Nayak A, Roy R J, Sharma A
Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180.
Ann Biomed Eng. 1994 Sep-Oct;22(5):501-13. doi: 10.1007/BF02367086.
A time-frequency spectral representation (TFSR) has been used to study the nonstationary information in the EEG as an aid in determining the anesthetic depth. This paper uses a TFSR with an exponential weighting function for the purpose. Raw EEG data were collected form 10 mongrel dogs at various levels of halothane anesthesia. Depth of anesthesia was tested by observing the response to tail clamping, which is considered a supramaximal stimulus in dogs. A positive response was graded as awake (depth 0), and a negative response was graded as asleep (depth 1). The EEG obtained during a period of 30 sec tail clamp was processed into TFSRs. It was observed that at depth 0, the spectrum becomes localized in time and frequency. The percentage of energy in the delta (1-3.5 Hz) and theta (3.5-7.5 Hz) frequency bands increased. At depth 1, the spectrum remained unchanged throughout the period of tail clamp. The performance of the TFSR in detecting the patient's awareness was also compared with the power spectrum. It was concluded that under certain anesthetic conditions, the TFSR is superior to the power spectrum.
时频谱表示（TFSR）已被用于研究脑电图（EEG）中的非平稳信息，以辅助确定麻醉深度。本文为此目的使用了具有指数加权函数的TFSR。从10只杂种犬在不同水平的氟烷麻醉下收集原始脑电图数据。通过观察对夹尾的反应来测试麻醉深度，夹尾被认为是犬类的超强刺激。阳性反应被分级为清醒（深度0），阴性反应被分级为睡眠（深度1）。在30秒夹尾期间获得的脑电图被处理为时频谱表示。观察到在深度0时，频谱在时间和频率上变得局部化。δ（1 - 3.5Hz）和θ（3.5 - 7.5Hz）频段的能量百分比增加。在深度1时，在整个夹尾期间频谱保持不变。还将时频谱表示在检测患者意识方面的性能与功率谱进行了比较。得出的结论是，在某些麻醉条件下，时频谱表示优于功率谱。
