Multivariate modeling of cognitive-motor stimulation on neurovascular coupling: transcranial Doppler used to characterize myogenic and metabolic influences

2012 ◽  
Vol 303 (4) ◽  
pp. R395-R407 ◽  
Author(s):  
Ronney B. Panerai ◽  
Michelle Eyre ◽  
John F. Potter
Keyword(s):  
Transcranial Doppler ◽  
Cerebral Blood Flow Velocity ◽  
Moving Average ◽  
Neurovascular Coupling ◽  
Transcranial Doppler Ultrasound ◽  
Diagnostic Value ◽  
Cognitive Stimulation ◽  
Neural Activation ◽  
Arterial Blood ◽  
End Tidal

Neural activation induces changes in cerebral blood flow velocity (CBFV) with separate contributions from resistance-area product (VRAP) and critical closing pressure (VCrCP). We modeled the dependence of VRAP and VCrCP on arterial blood pressure (ABP), end-tidal CO2 (EtCO2), and cognitive stimulation to test the hypothesis that VRAP reflects myogenic activity while VCrCP reflects metabolic pathways. In 14 healthy subjects, CBFV was measured with transcranial Doppler ultrasound, ABP with the Finapres device and EtCO2 with infrared capnography. Two different paradigms (word or puzzle) were repeated 10 times (30 s on-off), and the corresponding square-wave signal was used, together with ABP and EtCO2, as inputs to autoregressive-moving average (ARMA) models, which allowed identification of the separate contributions of the three inputs to either VRAP or VCrCP. For both paradigms, the contribution of ABP was mainly manifested through VRAP ( P < 0.005 for word; P < 0.004 for puzzle), while stimulation mainly contributed to VCrCP ( P < 0.002 for word; P < 0.033, for puzzle). The contribution of EtCO2 was relatively small (<10%) with greater contribution to VCrCP ( P < 0.01 for puzzle; not significant for word). Separate step responses were also obtained for each of the three inputs. ARMA modeling of VRAP and VCrCP allows the separation of the effects of cerebral autoregulation and CO2 reactivity from the main effects of cognitive-motor stimulation and have the potential to improve the diagnostic value of neurovascular coupling testing in physiological and clinical studies.

Active, passive, and motor imagery paradigms: component analysis to assess neurovascular coupling

2013 ◽  
Vol 114 (10) ◽  
pp. 1406-1412 ◽  
Author(s):  
Angela S. M. Salinet ◽  
Thompson G. Robinson ◽  
Ronney B. Panerai
Keyword(s):  
Motor Imagery ◽  
Moving Average ◽  
Neurovascular Coupling ◽  
Neural Activation ◽  
Autoregressive Moving Average Model ◽  
Arterial Blood ◽  
Moving Average Model ◽  
End Tidal ◽  
The Right ◽  
Cognitive Paradigms

The association between neural activity and cerebral blood flow (CBF) has been used to assess neurovascular coupling (NVC) in health and diseases states, but little attention has been given to the contribution of simultaneous changes in peripheral covariates. We used an innovative approach to assess the contributions of arterial blood pressure (BP), PaCO2, and the stimulus itself to changes in CBF velocities (CBFv) during active (MA), passive (MP), and motor imagery (MI) paradigms. Continuous recordings of CBFv, beat-to-beat BP, heart rate, and breath-by-breath end-tidal CO2 (EtCO2) were performed in 17 right-handed subjects before, during, and after motor-cognitive paradigms performed with the right arm. A multivariate autoregressive-moving average model was used to calculate the separate contributions of BP, EtCO2, and the neural activation stimulus (represented by a metronome on-off signal) to the CBFv response during paradigms. Differences were found in the bilateral CBFv responses to MI compared with MA and MP, due to the contributions of stimulation ( P < 0.05). BP was the dominant contributor to the initial peaked CBFv response in all paradigms with no significant differences between paradigms, while the contribution of the stimulus explained the plateau phase and extended duration of the CBFv responses. Separating the neural activation contribution from the influences of other covariates, it was possible to detect differences between three paradigms often used to assess disease-related NVC. Apparently similar CBFv responses to different motor-cognitive paradigms can be misleading due to the contributions from peripheral covariates and could lead to inaccurate assessment of NVC, particularly during MI.

