neural activity, thus complicating the interpretation of functional imaging data. The presence of an anxiety disorder, as well as change in state anxiety, is often accompanied by respiratory alterations that affect arterial CO(2) tensions and produce significant changes in CBF that are independent of task-related neural activation. Therefore, the effects of trait and state anxiety need to be given close consideration in interpreting functional imaging findings. In this paper, we review the dependence of most brain functional imaging methods on localized changes in CBF and the potentially confounding effects of anxiety-related alterations of respiration on interpreting patterns of functional activation. Approaches for addressing these effects are discussed.
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Affiliation(s)
- Nicholas D Giardino
- Department of Radiology, University of Washington School of Medicine, Seattle, WA 98105, USA
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Claassen JAHR, Zhang R, Fu Q, Witkowski S, Levine BD. Transcranial Doppler estimation of cerebral blood flow and cerebrovascular conductance during modified rebreathing. J Appl Physiol (1985) 2006; 102:870-7. [PMID: 17110510 DOI: 10.1152/japplphysiol.00906.2006] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Clinical transcranial Doppler assessment of cerebral vasomotor reactivity (CVMR) uses linear regression of cerebral blood flow velocity (CBFV) vs. end-tidal CO(2) (Pet(CO(2))) under steady-state conditions. However, the cerebral blood flow (CBF)-Pet(CO(2)) relationship is nonlinear, even for moderate changes in CO(2). Moreover, CBF is increased by increases in arterial blood pressure (ABP) during hypercapnia. We used a modified rebreathing protocol to estimate CVMR during transient breath-by-breath changes in CBFV and Pet(CO(2)). Ten healthy subjects (6 men) performed 15 s of hyperventilation followed by 5 min of rebreathing, with supplemental O(2) to maintain arterial oxygen saturation constant. To minimize effects of changes in ABP on CVMR estimation, cerebrovascular conductance index (CVCi) was calculated. CBFV-Pet(CO(2)) and CVCi-Pet(CO(2)) relationships were quantified by both linear and nonlinear logistic regression. In three subjects, muscle sympathetic nerve activity was recorded. From hyperventilation to rebreathing, robust changes occurred in Pet(CO(2)) (20-61 Torr), CBFV (-44 to +104% of baseline), CVCi (-39 to +64%), and ABP (-19 to +23%) (all P < 0.01). Muscle sympathetic nerve activity increased by 446% during hypercapnia. The linear regression slope of CVCi vs. Pet(CO(2)) was less steep than that of CBFV (3 vs. 5%/Torr; P = 0.01). Logistic regression of CBF-Pet(CO(2)) (r(2) = 0.97) and CVCi-Pet(CO(2)) (r(2) = 0.93) was superior to linear regression (r(2) = 0.91, r(2) = 0.85; P = 0.01). CVMR was maximal (6-8%/Torr) for Pet(CO(2)) of 40-50 Torr. In conclusion, CBFV and CVCi responses to transient changes in Pet(CO(2)) can be described by a nonlinear logistic function, indicating that CVMR estimation varies within the range from hypocapnia to hypercapnia. Furthermore, quantification of the CVCi-Pet(CO(2)) relationship may minimize the effects of changes in ABP on the estimation of CVMR. The method developed provides insight into CVMR under transient breath-by-breath changes in CO(2).
