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Taboni A, Fagoni N, Fontolliet T, Vinetti G, Ferretti G. Baroreflex dynamics during the rest to exercise transient in acute normobaric hypoxia in humans. Eur J Appl Physiol 2024:10.1007/s00421-024-05485-4. [PMID: 38656378 DOI: 10.1007/s00421-024-05485-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Accepted: 03/26/2024] [Indexed: 04/26/2024]
Abstract
PURPOSE We hypothesised that during a rest-to-exercise transient in hypoxia (H), compared to normoxia (N), (i) the initial baroreflex sensitivity (BRS) decrease would be slower and (ii) the fast heart rate (HR) and cardiac output (CO) response would have smaller amplitude (A1) due to lower vagal activity in H than N. METHODS Ten participants performed three rest-to-50 W exercise transients on a cycle-ergometer in N (ambient air) and three in H (inspired fraction of O2 = 0.11). R-to-R interval (RRi, by electrocardiography) and blood pressure profile (by photo-plethysmography) were recorded non-invasively. Analysis of the latter provided mean arterial pressure (MAP) and stroke volume (SV). CO = HR·SV. BRS was calculated by modified sequence method. RESULTS Upon exercise onset in N, MAP fell to a minimum (MAPmin) then recovered. BRS decreased immediately from 14.7 ± 3.6 at rest to 7.0 ± 3.0 ms mmHg-1 at 50 W (p < 0.01). The first BRS sequence detected at 50 W was 8.9 ± 4.8 ms mmHg-1 (p < 0.05 vs. rest). In H, MAP showed several oscillations until reaching a new steady state. BRS decreased rapidly from 10.6 ± 2.8 at rest to 2.9 ± 1.5 ms mmHg-1 at 50 W (p < 0.01), as the first BRS sequence at 50 W was 5.8 ± 2.6 ms mmHg-1 (p < 0.01 vs. rest). CO-A1 was 2.96 ± 1.51 and 2.31 ± 0.94 l min-1 in N and H, respectively (p = 0.06). HR-A1 was 7.7 ± 4.6 and 7.1 ± 5.9 min-1 in N and H, respectively (p = 0.81). CONCLUSION The immediate BRS decrease in H, coupled with similar rapid HR and CO responses, is compatible with a withdrawal of residual vagal activity in H associated with increased sympathetic drive.
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Affiliation(s)
- Anna Taboni
- Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, Brescia, Italy.
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.
- Department of Anaesthesiology, Pharmacology, Intensive Care, and Emergencies, University of Geneva, Geneva, Switzerland.
| | - Nazzareno Fagoni
- Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, Brescia, Italy
- Department of Anaesthesiology, Pharmacology, Intensive Care, and Emergencies, University of Geneva, Geneva, Switzerland
| | - Timothée Fontolliet
- Department of Anaesthesiology, Pharmacology, Intensive Care, and Emergencies, University of Geneva, Geneva, Switzerland
| | - Giovanni Vinetti
- Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, Brescia, Italy
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Guido Ferretti
- Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, Brescia, Italy
- Department of Anaesthesiology, Pharmacology, Intensive Care, and Emergencies, University of Geneva, Geneva, Switzerland
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Suarez-Roca H, Mamoun N, Watkins LL, Bortsov AV, Mathew JP. Higher Cardiovagal Baroreflex Sensitivity Predicts Increased Pain Outcomes After Cardiothoracic Surgery. THE JOURNAL OF PAIN 2024; 25:187-201. [PMID: 37567546 PMCID: PMC10841280 DOI: 10.1016/j.jpain.2023.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 08/05/2023] [Accepted: 08/06/2023] [Indexed: 08/13/2023]
Abstract
Excessive postoperative pain can lead to extended hospitalization and increased expenses, but factors that predict its severity are still unclear. Baroreceptor function could influence postoperative pain by modulating nociceptive processing and vagal-mediated anti-inflammatory reflexes. To investigate this relationship, we conducted a study with 55 patients undergoing minimally invasive cardiothoracic surgery to evaluate whether cardiovagal baroreflex sensitivity (BRS) can predict postoperative pain. We assessed the spontaneous cardiovagal BRS under resting pain-free conditions before surgery. We estimated postoperative pain outcomes with the Pain, Enjoyment, and General Activity scale and pressure pain thresholds on the first (POD1) and second (POD2) postoperative days and persistent pain 3 and 6 months after hospital discharge. We also measured circulating levels of relevant inflammatory biomarkers (C-reactive protein, albumin, cytokines) at baseline, POD1, and POD2 to assess the contribution of inflammation to the relationship between BRS and postoperative pain. Our mixed-effects model analysis showed a significant main effect of preoperative BRS on postoperative pain (P = .013). Linear regression analysis revealed a significant positive association between preoperative BRS and postoperative pain on POD2, even after adjusting for demographic, surgical, analgesic treatment, and psychological factors. Moreover, preoperative BRS was linked to pain interfering with general activity and enjoyment but not with other pain parameters (pain intensity and pressure pain thresholds). Preoperative BRS had modest associations with postoperative C-reactive protein and IL-10 levels, but they did not mediate its relationship with postoperative pain. These findings indicate that preoperative BRS can independently predict postoperative pain, which could serve as a modifiable criterion for optimizing postoperative pain management. PERSPECTIVE: This article shows that preoperative BRS predicts postoperative pain outcomes independently of the inflammatory response and pain sensitivity to noxious pressure stimulation. These results provide valuable insights into the role of baroreceptors in pain and suggest a helpful tool for improving postoperative pain management.
