González Carmen, Garcia-Hernando Gabriel, Jensen Erik W, Vallverdú-Ferrer Montserrat
Biomedical Engineering Research Centre, CIBER of Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Universitat Politècnica de Catalunya, Barcelona, Spain.
Research and Development Department, Quantium Medical, Mataró, Spain.
Front Netw Physiol. 2022 Aug 29;2:912733. doi: 10.3389/fnetp.2022.912733. eCollection 2022.
Cerebral blood flow (CBF) reflects the rate of delivery of arterial blood to the brain. Since no nutrients, oxygen or water can be stored in the cranial cavity due to space and pressure restrictions, a continuous perfusion of the brain is critical for survival. Anesthetic procedures are known to affect cerebral hemodynamics, but CBF is only monitored in critical patients due, among others, to the lack of a continuous and affordable bedside monitor for this purpose. A potential solution through bioelectrical impedance technology, also known as rheoencephalography (REG), is proposed, that could fill the existing gap for a low-cost and effective CBF monitoring tool. The underlying hypothesis is that REG signals carry information on CBF that might be recovered by means of the application of advanced signal processing techniques, allowing to track CBF alterations during anesthetic procedures. The analysis of REG signals was based on geometric features extracted from the time domain in the first place, since this is the standard processing strategy for this type of physiological data. Geometric features were tested to distinguish between different anesthetic depths, and they proved to be capable of tracking cerebral hemodynamic changes during anesthesia. Furthermore, an approach based on Poincaré plot features was proposed, where the reconstructed attractors form REG signals showed significant differences between different anesthetic states. This was a key finding, providing an alternative to standard processing of REG signals and supporting the hypothesis that REG signals do carry CBF information. Furthermore, the analysis of cerebral hemodynamics during anesthetic procedures was performed by means of studying causal relationships between global hemodynamics, cerebral hemodynamics and electroencephalogram (EEG) based-parameters. Interactions were detected during anesthetic drug infusion and patient positioning (Trendelenburg positioning and passive leg raise), providing evidence of the causal coupling between hemodynamics and brain activity. The provided alternative of REG signal processing confirmed the hypothesis that REG signals carry information on CBF. The simplicity of the technology, together with its low cost and easily interpretable outcomes, should provide a new opportunity for REG to reach standard clinical practice. Moreover, causal relationships among the hemodynamic physiological signals and brain activity were assessed, suggesting that the inclusion of REG information in depth of anesthesia monitors could be of valuable use to prevent unwanted CBF alterations during anesthetic procedures.
脑血流量(CBF)反映了动脉血输送到大脑的速率。由于颅腔内因空间和压力限制无法储存营养物质、氧气或水,大脑的持续灌注对生存至关重要。已知麻醉程序会影响脑血流动力学,但由于缺乏用于此目的的连续且经济实惠的床边监测仪等原因,仅在重症患者中监测CBF。本文提出了一种通过生物电阻抗技术(也称为脑血流图,REG)的潜在解决方案,该技术可以填补现有低成本且有效的CBF监测工具的空白。其基本假设是REG信号携带有关CBF的信息,这些信息可能通过应用先进的信号处理技术得以恢复,从而能够在麻醉程序期间追踪CBF的变化。对REG信号的分析首先基于从时域提取的几何特征,因为这是此类生理数据的标准处理策略。测试几何特征以区分不同的麻醉深度,结果证明它们能够追踪麻醉期间的脑血流动力学变化。此外,还提出了一种基于庞加莱图特征的方法,其中REG信号重建的吸引子在不同麻醉状态之间显示出显著差异。这是一个关键发现,为REG信号的标准处理提供了替代方法,并支持REG信号确实携带CBF信息的假设。此外,通过研究整体血流动力学、脑血流动力学和基于脑电图(EEG)的参数之间的因果关系,对麻醉程序期间的脑血流动力学进行了分析。在麻醉药物输注和患者体位改变(头低脚高位和被动抬腿)期间检测到了相互作用,这为血流动力学与脑活动之间的因果耦合提供了证据。所提供的REG信号处理替代方法证实了REG信号携带CBF信息的假设。该技术的简单性及其低成本和易于解释的结果,应为REG进入标准临床实践提供新的机会。此外,评估了血流动力学生理信号与脑活动之间的因果关系,这表明在麻醉深度监测仪中纳入REG信息对于预防麻醉程序期间不必要的CBF变化可能具有重要价值。