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Affiliation(s)
- Jurgen A H R Claassen
- Department of Geriatric Medicine, Radbound University Nijmegen Medical Center, The Netherlands
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Albayrak R, Fidan F, Unlu M, Sezer M, Degirmenci B, Acar M, Haktanir A, Yaman M. Extracranial carotid Doppler ultrasound evaluation of cerebral blood flow volume in COPD patients. Respir Med 2006; 100:1826-33. [PMID: 16516456 DOI: 10.1016/j.rmed.2006.01.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2005] [Revised: 01/16/2006] [Accepted: 01/22/2006] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Doppler ultrasound of extracranial internal carotid artery (ICA) and vertebral artery (VA) were performed and total cerebral blood flow volume (tCBFV) was evaluated in chronic obstructive pulmonary disease (COPD) patients. CBFV changes due to blood gas changes were also evaluated. METHODS Bilateral ICA and VA have been examined with 7.5 MHz linear array transducer in COPD patients. Angle-corrected time averaged flow velocity and cross-sectional areas of vessels have been measured. Flow volumes and tCBFV have been calculated. Flow velocities and waveform parameters have been measured. RESULTS tCBFV, anterior-posterior CBFVs, left-right ICA flow volumes, bilateral ICA and VA cross-sectional areas and left ICA peak-systolic velocity were significantly higher in COPD patients than control group. Among COPD patients tCBFVs were highest in hypoxemic-hypercapnic ones, and lowest in normocapnic ones. Bilateral VA flow volumes, bilateral ICA (except left ICA V(ps)) and VA flow velocities and waveform parameters were not different in COPD patients compared with control group. When compared among the subgroups of COPD patients, there were no significant differences for all parameters. CONCLUSION tCBFVs were found to be significantly higher in COPD patients. This increment which is probably due to balancing the oxygen deficit is low with hypoxemia and high with hypercapnia and hypoxemia. Particularly, bilateral ICA and VA cross-sectional area changes and increased left ICA V(ps) were considered as the main reason for increased tCBFV in COPD patients.
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Affiliation(s)
- Ramazan Albayrak
- Department of Radiology, Faculty of Medicine, Afyon Kocatepe University, 03100, Afyon, Turkey.
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Xie A, Skatrud JB, Morgan B, Chenuel B, Khayat R, Reichmuth K, Lin J, Dempsey JA. Influence of cerebrovascular function on the hypercapnic ventilatory response in healthy humans. J Physiol 2006; 577:319-29. [PMID: 16931556 PMCID: PMC2000684 DOI: 10.1113/jphysiol.2006.110627] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
An important determinant of [H(+)] in the environment of the central chemoreceptors is cerebral blood flow. Accordingly we hypothesized that a reduction of brain perfusion or a reduced cerebrovascular reactivity to CO(2) would lead to hyperventilation and an increased ventilatory responsiveness to CO(2). We used oral indomethacin to reduce the cerebrovascular reactivity to CO(2) and tested the steady-state hypercapnic ventilatory response to CO(2) in nine normal awake human subjects under normoxia and hyperoxia (50% O(2)). Ninety minutes after indomethacin ingestion, cerebral blood flow velocity (CBFV) in the middle cerebral artery decreased to 77 +/- 5% of the initial value and the average slope of CBFV response to hypercapnia was reduced to 31% of control in normoxia (1.92 versus 0.59 cm(-1) s(-1) mmHg(-1), P < 0.05) and 37% of control in hyperoxia (1.58 versus 0.59 cm(-1) s(-1) mmHg(-1), P < 0.05). Concomitantly, indomethacin administration also caused 40-60% increases in the slope of the mean ventilatory response to CO(2) in both normoxia (1.27 +/- 0.31 versus 1.76 +/- 0.37 l min(-1) mmHg(-1), P < 0.05) and hyperoxia (1.08 +/- 0.22 versus 1.79 +/- 0.37 l min(-1) mmHg(-1), P < 0.05). These correlative findings are consistent with the conclusion that cerebrovascular responsiveness to CO(2) is an important determinant of eupnoeic ventilation and of hypercapnic ventilatory responsiveness in humans, primarily via its effects at the level of the central chemoreceptors.
