Department of Anaesthesiology, University of Auckland, Auckland, New Zealand.
Department of Anaesthesia, Auckland City Hospital, Auckland, New Zealand.
Diving Hyperb Med. 2023 Sep 30;53(3):268-280. doi: 10.28920/dhm53.3.268-280.
Hypoxia can cause central nervous system dysfunction and injury. Hypoxia is a particular risk during rebreather diving. Given its subtle symptom profile and its catastrophic consequences there is a need for reliable hypoxia monitoring. Electroencephalography (EEG) is being investigated as a real time monitor for multiple diving problems related to inspired gas, including hypoxia.
A systematic literature search identified articles investigating the relationship between EEG changes and acute cerebral hypoxia in healthy adults. Quality of clinical evidence was assessed using the Newcastle-Ottawa scale.
Eighty-one studies were included for analysis. Only one study investigated divers. Twelve studies described quantitative EEG spectral power differences. Moderate hypoxia tended to result in increased alpha activity. With severe hypoxia, alpha activity decreased whilst delta and theta activities increased. However, since studies that utilised cognitive testing during the hypoxic exposure more frequently reported opposite results it appears cognitive processing might mask hypoxic EEG changes. Other analysis techniques (evoked potentials and electrical equivalents of dipole signals), demonstrated sustained regulation of autonomic responses despite worsening hypoxia. Other studies utilised quantitative EEG analysis techniques, (Bispectral index [BISTM], approximate entropy and Lempel-Ziv complexity). No change was reported in BISTM value, whilst an increase in approximate entropy and Lempel-Ziv complexity occurred with worsening hypoxia.
Electroencephalographic frequency patterns change in response to acute cerebral hypoxia. There is paucity of literature on the relationship between quantitative EEG analysis techniques and cerebral hypoxia. Because of the conflicting results in EEG power frequency analysis, future research needs to quantitatively define a hypoxia-EEG response curve, and how it is altered by concurrent cognitive task loading.
缺氧可导致中枢神经系统功能障碍和损伤。在再呼吸潜水过程中，缺氧是一个特殊的风险。鉴于其症状不明显且后果严重，因此需要可靠的缺氧监测。脑电图（EEG）作为一种实时监测器，正在被研究用于监测与吸入气体相关的多种潜水问题，包括缺氧。
系统文献检索确定了研究健康成年人脑电图变化与急性脑缺氧之间关系的文章。使用纽卡斯尔-渥太华量表评估临床证据质量。
共纳入 81 项研究进行分析。只有一项研究调查了潜水员。12 项研究描述了定量脑电图频谱功率差异。中度缺氧往往导致 alpha 活动增加。随着严重缺氧，alpha 活动减少，而 delta 和 theta 活动增加。然而，由于在缺氧暴露期间进行认知测试的研究更频繁地报告了相反的结果，因此似乎认知处理可能掩盖了缺氧脑电图变化。其他分析技术（诱发电位和偶极子的电等效信号）表明，尽管缺氧情况恶化，但自主反应仍能持续调节。其他研究使用定量脑电图分析技术（双谱指数[BISTM]、近似熵和伦佩尔-齐夫复杂度）。BISTM 值没有变化，而近似熵和伦佩尔-齐夫复杂度随着缺氧的恶化而增加。
脑电图频率模式会随急性脑缺氧而变化。关于定量脑电图分析技术与脑缺氧之间关系的文献很少。由于脑电图功率频率分析的结果存在冲突，因此未来的研究需要定量定义缺氧-脑电图反应曲线，以及认知任务负荷如何改变该曲线。
