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Labrecque L, Burma JS, Roy MA, Smirl JD, Brassard P. Reproducibility and diurnal variation of the directional sensitivity of the cerebral pressure-flow relationship in men and women. J Appl Physiol (1985) 2021; 132:154-166. [PMID: 34855525 DOI: 10.1152/japplphysiol.00653.2021] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cerebral pressure-flow relationship has directional sensitivity, meaning the augmentation in cerebral blood flow is attenuated when mean arterial pressure (MAP) increases vs MAP decreases. We employed repeated squat-stands (RSS) to quantify it using a novel metric. However, its within-day reproducibility and the impacts of diurnal variation and biological sex are unknown. Study aims were to evaluate this metric for: 1) within-day reproducibility and diurnal variation in middle (MCA; ∆MCAvT/∆MAPT) and posterior cerebral arteries (PCA; ∆PCAvT/∆MAPT); 2) sex differences. ∆MCAvT/∆MAPT and ∆PCAvT/∆MAPT were calculated at seven time-points (08:00-17:00) in 18 participants (8 women; 24 ± 3 yrs) using the minimum-to-maximum MCAv or PCAv and MAP for each RSS at 0.05 Hz and 0.10 Hz. Relative metric values were also calculated (%MCAvT/%MAPT, %PCAvT/%MAPT). Intraclass correlation coefficient (ICC) evaluated reproducibility, which was good (0.75-0.90) to excellent (>0.90). Time-of-day impacted ∆MCAvT/∆MAPT (0.05 Hz: p = 0.002; 0.10 Hz: p = 0.001), %MCAvT/%MAPT (0.05 Hz: p = 0.035; 0.10 Hz: p = 0.009), and ∆PCAvT/∆MAPT (0.05 Hz: p = 0.024), albeit with small/negligible effect sizes. MAP direction impacted both arteries' metric at 0.10 Hz (all p < 0.024). Sex differences in the MCA only (p = 0.003) vanished when reported in relative terms. These findings demonstrate this metric is reproducible throughout the day in the MCA and PCA and is not impacted by biological sex.
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Affiliation(s)
- Lawrence Labrecque
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada.,Research center of the Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada
| | - Joel S Burma
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada.,Concussion Research Laboratory, Faculty of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Marc-Antoine Roy
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada.,Research center of the Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada
| | - Jonathan David Smirl
- Cerebrovascular Concussion Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Integrated Concussion Research Program, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.,Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada.,Concussion Research Laboratory, Faculty of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Patrice Brassard
- Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada.,Research center of the Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada
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2
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Labrecque L, Drapeau A, Rahimaly K, Imhoff S, Brassard P. Dynamic cerebral autoregulation and cerebrovascular carbon dioxide reactivity in middle and posterior cerebral arteries in young endurance-trained women. J Appl Physiol (1985) 2021; 130:1724-1735. [PMID: 33955257 DOI: 10.1152/japplphysiol.00963.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The integrated responses regulating cerebral blood flow are understudied in women, particularly in relation to potential regional differences. In this study, we compared dynamic cerebral autoregulation (dCA) and cerebrovascular reactivity to carbon dioxide (CVRco2) in the middle (MCA) and posterior cerebral arteries (PCA) in 11 young endurance-trained women (age, 25 ± 4 yr; maximal oxygen uptake, 48.1 ± 4.1 mL·kg-1·min-1). dCA was characterized using a multimodal approach including a sit-to-stand and a transfer function analysis (TFA) of forced blood pressure oscillations (repeated squat-stands executed at 0.05 Hz and 0.10 Hz). The hyperoxic rebreathing test was utilized to characterize CVRco2. Upon standing, the percent reduction in blood velocity per percent reduction in mean arterial pressure during initial orthostatic stress (0-15 s after sit-to-stand), the onset of the regulatory response, and the rate of regulation did not differ between MCA and PCA (all P > 0.05). There was an ANOVA effect of anatomical location for TFA gain (P < 0.001) and a frequency effect for TFA phase (P < 0.001). However, normalized gain was not different between arteries (P = 0.18). Absolute CVRco2 was not different between MCA and PCA (1.55 ± 0.81 vs. 1.30 ± 0.49 cm·s-1/Torr, P = 0.26). Relative CVRco2 was 39% lower in the MCA (2.16 ± 1.02 vs. 3.00 ± 1.09%/Torr, P < 0.01). These findings indicate that the cerebral pressure-flow relationship appears to be similar between the MCA and the PCA in young endurance-trained women. The absence of regional differences in absolute CVRco2 could be women specific, although a direct comparison with a group of men will be necessary to address that issue.NEW & NOTEWORTHY Herein, we describe responses from two major mechanisms regulating cerebral blood flow with a special attention on regional differences in young endurance-trained women. The novel findings are that dynamic cerebral autoregulation and absolute cerebrovascular reactivity to carbon dioxide appear similar between the middle and posterior cerebral arteries of these young women.
