Influence of CO2
 on neurovascular coupling: interaction with dynamic cerebral autoregulation and cerebrovascular reactivity

Cerebral blood flow (CBF) regulation can be impaired in acute ischemic stroke but the combined effects of dynamic cerebral autoregulation (CA), CO2 cerebrovascular reactivity (CVR), and neurovascular coupling (NVC), obtained from simultaneous measurements, have not been described. CBF velocity in the middle cerebral artery (MCA) (CBFv, transcranial Doppler), blood pressure (BP, Finometer), and end-tidal Pco2 (PetCO2, infrared capnography) were recorded during a 1-min passive movement of the arm in 27 healthy controls [mean age (SD) 61.4 (6.0) yr] and 27 acute stroke patients [age 63 (11.7) yr]. A multivariate autoregressive-moving average model was used to separate the contributions of BP, arterial Pco2 (PaCO2), and the neural activation to the CBFv responses. CBFv step responses for the BP, CO2, and stimulus inputs were also obtained. The contribution of the stimulus to the CBFv response was highly significant for the difference between the affected side [area under the curve (AUC) 104.5 (4.5)%] and controls [AUC 106.9 (4.3)%; P = 0.008]. CBFv step responses to CO2 [affected hemisphere 0.39 (0.7), unaffected 0.55 (0.8), controls 1.39 (0.9)%/mmHg; P = 0.01, affected vs. controls; P = 0.025, unaffected vs. controls] and motor stimulus inputs [affected hemisphere 0.20 (0.1), unaffected 0.22 (0.2), controls 0.37 (0.2) arbitrary units; P = 0.009, affected vs. controls; P = 0.02, unaffected vs. controls] were reduced in the stroke group compared with controls. The CBFv step responses to the BP input at baseline and during the paradigm were not different between groups ( P = 0.07), but PetCO2 was lower in the stroke group ( P < 0.05). These results provide new insights into the interaction of CA, CVR, and NVC in both health and disease states.

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Critical closing pressure as a proxy for PaCO2 in non-linear multivariate models for estimation of dynamic cerebral autoregulation and cerebrovascular reactivity

Journal of the Neurological Sciences ◽

10.1016/j.jns.2015.08.1313 ◽

2015 ◽

Vol 357 ◽

pp. e366

Author(s):

F.A. Bello Robles ◽

M. Chacon ◽

R.B. Panerai

Keyword(s):

Cerebral Autoregulation ◽

Cerebrovascular Reactivity ◽

Multivariate Models ◽

Critical Closing Pressure ◽

Non Linear ◽

Closing Pressure ◽

Dynamic Cerebral Autoregulation

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The Interaction of Dynamic Cerebral Autoregulation and Neurovascular Coupling in Cognitive Impairment

Current Alzheimer Research ◽

10.2174/1567205019666211227102936 ◽

2021 ◽

Vol 18 (14) ◽

pp. 1067-1076

Author(s):

Lucy C. Beishon ◽

Kannakorn Intharakham ◽

Victoria J. Haunton ◽

Thompson G. Robinson ◽

Ronney B. Panerai

Keyword(s):

Older Adults ◽

Cognitive Impairment ◽

Cerebral Autoregulation ◽

Function Analysis ◽

Neurovascular Coupling ◽

Cognitively Impaired ◽

Healthy Older Adults ◽

Transfer Function Analysis ◽

Dynamic Cerebral Autoregulation ◽

Task Activation

Background: Dynamic cerebral autoregulation (dCA) remains intact in both ageing and dementia, but studies of neurovascular coupling (NVC) have produced mixed findings. Objective: We investigated the effects of task-activation on dCA in healthy older adults (HOA), and patients with mild cognitive impairment (MCI) and Alzheimer’s Disease (AD). Methods: Resting and task-activated data from thirty HOA, twenty-two MCI, and thirty-four AD were extracted from a database. The autoregulation index (ARI) was determined at rest and during five cognitive tasks from transfer function analysis. NVC responses were present where group-specific thresholds of cross-correlation peak function and variance ratio were exceeded. Cumulative response rate (CRR) was the total number of positive responses across five tasks and two hemispheres. Results: ARI differed between groups in dominant (p=0.012) and non-dominant (p=0.042) hemispheres at rest but not during task-activation (p=0.33). ARI decreased during language and memory tasks in HOA (p=0.002) but not in MCI or AD (p=0.40). There was a significant positive correlation between baseline ARI and CRR in all groups (r=0.26, p=0.018), but not within sub-groups. Conclusion: dCA efficiency was reduced in task-activation in healthy but not cognitively impaired participants. These results indicate differences in neurovascular processing in healthy older adults relative to cognitively impaired individuals.

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Alterations in cerebral dynamics at high altitude following partial acclimatization in humans: wakefulness and sleep

Journal of Applied Physiology ◽

10.1152/japplphysiol.00911.2006 ◽

2007 ◽

Vol 102 (2) ◽

pp. 658-664 ◽

Cited By ~ 47

Author(s):

Philip N. Ainslie ◽

Katie Burgess ◽

Prajan Subedi ◽

Keith R. Burgess

Keyword(s):

Blood Pressure ◽

Sleep Apnea ◽

High Altitude ◽

Cerebral Autoregulation ◽

Central Sleep Apnea ◽

Cerebrovascular Reactivity ◽

Arterial Blood ◽

Transfer Function Analysis ◽

Low Altitude ◽

Dynamic Cerebral Autoregulation

We tested the hypothesis that, following exposure to high altitude, cerebrovascular reactivity to CO2 and cerebral autoregulation would be attenuated. Such alterations may predispose to central sleep apnea at high altitude by promoting changes in brain Pco2 and thus breathing stability. We measured middle cerebral artery blood flow velocity (MCAv; transcranial Doppler ultrasound) and arterial blood pressure during wakefulness in conditions of eucapnia (room air), hypocapnia (voluntary hyperventilation), and hypercapnia (isooxic rebeathing), and also during non-rapid eye movement (stage 2) sleep at low altitude (1,400 m) and at high altitude (3,840 m) in five individuals. At each altitude, sleep was studied using full polysomnography, and resting arterial blood gases were obtained. During wakefulness and polysomnographic-monitored sleep, dynamic cerebral autoregulation and steady-state changes in MCAv in relation to changes in blood pressure were evaluated using transfer function analysis. High altitude was associated with an increase in central sleep apnea index (0.2 ± 0.4 to 20.7 ± 23.2 per hour) and an increase in mean blood pressure and cerebrovascular resistance during wakefulness and sleep. MCAv was unchanged during wakefulness, whereas there was a greater decrease during sleep at high altitude compared with low altitude (−9.1 ± 1.7 vs. −4.8 ± 0.7 cm/s; P < 0.05). At high altitude, compared with low altitude, the cerebrovascular reactivity to CO2 in the hypercapnic range was unchanged (5.5 ± 0.7 vs. 5.3 ± 0.7%/mmHg; P = 0.06), while it was lowered in the hypocapnic range (3.1 ± 0.7 vs. 1.9 ± 0.6%/mmHg; P < 0.05). Dynamic cerebral autoregulation was further reduced during sleep ( P < 0.05 vs. low altitude). Lowered cerebrovascular reactivity to CO2 and reduction in both dynamic cerebral autoregulation and MCAv during sleep at high altitude may be factors in the pathogenesis of breathing instability.

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