Significance Combining diffuse correlation spectroscopy (DCS) and near-infrared spectroscopy (NIRS) permits simultaneous monitoring of multiple cerebral hemodynamic parameters related to cerebral autoregulation; however, interpreting these optical measurements can be confounded by signal contamination from extracerebral tissue. Aim We aimed to evaluate extracerebral signal contamination in NIRS/DCS data acquired during transient hypotension and assess suitable means of separating scalp and brain signals. Approach A hybrid time-resolved NIRS/multidistance DCS system was used to simultaneously acquire cerebral oxygenation and blood flow data during transient orthostatic hypotension induced by rapid-onset lower body negative pressure (LBNP) in nine young, healthy adults. Changes in microvascular flow were verified against changes in middle cerebral artery velocity (MCAv) measured by transcranial Doppler ultrasound. Results LBNP significantly decreased arterial blood pressure (-18%±14%), scalp blood flow (>30%), and scalp tissue oxygenation (all p≤0.04 versus baseline). However, implementing depth-sensitive techniques for both DCS and time-resolved NIRS indicated that LBNP did not significantly alter microvascular cerebral blood flow and oxygenation relative to their baseline values (all p≥0.14). In agreement, there was no significant reduction in MCAv (8%±16%; p=0.09). Conclusion Transient hypotension caused significantly larger blood flow and oxygenation changes in the extracerebral tissue compared to the brain. We demonstrate the importance of accounting for extracerebral signal contamination within optical measures of cerebral hemodynamics during physiological paradigms designed to test cerebral autoregulation.

中文翻译：

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使用深度增强漫相关光谱和近红外光谱分离短暂性低血压期间的脑血流动力学。

意义 结合漫反射相关光谱 (DCS) 和近红外光谱 (NIRS) 可以同时监测与脑自动调节相关的多个脑血流动力学参数；然而，解释这些光学测量可能会被来自大脑外组织的信号污染所混淆。目的 我们旨在评估短暂性低血压期间获取的 NIRS/DCS 数据中的脑外信号污染，并评估分离头皮和大脑信号的合适方法。方法 使用混合时间分辨 NIRS/多距离 DCS 系统，在 9 名年轻健康成年人中，在由快速下半身负压 (LBNP) 引起的短暂直立性低血压期间同时采集脑氧合和血流数据。微血管流量的变化根据经颅多普勒超声测量的大脑中动脉速度 (MCAv) 的变化进行了验证。结果 LBNP 显着降低了动脉血压 (-18%±14%)、头皮血流量 (>30%) 和头皮组织氧合作用（与基线相比，所有 p ≤ 0.04）。然而，对 DCS 和时间分辨 NIRS 实施深度敏感技术表明，LBNP 相对于其基线值没有显着改变微血管脑血流量和氧合（所有 p≥0.14）。一致认为，MCAv 没有显着降低 (8%±16%；p=0.09)。结论 与大脑相比，短暂性低血压导致大脑外组织的血流量和氧合变化显着增加。