Department of Biomedical Engineering, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland.
Department of Neurology, Poitiers University Hospital, Poitiers, France.
Acta Neurochir (Wien). 2024 Aug 2;166(1):321. doi: 10.1007/s00701-024-06209-5.
After a traumatic brain injury (TBI), monitoring of both macrovascular and microvascular blood circulation can potentially yield a better understanding of pathophysiology of potential secondary brain lesions. We investigated the changes in phase shift (PS) between cardiac-induced oscillations of cerebral blood flow (CBF) measured at macro (ultrasound Doppler) and microvascular (laser Doppler) level. Further we assessed the impact of intracranial pressure (ICP) on PS in TBI patients. A secondary aim was to compare PS to TCD-derived cerebral arterial time constant (τ), a parameter that reflects the circulatory transit time.
TCD blood flow velocities (FV) in the middle cerebral artery, laser Doppler blood microcirculation flux (LDF), arterial blood pressure (ABP), and ICP were monitored in 29 consecutive patients with TBI. Eight patients were excluded because of poor-quality signals. For the remaining 21 patients (median age = 23 (Q1: 20-Q3: 33); men:16,) data were retrospectively analysed. PS between the fundamental harmonics of FV and LDF signals was determined using spectral analysis. τ was estimated as a product of cerebrovascular resistance and compliance, based on the mathematical transformation of FV and ABP, ICP pulse waveforms.
PS was negative (median: -26 (Q1: -38-Q3: -15) degrees) indicating that pulse LDF at a heart rate frequency lagged behind TCD pulse. With rising mean ICP, PS became more negative (R = -0.51, p < 0.019) indicating that delay of LDF pulse increases. There was a significant correlation between PS and cerebrovascular time constant (R = -0.47, p = 0.03).
Pulse divergence between FV and LDF became greater with elevated ICP, likely reflecting prolonged circulatory travel time.
在创伤性脑损伤（TBI）后，监测宏观和微观血管的血流可以更好地了解潜在继发性脑损伤的病理生理学。我们研究了在宏观（超声多普勒）和微观（激光多普勒）水平测量的脑血流（CBF）的心脏诱导振荡之间的相位差（PS）的变化。进一步评估颅内压（ICP）对 TBI 患者 PS 的影响。次要目的是将 PS 与 TCD 衍生的脑动脉时间常数（τ）进行比较，τ 是反映循环转运时间的参数。
连续监测 29 例 TBI 患者的大脑中动脉 TCD 血流速度（FV）、激光多普勒血流微循环通量（LDF）、动脉血压（ABP）和 ICP。由于信号质量差，排除了 8 例患者。对于其余 21 名患者（中位数年龄=23（Q1：20-Q3：33）；男性：16），回顾性分析数据。使用频谱分析确定 FV 和 LDF 信号的基频谐波之间的 PS。τ 根据 FV 和 ABP、ICP 脉搏波的数学变换，作为脑血管阻力和顺应性的乘积来估计。
PS 为负（中位数：-26（Q1：-38-Q3：-15）度），表明在心率频率下 LDF 脉搏滞后。随着平均 ICP 的升高，PS 变得更负（R=-0.51，p<0.019），表明 LDF 脉搏的延迟增加。PS 与脑血管时间常数之间存在显著相关性（R=-0.47，p=0.03）。
随着 ICP 的升高，FV 和 LDF 之间的脉冲发散变得更大，这可能反映了循环时间的延长。
