Measurement of anesthesia depth based on heart rate variability

It is an important human-computer interface application to monitore the depth of anesthesia in surgery. This paper aims at investigating the relationship between the depth of anesthesia and the variation of heart rate variability (HRV). Nonlinear analysis has been applied to the study of HRV and a quantitative parameter of Lorenz Plot - SD1 (standard deviation along short axis), has been proven to be a valuable measurement in monitoring anesthetic conditions. By plotting SD1 against time, we acquired a curve named curve of depth of anesthesia. The curves were generated for 8 subjects that were under general anesthesia in an oral and maxillofacial surgery. Before intubation and after regaining consciousness, the curve is mainly above a certain value (usually it is 10), while in anesthesia state the curve is mainly under that value. As the value of this quantitative parameter changes dramatically before, during and after general anesthesia, it may be a promising indicator in measurement of depth of anesthesia.