ABSTRACT
Proper monitoring of anesthesia stages can guarantee the safe performance of clinical surgeries. In this study, different anesthesia stages were classified using near-infrared spectroscopy (NIRS) signals with machine learning. The cerebral hemodynamic variables of right proximal oxyhemoglobin (HbO2) in maintenance (MNT), emergence (EM) and the consciousness (CON) stage were collected and then the differences between the three stages were compared by phase-amplitude coupling (PAC). Then combined with time-domain including linear (mean, standard deviation, max, min and range), nonlinear (sample entropy) and power in frequency-domain signal features, feature selection was performed and finally classification was performed by support vector machine (SVM) classifier. The results show that the PAC of the NIRS signal was gradually enhanced with the deepening of anesthesia level. A good three-classification accuracy of 69.27% was obtained, which exceeded the result of classification of any single category feature. These results indicate the fesibility of NIRS signals in performing three or even more anesthesia stage classifications, providing insight into the development of new anesthesia monitoring modalities.
ABSTRACT
[2 + 2]-Cycloaddition is the most straightforward approach to the construction of cyclobutanes. In this paper, the intermolecular [2 + 2]-cycloaddition reaction of 3-alkylideneindolin-2-ones with alkenes was achieved. This reaction can be used in the synthesis of 3-spirocyclobutyl oxindoles, polycyclic oxindoles, and late stage modification of some drug molecules.
