Defining the characteristic relationship between arterial pressure and cerebral flow

Reliable assessment of cerebrovascular effectiveness in buffering against pressure fluctuations may have important implications for the timing and the outcome of therapy after adverse cerebrovascular events. Although linear approaches may indicate the presence or absence of cerebral autoregulation, they are inadequate to describe its characteristics and its effectiveness. Establishing a simple yet robust methodology to reliably measure the effectiveness of cerebral autoregulation could provide a tool to guide screening and clinical options to characterize and treat adverse cerebrovascular events associated with alterations in cerebral perfusion. To test the utility of one such methodology, an oscillatory lower body negative pressure of 30–40 mmHg was used at six frequencies from 0.03 to 0.08 Hz in 43 healthy volunteers, and the pressure-flow relation and the effectiveness of autoregulation was quantified using projection pursuit regression. Projection pursuit regression explained the majority of the relationship between pressure and cerebral blood flow fluctuations and revealed its nature consistently across individuals and across separate study days. The nature of this relationship entailed an autoregulatory region wherein slow arterial pressure fluctuations are effectively counterregulated and two passive regions wherein pressure fluctuations resulted in parallel changes in flow. The effectiveness of autoregulation was significantly reduced as pressure fluctuations became faster. These results demonstrate the characteristic relationship between arterial pressure and cerebral blood flow. Furthermore, the methodology utilized in this study provides a tool that can provide unique insight to integrated cerebrovascular control and may allow diagnosis of physiological alterations underlying impaired cerebral autoregulation.

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Assessing Cerebral Autoregulation via Oscillatory Lower Body Negative Pressure and Projection Pursuit Regression

Journal of Visualized Experiments ◽

10.3791/51082 ◽

2014 ◽

Cited By ~ 2

Author(s):

J. Andrew Taylor ◽

Can Ozan Tan ◽

J. W. Hamner

Keyword(s):

Negative Pressure ◽

Cerebral Autoregulation ◽

Lower Body Negative Pressure ◽

Projection Pursuit ◽

Lower Body ◽

Projection Pursuit Regression

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Mathematical Modelling of Cerebral Blood Circulation and Cerebral Autoregulation: Towards Preventing Intracranial Hemorrhages in Preterm Newborns

Computational and Mathematical Methods in Medicine ◽

10.1155/2014/965275 ◽

2014 ◽

Vol 2014 ◽

pp. 1-9 ◽

Cited By ~ 8

Author(s):

Renée Lampe ◽

Nikolai Botkin ◽

Varvara Turova ◽

Tobias Blumenstein ◽

Ana Alves-Pinto

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Arterial Pressure ◽

Cerebral Autoregulation ◽

Coupled Model ◽

Equation Model ◽

Polynomial Coefficients ◽

Arterial Blood ◽

Cerebral Blood Circulation ◽

Preterm Newborns

Impaired cerebral autoregulation leads to fluctuations in cerebral blood flow, which can be especially dangerous for immature brain of preterm newborns. In this paper, two mathematical models of cerebral autoregulation are discussed. The first one is an enhancement of a vascular model proposed by Piechnik et al. We extend this model by adding a polynomial dependence of the vascular radius on the arterial blood pressure and adjusting the polynomial coefficients to experimental data to gain the autoregulation behavior. Moreover, the inclusion of a Preisach hysteresis operator, simulating a hysteretic dependence of the cerebral blood flow on the arterial pressure, is tested. The second model couples the blood vessel system model by Piechnik et al. with an ordinary differential equation model of cerebral autoregulation by Ursino and Lodi. An optimal control setting is proposed for a simplified variant of this coupled model. The objective of the control is the maintenance of the autoregulatory function for a wider range of the arterial pressure. The control can be interpreted as the effect of a medicament changing the cerebral blood flow by, for example, dilation of blood vessels. Advanced numerical methods developed by the authors are applied for the numerical treatment of the control problem.