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Affiliation(s)
- Heberto Suarez-Roca
- Center for Translational Pain Medicine, Duke University Medical Center, Durham, North Carolina
| | - Negmeldeen Mamoun
- Division of Cardiothoracic Anesthesia and Critical Care Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
| | - Lana L Watkins
- Psychiatry and Behavioral Sciences Department, Duke University Medical Center, Durham, North Carolina
| | - Andrey V Bortsov
- Center for Translational Pain Medicine, Duke University Medical Center, Durham, North Carolina
| | - Joseph P Mathew
- Division of Cardiothoracic Anesthesia and Critical Care Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
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A century of exercise physiology: key concepts on coupling respiratory oxygen flow to muscle energy demand during exercise. Eur J Appl Physiol 2022; 122:1317-1365. [PMID: 35217911 PMCID: PMC9132876 DOI: 10.1007/s00421-022-04901-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 01/25/2022] [Indexed: 12/26/2022]
Abstract
After a short historical account, and a discussion of Hill and Meyerhof’s theory of the energetics of muscular exercise, we analyse steady-state rest and exercise as the condition wherein coupling of respiration to metabolism is most perfect. The quantitative relationships show that the homeostatic equilibrium, centred around arterial pH of 7.4 and arterial carbon dioxide partial pressure of 40 mmHg, is attained when the ratio of alveolar ventilation to carbon dioxide flow (\documentclass[12pt]{minimal}
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\begin{document}$${\dot{V}}_{A}/{\dot{V}}_{R}{CO}_{2}$$\end{document}V˙A/V˙RCO2) is − 21.6. Several combinations, exploited during exercise, of pertinent respiratory variables are compatible with this equilibrium, allowing adjustment of oxygen flow to oxygen demand without its alteration. During exercise transients, the balance is broken, but the coupling of respiration to metabolism is preserved when, as during moderate exercise, the respiratory system responds faster than the metabolic pathways. At higher exercise intensities, early blood lactate accumulation suggests that the coupling of respiration to metabolism is transiently broken, to be re-established when, at steady state, blood lactate stabilizes at higher levels than resting. In the severe exercise domain, coupling cannot be re-established, so that anaerobic lactic metabolism also contributes to sustain energy demand, lactate concentration goes up and arterial pH falls continuously. The \documentclass[12pt]{minimal}
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\begin{document}$${\dot{V}}_{A}/{\dot{V}}_{R}{CO}_{2}$$\end{document}V˙A/V˙RCO2 decreases below − 21.6, because of ensuing hyperventilation, while lactate keeps being accumulated, so that exercise is rapidly interrupted. The most extreme rupture of the homeostatic equilibrium occurs during breath-holding, because oxygen flow from ambient air to mitochondria is interrupted. No coupling at all is possible between respiration and metabolism in this case.
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Dabiri B, Brito J, Kaniusas E. Cardiovagal Baroreflex Hysteresis Using Ellipses in Response to Postural Changes. Front Neurosci 2021; 15:720031. [PMID: 34955708 PMCID: PMC8695984 DOI: 10.3389/fnins.2021.720031] [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: 06/03/2021] [Accepted: 11/10/2021] [Indexed: 11/20/2022] Open
Abstract
The cardiovagal branch of the baroreflex is of high clinical relevance when detecting disturbances of the autonomic nervous system. The hysteresis of the baroreflex is assessed using provoked and spontaneous changes in blood pressure. We propose a novel ellipse analysis to characterize hysteresis of the spontaneous respiration-related cardiovagal baroreflex for orthostatic test. Up and down sequences of pressure changes as well as the working point of baroreflex are considered. The EuroBaVar data set for supine and standing was employed to extract heartbeat intervals and blood pressure values. The latter values formed polygons into which a bivariate normal distribution was fitted with its properties determining proposed ellipses of baroreflex. More than 80% of ellipses are formed out of nonoverlapping and delayed up and down sequences highlighting baroreflex hysteresis. In the supine position, the ellipses are more elongated (by about 46%) and steeper (by about 4.3° as median) than standing, indicating larger heart interval variability (70.7 versus 47.9 ms) and smaller blood pressure variability (5.8 versus 8.9 mmHg) in supine. The ellipses show a higher baroreflex sensitivity for supine (15.7 ms/mmHg as median) than standing (7 ms/mmHg). The center of the ellipse moves from supine to standing, which describes the overall sigmoid shape of the baroreflex with the moving working point. In contrast to regression analysis, the proposed method considers gain and set-point changes during respiration, offers instructive insights into the resulting hysteresis of the spontaneous cardiovagal baroreflex with respiration as stimuli, and provides a new tool for its future analysis.
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Affiliation(s)
- Babak Dabiri
- Institute of Electrodynamics, Microwave and Circuit Engineering, Vienna University of Technology, Vienna, Austria
| | - Joana Brito
- Institute of Electrodynamics, Microwave and Circuit Engineering, Vienna University of Technology, Vienna, Austria
| | - Eugenijus Kaniusas
- Institute of Electrodynamics, Microwave and Circuit Engineering, Vienna University of Technology, Vienna, Austria
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Zhong B, Ma S, Wang DH. Ablation of TRPV1 Elevates Nocturnal Blood Pressure in Western Diet-fed Mice. Curr Hypertens Rev 2020; 15:144-153. [PMID: 30381083 PMCID: PMC6635649 DOI: 10.2174/1573402114666181031141840] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 09/24/2018] [Accepted: 10/24/2018] [Indexed: 12/28/2022]
Abstract
Background: This study tested the hypothesis that genetically ablation of transient receptor potential vanilloid type 1 (TRPV1) exacerbates impairment of baroreflex in mice fed a western diet (WD) and leads to distinct diurnal and nocturnal blood pressure patterns. Methods: TRPV1 gene knockout (TRPV1-/-) and wild-type (WT) mice were given a WD or normal diet (CON) for 4 months. Results: Capsaicin, a selective TRPV1 agonist, increased ipsilateral afferent renal nerve activity in WT but not TRPV1-/- mice. The sensitivity of renal sympathetic nerve activity and heart rate responses to baroreflex were reduced in TRPV1-/--CON and WT-WD and further decreased in TRPV1-/--WD compared to the WT-CON group. Urinary norepinephrine and serum insulin and leptin at day and night were increased in WT-WD and TRPV1-/--WD, with further elevation at night in TRPV1-/--WD. WD intake increased leptin, IL-6, and TNF-α in adipose tissue, and TNF-α antagonist III, R-7050, decreased leptin in TRPV1-/--WD. The urinary albumin level was higher in TRPV1-/--WD than WT-WD. Blood pressure was not dif-ferent during daytime among all groups, but increased at night in the TRPV1-/--WD group compared with other groups. Conclusions: TRPV1 ablation leads to elevated nocturnal but not diurnal blood pressure, which is probably attributed to fur-ther enhancement of sympathetic drives at night.
