Changes in EEG frequency characteristics during sevoflurane general anesthesia: feature extraction by variational...

Area of Science:

• Neuroscience
• Signal Processing
• Medical Informatics

Background:

• General anesthesia involves complex changes in brain activity, often monitored using electroencephalogram (EEG).
• Variational Mode Decomposition (VMD) is a signal processing technique for extracting intrinsic mode functions (IMFs) from time-series data.
• Analyzing EEG during anesthesia can provide insights into the depth and emergence from anesthetic states.

Purpose of the Study:

• To apply Variational Mode Decomposition (VMD) for analyzing electroencephalogram (EEG) signals during general anesthesia recovery.
• To develop and utilize an application, EEG Mode Decompositor, for decomposing EEG into IMFs and visualizing the Hilbert spectrogram.
• To identify and characterize changes in specific IMFs corresponding to emergence from general anesthesia.

Main Methods:

• EEG data were recorded from 10 adult patients undergoing sevoflurane anesthesia using a bispectral index monitor.
• The EEG Mode Decompositor application was used to decompose EEG signals into intrinsic mode functions (IMFs) via VMD.
• Central frequencies of the IMFs were analyzed during the 30-minute recovery period, correlating with bispectral index changes.

Main Results:

• A significant increase in the bispectral index from 47.1 to 97.4 was observed during recovery.
• The central frequency of IMF-1 significantly decreased from 0.4 Hz to 0.2 Hz.
• Significant increases in the central frequencies of IMF-2 through IMF-6 were observed, indicating dynamic changes in EEG components during emergence from anesthesia.

Conclusions:

• VMD is a valuable tool for analyzing EEG signals during general anesthesia, enabling the extraction of characteristic frequency changes.
• The identified IMF changes provide visualizable markers for monitoring emergence from anesthesia.
• This approach offers a novel method for understanding the neurophysiological effects of anesthetic agents.