scholarly journals Detection of Impaired Cerebral Autoregulation Improves by Increasing Arterial Blood Pressure Variability

2012 ◽  
Vol 33 (4) ◽  
pp. 519-523 ◽  
Author(s):  
Emmanuel Katsogridakis ◽  
Glen Bush ◽  
Lingke Fan ◽  
Anthony A Birch ◽  
David M Simpson ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Cerebral Autoregulation ◽  
Random Sequence ◽  
Step Response ◽  
Arterial Blood ◽  
The Status ◽  
Autoregulation Index ◽  
Spontaneous Fluctuations ◽  
Operator Curve

Although the assessment of dynamic cerebral autoregulation (CA) based on measurements of spontaneous fluctuations in arterial blood pressure (ABP) and cerebral blood flow (CBF) is a convenient and much used method, there remains uncertainty about its reliability. We tested the effects of increasing ABP variability, provoked by a modification of the thigh cuff method, on the ability of the autoregulation index to discriminate between normal and impaired CA, using hypercapnia as a surrogate for dynamic CA impairment. In 30 healthy volunteers, ABP (Finapres) and CBF velocity (CBFV, transcranial Doppler) were recorded at rest and during 5% CO2 breathing, with and without pseudo-random sequence inflation and deflation of bilateral thigh cuffs. The application of thigh cuffs increased ABP and CBFV variabilities and was not associated with a distortion of the CBFV step response estimates for both normocapnic and hypercapnic conditions ( P = 0.59 and P = 0.96, respectively). Sensitivity and specificity of CA impairment detection were improved with the thigh cuff method, with the area under the receiver–operator curve increasing from 0.746 to 0.859 ( P = 0.031). We conclude that the new method is a safe, efficient, and appealing alternative to currently existing assessment methods for the investigation of the status of CA.

scholarly journals Alternative representation of neural activation in multivariate models of neurovascular coupling in humans

2019 ◽  
Vol 122 (2) ◽  
pp. 833-843 ◽  
Author(s):  
Ronney B. Panerai ◽  
Martha F. Hanby ◽  
Thompson G. Robinson ◽  
Victoria J. Haunton
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Arterial Blood Pressure ◽  
Cerebral Autoregulation ◽  
Neurovascular Coupling ◽  
Neural Stimulation ◽  
Step Response ◽  
Neural Activation ◽  
Arterial Blood

Neural stimulation leads to increases in cerebral blood flow (CBF), but simultaneous changes in covariates, such as arterial blood pressure (BP) and [Formula: see text], rule out the use of CBF changes as a reliable marker of neurovascular coupling (NVC) integrity. Healthy subjects performed repetitive (1 Hz) passive elbow flexion with their dominant arm for 60 s. CBF velocity (CBFV) was recorded bilaterally in the middle cerebral artery with transcranial Doppler, BP with the Finometer device, and end-tidal CO2 (EtCO2) with capnography. The simultaneous effects of neural stimulation, BP, and [Formula: see text] on CBFV were expressed with a dynamic multivariate model, using BP, EtCO2, and stimulation [ s( t)] as inputs. Two versions of s( t) were considered: a gate function [ sG( t)] or an orthogonal decomposition [ sO( t)] function. A separate CBFV step response was extracted from the model for each of the three inputs, providing estimates of dynamic cerebral autoregulation [CA; autoregulation index (ARI)], CO2 reactivity [vasomotor reactivity step response (VMRSR)], and NVC [stimulus step response (STIMSR)]. In 56 subjects, 224 model implementations produced excellent predictive CBFV correlation (median r = 0.995). Model-generated sO( t), for both dominant (DH) and nondominant (NDH) hemispheres, was highly significant during stimulation (<10−5) and was correlated with the CBFV change ( r = 0.73, P = 0.0001). The sO( t) explained a greater fraction of CBFV variance (~50%) than sG( t) (44%, P = 0.002). Most CBFV step responses to the three inputs were physiologically plausible, with better agreement for the CBFV-BP step response yielding ARI values of 7.3 for both DH and NDH for sG( t), and 6.9 and 7.4 for sO( t), respectively. No differences between DH and NDH were observed for VMRSR or STIMSR. A new procedure is proposed to represent the contribution from other aspects of CBF regulation than BP and CO2 in response to sensorimotor stimulation, as a tool for integrated, noninvasive, assessment of the multiple influences of dynamic CA, CO2 reactivity, and NVC in humans. NEW & NOTEWORTHY A new approach was proposed to identify the separate contributions of stimulation, arterial blood pressure (BP), and arterial CO2 ([Formula: see text]) to the cerebral blood flow (CBF) response observed in neurovascular coupling (NVC) studies in humans. Instead of adopting an empirical gate function to represent the stimulation input, a model-generated function is derived as part of the modeling process, providing a representation of the NVC response, independent of the contributions of BP or [Formula: see text]. This new marker of NVC, together with the model-predicted outputs for the contributions of BP, [Formula: see text] and stimulation, has considerable potential to both quantify and simultaneously integrate the separate mechanisms involved in CBF regulation, namely, cerebral autoregulation, CO2 reactivity and other contributions.