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Affiliation(s)
- Beihua Zhong
- Division of Nanomedicine and Molecular Intervention, Department of Medicine, Michigan State University, East Lansing, Michigan MI 48824, United States
| | - Shuangtao Ma
- Division of Nanomedicine and Molecular Intervention, Department of Medicine, Michigan State University, East Lansing, Michigan MI 48824, United States
| | - Donna H Wang
- Division of Nanomedicine and Molecular Intervention, Department of Medicine, Michigan State University, East Lansing, Michigan MI 48824, United States.,Neuroscience Program, Michigan State University, East Lansing, Michigan MI 48824, United States.,Cell & Molecular Biology Program, Michigan State University, East Lansing, Michigan MI 48824, United States
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6
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Neuronal stretch reception – Making sense of the mechanosense. Exp Cell Res 2019; 378:104-112. [DOI: 10.1016/j.yexcr.2019.01.028] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 01/14/2019] [Accepted: 01/17/2019] [Indexed: 02/06/2023]
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Effects of exercise intensity on vascular and autonomic components of the baroreflex following glucose ingestion in adolescents. Eur J Appl Physiol 2019; 119:867-878. [PMID: 30730001 PMCID: PMC6423315 DOI: 10.1007/s00421-019-04076-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 01/06/2019] [Indexed: 12/14/2022]
Abstract
Purpose To investigate the effects of an oral glucose tolerance test (OGTT) on baroreflex sensitivity (BRS) in a sample of healthy adolescents, and how acute exercise bouts of different intensities alter the effects of the OGTT on BRS. Methods Thirteen male adolescents (14.0 ± 0.5 years) completed three conditions on separate days in a counterbalanced order: (1) high-intensity interval exercise (HIIE); (2) moderate-intensity interval exercise (MIIE); and (3) resting control (CON). At ~ 90 min following the conditions, participants performed an OGTT. Supine heart rate and blood pressure were monitored continuously at baseline, 60 min following the conditions, and 60 min following the OGTT. A cross-spectral method (LFgain) was used to determine BRS gain. Arterial compliance (AC) was assessed as the BRS vascular component. LFgain divided by AC (LFgain/AC) was used as the autonomic component. Results Although non-significant, LFgain moderately decreased post-OGTT when no exercise was performed (pre-OGTT = 24.4 ± 8.2 ms mmHg− 1; post-OGTT = 19.9 ± 5.6 ms mmHg− 1; ES = 0.64, P > 0.05). This was attributed to the decrease in LFgain/AC (pre-OGTT = 1.19 ± 0.5 ms µm− 1; post-OGTT = 0.92 ± 0.24 ms µm− 1; ES = 0.69, P > 0.05). Compared to CON (Δ = − 4.4 ± 8.7 ms mmHg− 1), there were no differences for the pre–post-OGTT delta changes in LF/gain for HIIE (Δ = − 3.5 ± 8.2 ms mmHg− 1) and MIIE (Δ = 1.3 ± 9.9 ms mmHg− 1) had no effects on BRS following the OGTT (all ES < 0.5). Similarly, compared to CON (Δ = − 0.23 ± 0.40 ms µm− 1) there were no differences for the pre–post-OGTT delta changes in LF/gain for HIIE (Δ = − 0.22 ± 0.49 ms µm− 1) and MIIE (Δ = 0.13 ± 0.36 ms µm− 1). Conclusion A moderate non-significant decrease in BRS was observed in adolescents following a glucose challenge with no apparent effects of exercise.
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Oliveira R, Barker AR, Debras F, O'Doherty A, Williams CA. Mechanisms of blood pressure control following acute exercise in adolescents: Effects of exercise intensity on haemodynamics and baroreflex sensitivity. Exp Physiol 2018; 103:1056-1066. [DOI: 10.1113/ep086999] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Accepted: 06/05/2018] [Indexed: 12/21/2022]
Affiliation(s)
- Ricardo Oliveira
- Children's Health and Exercise Research Centre; Sport and Health Sciences; College of Life and Environmental Sciences; University of Exeter; Exeter EX1 2LU UK
| | - Alan R. Barker
- Children's Health and Exercise Research Centre; Sport and Health Sciences; College of Life and Environmental Sciences; University of Exeter; Exeter EX1 2LU UK
| | - Florian Debras
- School of Physics and Astronomy; University of Exeter; Exeter EX4 4QL UK
- Ecole Normale Supérieure de Lyon; Lyon Cedex 07 69364 France
| | - Alexandra O'Doherty
- Children's Health and Exercise Research Centre; Sport and Health Sciences; College of Life and Environmental Sciences; University of Exeter; Exeter EX1 2LU UK
| | - Craig A. Williams
- Children's Health and Exercise Research Centre; Sport and Health Sciences; College of Life and Environmental Sciences; University of Exeter; Exeter EX1 2LU UK
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Katzelnick CG, Weir JP, Chiaravalloti ND, Wylie GR, Dyson-Hudson TA, Bauman WA, Wecht JM. Impact of Blood Pressure, Lesion Level, and Physical Activity on Aortic Augmentation Index in Persons with Spinal Cord Injury. J Neurotrauma 2017; 34:3407-3415. [DOI: 10.1089/neu.2017.5065] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- Caitlyn G. Katzelnick
- VA RR&D National Center for Medication Consequences of Spinal Cord Injury, James J Peters VA Medical Center, Bronx, New York
- Department of Research, Kessler Foundation, West Orange, New Jersey
| | - Joseph P. Weir
- Department of Health, Sport, and Exercise Science, University of Kansas, Lawrence, Kansas
| | - Nancy D. Chiaravalloti
- Department of Research, Kessler Foundation, West Orange, New Jersey
- Department of Physical Medicine and Rehabilitation, Rutgers New Jersey Medical School, Newark, New Jersey
| | - Glenn R. Wylie
- Department of Research, Kessler Foundation, West Orange, New Jersey
- The War Related Illness and Injury Study Center, VA New Jersey Health Care System, East Orange, New Jersey
| | - Trevor A. Dyson-Hudson
- Department of Research, Kessler Foundation, West Orange, New Jersey
- Department of Physical Medicine and Rehabilitation, Rutgers New Jersey Medical School, Newark, New Jersey
| | - William A. Bauman
- VA RR&D National Center for Medication Consequences of Spinal Cord Injury, James J Peters VA Medical Center, Bronx, New York
- Department of Medicine, The Icahn School of Medicine at Mount Sinai, New York, New York
| | - Jill M. Wecht
- VA RR&D National Center for Medication Consequences of Spinal Cord Injury, James J Peters VA Medical Center, Bronx, New York
- Department of Medicine, The Icahn School of Medicine at Mount Sinai, New York, New York
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Lacolley P, Regnault V, Segers P, Laurent S. Vascular Smooth Muscle Cells and Arterial Stiffening: Relevance in Development, Aging, and Disease. Physiol Rev 2017; 97:1555-1617. [DOI: 10.1152/physrev.00003.2017] [Citation(s) in RCA: 332] [Impact Index Per Article: 47.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 05/15/2017] [Accepted: 05/26/2017] [Indexed: 12/18/2022] Open
Abstract
The cushioning function of large arteries encompasses distension during systole and recoil during diastole which transforms pulsatile flow into a steady flow in the microcirculation. Arterial stiffness, the inverse of distensibility, has been implicated in various etiologies of chronic common and monogenic cardiovascular diseases and is a major cause of morbidity and mortality globally. The first components that contribute to arterial stiffening are extracellular matrix (ECM) proteins that support the mechanical load, while the second important components are vascular smooth muscle cells (VSMCs), which not only regulate actomyosin interactions for contraction but mediate also mechanotransduction in cell-ECM homeostasis. Eventually, VSMC plasticity and signaling in both conductance and resistance arteries are highly relevant to the physiology of normal and early vascular aging. This review summarizes current concepts of central pressure and tensile pulsatile circumferential stress as key mechanical determinants of arterial wall remodeling, cell-ECM interactions depending mainly on the architecture of cytoskeletal proteins and focal adhesion, the large/small arteries cross-talk that gives rise to target organ damage, and inflammatory pathways leading to calcification or atherosclerosis. We further speculate on the contribution of cellular stiffness along the arterial tree to vascular wall stiffness. In addition, this review provides the latest advances in the identification of gene variants affecting arterial stiffening. Now that important hemodynamic and molecular mechanisms of arterial stiffness have been elucidated, and the complex interplay between ECM, cells, and sensors identified, further research should study their potential to halt or to reverse the development of arterial stiffness.
