Reliability of dynamic cerebral autoregulation measurement using spontaneous fluctuations in blood pressure

2009 ◽  
Vol 116 (6) ◽  
pp. 513-520 ◽  
Author(s):  
Fiona G. Brodie ◽  
Emily R. Atkins ◽  
Thompson G. Robinson ◽  
Ronney B. Panerai
Keyword(s):  
Blood Pressure ◽  
Cerebral Autoregulation ◽  
Cerebral Blood Flow Velocity ◽  
Function Analysis ◽  
Transfer Function Analysis ◽  
Critical Closing Pressure ◽  
Subject Variability ◽  
Area Product ◽  
Spontaneous Fluctuations ◽  
Dynamic Cerebral Autoregulation

Spontaneous fluctuations in BP (blood pressure) and subsequent change in CBFV (cerebral blood flow velocity) in the MCA (middle cerebral artery) can be used to assess dynamic cerebral autoregulation using transfer function analysis; however, the reliability of this technique has not been assessed, in particular the contribution of intra-subject variability relative to inter-subject variability. Three bilateral CBFV, BP and RR interval recordings were performed in ten healthy volunteers on four separate occasions over a 2-week period. Data were analysed to provide the ARI (autoregulatory index), CBFV, RAP (resistance-area product) and CrCP (critical closing pressure). We also measured systolic and diastolic BP, and resting HR (heart rate). We calculated the SEM (standard error of measurement) and the ICC (intra-class correlation coefficient) and their 95% CIs (confidence intervals) for each parameter to assess their absolute (intra-subject) and relative (inter-subject) reliability. The CV (coefficient of variation) of SEM ranged from 1.7% (for CBFV) to 100.0% (for RAP), whereas the ICC was <0.5 for ARI, rising to >0.8 for CBFV and diastolic BP. These data demonstrate excellent absolute and relative reliability of CBFV, whereas ARI is of comparable reliability with the measurement of HR. Using these results it is possible to determine the sample size required to demonstrate a change in ARI, with a sample of 45 subjects in each group required to show a change in ARI of 1, whereas to detect a change in ARI >2 would require only 11 subjects per group. The results of the present study could be valuable to the future planning of cerebral autoregulation studies, but more work is needed to understand the determinants of intra-subject variability in autoregulatory parameters.

scholarly journals Cerebral critical closing pressure and resistance-area product: the influence of dynamic cerebral autoregulation, age, and sex

2021 ◽  
pp. 0271678X2110041
Author(s):  
Ronney B Panerai ◽  
Victoria J Haunton ◽  
Osian Llwyd ◽  
Jatinder S Minhas ◽  
Emmanuel Katsogridakis ◽  
...  
Keyword(s):  
Cerebral Autoregulation ◽  
Function Analysis ◽  
Step Response ◽  
Arterial Blood ◽  
Transfer Function Analysis ◽  
Critical Closing Pressure ◽  
Area Product ◽  
Closing Pressure ◽  
Dynamic Cerebral Autoregulation ◽  
Step Responses

Instantaneous arterial pressure-flow (or velocity) relationships indicate the existence of a cerebral critical closing pressure (CrCP), with the slope of the relationship expressed by the resistance-area product (RAP). In 194 healthy subjects (20–82 years, 90 female), cerebral blood flow velocity (CBFV, transcranial Doppler), arterial blood pressure (BP, Finapres) and end-tidal CO2 (EtCO2, capnography) were measured continuously for five minutes during spontaneous fluctuations of BP at rest. The dynamic cerebral autoregulation (CA) index (ARI) was extracted with transfer function analysis from the CBFV step response to the BP input and step responses were also obtained for the BP-CrCP and BP-RAP relationships. ARI was shown to decrease with age at a rate of −0.025 units/year in men (p = 0.022), but not in women (p = 0.40). The temporal patterns of the BP-CBFV, BP-CrCP and BP-RAP step responses were strongly influenced by the ARI (p < 0.0001), but not by sex. Age was also a significant determinant of the peak of the CBFV step response and the tail of the RAP response. Whilst the RAP step response pattern is consistent with a myogenic mechanism controlling dynamic CA, further work is needed to explore the potential association of the CrCP step response with the flow-mediated component of autoregulation.

scholarly journals Dynamic Cerebral Autoregulation Is Transiently Impaired for One Week after Large-Vessel Acute Ischemic Stroke

