BIS monitors, or Bispectral Index monitors, are medical devices designed to measure and display the depth of anesthesia or sedation during medical procedures. The Bispectral Index (BIS) is a dimensionless number that quantifies the depth of anesthesia based on the analysis of electroencephalogram (EEG) signals. BIS monitoring provides valuable information to anesthesiologists and healthcare providers, helping them optimize the level of anesthesia to ensure patient safety and comfort.