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Affiliation(s)
- Patrick Lacolley
- INSERM, U1116, Vandœuvre-lès-Nancy, France; Université de Lorraine, Nancy, France; IBiTech-bioMMeda, Department of Electronics and Information Systems, Ghent University, Gent, Belgium; Department of Pharmacology, European Georges Pompidou Hospital, Assistance Publique Hôpitaux de Paris, France; PARCC INSERM, UMR 970, Paris, France; and University Paris Descartes, Paris, France
| | - Véronique Regnault
- INSERM, U1116, Vandœuvre-lès-Nancy, France; Université de Lorraine, Nancy, France; IBiTech-bioMMeda, Department of Electronics and Information Systems, Ghent University, Gent, Belgium; Department of Pharmacology, European Georges Pompidou Hospital, Assistance Publique Hôpitaux de Paris, France; PARCC INSERM, UMR 970, Paris, France; and University Paris Descartes, Paris, France
| | - Patrick Segers
- INSERM, U1116, Vandœuvre-lès-Nancy, France; Université de Lorraine, Nancy, France; IBiTech-bioMMeda, Department of Electronics and Information Systems, Ghent University, Gent, Belgium; Department of Pharmacology, European Georges Pompidou Hospital, Assistance Publique Hôpitaux de Paris, France; PARCC INSERM, UMR 970, Paris, France; and University Paris Descartes, Paris, France
| | - Stéphane Laurent
- INSERM, U1116, Vandœuvre-lès-Nancy, France; Université de Lorraine, Nancy, France; IBiTech-bioMMeda, Department of Electronics and Information Systems, Ghent University, Gent, Belgium; Department of Pharmacology, European Georges Pompidou Hospital, Assistance Publique Hôpitaux de Paris, France; PARCC INSERM, UMR 970, Paris, France; and University Paris Descartes, Paris, France
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Bringard A, Adami A, Fagoni N, Fontolliet T, Lador F, Moia C, Tam E, Ferretti G. Dynamics of the RR-interval versus blood pressure relationship at exercise onset in humans. Eur J Appl Physiol 2017; 117:619-630. [PMID: 28238048 DOI: 10.1007/s00421-017-3564-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 02/07/2017] [Indexed: 10/20/2022]
Abstract
PURPOSE The dynamics of the postulated phenomenon of exercise baroreflex resetting is poorly understood, but can be investigated using closed-loop procedures. To shed light on some mechanisms and temporal relationships participating in the resetting process, we studied the time course of the relationship between the R-R interval (RRi) and arterial pressure with a closed-loop approach. METHODS On ten young volunteers at rest and during light exercise in supine and upright position, we continuously determined, on single-beat basis, RRi (electrocardiography), and arterial pressure (non-invasive finger pressure cuff). From pulse pressure profiles, we determined cardiac output (CO) by Modelflow, computed mean arterial pressure (MAP), and calculated total peripheral resistance (TPR). RESULTS At exercise start, RRi was lower than in quiet rest. As exercise started, MAP fell to a minimum (MAPm) of 72.8 ± 9.6 mmHg upright and 73.9 ± 6.2 supine, while RRi dropped. The initial RRi versus MAP relationship was linear, with flatter slope than resting baroreflex sensitivity, in both postures. TPR fell and CO increased. After MAPm, RRi and MAP varied in opposite direction toward exercise steady state, with further CO increase. CONCLUSION These results suggest that, initially, the MAP fall was corrected by a RRi reduction along a baroreflex curve, with lower sensitivity than at rest, but eventually in the same pressure range as at rest. After attainment of MAPm, a second phase started, where the postulated baroreflex resetting might have occurred. In conclusion, the change in baroreflex sensitivity and the resetting process are distinct phenomena, under different control systems.
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Affiliation(s)
- Aurélien Bringard
- Département d'Anesthésiologie, Pharmacologie et Soins Intensifs, Hôpitaux Universitaires de Genève, 4 rue Gabrielle-Perret-Gentil, CH-1211, Genève 4, Switzerland.,Département des Neurosciences Fondamentales, Université de Genève, 1 rue Michel Servet, CH-1211, Genève 4, Switzerland
| | - Alessandra Adami
- Département des Neurosciences Fondamentales, Université de Genève, 1 rue Michel Servet, CH-1211, Genève 4, Switzerland.,Division of Respiratory and Critical Care Physiology and Medicine, Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, 1124 W Carson St, Torrance, CA, 90502, USA
| | - Nazzareno Fagoni
- Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Viale Europa 11, 25123, Brescia, Italy
| | - Timothée Fontolliet
- Département d'Anesthésiologie, Pharmacologie et Soins Intensifs, Hôpitaux Universitaires de Genève, 4 rue Gabrielle-Perret-Gentil, CH-1211, Genève 4, Switzerland.,Département des Neurosciences Fondamentales, Université de Genève, 1 rue Michel Servet, CH-1211, Genève 4, Switzerland
| | - Frédéric Lador
- Service de Pneumologie, Programme Hypertension Pulmonaire, Département des Spécialités de Médecine, Hôpitaux Universitaires de Genève, 4 rue Gabrielle-Perret-Gentil, CH-1211, Genève, Switzerland
| | - Christian Moia
- Département d'Anesthésiologie, Pharmacologie et Soins Intensifs, Hôpitaux Universitaires de Genève, 4 rue Gabrielle-Perret-Gentil, CH-1211, Genève 4, Switzerland.,Département des Neurosciences Fondamentales, Université de Genève, 1 rue Michel Servet, CH-1211, Genève 4, Switzerland
| | - Enrico Tam
- Dipartimento di Scienze Neurologiche, Biomediche e del Movimento, Università di Verona, Via Felice Casorati 43, 37131, Verona, Italy
| | - Guido Ferretti
- Département d'Anesthésiologie, Pharmacologie et Soins Intensifs, Hôpitaux Universitaires de Genève, 4 rue Gabrielle-Perret-Gentil, CH-1211, Genève 4, Switzerland. .,Département des Neurosciences Fondamentales, Université de Genève, 1 rue Michel Servet, CH-1211, Genève 4, Switzerland. .,Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Viale Europa 11, 25123, Brescia, Italy.
