Individualized autoregulation-guided arterial blood pressure management in neurocritical care

Neurotherapeutics, Journal Year: 2025, Volume and Issue: unknown, P. e00526 - e00526

Published: Jan. 1, 2025

Language: Английский

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Time-domain methods for quantifying dynamic cerebral blood flow autoregulation: Review and recommendations. A white paper from the Cerebrovascular Research Network (CARNet)

Journal of Cerebral Blood Flow & Metabolism, Journal Year: 2024, Volume and Issue: 44(9), P. 1480 - 1514

Published: April 30, 2024

Cerebral Autoregulation (CA) is an important physiological mechanism stabilizing cerebral blood flow (CBF) in response to changes perfusion pressure (CPP). By maintaining adequate, relatively constant supply of flow, CA plays a critical role brain function. Quantifying under different and pathological states crucial for understanding its implications. This knowledge may serve as foundation informed clinical decision-making, particularly cases where become impaired. The quantification functionality typically involves constructing models that capture the relationship between CPP (or arterial pressure) experimental measures CBF. Besides describing normal function, these provide means detect possible deviations from latter. In this context, recent white paper Cerebrovascular Research Network focused on Transfer Function Analysis (TFA), which obtains frequency domain estimates dynamic CA. present paper, we consider use time-domain techniques alternative approach. Due their increased flexibility, methods enable mitigation measurement/physiological noise incorporation nonlinearities time variations dynamics. Here, practical recommendations guidelines support researchers clinicians effectively utilizing study

Language: Английский

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A systematic review, meta-analysis, and meta-regression amalgamating the driven approaches used to quantify dynamic cerebral autoregulation

Journal of Cerebral Blood Flow & Metabolism, Journal Year: 2024, Volume and Issue: 44(8), P. 1271 - 1297

Published: April 18, 2024

Numerous driven techniques have been utilized to assess dynamic cerebral autoregulation (dCA) in healthy and clinical populations. The current review aimed amalgamate this literature provide recommendations create greater standardization for future research. PubMed database was searched with inclusion criteria consisting of original research articles using dCA assessments humans. Risk bias were completed Scottish Intercollegiate Guidelines Network Methodological Index Non-Randomized Studies. Meta-analyses conducted coherence, phase, gain metrics at 0.05 0.10 Hz deep-breathing, oscillatory lower body negative pressure (OLBNP), sit-to-stand maneuvers, squat-stand maneuvers. A total 113 studies included, 40 these incorporating 4126 participants identified, younger adults (18–40 years) being the most studied population. common squat-stands (n = 43), deep-breathing 25), OLBNP 20), sit-to-stands 16). Pooled coherence point estimates were: 0.70 (95%CI:0.59–0.82), 0.87 (95%CI:0.79–0.95), 0.98 (95%CI:0.98–0.99) Hz; 0.90 (95%CI:0.81–0.99); 0.67 (95%CI:0.44–0.90); 0.99 (95%CI:0.99–0.99) Hz. This summarizes findings, discusses pros/cons 11 unique provides investigations into physiological intricacies dCA.

Language: Английский

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On the challenge of assessing dynamic cerebral autoregulation

Experimental Physiology, Journal Year: 2024, Volume and Issue: 109(7), P. 1020 - 1023