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Affiliation(s)
- Lawrence Labrecque
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Quebec City, Québec, Canada
| | - Audrey Drapeau
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Quebec City, Québec, Canada
| | - Kevan Rahimaly
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Quebec City, Québec, Canada
| | - Sarah Imhoff
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Quebec City, Québec, Canada
| | - Patrice Brassard
- Department of Kinesiology, Faculty of Medicine, Université Laval, Quebec City, Québec, Canada.,Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Quebec City, Québec, Canada
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3
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Favre ME, Lim V, Falvo MJ, Serrador JM. Cerebrovascular reactivity and cerebral autoregulation are improved in the supine posture compared to upright in healthy men and women. PLoS One 2020; 15:e0229049. [PMID: 32119678 PMCID: PMC7051088 DOI: 10.1371/journal.pone.0229049] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 01/28/2020] [Indexed: 12/04/2022] Open
Abstract
Cerebrovascular reactivity and cerebral autoregulation are two major mechanisms that regulate cerebral blood flow. Both mechanisms are typically assessed in either supine or seated postures, but the effects of body position and sex differences remain unclear. This study examined the effects of body posture (supine vs. seated vs. standing) on cerebrovascular reactivity during hyper and hypocapnia and on cerebral autoregulation during spontaneous and slow-paced breathing in healthy men and women using transcranial Doppler ultrasonography of the middle cerebral artery. Results indicated significantly improved cerebrovascular reactivity in the supine compared with seated and standing postures (supine = 3.45±0.67, seated = 2.72±0.53, standing = 2.91±0.62%/mmHg, P<0.0167). Similarly, cerebral autoregulatory measures showed significant improvement in the supine posture during slow-paced breathing. Transfer function measures of gain significantly decreased and phase significantly increased in the supine posture compared with seated and standing postures (gain: supine = 1.98±0.56, seated = 2.37±0.53, standing = 2.36±0.71%/mmHg; phase: supine = 59.3±21.7, seated = 39.8±12.5, standing = 36.5±9.7°; all P<0.0167). In contrast, body posture had no effect on cerebral autoregulatory measures during spontaneous breathing. Men and women had similar cerebrovascular reactivity and similar cerebral autoregulation during both spontaneous and slow-paced breathing. These data highlight the importance of making comparisons within the same body position to ensure there is not a confounding effect of posture.
