Slow Rhythmic Oscillations of Blood Pressure, Intracranial Pressure, Microcirculation, and Cerebral Oxygenation

Steinmeier, Ralf; Bauhuf, Christian; Hübner, Ulrich; Bauer, R.; Fahlbusch, Rudolf; Laumer, Rudolf; Bondàr, Imré

doi:10.1161/01.str.27.12.2236

Cited by 105 publications

(60 citation statements)

References 33 publications

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“…The cerebral microvasculature shows slow rhythmic activity known as vasomotion. It remains unclear whether these different microcirculatory and metabolic oscillations are localized to meet varying metabolic demands and whether they are synchronized by unknown mechanisms or are induced by systemic hemodynamic factors (35). The phase dynamics approach presented herein is particularly well suited to study of such complex problems.…”

Section: Discussionmentioning

confidence: 99%

Phase dynamics in cerebral autoregulation

Łątka

Turalska²,

Glaubic-Łatka³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

144

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plex continuous wavelet transforms are used to study the dynamics of instantaneous phase difference ⌬ between the fluctuations of arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) in a middle cerebral artery. For healthy individuals, this phase difference changes slowly over time and has an almost uniform distribution for the very low-frequency (0.02-0.07 Hz) part of the spectrum. We quantify phase dynamics with the help of the synchronization index ␥ ϭ ͗sin⌬͘ 2 ϩ ͗cos⌬͘ 2 that may vary between 0 (uniform distribution of phase differences, so the time series are statistically independent of one another) and 1 (phase locking of ABP and CBFV, so the former drives the latter). For healthy individuals, the groupaveraged index ␥ has two distinct peaks, one at 0.11 Hz [␥ ϭ 0.59 Ϯ 0.09] and another at 0.33 Hz (␥ ϭ 0.55 Ϯ 0.17). In the very low-frequency range (0.02-0.07 Hz), phase difference variability is an inherent property of an intact autoregulation system. Consequently, the average value of the synchronization parameter in this part of the spectrum is equal to 0.13 Ϯ 0.03. The phase difference variability sheds new light on the nature of cerebral hemodynamics, which so far has been predominantly characterized with the help of the high-pass filter model. In this intrinsically stationary approach, based on the transfer function formalism, the efficient autoregulation is associated with the positive phase shift between oscillations of CBFV and ABP. However, the method is applicable only in the part of the spectrum (0.1-0.3 Hz) where the coherence of these signals is high. We point out that synchrony analysis through the use of wavelet transforms is more general and allows us to study nonstationary aspects of cerebral hemodynamics in the very low-frequency range where the physiological significance of autoregulation is most strongly pronounced. cerebral blood flow; transcranial Doppler sonography; wavelets; synchronization THE STATISTICAL PROPERTIES of physiological fluctuations, such as those found in the time series for heartbeat dynamics (10, 28), respiration (1, 27, 40), human locomotion (11, 39), and posture control (4), have been the focus of interdisciplinary research for more than two decades. This research has underscored the significance of nonlinear and nonstationary aspects of intrinsic variability of many physiological phenomena. Such variability seems to indicate the adaptability of the underlying control systems. The change of paradigm, associated with how we view the dynamics of physiologic phenomena, has not, to date, significantly influenced the interpretation of fluctuations in cerebral hemodynamics. In particular, the mathematical analysis of the fluctuations in either intracranial pressure or cerebral blood flow (CBF) velocity (CBFV) in major arteries is largely confined to traditional spectral methods.A healthy human brain is perfused with blood flowing laminarly through cerebral vessels, providing brain tissue with substrates such as oxygen and glucose. It turns out that CBF...

