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Zhou H, Hou X, Cheng R, Zhao Y, Qiu J. Effects of Nasal Continuous Positive Airway Pressure on Cerebral Hemodynamics in Preterm Infants. Front Pediatr 2020; 8:487. [PMID: 32974250 PMCID: PMC7472537 DOI: 10.3389/fped.2020.00487] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 07/13/2020] [Indexed: 11/24/2022] Open
Abstract
Background: To evaluate the effects of pressure levels on cerebral hemodynamics in premature infants receiving nasal continuous positive airway pressure (nCPAP) during the first 3 days of life. Methods: Forty-four preterm infants treated with nCPAP were divided into two groups: very preterm infants [gestational age 1 (GA1), GA < 32 weeks, n = 24] and moderate/late preterm infants (GA2 group, GA 32-37 weeks, n = 20). During monitoring, pressure levels were set at 4 → 6 → 8 → 4 cmH2O, and cerebral hemodynamics was assessed by near-infrared spectroscopy (NIRS). Vital signs, peripheral oxygen saturation (SpO2) and transcutaneous carbon dioxide pressure (TcPCO2) were simultaneously recorded. Results: Pressures of 4-8 cmH2O had no significant influence on cerebral hemodynamics, TcPCO2, SpO2 or other vital signs. The tissue oxygenation index (TOI), the difference between oxygenated hemoglobin (ΔHbO2) and deoxygenated hemoglobin (ΔHHb) (ΔHbD), and cerebral blood volume (ΔCBV) were all significantly positively correlated with gestational and post-natal age, with fluctuations being greater in the GA1 group. ΔHbD and ΔCBV were also significantly positively correlated with TcPCO2. Conclusions: No significant differences were observed in cerebral hemodynamics when the nCPAP pressure was set to 4-8 cmH2O.
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Affiliation(s)
- Han Zhou
- Department of Newborn Infants, Children's Hospital of Nanjing Medical University, Nanjing, China.,Department of Paediatrics, Nantong First People's Hospital, Nantong, China
| | - Xuewen Hou
- Department of Newborn Infants, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Rui Cheng
- Department of Newborn Infants, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Youyan Zhao
- Department of Newborn Infants, Children's Hospital of Nanjing Medical University, Nanjing, China
| | - Jie Qiu
- Department of Newborn Infants, Children's Hospital of Nanjing Medical University, Nanjing, China
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Wang S, Wang L, Jing P, Guo P, Zheng W, Li J, Qian M. Aberrant patterns of brain cerebral blood flow in Chinese han first-episode drug-naïve depressive patients with and without a family history of depression. Oncotarget 2017; 8:79906-79913. [PMID: 29108372 PMCID: PMC5668105 DOI: 10.18632/oncotarget.20306] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 08/04/2017] [Indexed: 01/18/2023] Open
Abstract
A positive family history plays a key role in the brain pathology of depression patients and previous research has confirmed that disturbed mood maintenance may be related to abnormal regional cerebral blood flow (rCBF). However, little is known about whether the rCBF is different between depression patients with and without family histories. To address this question, we examined the rCBF in drug-naïve, first-episode depression patients with and without family histories of depression using a 3D pseudo-continuous arterial spin-labelling technique. We found that decreased rCBF was predominantly observed in the patients without family histories, while decreased and increased rCBF co-existed in patients with family histories. The observed brain regions with altered rCBF were associated with affection processing, such as the prefrontal, occipital and insular areas. However the patterns of rCBF alteration observed in the present study were different from those found in previous studies where patients were compared with healthy controls. Our present findings, together with the findings from previous studies have prompted the need of a long-term follow-up study to characterize the brain features of the developmental trajectory of depression and investigate the targets for precise, personalized treatments.