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Dynamic cerebral autoregulation is preserved during acute head-down tilt

Journal of Applied Physiology ◽

10.1152/japplphysiol.00524.2003 ◽

2003 ◽

Vol 95 (4) ◽

pp. 1439-1445 ◽

Cited By ~ 17

Author(s):

William H. Cooke ◽

Guy L. Pellegrini ◽

Olga A. Kovalenko

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Arterial Pressure ◽

Flow Velocity ◽

Blood Flow Velocity ◽

Cerebral Autoregulation ◽

Cerebral Blood Flow Velocity ◽

Spectral Power ◽

Low Frequency ◽

Dynamic Cerebral Autoregulation

Complete ganglion blockade alters dynamic cerebral autoregulation, suggesting links between systemic autonomic traffic and regulation of cerebral blood flow velocity. We tested the hypothesis that acute head-down tilt, a physiological maneuver that decreases systemic sympathetic activity, would similarly disrupt normal dynamic cerebral autoregulation. We studied 10 healthy young subjects (5 men and 5 women; age 21 ± 0.88 yr, height 169 ± 3.1 cm, and weight 76 ± 6.1 kg). ECG, beat-by-beat arterial pressure, respiratory rate, end-tidal CO2 concentration, and middle cerebral blood flow velocity were recorded continuously while subjects breathed to a metronome. We recorded data during 5-min periods and averaged responses from three Valsalva maneuvers with subjects in both the supine and -10° head-down tilt positions (randomized). Controlled-breathing data were analyzed in the frequency domain with power spectral analysis. The magnitude of input-output relations were determined with cross-spectral techniques. Head-down tilt significantly reduced Valsalva phase IV systolic pressure overshoot from 36 ± 4.0 (supine position) to 25 ± 4.0 mmHg (head down) ( P = 0.03). Systolic arterial pressure spectral power at the low frequency decreased from 5.7 ± 1.6 (supine) to 4.4 ± 1.6 mmHg2 (head down) ( P = 0.02), and mean arterial pressure spectral power at the low frequency decreased from 3.3 ± 0.79 (supine) to 2.0 ± 0.38 mmHg2 (head down) ( P = 0.05). Head-down tilt did not affect cerebral blood flow velocity or the transfer function magnitude and phase angle between arterial pressure and cerebral blood flow velocity. Our results show that in healthy humans, mild physiological manipulation of autonomic activity with acute head-down tilt has no effect on the ability of the cerebral vasculature to regulate flow velocity.

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Cerebral hemodynamics: a mathematical model including autoregulation, baroreflex and extracranial peripheral circulation

10.1101/2021.06.11.448061 ◽

2021 ◽

Author(s):

Francisco Ambrosio Garcia ◽

Deusdedit Lineu Spavieri Junior ◽

Andreas Linninger

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Mean Arterial Pressure ◽

Arterial Pressure ◽

Cerebral Autoregulation ◽

Peripheral Circulation ◽

Flow Regulation ◽

Pressure Waves ◽

Vascular Bed ◽

Blood Flow Regulation

Increasing evidence supports that cerebral autoregulation and mean arterial pressure regulation via baroreflex contribute to cerebral blood flow regulation. It is unclear whether the extracranial vascular bed of the head and neck helps reestablishing cerebral blood flow during changes in mean arterial pressure. Current computational models of cerebral blood flow regulation do not address the relationships between the intracranial and extracranial blood flow dynamics. We present a model of cerebral autoregulation, extracranial peripheral circulation and baroreflex control of heart rate and of peripheral vasculature that was included to the model of intracranial dynamics proposed by Linninger et al. (2009), which incorporates the fully coupled blood, cerebrospinal fluid and brain parenchyma systems. Autoregulation was modelled as being pressure-mediated at the arteries and arterioles and flow-mediated at the microcirculation. During simulations of a bout of acute hypotension, cerebral blood flow returns rapidly to baseline levels with a very small overshoot, whereas the blood flow to the peripheral circulation of the head and neck suffers a prolonged suppression in accordance with experimental evidence. The inclusion of baroreflex regulation at the extracranial vascular bed had a negligible effect on cerebral blood flow regulation during dynamic changes in mean arterial pressure. Moreover, the results suggest that the extracranial blood flow carries only modest information about cerebral blood flow in dynamic situations in which cerebral autoregulation is preserved and mean arterial pressure suffers alterations. This information is likely higher when the autoregulation is impaired. Steady-state cerebral blood flow in the model is kept within normal ranges despite variations in mean arterial pressure from 50 to 175 mmHg. By inputting aortic pressure waves from individuals with increasing arterial rigidity, increasing arterial systolic and pulse pressures, the model predicts the generation of intracranial pressure waves with accordingly increasing peaks and amplitudes.