2015 ◽  
Vol 39 (2) ◽  
pp. 144-150 ◽  
Author(s):  
Nils H. Petersen ◽  
Santiago Ortega-Gutierrez ◽  
Andrés Reccius ◽  
Arjun Masurkar ◽  
Amy Huang ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Ischemic Stroke ◽  
Cerebral Autoregulation ◽  
Function Analysis ◽  
Large Vessel ◽  
Unaffected Side ◽  
Transfer Function Analysis ◽  
Dynamic Cerebral Autoregulation ◽  
Over Time

Background: Dynamic cerebral autoregulation (DCA) is the continuous counterregulation of cerebral blood flow to fluctuations in blood pressure. DCA can become impaired after acute stroke, but it remains unclear to what extent and over what interval this occurs. Methods: We included 28 patients (NIHSS = 12 ± 6.5, age = 68.4 ± 17.1, 16F) with acute large-vessel ischemic stroke in the middle cerebral artery territory and 29 healthy controls (mean age 54.9 ± 9, 16F). DCA was assessed by simultaneous measurement of blood pressure together with blood flow velocities using finger plethysmography/arterial catheter and transcranial Doppler over three 10-minute recordings on days 0-2, 3-6 and ≥7 days after stroke. Transfer function analysis was applied to calculate average phase shift (PS) in the low frequency range (0.06-0.12 Hz). Less PS indicated poorer autoregulation. The affected side was compared with the unaffected side and controls. Univariate comparisons of data were performed using t tests at single time points, and generalized estimating equations with an exchangeable correlation matrix to examine the change in PS over time. Results: At mean 1.3 ± 0.5 days after stroke the average PS in the affected hemisphere was 29.6 ± 10.5 vs. 42.5 ± 13 degrees in the unaffected hemisphere (p = 0.004). At 4.1 ± 1 days, the PS in affected and unaffected hemisphere was 23.2 ± 19.1 vs. 41.7 ± 18.5 degrees, respectively (p = 0.003). At mean 9.75 ± 2.2 days stroke there was no difference between the affected and the unaffected hemisphere (53.2 ± 28.2 vs. 50.7 ± 29.2 degrees, p = 0.69). Control subjects had an average PS = 47.9 ± 16.8, significantly different from patients' affected hemisphere at the first two measurements (p = 0.001), but not the third (p = 0.37). The PS in controls remained unchanged on repeat testing after an average 19.1 days (48.4 ± 17.1, p = 0.61). Using the last recording as the reference, the average PS in the affected hemisphere was -23.54 (-44.1, -3) degrees lower on recording one (p = 0.025), and -31.6 (-56.1, -7.1) degrees lower on recording two (p < 0.011). Changes in the unaffected hemisphere over time were nonsignificant. Discussion: These data suggest that dynamic cerebral autoregulation is impaired in the affected hemisphere throughout the first week after large-vessel ischemic stroke, and then normalizes by week two. These findings may have important implications for acute blood pressure management after stroke.

scholarly journals Impaired Dynamic Cerebral Autoregulation in Cerebral Venous Thrombosis

2020 ◽  
Author(s):  
Jie Chen ◽  
Jia Liu ◽  
Kehui Dong ◽  
Yilong Wang ◽  
Xingquan Zhao ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Intracranial Pressure ◽  
Venous Thrombosis ◽  
Cerebral Venous Thrombosis ◽  
Cerebral Autoregulation ◽  
Cerebral Blood Flow Velocity ◽  
Function Analysis ◽  
Arterial Blood ◽  
Transfer Function Analysis ◽  
Rate Of Recovery

Abstract Background: Cerebral autoregulation is crucial in traumatic brain injury, which might be used for determination the optimal intracranial pressure. Cerebral venous thrombosis is a cerebral vascular disease with the feature of high intracranial pressure, but the autoregulatory mechanism of which remains unknow. We aimed to investigate the capacity of cerebral autoregulation in patients with cerebral venous thrombosis. Methods: Twenty-three patients with cerebral venous thrombosis and 16 controls were enrolled. Cerebral autoregulation was assessed by transfer function analysis (rate of recovery / phase / gain) from spontaneous oscillations of cerebral blood flow velocity and arterial blood pressure. Results: A total of 76 middle cerebral arteries (MCAs) were investigated including 44 MCAs from CVT patients and 32 normal ones. Phase shift and rate of recovery estimated from CVT patients was significantly different from controls (37.63 ± 33.94 vs. 54.49 ± 26.44, p = 0.23; 29.74 ± 59.55 vs. 37.95 ± 22.55, p = 0.01, respectively). The bilateral impairment of cebral autoregulation was demonstrated, even in the hemispheres without severe sinus stenosis and brain parenchymal lesion. Conclusion: Our findings for the first time indicated that patients with cerebral venous thrombosis were more likely to have impaired cerebral autoregulation and suggest that cautious blood pressure control is required in such patients to prevent hyper or hypo-perfusion.