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Affiliation(s)
- Michelle E. Favre
- Department of Pharmacology, Physiology and Neuroscience, Rutgers Biomedical and Health Sciences, Newark, New Jersey, United States of America
| | - Valerie Lim
- Department of Pharmacology, Physiology and Neuroscience, Rutgers Biomedical and Health Sciences, Newark, New Jersey, United States of America
| | - Michael J. Falvo
- Department of Pharmacology, Physiology and Neuroscience, Rutgers Biomedical and Health Sciences, Newark, New Jersey, United States of America
- Department of Physical Medicine and Rehabilitation, Rutgers Biomedical and Health Sciences, Newark, New Jersey, United States of America
- Department of Veterans Affairs, War Related Illness and Injury Study Center, East Orange, New Jersey, United States of America
| | - Jorge M. Serrador
- Department of Pharmacology, Physiology and Neuroscience, Rutgers Biomedical and Health Sciences, Newark, New Jersey, United States of America
- Department of Cardiovascular Electronics, National University of Ireland Galway, Galway, Ireland
- * E-mail:
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4
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Herrington BA, Thrall SF, Mann LM, Tymko MM, Day TA. The effect of steady-state CO 2 on regional brain blood flow responses to increases in blood pressure via the cold pressor test. Auton Neurosci 2019; 222:102581. [PMID: 31654818 DOI: 10.1016/j.autneu.2019.102581] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 07/08/2019] [Accepted: 08/19/2019] [Indexed: 10/26/2022]
Abstract
The pressure-passive cerebrovasculature is affected by alterations in cerebral perfusion pressure (CPP) and arterial blood gases (e.g., pressure of arterial [Pa]CO2), where acute changes in either stimulus can influence cerebral blood flow (CBF). The effect of superimposed increases in CPP at different levels of steady-state PaCO2 on regional CBF regulation is unclear. In 17 healthy participants, we simultaneously recorded continuous heart rate (electrocardiogram), blood pressure (finometer), pressure of end-tidal CO2 (PETCO2; gas analyzer), and middle (MCA) and posterior (PCA) cerebral artery blood velocity (CBV; transcranial Doppler ultrasound). Three separate CPTs were administered by passive immersion of both feet into 0-1 °C of ice water for 3-min under three randomized and coached steady-state PETCO2 conditions: normocapnia (room air), hypocapnia (-10 Torr; hyperventilation) and hypercapnia (+9 Torr; 5% inspired CO2;). CBV responses were calculated as the absolute difference (∆) between baseline and mean MCAv and PCAv during the 3-min CPT. Both the ∆MCAv and ∆PCAv responses to the CPT were larger under hypercapnic conditions. The absolute ∆MCAv response was larger than the ∆PCAv during the CPT across all three CO2 trials. Cerebrovascular CO2 reactivity (CVR) was larger in the MCA than PCA in both CPT and baseline conditions, but there were no differences in CVR between CPT and baseline conditions. Our data indicate that (a) increases in CO2 increases the CBV responses to a CPT, (b) the anterior cerebrovasculature is more responsive to a CPT-induced increases in MAP, and (c) although unchanged during a CPT, CVR is larger in the anterior cerebral circulation.
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Affiliation(s)
- Brittney A Herrington
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada
| | - Scott F Thrall
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada
| | - Leah M Mann
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada
| | - Michael M Tymko
- Centre for Heart, Lung and Vascular Health, University of British Columbia, British Columbia, Canada
| | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Canada.
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Scherle Matamoros C, Rivero Rodríguez D. Transcranial Doppler ultrasound measurements of cerebral hemodynamic parameters in healthy volunteers at 2850 meters altitude. RADIOLOGIA 2019. [DOI: 10.1016/j.rxeng.2019.06.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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6
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Scherle Matamoros CE, Rivero Rodríguez D. Transcranial Doppler ultrasound measurements of cerebral hemodynamic parameters in healthy volunteers at 2850 meters altitude. RADIOLOGIA 2019; 61:405-411. [PMID: 31164236 DOI: 10.1016/j.rx.2019.04.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 02/13/2019] [Accepted: 04/10/2019] [Indexed: 10/26/2022]
Abstract
BACKGROUND Transcranial Doppler ultrasound (TDU) is useful in cerebrovascular patients. TDU findings are operator-dependent; they can also be influenced by anatomical and physiological variables as well as by the altitude at which the study is done. OBJECTIVE To report the cerebral hemodynamic parameters measured by TDU in subjects who live in Quito, Ecuador (altitude 2850 meters). MATERIAL AND METHODS We recruited 47 volunteers with no history or clinical evidence of stroke, hypertension, metabolic disorders, or hematologic disorders; 2 patients were excluded because they did not have a viable cranial window for TDU study. Thus, we recorded mean cerebral blood flow velocity, peak systolic flow velocity, end-diastolic flow velocity, and pulsatility indices in 45 patients (28 (62.2%) women; mean age, 35.9 years). We recorded patients' age, sex, and hematocrit. We analyzed cerebrovascular hemodynamic parameters by sex and age group. RESULTS No significant differences between hemispheres were observed in mean flow velocities, except in the anterior cerebral arteries with right predominance. Flow velocities were higher in women and in the youngest age group. No significant differences in the pulsatility indices were found between sexes or between age groups. The flow velocities in this series are lower than those reported for other series. CONCLUSIONS The hemodynamic parameters in this series are lower than in other series and are influenced by the altitude, age, and sex.