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Transfer function analysis of dynamic cerebral autoregulation in humans

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1998.274.1.h233 ◽

1998 ◽

Vol 274 (1) ◽

pp. H233-H241 ◽

Cited By ~ 237

Author(s):

Rong Zhang ◽

Julie H. Zuckerman ◽

Cole A. Giller ◽

Benjamin D. Levine

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Transfer Function ◽

Arterial Pressure ◽

Cerebral Autoregulation ◽

Coherence Function ◽

Frequency Range ◽

Cuff Deflation ◽

Transfer Function Analysis ◽

Acute Hypotension

To test the hypothesis that spontaneous changes in cerebral blood flow are primarily induced by changes in arterial pressure and that cerebral autoregulation is a frequency-dependent phenomenon, we measured mean arterial pressure in the finger and mean blood flow velocity in the middle cerebral artery (V˙MCA) during supine rest and acute hypotension induced by thigh cuff deflation in 10 healthy subjects. Transfer function gain, phase, and coherence function between changes in arterial pressure andV˙MCA were estimated using the Welch method. The impulse response function, calculated as the inverse Fourier transform of this transfer function, enabled the calculation of transient changes inV˙MCA during acute hypotension, which was compared with the directly measured change in V˙MCA during thigh cuff deflation. Beat-to-beat changes inV˙MCA occurred simultaneously with changes in arterial pressure, and the autospectrum of V˙MCA showed characteristics similar to arterial pressure. Transfer gain increased substantially with increasing frequency from 0.07 to 0.20 Hz in association with a gradual decrease in phase. The coherence function was >0.5 in the frequency range of 0.07–0.30 Hz and <0.5 at <0.07 Hz. Furthermore, the predicted change inV˙MCA was similar to the measuredV˙MCA during thigh cuff deflation. These data suggest that spontaneous changes inV˙MCA that occur at the frequency range of 0.07–0.30 Hz are related strongly to changes in arterial pressure and, furthermore, that short-term regulation of cerebral blood flow in response to changes in arterial pressure can be modeled by a transfer function with the quality of a high-pass filter in the frequency range of 0.07–0.30 Hz.

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Faculty Opinions recommendation of Assessment of dynamic cerebral autoregulation and cerebrovascular CO2 reactivity in ageing by measurements of cerebral blood flow and cortical oxygenation.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.718215725.793489058 ◽

2013 ◽

Author(s):

James Duffin

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Cerebral Autoregulation ◽

Co2 Reactivity ◽

Cortical Oxygenation ◽

Cerebrovascular Co2 Reactivity ◽

Dynamic Cerebral Autoregulation

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Autoregulation of Cerebral Blood Flow to Changes in Arterial Pressure in Mild Alzheimer's Disease

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.2010.135 ◽

2010 ◽

Vol 30 (11) ◽

pp. 1883-1889 ◽

Cited By ~ 17

Author(s):

Allyson R Zazulia ◽

Tom O Videen ◽

John C Morris ◽

William J Powers

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Arterial Pressure ◽

The Elderly ◽

Local Defect ◽

Clinical Dementia Rating ◽

Positron Emission ◽

Before And After

Studies in transgenic mice overexpressing amyloid precursor protein (APP) demonstrate impaired autoregulation of cerebral blood flow (CBF) to changes in arterial pressure and suggest that cerebrovascular dysfunction may be critically important in the development of pathological Alzheimer's disease (AD). Given the relevance of such a finding for guiding hypertension treatment in the elderly, we assessed autoregulation in individuals with AD. Twenty persons aged 75±6 years with very mild or mild symptomatic AD (Clinical Dementia Rating 0.5 or 1.0) underwent 15O-positron emission tomography (PET) CBF measurements before and after mean arterial pressure (MAP) was lowered from 107±13 to 92±9 mm Hg with intravenous nicardipine; 11C-PIB-PET imaging and magnetic resonance imaging (MRI) were also obtained. There were no significant differences in mean CBF before and after MAP reduction in the bilateral hemispheres (−0.9±5.2 mL per 100 g per minute, P=0.4, 95% confidence interval (CI)=−3.4 to 1.5), cortical borderzones (−1.9±5.0 mL per 100 g per minute, P=0.10, 95% CI=−4.3 to 0.4), regions of T2W-MRI-defined leukoaraiosis (−0.3±4.4 mL per 100 g per minute, P=0.85, 95% CI=−3.3 to 3.9), or regions of peak 11C-PIB uptake (−2.5±7.7 mL per 100 g per minute, P=0.30, 95% CI=−7.7 to 2.7). The absence of significant change in CBF with a 10 to 15 mm Hg reduction in MAP within the normal autoregulatory range demonstrates that there is neither a generalized nor local defect of autoregulation in AD.

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