Published: May 7, 2024

Connections link a sequence of three related research papers. The central article which links the other two papers has been published in Experimental Physiology. In article, an author (or authors) outlines its principal novel findings, tracing how they were influenced by first and contributed to developments made third article. author(s) may also speculate on direction future field. articles aim set wide context. Dynamic cerebral autoregulation (dCA) represents ability cerebrovasculature respond transient changes arterial blood pressure (ABP). quantification dCA remains complex endeavour considering that gold-standard examine black-box nature this entity does not exist. Over years, investigators have applied numerous methods approaches used diverse metrics quantify based single change, or oscillations (spontaneous/forced), ABP (reviewed Brassard et al., 2023). Unfortunately, limited included multi-method strategies completed comparisons between analytical when assessing dCA. Distinctive stressors (e.g., spontaneous vs. forced oscillation; increase decrease ABP) can differently engage challenge regulatory mechanisms associated with dCA, thus providing different physiological information. As most appear unrelated each other, comparing findings across is challenging. To help illustrate interpreting using stresses methods, we will use results from reports focusing influence exercise training modalities (i.e., endurance resistance training) young healthy individuals. Endurance induce distinct adaptations, likely because haemodynamic responses induced these types. Generally, habitual leads beneficial cerebrovascular function such as resting perfusion carbon dioxide reactivity. However, existing evidence shows absence impact, even detrimental effects, some aspects function, These equivocal partly be consequence differences types participants. Despite modality-dependent responses, recent cross-sectional study suggest effect derived transfer analysis (TFA) velocity (CBv: surrogate flow) repeated squat–stands performed at 0.05 0.10 Hz (Perry 2019). objective TFA, popular method estimate variables reflecting dynamic behaviour supposing latter linear control system input (ABP) output (CBv). TFA are: coherence fraction linearly CBv), gain CBv amplitude change for given change), phase timing difference waveforms). Spontaneous rest) driven are utilized TFA. fluctuations attractive those who want populations whom it possible, safe, force larger (e.g. patients diseases). low signal-to-noise ratio) usually lead less reliable reproducible estimations Techniques, squat–stands, augment power enhance interpretability reproducibility metrics. shown vessels act high-pass filter, means slower than 0.20 dampened above pass through unimpeded. frequencies often literature forcing large (0.05 Hz) frequency bands where thought important pressure–flow dynamics (historically, being 0.02–0.07 very 0.07−0.20 frequency). Also, prevalent could reveal information about potential mechanisms. their study, Perry al. (2019) reported non-significant trend lowered resistance-trained individuals, compared endurance-trained sedentary suggesting no clear impact modality Do necessarily mean cannot dCA? One must consider assumes symmetric, case. For instance, accumulating clearly suggests react increases, comparison decreases, ABP. Specifically, elevations attenuated increases. This phenomenon steady-state changes, well oscillations. all take into consideration (TFA example). Our group recently suggested utilization directional sensitivity metric non-pharmacological approach relationship increases decreases. series studies (detailed below), middle artery (MCAv) (MAP) higher Hz: indicative sympathetic tone Mayer waves) only. same cohort endurance- individuals (2019), subsequently quantified our proposed (Roy 2022). calculated absolute (ΔMCAvT/ΔMAPT) relative (%MCAvT/%MAPT) respect transition time intervals both calculate time-adjusted ratio MAP direction, averaged over 5-min squat–stands. Using analysis, ΔMCAvT/ΔMAPT %MCAvT/%MAPT lower during decreases but participants ratios sedentary, Hz, previously influences directionality specifically participants, presence selectively defends microcirculation overperfusion surges. hysteresis-like pattern interpreted alternatively, improved Considering did provide groups 2019), represent more sensitive detect changes. sharp contrast longitudinal examined (Thomas 2021). cross-over design 68 young, randomized complete 3 months modality, following comparable mentioned, offer greater coherence, addition Accordingly, robust stressor quantifying aspect via Although seems promising relationship, further warranted experimental conditions clinical/pathological flesh out key logistical aspects. double-ratio calculation validated truly reflect flow regulation, additional work necessary whether, hypercapnia, hypoxia hyperthermia, conditions, ageing, cardiovascular diseases. Interestingly, exist characterize relationship. example, previous work, squat–stand model only described better response autoregulatory index. Panerai (2023) new autoregressive-moving average models dividing signal components—first including beat-to-beat positive derivative information, then corresponding negative time-series. contrary advantage method, relatively small (Panerai Discrepancies 2022) methodological drive depth squat was (participants went 45-degree knee flexion angle) al.'s squatted down felt able) Alternatively, pointed (which tends oscillations) They argue sample size (n = 12/group) too low, bootstrap procedure evaluate number needed identify significant (critical number: n 24 squat–stands) Both reasons why detected Hz. A next logical step would compare analyses within performing one appreciate, population (in case, endurance-trained, individuals) (spontaneous analysis) interpretations. while Thomas (2021) do optimal strategy knowing high variability poor Finally, although improves searching alternatives crucial consideration, exists support sensitivity. We still early stages assessment, here again, squat–stands). Continued efforts find best metric, collection several stresses, adequately assess improve interpretation All authors read approved final version manuscript agree accountable ensuring questions accuracy integrity any part appropriately investigated resolved. persons designated qualify authorship, authorship listed. declare conflicts interest. No funding received work.

Language: Английский

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Lower Dynamic Cerebral Autoregulation following Acute Bout of Low-Volume High-Intensity Interval Exercise in Chronic Stroke Compared to Healthy Adults

Journal of Applied Physiology, Journal Year: 2024, Volume and Issue: unknown

Published: Feb. 15, 2024

Fluctuating arterial blood pressure during high-intensity interval exercise (HIIE) may challenge dynamic cerebral autoregulation (dCA), specifically after stroke an injury to the cerebrovasculature. We hypothesized that dCA would be attenuated at rest and a sit-to-stand transition immediately 30 min HIIE in individuals poststroke compared with age- sex-matched control subjects (CON). switched every minute between 70% 10% estimated maximal watts for 10 min. Mean (MAP) middle artery velocity (MCAv) were recorded. was quantified spontaneous fluctuations MAP MCAv via transfer function analysis. For sit-to-stand, time delay before increase cerebrovascular conductance index (CVCi = MCAv/MAP), rate of regulation, % change measured. Twenty-two (age 60 ± 12 yr, 31 16 mo) twenty-four CON 13 yr) completed study. Very low frequency (VLF) gain (