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Affiliation(s)
- Ailiang Xie
- Department of Medicine, University of Wisconsin, Madison, WI, USA
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42
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Mitsis GD, Zhang R, Levine BD, Marmarelis VZ. Cerebral hemodynamics during orthostatic stress assessed by nonlinear modeling. J Appl Physiol (1985) 2006; 101:354-66. [PMID: 16514006 DOI: 10.1152/japplphysiol.00548.2005] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effects of orthostatic stress, induced by lower body negative pressure (LBNP), on cerebral hemodynamics were examined in a nonlinear context. Spontaneous fluctuations of beat-to-beat mean arterial blood pressure (MABP) in the finger, mean cerebral blood flow velocity (MCBFV) in the middle cerebral artery, as well as breath-by-breath end-tidal CO2 concentration (PetCO2) were measured continuously in 10 healthy subjects under resting conditions and during graded LBNP to presyncope. A two-input nonlinear Laguerre-Volterra network model was employed to study the dynamic effects of MABP and PetCO2 changes, as well as their nonlinear interactions, on MCBFV variations in the very low (VLF; below 0.04 Hz), low (LF; 0.04–0.15 Hz), and high frequency (HF; 0.15–0.30 Hz) ranges. Dynamic cerebral autoregulation was described by the model terms corresponding to MABP, whereas cerebral vasomotor reactivity was described by the model PetCO2 terms. The nonlinear model terms reduced the output prediction normalized mean square error substantially (by 15–20%) and had a prominent effect in the VLF range, both under resting conditions and during LBNP. Whereas MABP fluctuations dominated in the HF range and played a significant role in the VLF and LF ranges, changes in PetCO2 accounted for a considerable fraction of the VLF and LF MCBFV variations, especially at high LBNP levels. The magnitude of the linear and nonlinear MABP-MCBFV Volterra kernels increased substantially above −30 mmHg LBNP in the VLF range, implying impaired dynamic autoregulation. In contrast, the magnitude of the PetCO2-MCBFV kernels reduced during LBNP at all frequencies, suggesting attenuated cerebral vasomotor reactivity under dynamic conditions. We speculate that these changes may reflect a progressively reduced cerebrovascular reserve to compensate for the increasingly unstable systemic circulation during orthostatic stress that could ultimately lead to cerebral hypoperfusion and syncope.
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Affiliation(s)
- Georgios D Mitsis
- Department of Biomedical Engineering, University of Southern California, Los Angeles, USA.
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43
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Peltonen JE, Kowalchuk JM, Paterson DH, DeLorey DS, duManoir GR, Petrella RJ, Shoemaker JK. Cerebral and muscle tissue oxygenation in acute hypoxic ventilatory response test. Respir Physiol Neurobiol 2006; 155:71-81. [PMID: 16697712 DOI: 10.1016/j.resp.2006.03.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Revised: 03/10/2006] [Accepted: 03/28/2006] [Indexed: 11/26/2022]
Abstract
Eight men were exposed to progressive isocapnic hypoxia for 10 min to test the hypothesis that (i) cerebral and muscle tissue would follow similar deoxygenation profiles during an acute hypoxic ventilatory response (AHVR) test; and (ii) strong cerebrovascular responsiveness to hypoxia would be related to attenuated cerebral deoxygenation. End-tidal O(2) concentration was reduced from normoxia (approximately 102 mmHg) to approximately 45 mmHg while arterial oxygen saturation (SpO2 %) declined from 98+/-1% to 77+/-7% (P<0.001). Near-infrared spectroscopy (NIRS)-derived local cerebral tissue (frontal lobe) deoxyhemoglobin increased 5.55+/-2.22 microM, while oxyhemoglobin and tissue oxygenation index decreased 2.57+/-1.99 microM and 6.2+/-3.4%, respectively (all P<0.001). In muscle (m. vastus lateralis) the NIRS changes from the initial normoxic level were non-significant. Cerebral blood velocity (V(mean), transcranial Doppler) in the middle cerebral artery increased from 53.4+/-10.4 to 60.6+/-11.6 cms(-1) (P<0.001). In relation to the decline in SpO2 % the mean rate of increase of V(mean) and AHVR were 0.33+/-0.19 cms(-1)%(-1) and 0.52+/-0.20l min(-1)%(-1), respectively. We conclude that cerebral, but not muscle, tissue shows changes reflecting a greater deoxygenation during acute hypoxia. However, the changes in NIRS parameters were not related to cerebrovascular responsiveness or ventilatory chemosensitivity during graded hypoxia.
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Affiliation(s)
- Juha E Peltonen
- Unit for Sports and Exercise Medicine, Institute of Clinical Medicine, University of Helsinki, Helsinki, Finland.