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Affiliation(s)
- C E Scherle Matamoros
- Especialistas en neurología, Servicio de neurología, Unidad de ictus, Hospital de especialidades Eugenio Espejo, Universidad San Francisco de Quito USFQ, Quito, Ecuador.
| | - D Rivero Rodríguez
- Especialistas en neurología, Servicio de neurología, Unidad de ictus, Hospital de especialidades Eugenio Espejo, Universidad San Francisco de Quito USFQ, Quito, Ecuador
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7
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Labrecque L, Rahimaly K, Imhoff S, Paquette M, Le Blanc O, Malenfant S, Drapeau A, Smirl JD, Bailey DM, Brassard P. Dynamic cerebral autoregulation is attenuated in young fit women. Physiol Rep 2019; 7:e13984. [PMID: 30652420 PMCID: PMC6335382 DOI: 10.14814/phy2.13984] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 12/28/2018] [Indexed: 02/07/2023] Open
Abstract
Young women exhibit higher prevalence of orthostatic hypotension with presyncopal symptoms compared to men. These symptoms could be influenced by an attenuated ability of the cerebrovasculature to respond to rapid blood pressure (BP) changes [dynamic cerebral autoregulation (dCA)]. The influence of sex on dCA remains unclear. dCA in 11 fit women (25 ± 2 years) and 11 age-matched men (24 ± 1 years) was compared using a multimodal approach including a sit-to-stand (STS) and forced BP oscillations (repeated squat-stand performed at 0.05 and 0.10 Hz). Prevalence of initial orthostatic hypotension (IOH; decrease in systolic ≥ 40 mmHg and/or diastolic BP ≥ 20 mmHg) during the first 15 sec of STS was determined as a functional outcome. In women, the decrease in mean middle cerebral artery blood velocity (MCAvmean ) following the STS was greater (-20 ± 8 vs. -11 ± 7 cm sec-1 ; P = 0.018) and the onset of the regulatory change (time lapse between the beginning of the STS and the increase in the conductance index (MCAvmean /mean arterial pressure) was delayed (P = 0.007). Transfer function analysis gain during 0.05 Hz squat-stand was ~48% higher in women (6.4 ± 1.3 vs. 3.8 ± 2.3 cm sec-1 mmHg-1 ; P = 0.017). Prevalence of IOH was comparable between groups (women: 4/9 vs. men: 5/9, P = 0.637). These results indicate the cerebrovasculature of fit women has an attenuated ability to react to rapid changes in BP in the face of preserved orthostasis, which could be related to higher resting cerebral blood flow allowing women to better face transient hypotension.
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Affiliation(s)
- Lawrence Labrecque
- Department of KinesiologyFaculty of MedicineUniversité LavalQuébecCanada
- Research center of the Institut universitaire de cardiologie et de pneumologie de QuébecQuébecCanada
| | - Kevan Rahimaly
- Department of KinesiologyFaculty of MedicineUniversité LavalQuébecCanada
- Research center of the Institut universitaire de cardiologie et de pneumologie de QuébecQuébecCanada
| | - Sarah Imhoff
- Department of KinesiologyFaculty of MedicineUniversité LavalQuébecCanada
- Research center of the Institut universitaire de cardiologie et de pneumologie de QuébecQuébecCanada
| | - Myriam Paquette
- Department of KinesiologyFaculty of MedicineUniversité LavalQuébecCanada
- Research center of the Institut universitaire de cardiologie et de pneumologie de QuébecQuébecCanada
| | - Olivier Le Blanc
- Department of KinesiologyFaculty of MedicineUniversité LavalQuébecCanada
- Research center of the Institut universitaire de cardiologie et de pneumologie de QuébecQuébecCanada
| | - Simon Malenfant
- Department of KinesiologyFaculty of MedicineUniversité LavalQuébecCanada
- Research center of the Institut universitaire de cardiologie et de pneumologie de QuébecQuébecCanada
| | - Audrey Drapeau
- Department of KinesiologyFaculty of MedicineUniversité LavalQuébecCanada
- Research center of the Institut universitaire de cardiologie et de pneumologie de QuébecQuébecCanada
| | - Jonathan D. Smirl
- Concussion Research LaboratoryHealth and Exercise SciencesUniversity of British Columbia OkanaganBritish ColumbiaCanada
| | - Damian M. Bailey
- Neurovascular Research LaboratoryFaculty of Life Sciences and EducationUniversity of South WalesSouth WalesUnited Kingdom
| | - Patrice Brassard
- Department of KinesiologyFaculty of MedicineUniversité LavalQuébecCanada
- Research center of the Institut universitaire de cardiologie et de pneumologie de QuébecQuébecCanada
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8
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van Campen CLMC, Verheugt FWA, Visser FC. Cerebral blood flow changes during tilt table testing in healthy volunteers, as assessed by Doppler imaging of the carotid and vertebral arteries. Clin Neurophysiol Pract 2018; 3:91-95. [PMID: 30215015 PMCID: PMC6133915 DOI: 10.1016/j.cnp.2018.02.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Revised: 02/17/2018] [Accepted: 02/20/2018] [Indexed: 01/13/2023] Open
Abstract
Extracranial cerebral artery Doppler imaging show CBF changes during tilt testing. Total CBF during tilt testing decreases 6% in healthy volunteers. Flow decrease of internal carotid and vertebral arteries during tilting is similar.
