Cerebral autoregulation(CA)is the mechanism that maintains stable cerebral blood flow(CBF)despite fluctuations in systemic blood pressure,crucial for brain homeostasis.Recent evidence highlights distinct regional vari...Cerebral autoregulation(CA)is the mechanism that maintains stable cerebral blood flow(CBF)despite fluctuations in systemic blood pressure,crucial for brain homeostasis.Recent evidence highlights distinct regional variations in CA between the anterior(carotid)and posterior(vertebrobasilar)circulations.Noninvasive neuromonitoring techniques,such as transcranial Doppler,transfer function analysis,and near-infrared spectroscopy,facilitate the dynamic assessment of CBF and autoregulation.Studies indicate a robust autoregulatory capacity in the anterior circulation,characterized by rapid adjustments in vascular resistance.On the contrary,the posterior circulation,mainly supplied by the vertebral arteries,may have a lower autoregulatory capacity.in acute brain injuries such as intracerebral and subarachnoid hemorrhage,and traumatic brain injuries,dynamic CA can be significantly altered in the posterior circulation.Proposed physiological mechanisms of impaired CA in the posterior circulation include:(1)Decreased sympathetic innervation of the vasculature impairing compensatory vasoreactivity;(2)Endothelial dysfunction;(3)Increased cerebral metabolic rate of oxygen consumption within the visual cortex causing CBFmetabolism(i.e.,neurovascular)uncoupling;and(4)Impaired blood-brain barrier integrity leading to impaired astrocytic mediated release of vasoactive substances(e.g.nitric oxide,potassium,and calcium ions).Furthermore,more research is needed on the effects of collateral circulation,as well as the circle of Willis variants,such as the fetal-type posterior cerebral artery,on dynamic CA.Improving our understanding of these mechanisms is crucial to improving the diagnosis,prognosis,and management of various cerebrovascular disorders.展开更多
[SUMMARY] TTTT is a non-invasive and new investigative examination,and a most important method of clinical diagnosis for many diseases,specially for orthostatic syncope,autonomic failure,intracranial hypertension,neur...[SUMMARY] TTTT is a non-invasive and new investigative examination,and a most important method of clinical diagnosis for many diseases,specially for orthostatic syncope,autonomic failure,intracranial hypertension,neurodegenerative diseases,CVAs and so on.At the same time,TCD technique for non-invasive monitoring of CBFV has also provided a new tool for investigating CA.In clinical circumstance,we may carry on assessment of dynamic CA by TTTT,and this kind of method has been proved to be appropriate to examine patients and monitor.we can choose different tilt positions by tilt-table according to the different demands for clinical diagnosis or researches,and record the different appearances of various index signs,we can take advantage of the technique of transfer function analysis of power spectrum between spontaneous changes in CBF and other factors(such as arterial pressure) to do research on the specific mechanism of impaired CA.展开更多
Obstructive sleep apnea(OSA)and central sleep apnea(CSA)are two main types of sleep disordered breathing(SDB).While the changes in cerebral hemodynamics triggered by OSA events have been well studied using near-infrar...Obstructive sleep apnea(OSA)and central sleep apnea(CSA)are two main types of sleep disordered breathing(SDB).While the changes in cerebral hemodynamics triggered by OSA events have been well studied using near-infrared spectroscopy(NIRS),they are essentially unknown in CSA in adults.Therefore,in this study,we compared the changes in cerebral oxygenation between OSA and CSA events in adult patients using NIRS.Cerebral tissue oxygen saturation(StO_(2))in 13 severe SDB patients who had both CSA and OSA events was measured using frequency-domain NIRS.The changes in cerebral StO_(2)desaturation and blood volume(BV)in the¯rst hour of natural sleep were compared between different types of respiratory events(i.e.,277 sleep hypopneas,161 OSAs and 113 CSAs)with linear mixed-effect models controlling for confounders.All respiratory events occurred during non-rapid eye movement(NREM)sleep.We found that apnea events induced greater cerebral desaturations and BV°uctuations compared to hypopneas,but there was no difference between OSA and CSA.These results suggest that cerebral autoregulation in our patients are still capable to counteract the pathomechanisms of apneas,in particularly the negative intrathoracic pressure(ITP)caused by OSA events.Otherwise larger BV°uctuations in OSA compared to CSA should be observed due to the negative ITP that reduces cardiac stroke volume and leads to lower systematic blood supply.Our study suggests that OSA and CSA may have similar impact on cerebral oxygenation during NREM sleep in adult patients with SDB.展开更多