Language: Английский

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Directional sensitivity of the cerebral pressure-flow relationship during forced oscillations induced by oscillatory lower body negative pressure

Journal of Cerebral Blood Flow & Metabolism, Journal Year: 2024, Volume and Issue: 44(10), P. 1827 - 1839

Published: April 13, 2024

A directional sensitivity of the cerebral pressure-flow relationship has been described using repeated squat-stands. Oscillatory lower body negative pressure (OLBNP) is a reproducible method to characterize dynamic autoregulation (dCA). It could represent safer examine within clinical populations and/or during pharmaceutical administration. Therefore, examining an OLBNP-induced cyclic physiological stress crucial. We calculated changes in middle artery mean blood velocity (MCAv) per alterations arterial (MAP) compute ratios adjusted for time intervals (ΔMCAv T /ΔMAP ) with respect minimum-to-maximum MCAv and MAP, each OLBNP transition (0 −90 Torr), 0.05 Hz 0.10 OLBNP. then compared averaged ΔMCAv MAP increases (INC) /[Formula: see text]) decreases (DEC) text]). Nineteen healthy participants [9 females; 30 ± 6 years] were included. There no differences between INC DEC at Hz. text] (1.06 0.35 vs. 1.33 0.60 cm⋅s −1 /mmHg; p = 0.0076) was than These results support as model evaluate relationship.

Language: Английский

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Physiological influences on neurovascular coupling: A systematic review of multimodal imaging approaches and recommendations for future study designs

Experimental Physiology, Journal Year: 2024, Volume and Issue: unknown

Published: Oct. 11, 2024

Abstract In this review, we have amalgamated the literature, taking a multimodal neuroimaging approach to quantify relationship between neuronal firing and haemodynamics during task paradigm (i.e., neurovascular coupling response), while considering confounding physiological influences. Original research articles that used concurrent haemodynamic quantification in humans ( n ≥ 10) were included from PubMed, Scopus, Web of Science, EMBASE PsychINFO. Articles published before 31 July 2023 considered for eligibility. Rapid screening was completed by first author. Two authors title/abstract full‐text screening. Article quality assessed using modified version National Institutes Health Quality Assessment Tool Observational Cohort Cross‐Sectional Studies. A total 364 following The most common combination EEG/functional MRI (68.7%), with cognitive (48.1%) visual (27.5%) tasks being common. majority studies displayed an absence/minimal control blood pressure, arterial gas concentrations and/or heart rate (92.9%), only 1.3% monitored these factors. minority restricted or collected data pertaining caffeine (7.4%), exercise (0.8%), food (0.5%), nicotine (2.7%), menstrual cycle (0.3%) cardiorespiratory fitness levels (0.5%). cerebrovasculature is sensitive numerous factors; thus, understand response fully, better influences pressure respiratory metrics imperative study‐design formulation. Moreover, further work should continue examine sex‐based differences, influence sex steroid hormone fitness.

Language: Английский

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Cardiac and respiratory activities induce temporal changes in cerebral blood volume, balanced by a mirror CSF volume displacement in the spinal canal

NeuroImage, Journal Year: 2024, Volume and Issue: 305, P. 120988 - 120988

Published: Dec. 25, 2024

Language: Английский

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Unveiling the enigma from sick to beauty: Hungry to standardize metrics for dynamic cerebral autoregulation

Experimental Physiology, Journal Year: 2024, Volume and Issue: 109(4), P. 472 - 473

Published: Feb. 25, 2024

Language: Английский

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Letter to the editor: Deriving transfer function analysis metrics from driven methods

Journal of Cerebral Blood Flow & Metabolism, Journal Year: 2024, Volume and Issue: 44(6), P. 1053 - 1056

Published: March 11, 2024

Driven and spontaneous methods have been used to quantify the cerebral pressure-flow relationship via transfer function analysis (TFA). Commonly, TFA derived estimates are assessed using band averages within very-low (0.02-0.07 Hz) low (0.07-0.20 frequency during oscillations but quantified at frequencies of interest where blood pressure driven (e.g., 0.05 and/or 0.10 Hz). more closely resemble autoregulatory challenges individuals experience on a daily basis, while also eliciting higher levels reliability. While with point-estimates not feasible for all clinical populations, these approaches increase ability understand pathophysiological changes.

Language: Английский

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