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Spicuzza L, Porta C, Bramanti A, Maffeis M, Casucci G, Casiraghi N, Bernardi L. Interaction between central-peripheral chemoreflexes and cerebro-cardiovascular control. Clin Auton Res 2006; 15:373-81. [PMID: 16362539 DOI: 10.1007/s10286-005-0284-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2005] [Accepted: 03/24/2005] [Indexed: 10/25/2022]
Abstract
We investigated the interaction between hypoxia and hypercapnia on ventilation and on cerebro-cardio-vascular control. A group of 12 healthy subjects performed rebreathing tests to determine the ventilatory response to hypoxia, at different levels of carbon dioxide (CO(2)), and to normoxic hypercapnia. Oxygen saturation (SaO(2)), end-tidal CO(2) (et-CO(2)), minute ventilation, blood pressure, R-R interval and mid-cerebral artery flow velocity (MCFV) were continuously recorded. The hypoxic ventilatory response significantly increased under hypercapnia and decreased under hypocapnia (slopes L/min/% Sa O(2): -0.33 +/- 0.05, -0.74 +/- 0.02 and -1.59 +/- 0.3, p < 0.0001, in hypocapnia, normocapnia and hypercapnia, respectively). At similar degrees of ventilation, MCFV increased more markedly during normocapnic hypoxia than normoxic hypercapnia; the slopes linking MCFV to hypoxia remained unchanged at increasing levels of et-CO(2), whereas the regression lines were shifted upward. The R-R interval decreased more markedly during normocapnic hypoxia than normoxic hypercapnia and the arterial baroreflex sensitivity was decreased only by hypoxia. Cardiovascular responses to hypoxia were not affected by different levels of et-CO(2). We conclude that concomitant hypoxia and hypercapnia, while increasing ventilation synergistically, exert an additive effect on cerebral blood flow. Increased sympathetic activity (and reduced baroreflex sensitivity) is one of the mechanisms by which hypoxia stimulates cardiac sympathetic activity.
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Affiliation(s)
- Lucia Spicuzza
- Dept. of Internal Medicine, University of Catania, Italy
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Corfield DR, Meadows GE. Control of cerebral blood flow during sleep and the effects of hypoxia. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2006; 588:65-73. [PMID: 17089880 DOI: 10.1007/978-0-387-34817-9_7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
During wakefulness, cerebral blood flow (CBF) is closely coupled to regional cerebral metabolism; however CBF is also strongly modulated by breathing, increasing in response to both hypercapnia and hypoxia. During stage III/IV non-rapid eye (NREM) sleep, cerebral metabolism and CBF decrease whilst the partial pressure of arterial CO2 increases due to a reduction in alveolar ventilation. The reduction in CBF during NREM sleep therefore occurs despite a relative state of hypercapnia. We have used transcranial Doppler ultrasound to determine middle cerebral artery velocity, as an index of CBF, and have determined that NREM sleep is associated with a reduction in the cerebrovascular response to hypercapnia. This reduction in reactivity would, at least in part, allow the observed reductions in CBF in this state. Similarly, we have observed that the CBF response to hypoxia is absent during stage III/IV NREM sleep. Nocturnal hypoxia and hypercapnia are major pathogenic factor associated with cardio-respiratory diseases. These marked changes in cerebrovascular control that occur during sleep suggest that the cerebral circulation may be particularly vulnerable to cardio-respiratory insults during this period.
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Affiliation(s)
- Douglas R Corfield
- Institute of Science and Technology in Medicine, School of Life Sciences, Keele University, Keele, UK.
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Brühwiler PA, Stämpfli R, Huber R, Camenzind M. CO2 and O2 concentrations in integral motorcycle helmets. APPLIED ERGONOMICS 2005; 36:625-33. [PMID: 15893291 DOI: 10.1016/j.apergo.2005.01.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2004] [Revised: 10/11/2004] [Accepted: 01/10/2005] [Indexed: 05/02/2023]
Abstract
Inhaling air which contains excess CO2 and/or is oxygen-deficient is known to present health risks and to diminish human cognitive abilities. The average CO2 concentrations relevant to a motorcyclist wearing an integral helmet were measured 20 years ago and found to be alarmingly large. The purpose of the present study was to examine gas concentrations typically inhaled by a motorcyclist. Average concentrations of CO2 near the upper lip for persons (n = 4) wearing integral motorcycle helmets were measured in the laboratory and the field to facilitate comparison to previous work, and similarly high average concentrations were found: above 2% when stationary, well below 1% for speeds of 50 km/h or more. Very good agreement was obtained between laboratory and field measurements. Detailed measurements of the time-dependent CO2 concentrations passing through a mouthpiece for mouth-breathing showed inhaled levels slightly over half of the corresponding average concentrations, including 1.3+/-0.3% at standstill, though higher concentrations (4% or more) were inhaled at the beginning of each breath. Opening the visor at standstill had on average no effect. At a speed of 50 km/h the inhaled CO2 concentration resembles that for a person without a helmet in still air, at about 0.2%. The oxygen deficiency is generally equal to the CO2 concentration, and could also contribute negatively to a motorcyclist's cognitive abilities.