A novel hemodynamic model has been recently introduced,which provides analytical relation-ships between the changes in cerebral blood volume(CBV),cerebral blood flow(CBF),andcerebral metabolic rate of oxy gen(CMRO2),a...A novel hemodynamic model has been recently introduced,which provides analytical relation-ships between the changes in cerebral blood volume(CBV),cerebral blood flow(CBF),andcerebral metabolic rate of oxy gen(CMRO2),and associat ed changes in the tissue concentrationsof oxy-and deoxy-hemoglobin(AO and AD)measured with near-infrared,spectroscopy(NIRS)[S.Fantini,Neuroimage 85,202-221(2014)].This novel model can be applied tomeasurements of the amplit ude and phase of induced hemodynamic oscillations as a function ofthe frequency of oscillation,realizing the novel technique of coherent hemodynamics spectroscopy(CHS)[S.Fantini,Neuroimage 85,202-221(2014);M.L.Pierro et al.,Neuroimage 85,222-233(2014)]:In a previous work,,we have demonstrated an in vivo application of CiHS on hunanSubjects during paced breat hing[M.L.Pierro et al,Neuroimage 85,222-233(2014)].In thiswork,we present a new analysis of the collected data duringpaced breat hing based on a slightlyrevised formulation of the hemodynamic model and ann efficient fitting procedure.While we haveinitially treated all 12 model parameindeependent,we have found that,in this new in-plementation of CHS,the number of independent is eight.In this article,we identifythe eight independent model parameters and,we show that our previous results are consistentwith the new formulation,once the individual parameters of the earlier analysis are combinedinto the new set of independent parameters.展开更多
文摘Cerebral autoregulation(CA)is the mechanism that maintains stable cerebral blood flow(CBF)despite fluctuations in systemic blood pressure,crucial for brain homeostasis.Recent evidence highlights distinct regional variations in CA between the anterior(carotid)and posterior(vertebrobasilar)circulations.Noninvasive neuromonitoring techniques,such as transcranial Doppler,transfer function analysis,and near-infrared spectroscopy,facilitate the dynamic assessment of CBF and autoregulation.Studies indicate a robust autoregulatory capacity in the anterior circulation,characterized by rapid adjustments in vascular resistance.On the contrary,the posterior circulation,mainly supplied by the vertebral arteries,may have a lower autoregulatory capacity.in acute brain injuries such as intracerebral and subarachnoid hemorrhage,and traumatic brain injuries,dynamic CA can be significantly altered in the posterior circulation.Proposed physiological mechanisms of impaired CA in the posterior circulation include:(1)Decreased sympathetic innervation of the vasculature impairing compensatory vasoreactivity;(2)Endothelial dysfunction;(3)Increased cerebral metabolic rate of oxygen consumption within the visual cortex causing CBFmetabolism(i.e.,neurovascular)uncoupling;and(4)Impaired blood-brain barrier integrity leading to impaired astrocytic mediated release of vasoactive substances(e.g.nitric oxide,potassium,and calcium ions).Furthermore,more research is needed on the effects of collateral circulation,as well as the circle of Willis variants,such as the fetal-type posterior cerebral artery,on dynamic CA.Improving our understanding of these mechanisms is crucial to improving the diagnosis,prognosis,and management of various cerebrovascular disorders.
文摘[SUMMARY] TTTT is a non-invasive and new investigative examination,and a most important method of clinical diagnosis for many diseases,specially for orthostatic syncope,autonomic failure,intracranial hypertension,neurodegenerative diseases,CVAs and so on.At the same time,TCD technique for non-invasive monitoring of CBFV has also provided a new tool for investigating CA.In clinical circumstance,we may carry on assessment of dynamic CA by TTTT,and this kind of method has been proved to be appropriate to examine patients and monitor.we can choose different tilt positions by tilt-table according to the different demands for clinical diagnosis or researches,and record the different appearances of various index signs,we can take advantage of the technique of transfer function analysis of power spectrum between spontaneous changes in CBF and other factors(such as arterial pressure) to do research on the specific mechanism of impaired CA.
基金supported by Clinic Barmelweid Scientific Foundation.The data acquisition work was supported by the Research Fund of the Swiss Lung Association No.2014-22.
