scholarly journals Dynamic Cerebral Autoregulation and Critical Closing Pressure in Experimental Human Endotoxemia and Sepsis Patients

Med One ◽  
2019 ◽  
Keyword(s):  
Cerebral Autoregulation ◽  
Human Endotoxemia ◽  
Critical Closing Pressure ◽  
Closing Pressure ◽  
Dynamic Cerebral Autoregulation

scholarly journals The critical closing pressure contribution to dynamic cerebral autoregulation in humans: influence of arterial partial pressure of CO 2

2020 ◽  
Vol 598 (24) ◽  
pp. 5673-5685
Author(s):  
Ronney B. Panerai ◽  
Jatinder S. Minhas ◽  
Osian Llwyd ◽  
Angela S. M. Salinet ◽  
Emmanuel Katsogridakis ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Cerebral Autoregulation ◽  
Arterial Partial Pressure ◽  
Critical Closing Pressure ◽  
Closing Pressure ◽  
Dynamic Cerebral Autoregulation

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 Does hypercapnia-induced impairment of cerebral autoregulation affect neurovascular coupling? A functional TCD study

2013 ◽  
Vol 115 (4) ◽  
pp. 491-497 ◽  
Author(s):  
Paola Maggio ◽  
Angela S. M. Salinet ◽  
Ronney B. Panerai ◽  
Thompson G. Robinson
Keyword(s):  
Cerebral Autoregulation ◽  
Cerebral Blood Flow Velocity ◽  
Cerebral Arteries ◽  
Neurovascular Coupling ◽  
Relative Contribution ◽  
Middle Cerebral Arteries ◽  
Critical Closing Pressure ◽  
Area Product ◽  
End Tidal ◽  
Closing Pressure

Neurovascular coupling (NVC) and dynamic cerebral autoregulation (dCA) are both impaired in the acute phase of ischemic stroke, but their reciprocal interactions are difficult to predict. To clarify these aspects, the present study explored NVC in a healthy volunteer population during a surrogate state of impaired dCA induced by hypercapnia. This study aimed to test whether hypercapnia leads to a depression of NVC through an impairment of dCA. Continuous recordings of middle cerebral arteries cerebral blood flow velocity (CBFv), blood pressure (BP), heart rate, and end-tidal CO2 were performed in 19 right-handed subjects (aged >45 yr) before, during, and after 60 s of a passive paradigm during normocapnia and hypercapnia. The CBFv response was broken down into subcomponents describing the relative contributions of BP (VBP), critical closing pressure (VCrCP), and resistance area product (VRAP). VRAP reflects myogenic activity in response to BP changes, whereas VCrCP is more indicative of metabolic control. The results revealed that hypercapnia significantly affected NVC, with significant reductions in the relative contribution of VCrCP to the paradigm-induced increase in CBFv. The present study suggests that hypercapnia impairs both dCA and NVC, probably acting through an impairment of the metabolic component of CBF control.

Critical closing pressure in preterm neonates: Towards a comprehensive model of cerebral autoregulation

1995 ◽  
Vol 17 (2) ◽  
pp. 149-155 ◽  
Author(s):  
Erik Miche ◽  
Boris zernikow ◽  
Johanna von wickel ◽  
Stefanie Hillebrand ◽  
Gerd Jorch
Keyword(s):  
Cerebral Autoregulation ◽  
Preterm Neonates ◽  
Comprehensive Model ◽  
Critical Closing Pressure ◽  
Closing Pressure

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 Impaired Cerebrovascular Hemodynamics are Associated with Cerebral White Matter Damage

2013 ◽  
Vol 34 (2) ◽  
pp. 228-234 ◽  
Author(s):  
Sushmita Purkayastha ◽  
Otite Fadar ◽  
Aujan Mehregan ◽  
David H Salat ◽  
Nicola Moscufo ◽  
...  
Keyword(s):  
White Matter ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Cerebral Autoregulation ◽  
Structural Integrity ◽  
Cerebral White Matter ◽  
Elderly Individuals ◽  
Transfer Function Analysis ◽  
Dynamic Cerebral Autoregulation ◽  
Cerebrovascular Hemodynamics

White matter hyperintensities (WMH) in elderly individuals with vascular diseases are presumed to be due to ischemic small vessel diseases; however, their etiology is unknown. We examined the cross-sectional relationship between cerebrovascular hemodynamics and white matter structural integrity in elderly individuals with vascular risk factors. White matter hyperintensity volumes, fractional anisotropy (FA), and mean diffusivity (MD) were obtained from MRI in 48 subjects (75±7years). Pulsatility index (PI) and dynamic cerebral autoregulation (dCA) was assessed using transcranial Doppler ultrasound of the middle cerebral artery. Dynamic cerebral autoregulation was calculated from transfer function analysis (phase and gain) of spontaneous blood pressure and flow velocity oscillations in the low (LF, 0.03 to 0.15 Hz) and high (HF, 0.16 to 0.5 Hz) frequency ranges. Higher PI was associated with greater WMH ( P<0.005). Higher phase across all frequency ranges was associated with greater FA and lower MD ( P<0.005). Lower gain was associated with higher FA in the LF range ( P=0.001). These relationships between phase and FA were significant in the territories limited to the middle cerebral artery as well as across the entire brain. Our results show a strong relationship between impaired cerebrovascular hemodynamics (PI and dCA) and loss of cerebral white matter structural integrity (WMH and DTI metrics) in elderly individuals.

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