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Section: Discussionmentioning

confidence: 99%

Phase dynamics in cerebral autoregulation

Łątka

Turalska²,

Glaubic-Łatka³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

144

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“…5,12,16,30,32 These biological signals will show frequency peaks within certain frequency bands.6,11 They can be categorized into two groups: 1) the B waves that occur at approximately 0.5-3 cycles per minute, which corresponds to a frequency of 0.008-0.05 Hz;5,16,23 and 2) M waves, which occur at approximately 4-9 cycles per minute, which corresponds to a frequency of 0.07-0.15 Hz. 7,12,22 The 6 ventiabbreviatioNs ABP = arterial blood pressure; CPPopt = optimal cerebral perfusion pressure; GCS = Glasgow Coma Scale; GOS = Glasgow Outcome Scale; ICP = intracranial pressure; IQR = interquartile range; L-PRx = long pressure reactivity index; PVS = persistent vegetative state; TBI = traumatic brain injury.…”

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confidence: 99%

Short pressure reactivity index versus long pressure reactivity index in the management of traumatic brain injury

Lang

Kasprowicz

Smielewski

et al. 2015

JNS

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A rteriAl blood pressure (ABP), intracranial pressure (ICP), cerebral blood flow velocity measured with transcranial Doppler ultrasonography, and cerebral microcirculation assessed by laser Doppler flow are periodical biological signals that can be continuously monitored and recorded in both routine and ICU settings by using invasive and noninvasive techniques and devices. 5,12,16,30,32 These biological signals will show frequency peaks within certain frequency bands.6,11 They can be categorized into two groups: 1) the B waves that occur at approximately 0.5-3 cycles per minute, which corresponds to a frequency of 0.008-0.05 Hz;5,16,23 and 2) M waves, which occur at approximately 4-9 cycles per minute, which corresponds to a frequency of 0.07-0.15 Hz. 7,12,22 The 6 ventiabbreviatioNs ABP = arterial blood pressure; CPPopt = optimal cerebral perfusion pressure; GCS = Glasgow Coma Scale; GOS = Glasgow Outcome Scale; ICP = intracranial pressure; IQR = interquartile range; L-PRx = long pressure reactivity index; PVS = persistent vegetative state; TBI = traumatic brain injury. obJect The pressure reactivity index (PRx) correlates with outcome after traumatic brain injury (TBI) and is used to calculate optimal cerebral perfusion pressure (CPPopt). The PRx is a correlation coefficient between slow, spontaneous changes (0.003-0.05 Hz) in intracranial pressure (ICP) and arterial blood pressure (ABP). A novel index-the so-called long PRx (L-PRx)-that considers ABP and ICP changes (0.0008-0.008 Hz) was proposed. methods The authors compared PRx and L-PRx for 6-month outcome prediction and CPPopt calculation in 307 patients with TBI. The PRx- and L-PRx-based CPPopt were determined and the predictive power and discriminant abilities were compared. results The PRx and L-PRx correlation was good (R = 0.7, p < 0.00001; Spearman test). The PRx, age, CPP, and Glasgow Coma Scale score but not L-PRx were significant fatal outcome predictors (death and persistent vegetative state). There was a significant difference between the areas under the receiver operating characteristic curves calculated for PRx and L-PRx (0.61 ± 0.04 vs 0.51 ± 0.04; z-statistic = -3.26, p = 0.011), which indicates a better ability by PRx than L-PRx to predict fatal outcome. The CPPopt was higher for L-PRx than for PRx, without a statistical difference (median CPPopt for L-PRx: 76.9 mm Hg, interquartile range [IQR] ± 10.1 mm Hg; median CPPopt for PRx: 74.7 mm Hg, IQR ± 8.2 mm Hg). Death was associated with CPP below CPPopt for PRx (c 2 = 30.6, p < 0.00001), and severe disability was associated with CPP above CPPopt for PRx (c 2 = 7.8, p = 0.005). These relationships were not statistically significant for CPPopt for L-PRx. coNclusioNs The PRx is superior to the L-PRx for TBI outcome prediction. Individual CPPopt for L-PRx and PRx are not statistically different. Deviations between CPP and CPPopt for PRx are relevant for outcome prediction; those between CPP and CPPopt for L-PRx are not. The PRx uses the entire B-wave spectrum for index calculation, whereas the ...