scholarly journals Transfer function analysis of dynamic cerebral autoregulation: A white paper from the International Cerebral Autoregulation Research Network

2016 ◽  
Vol 36 (4) ◽  
pp. 665-680 ◽  
Author(s):  
Jurgen AHR Claassen ◽  
Aisha SS Meel-van den Abeelen ◽  
David M Simpson ◽  
Ronney B Panerai ◽  
Keyword(s):  
Blood Pressure ◽  
Transfer Function ◽  
Cerebral Autoregulation ◽  
Function Analysis ◽  
White Paper ◽  
Theoretical Background ◽  
Research Network ◽  
Dynamic Relationship ◽  
Transfer Function Analysis ◽  
Dynamic Cerebral Autoregulation

Cerebral autoregulation is the intrinsic ability of the brain to maintain adequate cerebral perfusion in the presence of blood pressure changes. A large number of methods to assess the quality of cerebral autoregulation have been proposed over the last 30 years. However, no single method has been universally accepted as a gold standard. Therefore, the choice of which method to employ to quantify cerebral autoregulation remains a matter of personal choice. Nevertheless, given the concept that cerebral autoregulation represents the dynamic relationship between blood pressure (stimulus or input) and cerebral blood flow (response or output), transfer function analysis became the most popular approach adopted in studies based on spontaneous fluctuations of blood pressure. Despite its sound theoretical background, the literature shows considerable variation in implementation of transfer function analysis in practice, which has limited comparisons between studies and hindered progress towards clinical application. Therefore, the purpose of the present white paper is to improve standardisation of parameters and settings adopted for application of transfer function analysis in studies of dynamic cerebral autoregulation. The development of these recommendations was initiated by (but not confined to) the Cerebral Autoregulation Research Network (CARNet – www.car-net.org ).

scholarly journals Differentiating Dynamic Cerebral Autoregulation Across Vascular Territories

2021 ◽  
Vol 12 ◽  
Author(s):  
Navpreet Reehal ◽  
Stephanie Cummings ◽  
Michael T. Mullen ◽  
Wesley B. Baker ◽  
David Kung ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Flow Velocity ◽  
Cerebral Artery ◽  
Transcranial Doppler ◽  
Cerebral Autoregulation ◽  
Posterior Cerebral Artery ◽  
Function Analysis ◽  
Arterial Blood ◽  
Transfer Function Analysis ◽  
Dynamic Cerebral Autoregulation

Objective: Transcranial Doppler is commonly used to calculate cerebral autoregulation, but measurements are typically restricted to a single cerebral artery. In exploring topographic heterogeneity, this study reports the first thorough comparison of autoregulation in all major cerebral vessels.Methods: In forty healthy adults, flow velocity was monitored in the anterior, middle, and posterior cerebral arteries, and synchronized with arterial blood pressure. A transfer function analysis provided characteristics of autoregulation by quantifying the relationship between blood pressure and cerebral blood flow velocity.Results: Phase, which quantifies the time course of autoregulation, was similar in all vessels. Gain, which quantifies the magnitude of hemodynamic regulation, was lower in posterior cerebral artery, indicative of tighter regulation. However, after adjusting for baseline flow differences in each vascular territory, normalized gain was similar in all vessels.Conclusions: Discriminating dynamic cerebral autoregulation between cerebrovascular territories is feasible with a transcranial doppler based approach. In the posterior cerebral artery of healthy volunteers, absolute flow is more tightly regulated, but relative flow regulation is consistent across cerebrovascular territories.Significance: The methodology can be applied to focal disease states such as stroke or posterior reversible encephalopathy syndrome, in which the topographic distribution of autoregulation may be particularly critical.

