Characteristics of respiratory measures in young adults scanned at rest, including systematic changes and "missed" deep breaths
Characteristics of respiratory measures in young adults scanned at rest, including systematic changes and "missed" deep breaths
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DOI：
10.1016/j.neuroimage.2019.116234
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发表时间：
2020-01-01
期刊：
影响因子：
5.7
通讯作者：
Jones, Rebecca M.
中科院分区：
文献类型：
--
作者：
Power, Jonathan D.;Lynch, Charles J.;Jones, Rebecca M.
呼吸频率和深度影响血液中二氧化碳的浓度，改变脑血流量，从而改变功能性磁共振成像（fMRI）信号。这样的呼吸波动可以有很大的影响，在研究中的fMRI信号的协方差在休息，所谓的“休息状态功能连接”的技术。如果在功能磁共振成像扫描期间监测呼吸，则通常使用围绕受试者腹部的腰带来记录腹围。已从这些带记录中导出若干测量值，包括波形的窗口包络（ENV）、波形的窗口方差（呼吸变化，RV）以及每次呼吸的振幅除以呼吸的循环时间的测量值（每次呼吸量，RVT）。任何试图测量呼吸对功能磁共振成像信号的贡献的尝试都需要呼吸测量，但是关于这些测量如何相互比较，或者它们在最初提出的小型研究之外如何表现，我们知之甚少。在这里，我们研究了数百名健康的年轻人在休息时扫描一小时的这些措施的属性，这是人类连接组项目的一个子集，选择了高质量的生理记录。我们发现：1）ENV、RV和RVT都是相关的，并且ENV和RV彼此的相关性比与RVT的相关性更高; 2）呼吸事件如深呼吸表现出特征性心率升高、fMRI信号变化、头部运动和图像质量异常，这些特征性心率升高、fMRI信号变化、头部运动和图像质量异常被时间锁定到带迹线中的大偏转; 3）所有测量都可能“错过”深呼吸; 4）RVT比ENV或RV更多地“错过”深呼吸; 5）在14.4分钟的扫描过程中，所有呼吸测量都会发生系统性变化。我们讨论了这些研究结果对文献的影响，以及如何在模拟呼吸对功能磁共振成像扫描的影响方面取得进展。
Breathing rate and depth influence the concentration of carbon dioxide in the blood, altering cerebral blood flow and thus functional magnetic resonance imaging (fMRI) signals. Such respiratory fluctuations can have substantial influence in studies of fMRI signal covariance in subjects at rest, the so-called "resting state functional connectivity" technique. If respiration is monitored during fMRI scanning, it is typically done using a belt about the subject's abdomen to record abdominal circumference. Several measures have been derived from these belt records, including the windowed envelope of the waveform (ENV), the windowed variance in the waveform (respiration variation, RV), and a measure of the amplitude of each breath divided by the cycle time of the breath (respiration volume per time, RVT). Any attempt to gauge respiratory contributions to fMRI signals requires a respiratory measure, but little is known about how these measures compare to each other, or how they perform beyond the small studies in which they were initially proposed. Here, we examine the properties of these measures in hundreds of healthy young adults scanned for an hour each at rest, a subset of the Human Connectome Project chosen for having high-quality physiological records. We find: 1) ENV, RV, and RVT are all correlated, and ENV and RV are more highly correlated to each other than to RVT; 2) respiratory events like deep breaths exhibit characteristic heart rate elevations, fMRI signal changes, head motions, and image quality abnormalities time-locked to large deflections in the belt traces; 3) all measures can "miss" deep breaths; 4) RVT "misses" deep breaths more than ENV or RV; 5) all respiratory measures change systematically over the course of a 14.4-min scan. We discuss the implications of these findings for the literature and ways to move forward in modeling respiratory influences on fMRI scans.