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Klassen SA, Chirico D, Dempster KS, Shoemaker JK, O'Leary DD. Role of aortic arch vascular mechanics in cardiovagal baroreflex sensitivity. Am J Physiol Regul Integr Comp Physiol 2016; 311:R24-32. [PMID: 27122371 DOI: 10.1152/ajpregu.00491.2015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 04/26/2016] [Indexed: 01/06/2023]
Abstract
Cardiovagal baroreflex sensitivity (cvBRS) measures the efficiency of the cardiovagal baroreflex to modulate heart rate in response to increases or decreases in systolic blood pressure (SBP). Given that baroreceptors are located in the walls of the carotid sinuses (CS) and aortic arch (AA), the arterial mechanics of these sites are important contributors to cvBRS. However, the relative contribution of CS and AA mechanics to cvBRS remains unclear. This study employed sex differences as a model to test the hypothesis that differences in cvBRS between groups would be explained by the vascular mechanics of the AA but not the CS. Thirty-six young, healthy, normotensive individuals (18 females; 24 ± 2 yr) were recruited. cvBRS was measured using transfer function analysis of the low-frequency region (0.04-0.15 Hz). Ultrasonography was performed at the CS and AA to obtain arterial diameters for the measurement of distensibility. Local pulse pressure (PP) was taken at the CS using a hand-held tonometer, whereas AA PP was estimated using a transfer function of brachial PP. Both cvBRS (25 ± 11 vs. 19 ± 7 ms/mmHg, P = 0.04) and AA distensibility (16.5 ± 6.0 vs. 10.5 ± 3.8 mmHg(-1) × 10(-3), P = 0.02) were greater in females than males. Sex differences in cvBRS were eliminated after controlling for AA distensibility (P = 0.19). There were no sex differences in CS distensibility (5.32 ± 2.3 vs. 4.63 ± 1.3 mmHg(-1) × 10(-3), P = 0.32). The present data demonstrate that AA mechanics are an important contributor to differences in cvBRS.
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Affiliation(s)
- Stephen A Klassen
- Faculty of Applied Health Sciences, Brock University, St. Catharines, Ontario, Canada; Brock-Niagara Centre for Health and Well-Being, Brock University, St. Catharines, Ontario, Canada; and
| | - Daniele Chirico
- Faculty of Applied Health Sciences, Brock University, St. Catharines, Ontario, Canada; Brock-Niagara Centre for Health and Well-Being, Brock University, St. Catharines, Ontario, Canada; and
| | - Kylie S Dempster
- Faculty of Applied Health Sciences, Brock University, St. Catharines, Ontario, Canada; Brock-Niagara Centre for Health and Well-Being, Brock University, St. Catharines, Ontario, Canada; and
| | - J Kevin Shoemaker
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada
| | - Deborah D O'Leary
- Faculty of Applied Health Sciences, Brock University, St. Catharines, Ontario, Canada; Brock-Niagara Centre for Health and Well-Being, Brock University, St. Catharines, Ontario, Canada; and
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Taylor CE, Willie CK, Ainslie PN, Tzeng YC. Assessment of human baroreflex function using carotid ultrasonography: what have we learnt? Acta Physiol (Oxf) 2014; 211:297-313. [PMID: 24739079 DOI: 10.1111/apha.12302] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 04/09/2014] [Indexed: 12/13/2022]
Abstract
The arterial baroreflex is critical to both short- and long-term regulation of blood pressure. However, human baroreflex research has been largely limited to the association between blood pressure and cardiac period (or heart rate) or indices of vascular sympathetic function. Over the past decade, emerging techniques based on carotid ultrasound imaging have allowed new means of understanding and measuring the baroreflex. In this review, we describe the assessment of the mechanical and neural components of the baroreflex through the use of carotid ultrasound imaging. The mechanical component refers to the change in carotid artery diameter in response to changes in arterial pressure, and the neural component refers to the change in R-R interval (cardiac baroreflex) or muscle sympathetic nerve activity (sympathetic baroreflex) in response to this barosensory vessel stretch. The key analytical concepts and techniques are discussed, with a focus on the assessment of baroreflex sensitivity via the modified Oxford method. We illustrate how the application of carotid ultrasound imaging has contributed to a greater understanding of baroreflex physiology in humans, covering topics such as ageing and diurnal variation, and physiological challenges including exercise, postural changes and mental stress.
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Affiliation(s)
- C. E. Taylor
- School of Science and Health; University of Western Sydney; Sydney NSW Australia
| | - C. K. Willie
- School of Health and Exercise Sciences; Centre for Heart Lung and Vascular Health; University of British Columbia Okanagan; Kelowna BC Canada
| | - P. N. Ainslie
- School of Health and Exercise Sciences; Centre for Heart Lung and Vascular Health; University of British Columbia Okanagan; Kelowna BC Canada
| | - Y.-C. Tzeng
- Cardiovascular Systems Laboratory; Centre for Translational Physiology; University of Otago; Wellington New Zealand
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15
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Phillips AA, Krassioukov AV, Ainslie PN, Cote AT, Warburton DER. Increased central arterial stiffness explains baroreflex dysfunction in spinal cord injury. J Neurotrauma 2014; 31:1122-8. [PMID: 24634993 DOI: 10.1089/neu.2013.3280] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
After cervical spinal cord injury (SCI), orthostatic hypotension and intolerance commonly ensue. The cardiovagal baroreflex plays an important role in the acute regulation of blood pressure (BP) and is associated with the onset of presyncope. The cardiovagal baroreflex is dysfunctional after SCI; however, this may be influenced by either increased stiffening of the arteries containing the stretch-receptors (which has been shown in SCI) or a more downstream neural mechanism (i.e., solitary nucleus, sinoatrial node). Identifying where along this pathway baroreflex dysfunction occurs may highlight a potential therapeutic target. This study examined the relationship between spontaneous cardiovagal baroreflex sensitivity (BRS) and common carotid artery (CCA) stiffness in those with high level SCI before and after midodrine (alpha1-agonist) administration, as well as in able-bodied controls, to evaluate: (1) the role arterial stiffening plays mediating baroreflex function after SCI and (2) the effect of normalizing BP on these parameters. Three to five min recordings of beat-by-beat BP and heart rate, as well as 30 sec duration recordings of CCA diameter were used for analysis. All participants were tested supine and during upright-tilt. Arterial stiffness (β-stiffness index) was elevated in those with SCI when upright (+12%; p<0.05). Further, β-stiffness index was negatively related to reduced BRS in those with SCI when upright (R2=0.55; p<0.05), but not in able-bodied persons. Normalizing BP did not improve BRS or CCA stiffness. This study clearly shows that reduced BRS is closely related to increased arterial stiffness in the population with SCI.