Influence of noninvasive peripheral arterial blood pressure measurements on assessment of dynamic cerebral autoregulation

2007 ◽  
Vol 103 (1) ◽  
pp. 369-375 ◽  
Author(s):  
Emily L. Sammons ◽  
Nilesh J. Samani ◽  
Stephen M. Smith ◽  
Wendy E. Rathbone ◽  
Steve Bentley ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Transfer Function ◽  
Arterial Blood Pressure ◽  
Cerebral Autoregulation ◽  
Aortic Pressure ◽  
Step Response ◽  
Pressure Measurements ◽  
Arterial Blood ◽  
Surface Ecg ◽  
Dynamic Cerebral Autoregulation

Assessment of dynamic cerebral autoregulation (CA) requires continuous recording of arterial blood pressure (ABP). In humans, noninvasive ABP recordings with the Finapres device have often been used for this purpose. We compared estimates of dynamic CA derived from Finapres with those from invasive recordings in the aorta. Measurements of finger noninvasive ABP (Finapres), intra-aortic ABP (Millar catheter), surface ECG, transcutaneous CO2, and bilateral cerebral blood flow velocity (CBFV) in the middle cerebral arteries were simultaneously and continuously recorded in 27 patients scheduled for percutaneous coronary interventions. Phase, gain, coherence, and CBFV step response from both the Finapres and intra-arterial catheter were estimated by transfer function analysis. A dynamic autoregulation index (ARI) was also calculated. For both hemispheres, the ARI index and the CBFV step response recovery at 4 s were significantly greater for the Finapres-derived estimates than for the values obtained from aortic pressure. The transfer function gain for frequencies <0.1 Hz was significantly smaller for the Finapres estimates. The phase frequency response was significantly greater for the Finapres estimates at frequencies >0.1 Hz, but not at lower frequencies. The Finapres gives higher values for the efficiency of dynamic CA compared with values derived from aortic pressure measurements, as indicated by biases in the ARI index, CBFV step response, gain, and phase. Despite the significance of these biases, their relatively small amplitude indicates a good level of agreement between indexes of CA derived from the Finapres compared with corresponding estimates obtained from invasive measurements of aortic ABP.

Cerebral blood flow velocity response to induced and spontaneous sudden changes in arterial blood pressure

2001 ◽  
Vol 280 (5) ◽  
pp. H2162-H2174 ◽  
Author(s):  
Ronney B. Panerai ◽  
Suzanne L. Dawson ◽  
Penelope J. Eames ◽  
John F. Potter
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Flow Velocity ◽  
Arterial Blood Pressure ◽  
Blood Flow Velocity ◽  
Cerebral Blood Flow Velocity ◽  
Step Response ◽  
Arterial Blood ◽  
Step Responses

The influence of different types of maneuvers that can induce sudden changes of arterial blood pressure (ABP) on the cerebral blood flow velocity (CBFV) response was studied in 56 normal subjects (mean age 62 yr, range 23–80). ABP was recorded in the finger with a Finapres device, and bilateral recordings of CBFV were performed with Doppler ultrasound of the middle cerebral arteries. Recordings were performed at rest (baseline) and during the thigh cuff test, lower body negative pressure, cold pressor test, hand grip, and Valsalva maneuver. From baseline recordings, positive and negative spontaneous transients were also selected. Stability of Pco 2 was monitored with transcutaneous measurements. Dynamic autoregulatory index (ARI), impulse, and step responses were obtained for 1-min segments of data for the eight conditions by fitting a mathematical model to the ABP-CBFV baseline and transient data (Aaslid's model) and by the Wiener-Laguerre moving-average method. Impulse responses were similar for the right- and left-side recordings, and their temporal pattern was not influenced by type of maneuver. Step responses showed a sudden rise at time 0 and then started to fall back to their original level, indicating an active autoregulation. ARI was also independent of the type of maneuver, giving an overall mean of 4.7 ± 2.9 ( n = 602 recordings). Amplitudes of the impulse and step responses, however, were significantly influenced by type of maneuver and were highly correlated with the resistance-area product before the sudden change in ABP ( r = −0.93, P < 0.0004). These results suggest that amplitude of the CBFV step response is sensitive to the point of operation of the instantaneous ABP-CBFV relationship, which can be shifted by different maneuvers. Various degrees of sympathetic nervous system activation resulting from different ABP-stimulating maneuvers were not reflected by CBFV dynamic autoregulatory responses within the physiological range of ABP.

scholarly journals Grading of Cerebral Dynamic Autoregulation From Spontaneous Fluctuations in Arterial Blood Pressure

Stroke ◽  
1998 ◽  
Vol 29 (11) ◽  
pp. 2341-2346 ◽  
Author(s):  
Ronney B. Panerai ◽  
Richard P. White ◽  
Hugh S. Markus ◽  
David H. Evans
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Arterial Blood ◽  
Spontaneous Fluctuations
Sign in / Sign up

Export Citation Format

Share Document