Objectives Using different techniques, reduction of cerebral blood flow (CBF) during orthostatic stress were demonstrated. One study reported flow reduction of the right internal carotid (ICA) and vertebral (VA) artery during orthostatic stress by Doppler imaging, with different effects on the 2 vessels. Global CBF changes, using this technique, have not been reported. Therefore, flow of the ICA, VA and global CBF were measured during head-up tilt testing. Methods 33 healthy volunteers underwent tilt testing. At three time points (supine, half way and at the end of the test) Doppler imaging of the ICA and VA was performed, as well as PetCO2 measurements. Results Global CBF was significantly reduced by 4.5 ± 2.8% halfway the test and by 6.0 ± 3.4% at the end. All 4 artery flows were significantly reduced during the tilt, without differences between them. Despite small changes in PetCO2 there was a significant relation between de CBF decrease and PetCO2 decrease (p < 0.05). Conclusions Orthostatic stress in HV results in a small but significant reduction of CBF by a homogenous reduction in the four cerebral vessels and is modulated by PetCO2 changes. Significance CBF changes can be measured during tilt testing using Doppler VA and ICA imaging.
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Affiliation(s)
| | - Freek W A Verheugt
- Radboud UMC, Geert Grooteplein Zuid 10, 6525 GA Nijmegen, The Netherlands
| | - Frans C Visser
- Stichting CardioZorg, Planetenweg 5, 2132 HN Hoofddorp, The Netherlands
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9
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Washio T, Sasaki H, Ogoh S. Transcranial Doppler-determined change in posterior cerebral artery blood flow velocity does not reflect vertebral artery blood flow during exercise. Am J Physiol Heart Circ Physiol 2017; 312:H827-H831. [PMID: 28188214 DOI: 10.1152/ajpheart.00676.2016] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 01/30/2017] [Accepted: 01/31/2017] [Indexed: 11/22/2022]
Abstract
We examined whether a change in posterior cerebral artery flow velocity (PCAv) reflected the posterior cerebral blood flow in healthy subjects during both static and dynamic exercise. PCAv and vertebral artery (VA) blood flow, as an index of posterior cerebral blood flow, were continuously measured during an exercise trial using transcranial Doppler (TCD) ultrasonography and Doppler ultrasound, respectively. Static handgrip exercise significantly increased both PCAv and VA blood flow. Increasing intensity of dynamic exercise further increased VA blood flow from moderate exercise, while PCAv decreased to almost resting level. During both static and dynamic exercise, the PCA cerebrovascular conductance (CVC) index significantly decreased from rest (static and high-intensity dynamic exercise, -11.5 ± 12.2% and -18.0 ± 16.8%, means ± SD, respectively) despite no change in the CVC of VA. These results indicate that vasoconstriction occurred at PCA but not VA during exercise-induced hypertension. This discrepancy in vascular response to exercise between PCA and VA may be due to different cerebral arterial characteristics. Therefore, to determine the effect of exercise on posterior cerebral circulation, at least, we need to carefully consider which cerebral artery to measure, regardless of exercise mode.NEW & NOTEWORTHY We examined whether transcranial Doppler-determined flow velocity in the posterior cerebral artery can be used as an index of cerebral blood flow during exercise. However, the changes in posterior cerebral artery flow velocity during exercise do not reflect vertebral artery blood flow.
