Search results for "Cerebral Autoregulation"
showing 10 items of 16 documents
Spectral decomposition of cerebrovascular and cardiovascular interactions in patients prone to postural syncope and healthy controls.
2022
We present a framework for the linear parametric analysis of pairwise interactions in bivariate time series in the time and frequency domains, which allows the evaluation of total, causal and instantaneous interactions and connects time- and frequency-domain measures. The framework is applied to physiological time series to investigate the cerebrovascular regulation from the variability of mean cerebral blood flow velocity (CBFV) and mean arterial pressure (MAP), and the cardiovascular regulation from the variability of heart period (HP) and systolic arterial pressure (SAP). We analyze time series acquired at rest and during the early and late phase of head-up tilt in subjects developing or…
Nonlinear effects of respiration on the crosstalk between cardiovascular and cerebrovascular control systems.
2016
Cardiovascular and cerebrovascular regulatory systems are vital control mechanisms responsible for guaranteeing homeostasis and are affected by respiration. This work proposes the investigation of cardiovascular and cerebrovascular control systems and the nonlinear influences of respiration on both regulations through joint symbolic analysis (JSA), conditioned or unconditioned on respiration. Interactions between cardiovascular and cerebrovascular regulatory systems were evaluated as well by performing correlation analysis between JSA indexes describing the two control systems. Heart period, systolic and mean arterial pressure, mean cerebral blood flow velocity and respiration were acquired…
Cerebral Blood Flow Regulation Under the Conditions of Arterial Hypoxia
1978
Pronounced arterial hypoxia induces a decrease of cerebrovascular resistance and an increase of total and regional cerebral blood flow. Under the conditions of normal arterial blood pressure and normal acid base status, the changes of both parameters commence when the oxygen tension in the arterial blood decreases below approximately 50 mm Hg. At the same time, the oxygen tension in the cerebral venous blood reaches values below approximately 28 mm Hg. Different authors [23, 28, 30, 31, 33] reported that cerebral blood flow responses to PaO2 decrease are threshold at these oxygen tensions. The threshold oxygen tension of cerebral venous blood was accorded a special significance because Noel…
Investigating the mechanisms of cardiovascular and cerebrovascular regulation in orthostatic syncope through an information decomposition strategy
2012
Some previous evidence suggests that postural related syncope is associated with defective mechanisms of cerebrovascular (CB) and cardiovascular (CV) control. We characterized the information processing in short-term CB regulation, from the variability of mean cerebral blood flow velocity (CBFV) and mean arterial pressure (AP), and in CV regulation, from the variability of heart period (HP) and systolic AP (SAP), in ten young subjects developing orthostatic syncope in response to prolonged head-up tilt testing. We exploited a novel information-theoretic approach that decomposes the information associated with a variability series into three amounts: the information stored in the series, the…
Correlation between Baroreflex Sensitivity and Cerebral Autoregulation Index in Healthy Subjects
2021
Despite the acknowledged interaction between baroreflex and cerebral autoregulation (CA), their functional relationship remains controversial. The study investigates this relationship in a healthy population undergoing an orthostatic challenge. Thirteen healthy subjects (age: 27pm 8 yrs; 5 males) underwent electrocardiogram, arterial pressure (AP) and cerebral blood flow velocity (CBFV) recordings at supine resting (REST) and during 60° head-up tilt (TILT). CA was assessed via the autoregulation index (ARI) from spontaneous variations of mean AP and mean CBFV. The cardiac control and baroreflex were evaluated via frequency domain and transfer function analyses applied to systolic AP and hea…
Cerebrovascular and cardiovascular variability interactions investigated through conditional joint transfer entropy in subjects prone to postural syn…
2017
Objective: A model-based conditional transfer entropy approach was exploited to quantify the information transfer in cerebrovascular (CBV) and cardiovascular (CV) systems in subjects prone to develop postural syncope. Approach: Spontaneous beat-to-beat variations of mean cerebral blood flow velocity (MCBFV) derived from a transcranial Doppler device, heart period (HP) derived from surface electrocardiogram, mean arterial pressure (MAP) and systolic arterial pressure (SAP) derived from finger plethysmographic arterial pressure device were monitored at rest in supine position (REST) and during 60° head-up tilt (TILT) in 13 individuals (age mean ± standard deviation: 28 ± 9 years, min-max r…
Computation of Mean Cerebral Blood Flow Velocity for the Assessment of Cerebral Autoregulation: Comparison of Different Strategies
2019
Cerebral autoregulation (CA) is a complex mechanism stabilizing cerebral blood flow (CBF) against arterial pressure (AP) changes. CBF is commonly surrogated with the CBF velocity (CBFV) recorded via transcranial Doppler device from the middle cerebral artery. Most of the studies evaluating CA compute mean CBFV (MCBFV) on a beat-to-beat basis along with mean AP (MAP), but there is not a standard approach to derive MCBFV. In this study, we compare three different strategies to calculate MCBFV: i) between two consecutive diastolic points detected on the CBFV signal (MCBFVCBFV); ii) between two consecutive diastolic points detected on the AP signal (MCBFVAP); iii) between two consecutive R-wave…
Cerebral Autoregulation in Non-Brain Injured Patients: A Systematic Review.
2021
Introduction: Cerebral autoregulation (CA) plays a fundamental role in the maintenance of adequate cerebral blood flow (CBF). CA monitoring, through direct and indirect techniques, may guide an appropriate therapeutic approach aimed at improving CBF and reducing neurological complications; so far, the role of CA has been investigated mainly in brain-injured patients. The aim of this study is to investigate the role of CA in non-brain injured patients.Methods: A systematic consultation of literature was carried out. Search terms included: “CA and sepsis,” “CA and surgery,” and “CA and non-brain injury.”Results: Our research individualized 294 studies and after screening, 22 studies were anal…
Effects of Fenoldopam on Intracranial Pressure and Hemodynamic Variables at Normal and Elevated Intracranial Pressure in Anesthetized Pigs
1994
Fenoldopam (FE), a dopamine DA1-receptor agonist, has been introduced for treatment of arterial hypertension and heart failure and for preservation of renal function. Vasodilators are generally assumed to affect all vascular beds including the cerebral circulation. We have evaluated effects of FE-induced (4 micrograms.kg-1.min-1) arterial hypotension on intracranial pressure (ICP) and intraocular pressure (IOP) under conditions of normal and increased intracranial elastance. ICP and IOP responses to hypertension were tested by infusion of angiotensin II (15 micrograms.kg-1.min-1), and the response to hypercapnia was tested by elimination and reintegration of soda lime canisters in the breat…
Transcranial Doppler ultrasound study of the effects of nitrous oxide on cerebral autoregulation during neurosurgical anesthesia: a randomized contro…
2003
Object. Nitrous oxide has an adverse effect on cerebrovascular hemodynamics. Increased intracranial pressure, cerebral blood flow (CBF), cerebral metabolic rate of O2 (CMRO2), and reduced autoregulation indices have been reported, but their magnitudes are still being debated. This study was designed to evaluate the effect of N2O on CBF and autoregulatory indexes during N2O—sevoflurane anesthesia in a prospective randomized controlled series of patients. Methods. Two groups of 20 patients were studied on the basis of the use of N2O in the anesthetic gas mixture. The transient hyperemic response test, which relies on transcranial Doppler ultrasound techniques, was used to assess cerebral hemo…