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Affiliation(s)
- P A Brühwiler
- Empa, Materials Science and Technology, Lerchenfeldstrasse 5, CH-9014 St. Gallen, Switzerland.
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Mitsis GD, Poulin MJ, Robbins PA, Marmarelis VZ. Nonlinear modeling of the dynamic effects of arterial pressure and CO2 variations on cerebral blood flow in healthy humans. IEEE Trans Biomed Eng 2004; 51:1932-43. [PMID: 15536895 DOI: 10.1109/tbme.2004.834272] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The effect of spontaneous beat-to-beat mean arterial blood pressure fluctuations and breath-to-breath end-tidal CO2 fluctuations on beat-to-beat cerebral blood flow velocity variations is studied using the Laguerre-Volterra network methodology for multiple-input nonlinear systems. The observations made from experimental measurements from ten healthy human subjects reveal that, whereas pressure fluctuations explain most of the high-frequency blood flow velocity variations (above 0.04 Hz), end-tidal CO2 fluctuations as well as nonlinear interactions between pressure and CO2 have a considerable effect in the lower frequencies (below 0.04 Hz). They also indicate that cerebral autoregulation is strongly nonlinear and dynamic (frequency-dependent). Nonlinearities are mainly active in the low-frequency range (below 0.04 Hz) and are more prominent in the dynamics of the end-tidal CO2-blood flow velocity relationship. Significant nonstationarities are also revealed by the obtained models, with greater variability evident for the effects of CO2 on blood flow velocity dynamics.
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Affiliation(s)
- Georgios D Mitsis
- Department of Biomedical Engineering, University of Southern California, University Park, Los Angeles, CA 90089, USA.
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Steiner LA, Balestreri M, Johnston AJ, Czosnyka M, Coles JP, Chatfield DA, Smielewski P, Pickard JD, Menon DK. Sustained moderate reductions in arterial CO2 after brain trauma Time-course of cerebral blood flow velocity and intracranial pressure. Intensive Care Med 2004; 30:2180-7. [PMID: 15480563 DOI: 10.1007/s00134-004-2463-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2004] [Accepted: 09/07/2004] [Indexed: 11/29/2022]
Abstract
OBJECTIVE In healthy volunteers cerebral blood flow starts to recover towards baseline within a few minutes of continued hyperventilation due to normalisation of perivascular pH. We investigated the time-course of changes in middle cerebral artery mean flow velocity (FVm) and intracranial pressure (ICP) in head-injured patients during sustained moderate reductions in arterial partial pressure of CO(2) (PaCO(2)). DESIGN Observational study. PATIENTS Twenty-seven sedated, mechanically ventilated patients with severe head injury. INTERVENTIONS Measurements were made during and after routine determination of CO(2)-reactivity: an acute 20% increase in respiratory minute volume was followed by a 10-min stabilisation period and 50 min of continued moderate hyperventilation at a constant PaCO(2) (>3.5 kPa). MEASUREMENTS AND RESULTS FVm was monitored with transcranial Doppler, ICP was monitored with intraparenchymal probes. During the 50-min period with stable PaCO(2) FVm increased in 36% of patients. All other patients showed a decline in FVm over the same time period. Overall FVm recovery was -0.03+/-0.14%.min(-1). The time-course of ICP changes was significantly different from that of FVm, with ICP reaching its lowest value earlier than FVm (23+/-12 vs 37+/-20 min; P = 0.001) and returning more rapidly towards baseline than FVm (0.23+/-0.23 vs -0.03+/-0.14%.min(-1); P< 0.0001). CONCLUSIONS Head-injured patients may adapt differently to hyperventilation than healthy volunteers. Potentially harmful reductions in cerebral blood flow may persist beyond the duration of useful ICP reduction.
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Affiliation(s)
- Luzius A Steiner
- Department of Anaesthesia, University Hospital Basel, 4031 Basel, Switzerland.