Midlife Aerobic Exercise and Dynamic Cerebral Autoregulation: Associations with Baroreflex Sensitivity and Central Arterial Stiffness

2021 ◽  
Author(s):  
Tsubasa Tomoto ◽  
Justin Repshas ◽  
Rong Zhang ◽  
Takashi Tarumi
Keyword(s):  
Arterial Stiffness ◽  
Aerobic Exercise ◽  
Cerebral Autoregulation ◽  
Baroreflex Sensitivity ◽  
Function Analysis ◽  
Middle Aged ◽  
Age Related ◽  
Transfer Function Analysis ◽  
Carotid Distensibility ◽  
Dynamic Cerebral Autoregulation

Midlife aerobic exercise may significantly impact age-related changes in the cerebro- and cardiovascular regulations. This study investigated the associations of midlife aerobic exercise with dynamic cerebral autoregulation (dCA), cardiovagal baroreflex sensitivity (BRS), and central arterial stiffness. Twenty middle-aged athletes (MA) who had aerobic training for >10 years were compared with 20 young (YS) and 20 middle-aged sedentary (MS) adults. Beat-to-beat cerebral blood flow velocity, blood pressure (BP), and heart rate were measured at rest and during forced BP oscillations induced by repeated sit-stand maneuvers at 0.05 Hz. Transfer function analysis was used to calculate dCA and BRS parameters. Carotid distensibility was measured by ultrasonography. MA had the highest peak oxygen uptake (VO2peak) among all groups. During forced BP oscillations, MS showed lower BRS gain than YS, but this age-related reduction was absent in MA. Conversely, dCA was similar among all groups. At rest, BRS and dCA gains at low frequency (~0.1 Hz) were higher in the MA compared with MS and YS groups. Carotid distensibility was similar between MA and YS groups, but it was lower in the MS. Across all subjects, VO2peak was positively associated with BRS gains at rest and during forced BP oscillations (r=0.257~0.382, p=0.003~0.050) and carotid distensibility (r=0.428~0.490, p=0.001). Furthermore, dCA gain at rest and carotid distensibility were positively correlated with BRS gain at rest in YS and MA groups (all p<0.05). These findings suggest that midlife aerobic exercise improves central arterial elasticity and BRS which may contribute to CBF regulation through dCA.

scholarly journals Assessment of cerebral autoregulation in stroke: A systematic review and meta-analysis of studies at rest

2019 ◽  
Vol 39 (11) ◽  
pp. 2105-2116 ◽  
Author(s):  
Kannakorn Intharakham ◽  
Lucy Beishon ◽  
Ronney B Panerai ◽  
Victoria J Haunton ◽  
Thompson G Robinson
Keyword(s):  
Systematic Review ◽  
Cerebral Autoregulation ◽  
Hemorrhagic Stroke ◽  
Function Analysis ◽  
Meta Analysis ◽  
Cerebrovascular Diseases ◽  
Transfer Function Analysis ◽  
Autoregulation Index ◽  
Meta Analyses ◽  
Dynamic Cerebral Autoregulation

Dynamic cerebral autoregulation (dCA) has been shown to be impaired in cerebrovascular diseases, but there is a lack of consistency across different studies and the different metrics that have been proposed for assessment. We performed a systematic review and meta-analyses involving assessment of dCA in ischemic and hemorrhagic stroke. Thirty-three articles describing assessment of dCA with transfer function analysis (TFA) were included, with meta-analyses performed for derived parameters of gain, phase and autoregulation index (ARI). A total of 1233 patients were pooled from 12 studies on acute ischemic stroke (AIS) and two studies on intracerebral hemorrhage (ICH). In comparison with controls, TFA phase of AIS was significantly reduced (nine studies), in both hemispheres ( P < 0.0001). TFA gain provided inconsistent results, with reduced values in relation to controls, for both hemispheres. The ARI (six studies) was reduced compared to controls, in both hemispheres ( P < 0.005). In ICH, gain showed higher values compared to controls for the unaffected ( P = 0.01), but not for the affected hemisphere. Meta-analyses in AIS have demonstrated that phase and the ARI index can show highly significant differences in comparison with healthy controls, while ICH have been limited by the scarcity of studies and the diversity of units adopted for gain.

scholarly journals N‐Terminal Pro Brain, N‐Terminal Pro Atrial Natriuretic Peptides, and Dynamic Cerebral Autoregulation

2020 ◽  
Vol 9 (20) ◽  
Author(s):  
Simin Mahinrad ◽  
Behnam Sabayan ◽  
Chaney R. Garner ◽  
Donald M. Lloyd‐Jones ◽  
Farzaneh A. Sorond
Keyword(s):  
Natriuretic Peptides ◽  
Cerebral Autoregulation ◽  
Small Vessel Disease ◽  
Function Analysis ◽  
Transcranial Doppler Ultrasound ◽  
Linear Regression Models ◽  
Lower Phase ◽  
Cerebrovascular Function ◽  
Transfer Function Analysis ◽  
Dynamic Cerebral Autoregulation