Ventilatory, cerebrovascular, and cardiovascular interactions in acute hypoxia: regulation by carbon dioxide

2004 ◽  
Vol 97 (1) ◽  
pp. 149-159 ◽  
Author(s):  
Philip N. Ainslie ◽  
Marc J. Poulin
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Cerebral Blood Flow Velocity ◽  
Acute Hypoxia ◽  
Random Order ◽  
Transcranial Doppler Ultrasound ◽  
Individual Variability ◽  
Cerebral Vasoconstriction ◽  
Arterial Blood ◽  
End Tidal

This study examined the effect of high, normal, and uncontrolled end-tidal Pco2 (PetCO2) on the ventilatory, peak cerebral blood flow velocity ( V̄p), and mean arterial blood pressure (MAP) responses to acute hypoxia. Nine healthy subjects undertook, in random order, three hypoxic protocols (end-tidal Po2 was held at eight steps between 300 and 45 Torr) in conditions of hypercapnia, isocapnia, or poikilocapnia (PetCO2 +7.5 Torr, +1.0 Torr, or uncontrolled, respectively). Transcranial Doppler ultrasound was used to measure V̄p in the middle cerebral artery. The slopes of the linear regressions of ventilation, V̄p, and MAP with arterial O2 saturation were significantly greater in hypercapnia than in both isocapnia and poikilocapnia ( P < 0.05). Strong, significant correlations were observed between ventilation, V̄p, and MAP with each PetCO2 condition. These data suggest that 1) a high acute hypoxic ventilatory response (AHVR) decreases the acute hypoxic cerebral blood flow responses during poikilocapnia hypoxia, due to hypocapnic-induced cerebral vasoconstriction; and 2) in hypercapnic hypoxia, a high AHVR is associated with a high acute hypoxic cerebral blood flow response, demonstrating a linkage of individual sensitivities of ventilation and cerebral blood flow to the interaction of PetCO2 and hypoxia. In summary, the between-individual variability in AHVR is shown to be firmly linked to the variability in V̄p and MAP responses to hypoxia. Individuals with a high AHVR are found also to have high V̄p and MAP responses to hypoxia.

scholarly journals Cerebrovascular effects of the thigh cuff maneuver

2015 ◽  
Vol 308 (7) ◽  
pp. H688-H696 ◽  
Author(s):  
R. B. Panerai ◽  
N. P. Saeed ◽  
T. G. Robinson
Keyword(s):  
Cerebral Blood Flow Velocity ◽  
Moving Average ◽  
Autoregressive Moving Average ◽  
Strongly Correlated ◽  
Mean Values ◽  
Autoregressive Moving Average Model ◽  
Arterial Blood ◽  
Moving Average Model ◽  
Area Product ◽  
End Tidal

Arterial hypotension can be induced by sudden release of inflated thigh cuffs (THC), but its effects on the cerebral circulation have not been fully described. In nine healthy subjects [aged 59 (9) yr], bilateral cerebral blood flow velocity (CBFV) was recorded in the middle cerebral artery (MCA), noninvasive arterial blood pressure (BP) in the finger, and end-tidal CO2 (ETCO2) with nasal capnography. Three THC maneuvers were performed in each subject with cuff inflation 20 mmHg above systolic BP for 3 min before release. Beat-to-beat values were extracted for mean CBFV, BP, ETCO2, critical closing pressure (CrCP), resistance-area product (RAP), and heart rate (HR). Time-varying estimates of the autoregulation index [ARI( t)] were also obtained using an autoregressive-moving average model. Coherent averages synchronized by the instant of cuff release showed significant drops in mean BP, CBFV, and RAP with rapid return of CBFV to baseline. HR, ETCO2, and ARI( t) were transiently increased, but CrCP remained relatively constant. Mean values of ARI( t) for the 30 s following cuff release were not significantly different from the classical ARI [right MCA 5.9 (1.1) vs. 5.1 (1.6); left MCA 5.5 (1.4) vs. 4.9 (1.7)]. HR was strongly correlated with the ARI( t) peak after THC release (in 17/22 and 21/24 recordings), and ETCO2 was correlated with the subsequent drop in ARI( t) (19/22 and 20/24 recordings). These results suggest a complex cerebral autoregulatory response to the THC maneuver, dominated by myogenic mechanisms and influenced by concurrent changes in ETCO2 and possible involvement of the autonomic nervous system and baroreflex.

scholarly journals Transcranial Doppler Ultrasound: A Review of the Physical Principles and Major Applications in Critical Care

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Jawad Naqvi ◽  
Kok Hooi Yap ◽  
Gulraiz Ahmad ◽  
Jonathan Ghosh
Keyword(s):  
Transcranial Doppler ◽  
Cerebral Blood Flow Velocity ◽  
Cerebral Arteries ◽  
Low Frequency ◽  
Transcranial Doppler Ultrasound ◽  
Arterial Stenosis ◽  
Dynamic Monitoring ◽  
High Temporal Resolution ◽  
Thin Bone ◽  
Cerebral Microembolism