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Edwards MR, Devitt DL, Hughson RL. Two-breath CO2 test detects altered dynamic cerebrovascular autoregulation and CO2 responsiveness with changes in arterial Pco2. Am J Physiol Regul Integr Comp Physiol 2004; 287:R627-32. [PMID: 15044183 DOI: 10.1152/ajpregu.00384.2003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The new two-breath CO2 method was employed to test the hypotheses that small alterations in arterial Pco2 had an impact on the magnitude and dynamic response time of the CO2 effect on cerebrovascular resistance (CVRi) and the dynamic autoregulatory response to fluctuations in arterial pressure. During a 10-min protocol, eight subjects inspired two breaths from a bag with elevated Pco2, four different times, while end-tidal Pco2 was maintained at three levels: hypocapnia (LoCO2, 8 mmHg below resting values), normocapnia, and hypercapnia (HiCO2, 8 mmHg above resting values). Continuous measurements were made of mean blood pressure corrected to the level of the middle cerebral artery (BPMCA), Pco2 (estimated from expired CO2), and mean flow velocity (MFV, of the middle cerebral artery by Doppler ultrasound), with CVRi = BPMCA/MFV. Data were processed by a system identification technique (autoregressive moving average analysis) with gain and dynamic response time of adaptation estimated from the theoretical step responses. Consistent with our hypotheses, the magnitude of the Pco2-CVRi response was reduced from LoCO2 to HiCO2 [from −0.04 (SD 0.02) to −0.01 (SD 0.01) (mmHg·cm−1·s)·mmHg Pco2−1] and the time to reach 95% of the step plateau increased from 12.0 ± 4.9 to 20.5 ± 10.6 s. Dynamic autoregulation was impaired with elevated Pco2, as indicated by a reduction in gain from LoCO2 to HiCO2 [from 0.021 ± 0.012 to 0.007 ± 0.004 (mmHg·cm−1·s)·mmHg BPMCA−1], and time to reach 95% increased from 3.7 ± 2.8 to 20.0 ± 9.6 s. The two-breath technique detected dependence of the cerebrovascular CO2 response on Pco2 and changes in dynamic autoregulation with only small deviations in estimated arterial Pco2.
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Affiliation(s)
- Michael R Edwards
- Cardiorespiratory and Vascular Dynamics Laboratory, Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada N2L 3G1
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Vovk A, Smith WDF, Paterson ND, Cunningham DA, Paterson DH. Peripheral chemoreceptor control of ventilation following sustained hypoxia in young and older adult humans. Exp Physiol 2004; 89:647-56. [PMID: 15258116 DOI: 10.1113/expphysiol.2004.027532] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The rate and duration of peripheral chemoreceptor resensitization following sustained hypoxia was characterized in young and older (74-year-old) adults. In addition, cerebral blood velocity (CBV) was measured in young subjects during and following the relief from sustained hypoxia. Following 20 min of sustained eucapnic hypoxia (50 mmHg), subjects were re-exposed to brief (1.5 min) hypoxic pulses (50 mmHg), and the magnitude of the ventilatory response was used to gauge peripheral chemosensitivity. Five minutes after the relief from sustained hypoxia, ventilation (V(E)) increased to 40.3 +/- 4.5% of the initial hypoxic ventilatory response, and by 36 min V(E) increased to 100%, indicating that peripheral chemosensitivity to hypoxia was restored. The V(E) response magnitude plotted versus time demonstrated that V(E), hence peripheral chemosensitivity, was restored at a rate of 1.9% per minute. Cerebral blood flow (CBF, inferred from CBV) remained constant during sustained hypoxia and increased by the same magnitude during the hypoxic pulses, suggesting that CBF has a small, if any, impact on the decline in V(E) during hypoxia and its subsequent recovery. To address the issue of whether hypoxic pulses affect subsequent challenges, series (continuous hypoxic pulses at various recovery intervals) and parallel (only 1 pulse per trial) methods were used. There were no differences in the ventilatory responses between the series and parallel methods. Older adults demonstrated a similar rate of recovery as in the young, suggesting that ageing in active older adults does not affect the peripheral chemoreceptor response.
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Affiliation(s)
- Andrea Vovk
- Canadian Centre for Activity and Ageing, The University of Western Ontario, London, Ontario, Canada
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