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Affiliation(s)
- Shikai Wang
- Department of Psychological Medicine, Huzhou Third People’s Hospital, Huzhou, China
| | - Lina Wang
- Department of Psychological Medicine, Tianjin Anding Hospital, Tianjin, China
| | - Ping Jing
- Department of Psychological Medicine, Wenzhou Seventh People’s Hospital, Wenzhou, China
| | - Ping Guo
- Department of Psychological Medicine, Huzhou Third People’s Hospital, Huzhou, China
| | - Weifang Zheng
- Department of Psychological Medicine, Wenzhou Seventh People’s Hospital, Wenzhou, China
| | - Jie Li
- Department of Psychological Medicine, Tianjin Anding Hospital, Tianjin, China
| | - Mincai Qian
- Department of Psychological Medicine, Huzhou Third People’s Hospital, Huzhou, China
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Yiallourou TI, Schmid Daners M, Kurtcuoglu V, Haba-Rubio J, Heinzer R, Fornari E, Santini F, Sheffer DB, Stergiopulos N, Martin BA. Continuous positive airway pressure alters cranial blood flow and cerebrospinal fluid dynamics at the craniovertebral junction. INTERDISCIPLINARY NEUROSURGERY 2015. [DOI: 10.1016/j.inat.2015.06.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Hayen A, Herigstad M, Kelly M, Okell TW, Murphy K, Wise RG, Pattinson KTS. The effects of altered intrathoracic pressure on resting cerebral blood flow and its response to visual stimulation. Neuroimage 2012; 66:479-88. [PMID: 23108273 PMCID: PMC3547172 DOI: 10.1016/j.neuroimage.2012.10.049] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Revised: 10/04/2012] [Accepted: 10/06/2012] [Indexed: 11/19/2022] Open
Abstract
Investigating how intrathoracic pressure changes affect cerebral blood flow (CBF) is important for a clear interpretation of neuroimaging data in patients with abnormal respiratory physiology, intensive care patients receiving mechanical ventilation and in research paradigms that manipulate intrathoracic pressure. Here, we investigated the effect of experimentally increased and decreased intrathoracic pressures upon CBF and the stimulus-evoked CBF response to visual stimulation. Twenty healthy volunteers received intermittent inspiratory and expiratory loads (plus or minus 9cmH2O for 270s) and viewed an intermittent 2Hz flashing checkerboard, while maintaining stable end-tidal CO2. CBF was recorded with transcranial Doppler sonography (TCD) and whole-brain pseudo-continuous arterial spin labeling magnetic resonance imaging (PCASL MRI). Application of inspiratory loading (negative intrathoracic pressure) showed an increase in TCD-measured CBF of 4% and a PCASL-measured increase in grey matter CBF of 5%, but did not alter mean arterial pressure (MAP). Expiratory loading (positive intrathoracic pressure) did not alter CBF, while MAP increased by 3%. Neither loading condition altered the perfusion response to visual stimulation in the primary visual cortex. In both loading conditions localized CBF increases were observed in the somatosensory and motor cortices, and in the cerebellum. Altered intrathoracic pressures, whether induced experimentally, therapeutically or through a disease process, have possible significant effects on CBF and should be considered as a potential systematic confound in the interpretation of perfusion-based neuroimaging data.
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Affiliation(s)
- Anja Hayen
- Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK.
| | - Mari Herigstad
- Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK.
| | - Michael Kelly
- Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK.
| | - Thomas W Okell
- Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK.
| | - Kevin Murphy
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Park Place, CF10 3AT, Cardiff, UK.
| | - Richard G Wise
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Park Place, CF10 3AT, Cardiff, UK.
| | - Kyle T S Pattinson
- Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK.
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Stolz E, Fox BC, Hoffmann O, Gerriets T, Blaes F, Kraus J, Kaps M. Cranial venous outflow under lower body positive and negative pressure conditions and head-up and -down tilts. J Neuroimaging 2008; 19:31-6. [PMID: 18798778 DOI: 10.1111/j.1552-6569.2008.00250.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Although there exists a large body of knowledge on the regulation of arterial cerebral hemodynamics, little is known about the cerebral venous outflow (CVO). METHODS In 19 healthy volunteers, the middle cerebral artery and the straight sinus were examined using transcranial Doppler sonography. Arterial and venous mean flow velocities (aFV(mean), vFV(mean), respectively) were registered continuously while applying lower body positive (LBPP) or negative (LBNP) pressure of 30 mmHg and performing head-down (-20 degrees , HDT) and -up (+30 degrees , HUT) tilt manoeuvres. The arterial blood pressure was registered simultaneously with a noninvasive finger blood pressure monitor. Relative changes in parameters compared to the proceeding no-pressure, no-tilt baseline were used for analysis. RESULTS While aFV(mean) did not change significantly, vFV(mean) inc reased during LBPP by 10.5 +/- 2.9% and decreased during LBNP by 15.1 +/- 3.5% (mean +/- standard error of mean [SEM], P < .01). HUT resulted in a decrease in vFV(mean) by 25.5 +/- 3.3% and HDT, in an increase by 7.8 +/- 3.2% (P < .01) without alteration in aFV(mean). This may imply a decrease of cerebral blood volume (CBV) during LBPP and HDT and an increase during LBNP and HUT. CONCLUSIONS CVO cannot be neglected when studying cerebral hemodynamics because it might affect the CBV.
