Abstract：
Postural change from supine or sitting to standing up leads to displacement of 300 to 1000 mL of blood from the central parts of the body to the lower limb, which causes a decrease in venous return to the heart, hence decrease in cardiac output, causing a drop in blood pressure. This may lead to falling down, syncope, and in general reducing the quality of daily activities, especially in the elderly and anyone suffering from nervous system disorders such as Parkinson\'s or orthostatic hypotension (OH). Among different modalities to study brain function, functional near-infrared spectroscopy (fNIRS) is a neuroimaging method that optically measures the hemodynamic response in brain tissue. Concentration changes in oxygenated hemoglobin (HbO2) and deoxygenated hemoglobin (HHb) are associated with brain neural activity. fNIRS is significantly more tolerant to motion artifacts compared to fMRI, PET, and EEG. At the same time, it is portable, has a simple structure and usage, is safer, and much more economical. In this article, we systematically reviewed the literature to examine the history of using fNIRS in monitoring brain oxygenation changes caused by sudden changes in body position and its relationship with the blood pressure changes. First, the theory behind brain hemodynamics monitoring using fNIRS and its advantages and disadvantages are presented. Then, a study of blood pressure variations as a result of postural changes using fNIRS is described. It is observed that only 58 % of the references concluded a positive correlation between brain oxygenation changes and blood pressure changes. At the same time, 3 % showed a negative correlation, and 39 % did not show any correlation between them.
摘要：
从仰卧或坐着到站立的姿势改变导致300至1000毫升的血液从身体的中央部分移位到下肢，导致心脏静脉回流减少，因此心输出量减少，导致血压下降.这可能会导致跌倒,晕厥,通常会降低日常活动的质量，尤其是老年人和患有神经系统疾病的人，如帕金森氏症或直立性低血压（OH）。在研究大脑功能的不同方式中，功能近红外光谱（fNIRS）是一种神经成像方法，可光学测量脑组织中的血液动力学反应。氧合血红蛋白（HbO2）和脱氧血红蛋白（HHb）的浓度变化与脑神经活动有关。与fMRI相比，fNIRS对运动伪影的耐受性明显更高，PET,和脑电图。同时,它是便携式的，具有简单的结构和用法，更安全,而且更经济。在这篇文章中,我们系统回顾了使用fNIRS监测体位突然变化引起的脑氧合变化的历史及其与血压变化的关系。首先,介绍了基于fNIRS的脑血流动力学监测原理及其优缺点。然后，描述了使用fNIRS对姿势变化导致的血压变化的研究。据观察，只有58％的参考文献得出结论，脑氧合变化与血压变化之间存在正相关。同时,3%呈负相关,39%没有显示它们之间的相关性。