Transcranial Doppler (TCD) is a noninvasive ultrasound (US) study used to measure cerebral blood flow velocity (CBF-V) in the major intracranial arteries. It involves use of low-frequency (≤2 MHz) US waves to insonate the basal cerebral arteries through relatively thin bone windows. TCD allows dynamic monitoring of CBF-V and vessel pulsatility, with a high temporal resolution. It is relatively inexpensive, repeatable, and portable. However, the performance of TCD is highly operator dependent and can be difficult, with approximately 10–20% of patients having inadequate transtemporal acoustic windows. Current applications of TCD include vasospasm in sickle cell disease, subarachnoid haemorrhage (SAH), and intra- and extracranial arterial stenosis and occlusion. TCD is also used in brain stem death, head injury, raised intracranial pressure (ICP), intraoperative monitoring, cerebral microembolism, and autoregulatory testing.

scholarly journals Directional sensitivity of dynamic cerebral autoregulation in squat-stand maneuvers

2018 ◽  
Vol 315 (4) ◽  
pp. R730-R740 ◽  
Author(s):  
Ronney B. Panerai ◽  
Sam C. Barnes ◽  
Mintu Nath ◽  
Naomi Ball ◽  
Thompson G. Robinson ◽  
...  
Keyword(s):  
Cerebral Autoregulation ◽  
Moving Average ◽  
Nonlinear Behavior ◽  
Directional Sensitivity ◽  
Autoregressive Moving Average Model ◽  
Arterial Blood ◽  
Cerebral Blood Velocity ◽  
Young Subjects ◽  
End Tidal ◽  
Dynamic Cerebral Autoregulation

Dynamic cerebral autoregulation (CA), the transient response of cerebral blood flow (CBF) to rapid changes in arterial blood pressure (BP), is usually modeled as a linear mechanism. We tested the hypothesis that dynamic CA can display nonlinear behavior resulting from differential efficiency dependent on the direction of BP changes. Cerebral blood velocity (CBV) (transcranial Doppler), heart rate (HR) (three-lead ECG), continuous BP (Finometer), and end-tidal CO2 (capnograph) were measured in 10 healthy young subjects during 15 squat-stand maneuvers (SSM) with a frequency of 0.05 Hz. The protocol was repeated with a median (interquartile range) of 44 (35–64) days apart. Dynamic CA was assessed with the autoregulation index (ARI) obtained from CBV step responses estimated with an autoregressive moving-average model. Mean BP, HR, and CBV were different (all P < 0.001) between squat and stand, regardless of visits. ARI showed a strong interaction ( P < 0.001) of SSM with the progression of transients; in general, the mean ARI was higher for the squat phase compared with standing. The changes in ARI were partially explained by concomitant changes in CBV ( P = 0.023) and pulse pressure ( P < 0.001), but there was no evidence that ARI differed between visits ( P = 0.277). These results demonstrate that dynamic CA is dependent on the direction of BP change, but further work is needed to confirm if this finding can be generalized to other physiological conditions and also to assess its dependency on age, sex and pathology.

A new two-breath technique for extracting the cerebrovascular response to arterial carbon dioxide

2003 ◽  
Vol 284 (3) ◽  
pp. R853-R859 ◽  
Author(s):  
Michael R. Edwards ◽  
Zigniew L. Topor ◽  
Richard L. Hughson
Keyword(s):  
Spontaneous Breathing ◽  
Closed Loop ◽  
Moving Average ◽  
Resistance Index ◽  
Transcranial Doppler Ultrasound ◽  
Loop Model ◽  
Mean Flow ◽  
Arterial Blood ◽  
Average Analysis ◽  
Spontaneous Fluctuations

Cerebrovascular autoregulation is evaluated from spontaneous fluctuations in mean flow velocity (MFV) by transcranial Doppler ultrasound of the middle cerebral artery (MCA) with respect to changes in arterial blood pressure (BPMCA), but the effects of spontaneous fluctuations in arterial Pco 2 on MFV have been largely ignored. Autoregressive moving average analysis (ARMA), a closed-loop system identification technique, was applied to data from nine healthy subjects during spontaneous breathing, during inspiration of 10% CO2 for two breaths once per minute for 4 min, and during sustained breathing of 7% CO2. Cerebrovascular resistance index (CVRi) was calculated (CVRi = BPMCA/MFV). Reliable estimates of gain for BPMCA → MFV were obtained for spontaneous breathing and the two-breath method. In contrast, reliable gain estimates for Pco 2 → MFV or Pco 2 → CVRi were achieved only under the two-breath method. Pco 2 → MFV gain was smaller with the two-breath method than during sustained 7% CO2 ( P < 0.05). BPMCA was elevated by 7% CO2 but not by the two-breath method. The closed-loop model provides insight into interactions between BPMCA and Pco 2 on cerebrovascular control, but reliable solutions for Pco 2effects with ARMA analysis require perturbation by the two-breath method.