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Affiliation(s)
- Takuro Washio
- Department of Biomedical Engineering, Toyo University, Kawagoe-shi, Japan
| | - Hiroyuki Sasaki
- Department of Biomedical Engineering, Toyo University, Kawagoe-shi, Japan
| | - Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe-shi, Japan
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10
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Lewis NCS, Bain AR, MacLeod DB, Wildfong KW, Smith KJ, Willie CK, Sanders ML, Numan T, Morrison SA, Foster GE, Stewart JM, Ainslie PN. Impact of hypocapnia and cerebral perfusion on orthostatic tolerance. J Physiol 2014; 592:5203-19. [PMID: 25217373 PMCID: PMC4262334 DOI: 10.1113/jphysiol.2014.280586] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 09/01/2014] [Indexed: 12/25/2022] Open
Abstract
We examined two novel hypotheses: (1) that orthostatic tolerance (OT) would be prolonged when hyperventilatory-induced hypocapnia (and hence cerebral hypoperfusion) was prevented; and (2) that pharmacological reductions in cerebral blood flow (CBF) at baseline would lower the 'CBF reserve', and ultimately reduce OT. In study 1 (n = 24; aged 25 ± 4 years) participants underwent progressive lower-body negative pressure (LBNP) until pre-syncope; end-tidal carbon dioxide (P ET , CO 2) was clamped at baseline levels (isocapnic trial) or uncontrolled. In study 2 (n = 10; aged 25 ± 4 years), CBF was pharmacologically reduced by administration of indomethacin (INDO; 1.2 mg kg(-1)) or unaltered (placebo) followed by LBNP to pre-syncope. Beat-by-beat measurements of middle cerebral artery blood flow velocity (MCAv; transcranial Doppler), heart rate (ECG), blood pressure (BP; Finometer) and end-tidal gases were obtained continuously. In a subset of subjects' arterial-to-jugular venous differences were obtained to examine the independent impact of hypocapnia or cerebral hypoperfusion (following INDO) on cerebral oxygen delivery and extraction. In study 1, during the isocapnic trial, P ET , CO 2 was successfully clamped at baseline levels at pre-syncope (38.3 ± 2.7 vs. 38.5 ± 2.5 mmHg respectively; P = 0.50). In the uncontrolled trial, P ET , CO 2 at pre-syncope was reduced by 10.9 ± 3.9 mmHg (P ≤ 0.001). Compared to the isocapnic trial, the decline in mean MCAv was 15 ± 4 cm s(-1) (35%; P ≤ 0.001) greater in the uncontrolled trial, yet the time to pre-syncope was comparable between trials (544 ± 130 vs. 572 ± 180 s; P = 0.30). In study 2, compared to placebo, INDO reduced resting MCAv by 19 ± 4 cm s(-1) (31%; P ≤ 0.001), but time to pre-syncope remained similar between trials (placebo: 1123 ± 138 s vs. INDO: 1175 ± 212 s; P = 0.53). The brain extracted more oxygen in face of hypocapnia (34% to 53%) or cerebral hypoperfusion (34% to 57%) to compensate for reductions in delivery. In summary, cerebral hypoperfusion either at rest or induced by hypocapnia at pre-syncope does not impact OT, probably due to a compensatory increase in oxygen extraction.