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Affiliation(s)
- Erwin Stolz
- Department of Neurology, Justus-Liebig-University, Giessen, Germany.
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Dani C, Bertini G, Cecchi A, Corsini I, Pratesi S, Rubaltelli FF. Brain haemodynamic effects of nasal continuous airway pressure in preterm infants of less than 30 weeks' gestation. Acta Paediatr 2007; 96:1421-5. [PMID: 17714539 DOI: 10.1111/j.1651-2227.2007.00453.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
AIM To evaluate the hypothesis that increasing levels of nasal continuous positive airway pressure (NCPAP) may decrease cerebral blood volume (CBV) and cerebral oxygenation in infants with gestational age (GA) less than 30 weeks. METHODS We prospectively studied a cohort of preterm infants treated with NCPAP using near-infrared spectroscopy (NIRS). The pressure limit of NCPAP was set at 2, 4, 6 and again 2 cm H(2)O for 30 min. RESULTS Changes of pressure levels were not followed by significant changes of oxygenated haemoglobin (O(2)Hb), deoxygenated haemoglobin (HHb), cerebral intravascular oxygenation (HbD), oxidized-reduced cytochrome aa3 (CtOx), tissue oxygenation index (TOI), tissue haemoglobin index (THI) and cerebral blood volume (DeltaCBV). CONCLUSION NCPAP at 2-6 cm H(2)O pressure levels did not affect cerebral oxygenation and CBV. These findings are reassuring and confirm the safety of NCPAP in preterm infants with GA less than 30 weeks.
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Affiliation(s)
- Carlo Dani
- Section of Neonatology, Department of Surgical and Medical Critical Care, Careggi University Hospital of Florence, Viale Morgagni 85, 50134 Florence, Italy.
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Højlund Rasmussen J, Mantoni T, Belhage B, Pott FC. Influence of upper body position on middle cerebral artery blood velocity during continuous positive airway pressure breathing. Eur J Appl Physiol 2007; 101:369-75. [PMID: 17638008 DOI: 10.1007/s00421-007-0513-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/25/2007] [Indexed: 10/23/2022]
Abstract
Continuous positive airway pressure (CPAP) is a treatment modality for pulmonary oxygenation difficulties. CPAP impairs venous return to the heart and, in turn, affects cerebral blood flow (CBF) and augments cerebral blood volume (CBV). We considered that during CPAP, elevation of the upper body would prevent a rise in CBV, while orthostasis would challenge CBF. To determine the body position least affecting indices of CBF and CBV, the middle cerebral artery mean blood velocity (MCA V(mean)) and the near-infrared spectroscopy determined frontal cerebral hemoglobin content (cHbT) were evaluated in 11 healthy subjects during CPAP at different body positions (15 degrees head-down tilt, supine, 15 degrees, 30 degrees and 45 degrees upper body elevation). In the supine position, 10 cmH(2)O of CPAP reduced MCA V(mean) by 9 +/- 3% and increased cHbT by 4 +/- 2 micromol/L (mean +/- SEM); (P < 0.05). In the head-down position, CPAP increased cHbT to 13 +/- 2 micromol/L but left MCA V(mean) unchanged. Upper body elevation by 15 degrees attenuated the CPAP associated reduction in MCA V(mean) (-7 +/- 2%), while cHbT returned to baseline (1 +/- 2 micromol/L). With larger elevation of the upper body MCA V(mean) decreased progressively to -17 +/- 3%, while cHbT remained unchanged from baseline. These results suggest that upper body elevation by approximately 15 degrees during 10 cmH(2)O CPAP prevents an increase in cerebral blood volume with minimal effect on cerebral blood flow.
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Affiliation(s)
- J Højlund Rasmussen
- Bispebjerg Hospital Research Unit for Anaesthesia and Intensive Care, Department of Anaesthesia, Bispebjerg Hospital, University of Copenhagen, 2400, Copenhagen NV, Denmark.