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Affiliation(s)
- Aaron A Phillips
- 1 Cardiovascular Physiology and Rehabilitation Laboratory , Physical Activity Promotion and Chronic Disease Prevention Unit, University of British Columbia , Vancouver, Canada
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16
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Horsman HM, Peebles KC, Galletly DC, Tzeng YC. Cardiac baroreflex gain is frequency dependent: insights from repeated sit-to-stand maneuvers and the modified Oxford method. Appl Physiol Nutr Metab 2013; 38:753-9. [DOI: 10.1139/apnm-2012-0444] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Helen M. Horsman
- Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, 23A Mein Street, Wellington South, New Zealand
- Department of Surgery and Anaesthesia, University of Otago, Wellington South, New Zealand
| | - Karen C. Peebles
- Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, 23A Mein Street, Wellington South, New Zealand
- Department of Surgery and Anaesthesia, University of Otago, Wellington South, New Zealand
- Department of Physiology, University of Otago, Wellington South, New Zealand
| | - Duncan C. Galletly
- Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, 23A Mein Street, Wellington South, New Zealand
| | - Yu-Chieh Tzeng
- Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, 23A Mein Street, Wellington South, New Zealand
- Department of Surgery and Anaesthesia, University of Otago, Wellington South, New Zealand
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Fukuhara M, Arima H, Ninomiya T, Hata J, Hirakawa Y, Doi Y, Yonemoto K, Mukai N, Nagata M, Ikeda F, Matsumura K, Kitazono T, Kiyohara Y. White-coat and masked hypertension are associated with carotid atherosclerosis in a general population: the Hisayama study. Stroke 2013; 44:1512-7. [PMID: 23640825 DOI: 10.1161/strokeaha.111.000704] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE On the basis of combined measurements of clinic blood pressure (CBP) and home blood pressure (HBP), blood pressure status can be divided into normotension, white-coat hypertension (WCHT), masked hypertension (MHT), and sustained hypertension (SHT). Despite the clear impact of MHT and SHT on clinical and subclinical arterial disease, uncertainty about the influence of WCHT remains. The objective of this study was to investigate the associations of WCHT, MHT, and SHT with carotid atherosclerosis in a general population. METHODS This is a cross-sectional survey of 2915 community-dwelling Japanese aged ≥ 40 years. Normotension was defined as CBP<140/90 and HBP<135/85 mm Hg; WCHT, CBP ≥ 140/90 and HBP<135/85 mm Hg; MHT, CBP<140/90 and HBP ≥ 135/85 mm Hg; and SHT, CBP ≥ 140/90 and HBP ≥ 135/85 mm Hg. Mean intima-media thickness of carotid arteries was measured using a computer-automated system, and carotid stenosis was defined as diameter stenosis ≥ 30%. RESULTS There were 1374 subjects (47.1%) with normotension, 200 (6.9%) with WCHT, 639 (21.9%) with MHT, and 702 (24.1%) with SHT. The geometric average of mean intima-media thickness was significantly higher among subjects with WCHT (0.73 mm), MHT (0.77 mm), and SHT (0.77 mm) than those with normotension (0.67 mm; all P<0.001 versus normotension). Compared with normotension, all types of hypertension were also associated with increased likelihood of carotid stenosis (age- and sex-adjusted odds ratio, 2.36 [95% confidence interval, 1.27-4.37] for WCHT, 1.95 [1.25-3.03] for MHT, and 3.02 [2.01-4.54] for SHT). These associations remained significant even after adjustment for other cardiovascular risk factors. CONCLUSIONS WCHT, as well as MHT, and SHT were associated with carotid atherosclerosis in a general Japanese population.
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Affiliation(s)
- Masayo Fukuhara
- Department of Environmental Medicine, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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Taylor CE, Willie CK, Atkinson G, Jones H, Tzeng YC. Postural influences on the mechanical and neural components of the cardiovagal baroreflex. Acta Physiol (Oxf) 2013; 208:66-73. [PMID: 23432844 DOI: 10.1111/apha.12087] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 02/05/2013] [Accepted: 02/15/2013] [Indexed: 12/22/2022]
Abstract
AIM The ability to maintain arterial blood pressure when faced with a postural challenge has implications for the occurrence of syncope and falls. It has been suggested that posture-induced declines in the mechanical component of the baroreflex response drive reductions in cardiovagal baroreflex sensitivity associated with postural stress. However, these conclusions are largely based upon spontaneous methods of baroreflex assessment, the accuracy of which has been questioned. Therefore, the aim was to engage a partially open-loop approach to explore the influence of posture on the mechanical and neural components of the baroreflex. METHODS In nine healthy participants, we measured continuous blood pressure, heart rate, RR interval and carotid artery diameter during supine and standing postures. The modified Oxford method was used to quantify baroreflex sensitivity. RESULTS In response to falling pressures, baroreflex sensitivity was similar between postures (P = 0.798). In response to rising pressures, there was an attenuated (P = 0.042) baroreflex sensitivity (mean ± SE) in the standing position (-0.70 ± 0.11 beats min(-1) mmHg(-1)) compared with supine (-0.83 ± 0.06 beats min(-1) mmHg(-1)). This was explained by a diminished (P = 0.016) neural component whilst standing (-30.17 ± 4.16 beats min(-1) mm(-1)) compared with supine (-38.23 ± 3.31 beats min(-1) mm(-1)). These effects were consistent when baroreflex sensitivity was determined using RR interval. CONCLUSION Cardiovagal baroreflex sensitivity in response to rising pressures is reduced in young individuals during postural stress. Our data suggest that the mechanical component is unaffected by standing, and the reduction in baroreflex sensitivity is driven by the neural component.