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Affiliation(s)
- Nia C S Lewis
- Centre for Heart, Lung and Vascular Health, University of British Columbia, Okanagan, Canada
| | - Anthony R Bain
- Centre for Heart, Lung and Vascular Health, University of British Columbia, Okanagan, Canada
| | - David B MacLeod
- Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA
| | - Kevin W Wildfong
- Centre for Heart, Lung and Vascular Health, University of British Columbia, Okanagan, Canada
| | - Kurt J Smith
- Centre for Heart, Lung and Vascular Health, University of British Columbia, Okanagan, Canada
| | - Christopher K Willie
- Centre for Heart, Lung and Vascular Health, University of British Columbia, Okanagan, Canada
| | | | - Tianne Numan
- MIRA, University of Twente, Enschede, The Netherlands
| | - Shawnda A Morrison
- Centre for Heart, Lung and Vascular Health, University of British Columbia, Okanagan, Canada Jozef Stefan Institute, Ljubljana, Slovenia
| | - Glen E Foster
- Centre for Heart, Lung and Vascular Health, University of British Columbia, Okanagan, Canada
| | | | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, University of British Columbia, Okanagan, Canada
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11
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Staalsø JM, Edsen T, Kotinis A, Romner B, Springborg JB, Olsen NV. Association of the NOS3 intron-4 VNTR polymorphism with aneurysmal subarachnoid hemorrhage. J Neurosurg 2014; 121:587-92. [PMID: 24972130 DOI: 10.3171/2014.5.jns131572] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT The nitric oxide system has been linked to the pathogenesis of aneurysmal subarachnoid hemorrhage (SAH). The authors performed a case-control study to investigate the association between SAH and common genetic variants within the endothelial nitric oxide synthase gene (NOS3). METHODS Three hundred thirty-three Caucasian SAH patients and 498 controls were genotyped for the -922A > G (rs 1800779), -786T > C (rs2070744), and 894G > T (rs1799983) single nucleotide polymorphisms and the intron-4 27-bp variable number of tandem repeats polymorphism (27-bp-VNTR). RESULTS The b/b (5 repeats) genotype of the 27-bp-VNTR was overrepresented in cases (77%) versus controls (69%) (p = 0.02). In male patients the b/b genotype was found in 85% compared with 67% in male controls, whereas in women, the frequencies were 73% and 72%, respectively. This corresponds to an odds ratio of 2.8 (95% CI 1.5-5.6, p = 0.0005) for SAH in men with the b/b genotype versus men with a/b or a/a. In women, no such association was found (OR 1.1, 95% CI 0.7-1.6, p = 0.76). Stepwise logistic regression including arterial hypertension, smoking, sex, and age with interactions yielded similar effect estimates of the 27-bp-VNTR. Haplotype analysis revealed that no single haplotype containing the b-allele was responsible for the observed genotype effect. CONCLUSIONS The authors' results suggest that the NOS3 27-bp-VNTR b/b genotype independent of other risk factors act in concert with male sex to substantially increase risk of SAH. This effect is not mediated by any single NOS3 haplotype.
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Lin YJ, Po HL, Hsu HY, Chung CP, Sheng WY, Hu HH. Transcranial Doppler studies on cerebral autoregulation suggest prolonged cerebral vasoconstriction in a subgroup of patients with orthostatic intolerance. ULTRASOUND IN MEDICINE & BIOLOGY 2011; 37:1554-1560. [PMID: 21821354 DOI: 10.1016/j.ultrasmedbio.2011.06.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 06/17/2011] [Accepted: 06/21/2011] [Indexed: 05/31/2023]
Abstract
We studied the cerebral autoregulation in a subgroup of patients with orthostatic intolerance, who exhibited excessively decreased middle cerebral artery flow velocity (MCAFV) on transcranial Doppler sonography (TCD) during head-up tilt (HUT) test but without orthostatic hypotension or postural tachycardia. Twenty patients and 20 age- and sex-matched controls underwent Valsalva maneuver (VM) and HUT test with simultaneous monitoring of MCAFV by TCD and blood pressure, heart rate recordings. The pulsatility index (PI), cerebrovascular resistance (CVR) and autoregulatory indices were calculated. During HUT, patients had marked MCAFV reduction (-29.0 ± 5.25% vs. -8.01 ± 4.37%), paradoxically decreased PI (0.68 ± 0.17 vs. 0.96 ± 0.28) but increased CVR (45.7 ± 16.7% vs. 14.3 ± 12.6%). The MCAFV decreased similarly during early phase II of VM in both groups but did not recover to baseline in patients during late phase II, phase III and less overshoot in phase IV (-11 ± 16.7% vs. +2.2 ± 17.9 %; -15.4 ± 16.5% vs. -2.4 ± 17.8% and 16.7 ± 22.9% vs. 38.7 ± 26.5%, respectively). We concluded that in these patients, cerebrovascular vasoconstriction in response to physiologic stimulation was normal but relaxation during and after stimulation were impaired, indicating prolonged cerebral vasoconstriction.
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Affiliation(s)
- Ya-Ju Lin
- Institute of Emergency and Critical Care Medicine, National Yang-Ming University, Taipei, Taiwan
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