scholarly journals Multiple-input nonlinear modelling of cerebral haemodynamics using spontaneous arterial blood pressure, end-tidal CO 2  and heart rate measurements

2016 ◽  
Vol 374 (2067) ◽  
pp. 20150180 ◽  
Author(s):  
V. Z. Marmarelis ◽  
G. D. Mitsis ◽  
D. C. Shin ◽  
R. Zhang
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Arterial Blood Pressure ◽  
Prediction Error ◽  
Cerebral Blood Flow Velocity ◽  
Cerebral Arteries ◽  
Cerebral Haemodynamics ◽  
Functional Connection ◽  
Arterial Blood ◽  
End Tidal

In order to examine the effect of changes in heart rate (HR) upon cerebral perfusion and autoregulation, we include the HR signal recorded from 18 control subjects as a third input in a two-input model of cerebral haemodynamics that has been used previously to quantify the dynamic effects of changes in arterial blood pressure and end-tidal CO 2 upon cerebral blood flow velocity (CBFV) measured at the middle cerebral arteries via transcranial Doppler ultrasound. It is shown that the inclusion of HR as a third input reduces the output prediction error in a statistically significant manner, which implies that there is a functional connection between HR changes and CBFV. The inclusion of nonlinearities in the model causes further statistically significant reduction of the output prediction error. To achieve this task, we employ the concept of principal dynamic modes (PDMs) that yields dynamic nonlinear models of multi-input systems using relatively short data records. The obtained PDMs suggest model-driven quantitative hypotheses for the role of sympathetic and parasympathetic activity (corresponding to distinct PDMs) in the underlying physiological mechanisms by virtue of their relative contributions to the model output. These relative PDM contributions are subject-specific and, therefore, may be used to assess personalized characteristics for diagnostic purposes.

scholarly journals Middle cerebral O2 delivery during the modified Oxford maneuver increases with sodium nitroprusside and decreases during phenylephrine

2013 ◽  
Vol 304 (11) ◽  
pp. H1576-H1583 ◽  
Author(s):  
Julian M. Stewart ◽  
Marvin S. Medow ◽  
Andrew DelPozzi ◽  
Zachary R. Messer ◽  
Courtney Terilli ◽  
...  
Keyword(s):  
Sodium Nitroprusside ◽  
Doppler Ultrasound ◽  
Transcranial Doppler ◽  
Near Infrared ◽  
Cerebral Blood Flow Velocity ◽  
Transcranial Doppler Ultrasound ◽  
Venous Occlusion ◽  
Sample Volume ◽  
Total Hemoglobin ◽  
The Right

The modified Oxford maneuver is the reference standard for assessing arterial baroreflex function. The maneuver comprises a systemic bolus injection of 100 μg sodium nitroprusside (SNP) followed by 150 μg phenylephrine (PE). On the one hand, this results in an increase in oxyhemoglobin and total hemoglobin followed by a decrease within the cerebral sample volume illuminated by near-infrared spectroscopy (NIRS). On the other hand, it produces a decrease in cerebral blood flow velocity (CBFv) within the middle cerebral artery (MCA) during SNP and an increase in CBFv during PE as measured by transcranial Doppler ultrasound. To resolve this apparent discrepancy, we hypothesized that SNP dilates, whereas PE constricts, the MCA. We combined transcranial Doppler ultrasound of the right MCA with NIRS illuminating the right frontal cortex in 12 supine healthy subjects 18–24 yr old. Assuming constant O2 consumption and venous saturation, as estimated by partial venous occlusion plethysmography, we used conservation of mass (continuity) equations to estimate the changes in arterial inflow (ΔQa) and venous outflow (ΔQv) of the NIRS-illuminated area. Oxyhemoglobin and total hemoglobin, respectively, increased by 13.6 ± 1.6 and 15.2 ± 1.4 μmol/kg brain tissue with SNP despite hypotension and decreased by 6 ± 1 and 7 ± 1 μmol/kg with PE despite hypertension. SNP increased ΔQa by 0.36 ± .03 μmol·kg−1·s−1 (21.6 μmol·kg−1·min−1), whereas CBFv decreased from 71 ± 2 to 62 ± 2 cm/s. PE decreased ΔQa by 0.27 ± .2 μmol·kg−1·s−1 (16.2 μmol·kg−1·min−1), whereas CBFv increased to 75 ± 3 cm/s. These results are consistent with dilation of the MCA by SNP and constriction by PE.

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