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Affiliation(s)
- C. E. Taylor
- School of Science and Health; University of Western Sydney; Sydney; NSW; Australia
| | | | - G. Atkinson
- Health and Social Care Institute; Teesside University; Middlesbrough; UK
| | - H. Jones
- Research Institute for Sport and Exercise Sciences; Liverpool John Moores University; Middlesbrough; UK
| | - Y.-C. Tzeng
- Cardiovascular Systems Laboratory; Centre for Translational Physiology; University of Otago; Wellington; New Zealand
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Schwartz CE, Medow MS, Messer Z, Stewart JM. Spontaneous fluctuation indices of the cardiovagal baroreflex accurately measure the baroreflex sensitivity at the operating point during upright tilt. Am J Physiol Regul Integr Comp Physiol 2013; 304:R1107-13. [PMID: 23576616 DOI: 10.1152/ajpregu.00559.2012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Spontaneous fluctuation indices of cardiovagal baroreflex have been suggested to be inaccurate measures of baroreflex function during orthostatic stress compared with alternate open-loop methods (e.g. neck pressure/suction, modified Oxford method). We therefore tested the hypothesis that spontaneous fluctuation measurements accurately reflect local baroreflex gain (slope) at the operating point measured by the modified Oxford method, and that apparent differences between these two techniques during orthostasis can be explained by a resetting of the baroreflex function curve. We computed the sigmoidal baroreflex function curves supine and during 70° tilt in 12 young, healthy individuals. With the use of the modified Oxford method, slopes (gains) of supine and upright curves were computed at their maxima (Gmax) and operating points. These were compared with measurements of spontaneous indices in both positions. Supine spontaneous analyses of operating point slope were similar to calculated Gmax of the modified Oxford curve. In contrast, upright operating point was distant from the centering point of the reset curve and fell on the nonlinear portion of the curve. Whereas spontaneous fluctuation measurements were commensurate with the calculated slope of the upright modified Oxford curve at the operating point, they were significantly lower than Gmax. In conclusion, spontaneous measurements of cardiovagal baroreflex function accurately estimate the slope near operating points in both supine and upright position.
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20
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Sadat U, Howarth SPS, Usman A, Taviani V, Tang TY, Graves MJ, Gillard JH. Effect of Low-and High-Dose Atorvastatin on Carotid Artery Distensibility Using Carotid Magnetic Resonance Imaging ^|^mdash;A Post-Hoc Sub Group Analysis of ATHEROMA (Atorvastatin Therapy: Effects on Reduction of Macrophage Activity) Study. J Atheroscler Thromb 2013; 20:46-56. [DOI: 10.5551/jat.12633] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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21
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Phillips AA, Bredin SSD, Cote AT, Drury CT, Warburton DER. Aortic distensibility is reduced during intense lower body negative pressure and is related to low frequency power of systolic blood pressure. Eur J Appl Physiol 2012; 113:785-92. [DOI: 10.1007/s00421-012-2489-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Accepted: 08/29/2012] [Indexed: 12/18/2022]
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Sato K, Fisher JP, Seifert T, Overgaard M, Secher NH, Ogoh S. Blood flow in internal carotid and vertebral arteries during orthostatic stress. Exp Physiol 2012; 97:1272-80. [DOI: 10.1113/expphysiol.2012.064774] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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23
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Okada Y, Galbreath MM, Jarvis SS, Bivens TB, Vongpatanasin W, Levine BD, Fu Q. Elderly blacks have a blunted sympathetic neural responsiveness but greater pressor response to orthostasis than elderly whites. Hypertension 2012; 60:842-8. [PMID: 22777937 DOI: 10.1161/hypertensionaha.112.195313] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Neural control of blood pressure (BP) has been reported to differ between young blacks and whites. We hypothesized that elderly blacks have enhanced sympathetic neural responses during orthostasis compared with elderly whites. Muscle sympathetic nerve activity, arm-cuff BP, and heart rate were recorded continuously, and cardiac output, stroke volume, and total peripheral resistance were measured intermittently during supine and 5-minute 60° upright tilt in 10 blacks (65 [SD, 4] years; 4 women) and 20 whites (68 [6] years; 8 women). We found that muscle sympathetic nerve activity burst frequency was similar between blacks and whites in the supine position (44 [10] versus 42 [7] bursts per minute) and during upright tilt (59 [11] versus 60 [9] bursts per minute; P=0.846 for race, P<0.001 for posture, and P=0.622 for interaction). However, upright total muscle sympathetic nerve activity was smaller in blacks than in whites (162 [39] versus 243 [112]%; P=0.003). Systolic BP, heart rate, cardiac output, and stroke volume were not different between groups. Diastolic BP was similar in the supine position, increased in all of the subjects during tilting; upright diastolic BP was greater in blacks than in whites (80 [10] versus 71 [7] mmHg; P=0.008). Total peripheral resistance did not differ between blacks and whites in the supine position or during upright tilt (P=0.354 for race, P<0.001 for posture, P=0.825 for interaction). Thus, elderly blacks have a blunted sympathetic neural responsiveness but enhanced pressor response to orthostasis compared with elderly whites, which may be attributable to an augmented sympathetic vascular transduction and/or nonadrenergic vasoconstrictor mechanisms (ie, angiotensin II or the venoarteriolar response).
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Affiliation(s)
- Yoshiyuki Okada
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, TX, USA
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Sugawara J, Willie CK, Miyazawa T, Komine H, Ainsle PN, Ogoh S. Effects of transient change in carotid arterial stiffness on arterial baroreflex during mild orthostatic stimulation. Artery Res 2012. [DOI: 10.1016/j.artres.2012.05.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Niizeki K, Tominaga T, Saitoh T, Nishidate I, Takahashi T, Uchida K. Effects of lower-leg rhythmic cuff inflation on cardiovascular autonomic responses during quiet standing in healthy subjects. Am J Physiol Heart Circ Physiol 2011; 300:H1923-9. [PMID: 21378141 DOI: 10.1152/ajpheart.01288.2010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To determine the effects of muscle pump function on cardiac autonomic activity in response to quiet standing, we simulated the muscle pump effect by rhythmic lower-leg cuff inflation (RCI) with four cuff pressures of 0 (sham), 40, 80, and 120 mmHg at 5 cycles/min. The R-R interval (RRI) and beat-to-beat blood pressure (BP) were acquired in healthy subjects (6 males and 5 females, aged 21-24 yr). From the continuous BP measurement, stroke volume (SV) was calculated by a pulse-contour method. Using spectral and cross-spectral analysis, RRI and systolic BP variability as well as the gain of spontaneous cardiac baroreflex sensitivity (sBRS) were estimated for the low- and high-frequency (HF) bands. Compared with the sham condition, RCI with cuff pressures of 80 and 120 mmHg led to increases in the mean RRI (P < 0.01) and HF power of RRI fluctuation (P < 0.05 for 80 mmHg and P < 0.01 for 120 mmHg) during quiet standing. Reduction in SV during standing was suppressed, and the sBRS of the HF band for standing were increased by RCI for either cuff pressure (P < 0.05 for 80 mmHg and P < 0.01 for 120 mmHg). However, at 40 mmHg RCI, these remained unchanged. These results suggest that, during standing, RCI of the lower leg increases cardiac vagal outflow when the cuff pressure is raised enough to oppose the hydrostatic-induced venous pressure in the calf.