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“…Traditional PRx measurements rely on spontaneous ABP oscillations across a low-frequency bandwidth corresponding to low-frequency waves described in ICP tracings by Lundberg (Lundberg's slow waves) (19). Functional cerebral vasculature reacts to ABP changes lasting more than 10 s and is too slow to react against ABP changes lasting Ͻ4 s (1).…”

Section: Discussionmentioning

confidence: 99%

Positive end-expiratory pressure oscillation facilitates brain vascular reactivity monitoring

Brady

Easley

Kibler

et al. 2012

Journal of Applied Physiology

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Brady KM, Easley RB, Kibler K, Kaczka DW, Andropoulos D, Fraser CD 3rd, Smielewski P, Czosnyka M, Adams GJ, Rhee CJ, Rusin CG. Positive end-expiratory pressure oscillation facilitates brain vascular reactivity monitoring. J Appl Physiol 113: 1362-1368, 2012. First published September 13, 2012 doi:10.1152/japplphysiol.00853.2012.-The pressure reactivity index (PRx) identifies optimal cerebral perfusion pressure after traumatic brain injury. We describe a method to improve PRx precision by induced variations in arterial blood pressure (ABP) using positive end-expiratory pressure (PEEP) modulation (iPRx). Neonatal swine (n ϭ 10) were ventilated with static PEEP and then with PEEP oscillated between 5 and 10 cmH2O at a frequency of 1/min. PRx was recorded as a moving correlation coefficient between ABP and intracranial pressure (ICP) from spontaneous ABP activity (0.05-0.003 Hz) during static PEEP. iPRx was similarly recorded with PEEP oscillation-induced ABP waves. The lower limit of autoregulation (LLA) was delineated with continuous cortical laser Doppler flux monitoring. PEEP oscillation increased autoregulation-monitoring precision. The ratios of median absolute deviations to range of possible values for the PRx and iPRx were 9.5% (8.3-13.7%) and 6.2% (4.2-8.7%), respectively (P ϭ 0.006; median, interquartile range). The phase-angle difference between ABP and ICP above LLA was 161°(150°-166°) and below LLA, Ϫ31°(Ϫ42°to 12°, P Ͻ 0.0001). iPRx above LLA was Ϫ0.42 (Ϫ0.67 to Ϫ0.29) and below LLA, 0.32 (0.22-0.43, P ϭ 0.0004). A positive iPRx was 97% specific and 91% sensitive for perfusion pressure below LLA. PEEP oscillation caused stable, low-frequency ABP oscillations that reduced noise in the PRx. Safe translation of these findings to clinical settings is expected to yield more accurate and rapid delineation of individualized optimal perfusion-pressure goals for patients. cerebrovascular autoregulation; pressure reactivity; positive end-expiratory pressure; neonatal CEREBROVASCULAR PRESSURE AUTOREGULATION is a vital, homeostatic mechanism in the mammalian brain that constrains cerebral blood flow (CBF) during changes in arterial blood pressure (ABP). Dynamic cerebrovascular resistance (CVR), also known as pressure reactivity, mediates autoregulation.The pressure reactivity index (PRx) was first described in 1997 as a means of monitoring cerebrovascular reactivity by moving correlation between slow waves (0.05-0.008 Hz) of ABP and intracranial pressure (ICP) (9). When autoregulation is intact, vascular constriction occurs during increased ABP, and vascular dilatation occurs during decreased ABP. Dilatation and constriction of the cerebral vasculature due to autoregulation can be trended by ICP monitoring: ICP increases during vasodilation and decreases during vasoconstriction (13). Therefore, positive ABP-ICP correlation (positive PRx) indicates pressure-passive cerebral vasculature, a state seen when cerebral perfusion pressure (CPP) is either excessive or inadequate for cerebrovascular autoregulation. Convers...

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Slow Rhythmic Oscillations of Blood Pressure, Intracranial Pressure, Microcirculation, and Cerebral Oxygenation

Abstract: These results strongly support Rosner's theory that ICP B-waves are the autoregulatory response of spontaneous fluctuations of cerebral perfusion pressure. There is casuistic evidence that failure of autoregulation significantly modifies time delay and the correlation between aBP and ICP.

Cited by 105 publications

References 33 publications

Phase dynamics in cerebral autoregulation

Phase dynamics in cerebral autoregulation

Short pressure reactivity index versus long pressure reactivity index in the management of traumatic brain injury

Positive end-expiratory pressure oscillation facilitates brain vascular reactivity monitoring

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