www.masimo.com 13 Masimo
Chapter 1: Technology Overview
Theory of Operation
The Patient State Index (PSI) was constructed based upon multivariate combinations of
quantitative electroencephalogram (QEEG) variables found to be sensitive to changes in the
level of anesthesia but insensitive to the specific substances producing such changes. The
PSI is the result of a complex computation that combines weighted quantitative values
reflecting many dimensions of brain electrical activity, such as: (1) changes in power in
various EEG frequency bands, (2) changes in symmetry and synchronization between critical
brain regions, and (3) the inhibition of regions of the frontal cortex.
The PSI is computed from continuously monitored changes in the QEEG during surgery, using
statistical analysis to estimate the likelihood that the patient is anesthetized. SedLine
performs these computations automatically on the continuously recorded EEG after
automatic removal of data contaminated with artifact from physiological and environmental
signals. The computed PSI is periodically updated, displayed in numeric form, and presented
in a color-coded trend graphic for monitoring the effect of certain anesthetics on the state of
the brain.
To Next Page
Loading...
Need help?
General