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Zaramella P, Freato F, Grazzina N, Saraceni E, Vianello A, Chiandetti L. Does helmet CPAP reduce cerebral blood flow and volume by comparison with Infant Flow driver CPAP in preterm neonates? Intensive Care Med 2006; 32:1613-9. [PMID: 16896862 DOI: 10.1007/s00134-006-0289-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Accepted: 06/22/2006] [Indexed: 10/24/2022]
Abstract
OBJECTIVE We compared neonatal helmet continuous positive airway pressure (CPAP) and the conventional nasal Infant Flow driver (IFD) CPAP in the noninvasive assessment of absolute cerebral blood flow (CBF) and relative cerebral blood volume changes (DeltaCBV) by near-infrared spectroscopy. DESIGN AND SETTING A randomized crossover study in a tertiary referral NICU. PATIENTS AND INTERVENTIONS Assessment of CBF and DeltaCBV in 17 very low birth weight infants with respiratory distress (median age 5 days) treated with two CPAP devices at a continuous distending pressure of 4 mbar. MEASUREMENTS AND RESULTS Neonates were studied for two consecutive 60-min periods with helmet CPAP and with IFD CPAP. Basal chromophore traces enabled DeltaCBV changes to be calculated. CBF was calculated in milliliters per 100 grams per minute from the saturation rise integral and rate of rise O(2)Hb-HHb. Median (range) CBF with helmet CPAP was 27.37 (9.47-48.20) vs. IFD CBF 34.74 (13.59-60.10)(p=0.049) and DeltaCBV 0.15 (0.09-0.28) with IFD and 0.13 (0.07-0.27) with helmet CPAP (NS). Using helmet and IFD CPAP, the neonates showed no difference in mean physiological parameters (transcutaneous carbon dioxide and oxygen tension, pulse oximetry saturation, heart rate, breathing rate, mean arterial blood pressure, desaturation rate, axillary temperature). CONCLUSION Assessing CBF and DeltaCBV measured by near-infrared spectroscopy with two CPAP devices revealed no differences in relative blood volume, but CBF was lower with helmet CPAP. Greater active vasoconstriction and/or passive capillary and/or venous vessel compression seem the most likely reason, due to a positive pressure around the head, neck, and shoulders by comparison with the airway pressure.
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Affiliation(s)
- Patrizia Zaramella
- Department of Pediatrics, University of Padova, Neonatal Intensive Care Unit, Padua, Italy.
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Muench E, Bauhuf C, Roth H, Horn P, Phillips M, Marquetant N, Quintel M, Vajkoczy P. Effects of positive end-expiratory pressure on regional cerebral blood flow, intracranial pressure, and brain tissue oxygenation*. Crit Care Med 2005; 33:2367-72. [PMID: 16215394 DOI: 10.1097/01.ccm.0000181732.37319.df] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVE Acute respiratory dysfunction frequently occurs following severe aneurysmal subarachnoid hemorrhage requiring positive end-expiratory pressure (PEEP) ventilation to maintain adequate oxygenation. High PEEP levels, however, may negatively affect cerebral perfusion. The goal of this study was, to examine the influence of various PEEP levels on intracranial pressure, brain tissue oxygen tension, regional cerebral blood flow, and systemic hemodynamic variables. DESIGN Animal research and clinical intervention study. SETTING Surgical intensive care unit of a university hospital. SUBJECTS AND PATIENTS Experiments were carried out in five healthy pigs, followed by a clinical investigation of ten patients suffering subarachnoid hemorrhage. INTERVENTIONS Under continuous monitoring of intracranial pressure, brain tissue oxygen tension, regional cerebral blood flow, mean arterial pressure, and cardiac output, PEEP was applied in increments of 5 cm H2O from 5 to 25 cm H2O in the experimental part and from baseline to 20 cm H2O in the clinical part. MEASUREMENTS AND MAIN RESULTS In animals, high PEEP levels had no adverse effect on intracranial pressure, brain tissue oxygen tension, or regional cerebral blood flow. In patients with severe subarachnoid hemorrhage, stepwise elevation of PEEP resulted in a significant decrease of mean arterial pressure and regional cerebral blood flow. Analyses of covariance revealed that these changes of regional cerebral blood flow depended on mean arterial pressure changes as a result of a disturbed cerebrovascular autoregulation. Consequently, normalization of mean arterial pressure restored regional cerebral blood flow to baseline values. CONCLUSIONS Application of high PEEP does not impair intracranial pressure or regional cerebral blood flow per se but may indirectly affect cerebral perfusion via its negative effect on macrohemodynamic variables in case of a disturbed cerebrovascular autoregulation. Therefore, following severe subarachnoid hemorrhage, a PEEP-induced decrease of mean arterial pressure should be reversed to maintain cerebral perfusion.