文摘Obstructive sleep apnea(OSA)and central sleep apnea(CSA)are two main types of sleep disordered breathing(SDB).While the changes in cerebral hemodynamics triggered by OSA events have been well studied using near-infrared spectroscopy(NIRS),they are essentially unknown in CSA in adults.Therefore,in this study,we compared the changes in cerebral oxygenation between OSA and CSA events in adult patients using NIRS.Cerebral tissue oxygen saturation(StO_(2))in 13 severe SDB patients who had both CSA and OSA events was measured using frequency-domain NIRS.The changes in cerebral StO_(2)desaturation and blood volume(BV)in the¯rst hour of natural sleep were compared between different types of respiratory events(i.e.,277 sleep hypopneas,161 OSAs and 113 CSAs)with linear mixed-effect models controlling for confounders.All respiratory events occurred during non-rapid eye movement(NREM)sleep.We found that apnea events induced greater cerebral desaturations and BV°uctuations compared to hypopneas,but there was no difference between OSA and CSA.These results suggest that cerebral autoregulation in our patients are still capable to counteract the pathomechanisms of apneas,in particularly the negative intrathoracic pressure(ITP)caused by OSA events.Otherwise larger BV°uctuations in OSA compared to CSA should be observed due to the negative ITP that reduces cardiac stroke volume and leads to lower systematic blood supply.Our study suggests that OSA and CSA may have similar impact on cerebral oxygenation during NREM sleep in adult patients with SDB.
基金supported by the National Institutes of Health(Grant No.R01-CA154774)by the National Science Foundation(Award No.IIs-1065154).
文摘A novel hemodynamic model has been recently introduced,which provides analytical relation-ships between the changes in cerebral blood volume(CBV),cerebral blood flow(CBF),andcerebral metabolic rate of oxy gen(CMRO2),and associat ed changes in the tissue concentrationsof oxy-and deoxy-hemoglobin(AO and AD)measured with near-infrared,spectroscopy(NIRS)[S.Fantini,Neuroimage 85,202-221(2014)].This novel model can be applied tomeasurements of the amplit ude and phase of induced hemodynamic oscillations as a function ofthe frequency of oscillation,realizing the novel technique of coherent hemodynamics spectroscopy(CHS)[S.Fantini,Neuroimage 85,202-221(2014);M.L.Pierro et al.,Neuroimage 85,222-233(2014)]:In a previous work,,we have demonstrated an in vivo application of CiHS on hunanSubjects during paced breat hing[M.L.Pierro et al,Neuroimage 85,222-233(2014)].In thiswork,we present a new analysis of the collected data duringpaced breat hing based on a slightlyrevised formulation of the hemodynamic model and ann efficient fitting procedure.While we haveinitially treated all 12 model parameindeependent,we have found that,in this new in-plementation of CHS,the number of independent is eight.In this article,we identifythe eight independent model parameters and,we show that our previous results are consistentwith the new formulation,once the individual parameters of the earlier analysis are combinedinto the new set of independent parameters.
文摘目的:量化评价血管迷走性晕厥血压下降过程中的脑血流自动调节功能,用于在晕厥相关症状出现前预测其发生。方法:选取20位直立倾斜试验证实的血管迷走性晕厥患者,另选取20名正常对照者。所有被试在直立倾斜试验前都要平卧30 min,同时使用TCD 2 MHz Doppler监测探头监测双侧大脑中动脉血流速度,心电监护监测心率,使用连续每搏血压监测指端无创连续血压。在进行10 min基线数据采集后,被试继续进行70°直立倾斜试验,每位被试至少直立30 min,或在30 min内出现晕厥发作或晕厥前兆时或当被试出现突发血压下降≥20 mmHg时终止检查。利用多模态血流血压分析(multimodal pressure-flow analysis,MMPF)的非线性动力学方法对不同时相的脑血流自动调节功能进行分析。利用信号分析的方法将脑血流信号记录中的重搏切迹深度量化测量,定义新的预测参数晕厥指数(syncope index,SI)用于评估血压变化时的脑血管张力。结果:病例组在血管迷走性晕厥发生时的晕厥指数与倾斜试验开始时的基线数值相比存在明显下降(0.16±0.10 vs. 0.27±0.10, P <0.01),而对照组在倾斜试验结束时的晕厥指数与倾斜试验开始时的基线数值相比差异无统计学意义。对于血管迷走性晕厥组的患者,在晕厥发生前3 min,搏动指数与基线数据相比未见明显变化( P >0.05),但晕厥指数已出现明显下降( 0.23± 0.07 vs. 0.29±0.07, P <0.01)。结论:当血管迷走性晕厥发生时脑血流动态调节功能衰竭,小血管张力的丧失与脑血流自动调节功能的丧失是相关的;晕厥指数可以作为提前预测血管迷走性晕厥发生的一个有用的参数。