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Affiliation(s)
- Kyuichi Niizeki
- Department of Bio-System Engineering, Graduate School of Science and Technology, Yamagata University, Yonezawa, Japan.
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Taneja I, Medow MS, Clarke DA, Ocon AJ, Stewart JM. Postural change alters autonomic responses to breath-holding. Clin Auton Res 2009; 20:65-72. [PMID: 20012144 DOI: 10.1007/s10286-009-0046-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Accepted: 11/17/2009] [Indexed: 01/10/2023]
Abstract
OBJECTIVE We used breath-holding during inspiration as a model to study the effect of pulmonary stretch on sympathetic nerve activity. METHODS Twelve healthy subjects (7 females, 5 males; 19-27 years) were tested while they performed an inspiratory breath-hold, both supine and during a 60 degrees head-up tilt (HUT 60). Heart rate (HR), mean arterial blood pressure (MAP), respiration, muscle sympathetic nerve activity (MSNA), oxygen saturation (SaO(2)) and end tidal carbon dioxide (ETCO(2)) were recorded. Cardiac output (CO) and total peripheral resistance (TPR) were calculated. RESULTS While breath-holding, ETCO(2) increased significantly from 41 +/- 2 to 60 +/- 2 Torr during supine (p < 0.05) and 38 +/- 2 Torr to 58 +/- 2 during HUT60 (p < 0.05); SaO(2) decreased from 98 +/- 1.5% to 95 +/- 1.4% supine, and from 97 +/- 1.5% to 94 +/- 1.7% during HUT60 (p = NS). MSNA showed three distinctive phases, a quiescent phase due to pulmonary stretch associated with decreased MAP, HR, CO, and TPR; a second phase of baroreflex-mediated elevated MSNA which was associated with recovery of MAP and HR only during HUT60; CO and peripheral resistance returned to baseline while supine and HUT60; a third phase of further increased MSNA activity related to hypercapnia and associated with increased TPR. INTERPRETATION Breath-holding results in initial reductions of MSNA, MAP, and HR by the pulmonary stretch reflex followed by increased sympathetic activity related to the arterial baroreflex and chemoreflex.
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Affiliation(s)
- Indu Taneja
- Department of Pediatrics, New York Medical College, Valhalla, NY, USA.
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Sola J, Chetelat O, Luprano J. Continuous monitoring of coordinated cardiovascular responses. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2009; 2008:1423-6. [PMID: 19162936 DOI: 10.1109/iembs.2008.4649433] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The continuous separate monitoring of cardiac and vascular functions provide important insights on cardiovascular regulation. In the last years several attempts have failed at demonstrating the feasibility of using Pulse Wave Velocity as a surrogate indicator of arterial blood pressure. Upon the hypothesis that the cause of PWV unreliability is vasomotor activity, in this paper we develop an extended model of lumped arterial tree that copes with changes in vessels diameter. The benefit of this approach is twofold: on the one hand one might correct the effects of vasomotor activity on the estimation of arterial blood pressure on the basis of PWV, and on the other hand one obtains continuous non-invasive estimations of Cardiac Output and Total Peripheral Resistance.
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Affiliation(s)
- Josep Sola
- Swiss Center for Electronics and Microtechnology (CSEM), 2002 Neuchâtel, Switzerland.
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Salzer DA, Medeiros PJ, Craen R, Shoemaker JK. Neurogenic-nitric oxide interactions affecting brachial artery mechanics in humans: roles of vessel distensibility vs. diameter. Am J Physiol Regul Integr Comp Physiol 2008; 295:R1181-7. [PMID: 18685062 DOI: 10.1152/ajpregu.90333.2008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this investigation was to assess the interactive influence of sympathetic activation and supplemental nitric oxide (NO) on brachial artery distensibility vs. its diameter. It was hypothesized that 1) sympathetic activation and NO competitively impact muscular conduit artery (brachial artery) mechanics, and 2) neurogenic constrictor input affects conduit vessel stiffness independently of outright changes in conduit vessel diastolic diameter. Lower body negative pressure (LBNP) and a cold pressor stress (CPT) were used to study the changes in conduit vessel mechanics when the increased sympathetic outflow occurred with and without changes in heart rate (LBNP -40 vs. -15 mmHg) and blood pressure (CPT vs. LBNP). These maneuvers were performed in the absence and presence of nitroglycerin. Neither LBNP nor CPT altered brachial artery diastolic diameter; however, distensibility was reduced by 25 to 54% in each reflex (all P < 0.05). This impact of sympathetic activation on brachial artery distensibility was not altered by nitroglycerin supplementation (21-54%; P < 0.05), although baseline diameter was increased by the exogenous NO (P < 0.05). The results indicate that sympathetic excitation can reduce the distensibility of the brachial artery independently of concurrent changes in diastolic diameter, heart rate, and blood pressure. However, exogenous NO did not minimize or reverse brachial stiffening during sympathetic activation. Therefore, sympathetic outflow appears to impact the stiffness of this conduit vessel rather than its diastolic diameter or, by inference, its local resistance to flow.
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Affiliation(s)
- Deborah A Salzer
- Neurovascular Research Laboratory, School of Kinesiology, Rm. 3110 Thames Hall, The Univ. of Western Ontario, London, ON, Canada N6A 3K7
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Moore S, David T. A model of autoregulated blood flow in the cerebral vasculature. Proc Inst Mech Eng H 2008; 222:513-30. [DOI: 10.1243/09544119jeim298] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The circle of Willis is a ring-like arterial structure located in the base of the brain, and is responsible for the distribution of oxygenated blood throughout the cerebral mass. Among the general population, approximately 50 per cent have a complete circle of Willis; for the others a multitude of possible anatomical variations are present, with absent or hypoplastic vessels being common. Certain conditions such as a build-up of atherosclerotic plaque on the arterial wall can result in ischaemic damage and stroke-like symptoms. A three-dimensional computer model has been developed based on the results of magnetic resonance imaging data, incorporating a numerical algorithm to simulate the body's autoregulation mechanism, such that oxygen delivery to the cerebral territories can be predicted in response events, leading to a reduction in cerebral blood flow. Sample results are presented for combinations of occlusion and stenosis.
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Affiliation(s)
- S Moore
- Centre for Bioengineering, Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
| | - T David
- Centre for Bioengineering, Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
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