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Affiliation(s)
- Elke Muench
- Departments of Anesthesiology, Klinikum Mannheim, University of Heidelberg, Mannheim, Germany
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Keller E, Nadler A, Alkadhi H, Kollias SS, Yonekawa Y, Niederer P. Noninvasive measurement of regional cerebral blood flow and regional cerebral blood volume by near-infrared spectroscopy and indocyanine green dye dilution. Neuroimage 2003; 20:828-39. [PMID: 14568455 DOI: 10.1016/s1053-8119(03)00315-x] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2002] [Accepted: 05/28/2003] [Indexed: 12/16/2022] Open
Abstract
To find a suitable method for measuring regional cerebral blood flow (rCBF) rapidly at the bedside is still a matter of investigation. The purpose here was to develop a noninvasive method for bedside rCBF measurement and to validate it with a standard method such as perfusion-weighted magnetic resonance imaging (MRI). In 11 healthy volunteers 44 measurements with near-infrared spectroscopy (NIRS) and perfusion-weighted MRI without and with a mean continuous positive airway pressure (CPAP) of 10 mbar were carried out. Four (NIRS) optodes were placed bilaterally on the forehead and 25 mg indocyanine green (ICG) was injected. New algorithms were developed to calculate rCBFNIRS and rCBVNIRS. In 6 volunteers data analysis was successful. No complications associated with the method were observed. During CPAP breathing rCBFNIRS decreased from 18.5 + 6.9 16.1 + 6.2 ml/100 g/min (P = 0.034). Mean values for rCBFMRI decreased from 256 +/- 90 to 216 +/- 62 ml/100 g/min (P = 0.012). Bland and Altman plots showed that the differences did not vary in any systematic way over the range of rCBF or rCBV values assessed and 100% of differences were within the interval mean +/- 2 SD of differences. Limits of agreement (mean +/- 2 SD) were +/- 76.4 ml/100 g/min for rCBF and +/- 15.6 ml/100 g for rCBV. The NIRS ICG dye dilution technique is a promising method for serial noninvasive bedside CBF measurements. The preliminary data indicate that measurements are in agreement with values obtained by perfusion-weighted MRI.
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Affiliation(s)
- Emanuela Keller
- Department of Neurosurgery, University Hospital of Zurich, Zurich, Switzerland.
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Keller E, Nadler A, Alkadhi H. Measurement of Regional Cerebral Blood Flow by Near Infrared Spectroscopy and Indocyanine Green Dye Dilution. Intensive Care Med 2003. [DOI: 10.1007/978-1-4757-5548-0_69] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
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Lorenz IH, Kolbitsch C, Hörmann C, Schocke M, Kremser C, Zschiegner F, Felber S, Benzer A. Increasing mean airway pressure reduces functional MRI (fMRI) signal in the primary visual cortex. Magn Reson Imaging 2001; 19:7-11. [PMID: 11295340 DOI: 10.1016/s0730-725x(00)00229-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Changes in both blood flow and blood oxygenation determine the functional MRI (fMRI) signal. In the present study factors responsible for blood oxygenation (e.g., FiO(2)) were held constant so that changes in pixel count would above all reflect changes in regional cerebral blood flow (rCBF). Continuous positive airway pressure (CPAP) breathing at 12 cm H(2)O, which was previously shown to influence rCBF, was applied in human volunteers (n = 19) to investigate the sensitivity of fMRI for changes in rCBF caused by increased mean airway pressure. Increasing the mean airway pressure decreased the pixel count in the primary visual cortex (median (range)): baseline: 219 (58-425) pixels vs. CPAP (12 cm H(2)O): 92 (0-262) pixels). These findings indicate that fMRI is sensitive to detect a reduced rCBF-response in the primary visual cortex. The underlying mechanism is likely to be a reduced basal rCBF due to constriction and/or compression of postcapillary venoles during CPAP breathing. These findings are important for interpreting fMRI results in awake and in artificially respirated patients, in whom positive airway pressure is used to improve pulmonary function during the diagnostic procedure.
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Affiliation(s)
- I H Lorenz
- Department of Anesthesia and Intensive Care Medicine, University of Innsbruck, Austria
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