Background Elevated natriuretic peptides (NP) are associated with adverse cerebrovascular conditions including stroke, cerebral small vessel disease, and dementia. However, the mechanisms underlying these associations remain unclear. In this study, we examined the relationship of NT‐proBNP (N‐terminal pro brain NP) and NT‐proANP (N‐terminal pro atrial NP) with cerebrovascular function, measured by cerebral autoregulation. Methods and Results We included 154 participants (mean age 56±4 years old) from the CARDIA (Coronary Artery Risk Development in Young Adults) cohort. NT‐proBNP and NT‐proANP were measured in blood samples from the year 25 examination using electrochemiluminescence Immunoassay and enzyme‐linked immunoassay, respectively. Dynamic cerebral autoregulation (dCA) was assessed at the year 30 examination by transcranial Doppler ultrasound, using transfer function analysis (phase and gain) of spontaneous blood pressure and flow velocity oscillations, where lower phase and higher gain reflect less efficient cerebral autoregulation. We used multivariable linear regression models adjusted for demographics, vascular risk factors, and history of kidney and cardiac diseases. Higher NT‐proBNP levels at year 25 were associated with lower phase (β [95% CI]=−5.30 lower degrees of phase [−10.05 to −0.54]) and higher gain (β [95% CI]=0.06 higher cm/s per mm Hg of gain [0.004–0.12]) at year 30. Similarly, higher NT‐proANP levels were associated with lower phase (β [95% CI]=−9.08 lower degrees of phase [−16.46 to −1.70]). Conclusions Higher circulating levels of NT‐proBNP and NT‐proANP are associated with less efficient dCA 5 years later. These findings link circulating NP to cerebral autoregulation and may be one mechanism tying NP to adverse cerebrovascular outcomes.

Dynamic cerebral autoregulation during brain activation paradigms

2005 ◽  
Vol 289 (3) ◽  
pp. H1202-H1208 ◽  
Author(s):  
Ronney B. Panerai ◽  
Michelle Moody ◽  
Penelope J. Eames ◽  
John F. Potter
Keyword(s):  
Transfer Function ◽  
Cerebral Autoregulation ◽  
Function Analysis ◽  
Brain Activation ◽  
Hemispheric Lateralization ◽  
Step Response ◽  
Arterial Blood ◽  
Transfer Function Analysis ◽  
The Right ◽  
Dynamic Cerebral Autoregulation

Dynamic cerebral autoregulation (CA) describes the transient response of cerebral blood flow (CBF) to rapid changes in arterial blood pressure (ABP). We tested the hypothesis that the efficiency of dynamic CA is increased by brain activation paradigms designed to induce hemispheric lateralization. CBF velocity [CBFV; bilateral, middle cerebral artery (MCA)], ABP, ECG, and end-tidal Pco2 were continuously recorded in 14 right-handed healthy subjects (21–43 yr of age), in the seated position, at rest and during 10 repeated presentations (30 s on-off) of a word generation test and a constructional puzzle. Nonstationarities were not found during rest or activation. Transfer function analysis of the ABP-CBFV (i.e., input-output) relation was performed for the 10 separate 51.2-s segments of data during activation and compared with baseline data. During activation, the coherence function below 0.05 Hz was significantly increased for the right MCA recordings for the puzzle tasks compared with baseline values (0.36 ± 0.16 vs. 0.26 ± 0.13, P < 0.05) and for the left MCA recordings for the word paradigm (0.48 ± 0.23 vs. 0.29 ± 0.16, P < 0.05). In the same frequency range, significant increases in gain were observed during the puzzle paradigm for the right (0.69 ± 0.37 vs. 0.46 ± 0.32 cm·s−1·mmHg−1, P < 0.05) and left (0.61 ± 0.29 vs. 0.45 ± 0.24 cm·s−1·mmHg−1, P < 0.05) hemispheres and during the word tasks for the left hemisphere (0.66 ± 0.31 vs. 0.39 ± 0.15 cm·s−1·mmHg−1, P < 0.01). Significant reductions in phase were observed during activation with the puzzle task for the right (−0.04 ± 1.01 vs. 0.80 ± 0.86 rad, P < 0.01) and left (0.11 ± 0.81 vs. 0.57 ± 0.51 rad, P < 0.05) hemispheres and with the word paradigm for the right hemisphere (0.05 ± 0.87 vs. 0.64 ± 0.59 rad, P < 0.05). Brain activation also led to changes in the temporal pattern of the CBFV step response. We conclude that transfer function analysis suggests important changes in dynamic CA during mental activation tasks.

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