Sedation Monitoring

root Sedine monitor

Brain Function Monitoring

A More Complete Picture Starts with More Complete Data

About SedLine

SedLine® brain function monitoring advances neuromonitoring technologies to improve the care of patients under anaesthesia or sedation. The core product is a state-of-the-art EEG-based brain function monitor. Utilising 4 channels of information, the SedLine monitor measures the effects of anaesthesia and sedation by monitoring both sides of the brain's electrical activity to enable more individualised titration and improve the care of patients under anaesthesia or sedation.

In 2010, Masimo acquired SedLine, commercialised SedLine products through its worldwide distribution channels, and initiated next-generation brain function monitoring technology and product development.

EEG and Anaesthesia

EEG and Anaesthesia


Quantitative EEG (QEEG) Measures of Brain Activity in Response to Sedation/Anaesthesia Follow a Predictable Pattern

  • As the brain falls asleep, EEG activity declines according to a specific, invariant pattern1
    • In general, this drop in activity begins in the frontal lobes and moves toward the back of the brain

Shifts in EEG Power at Induction and Loss of Consciousness (LOC)

Masimo - EEG Power Shift Diagram showing shifts in EEG power at induction and loss of consciousness

These VARETA images depict changes in Delta wave (i.e., 3 to 5 Hz) activity. Anaesthesia (propofol shown here) spreads from the frontal lobes toward the back of the brain (note residual blue/white at induction). Even at LOC, the frontal lobes are more heavily anaesthetised areas.

  • When waking up, EEG activity increases across the brain in exactly the opposite sequence observed when falling asleep
  • These activity patterns have been shown to be invariant across a range of patient types and sedative/anaesthetic agents1
    • Propofol
    • Inhalation gas - Isoflurane, Sevoflurane and Desflurane
    • Nitrous/narcotic

PSi Algorithm

PSi Algorithm


A Sophisticated Algorithm

The SedLine device uses a sophisticated multivariate algorithm to assess the patient's EEG data from all 4 channels and determine the Patient State Index (PSi) value as a measure of anaesthetic depth.

SedLine technology is based on more than 10 years of technical and clinical development. The algorithm is based on extensive EEG records developed by the Brain Research Laboratory at New York University School of Medicine. The sensor technology was developed to improve the acquisition of EEG signals and was used in NASA's Sleep Studies in 1998. By providing an integrated algorithm based upon 4-channels of EEG data, demonstrated reliability under challenging clinical conditions and superior resistance to cautery, the SedLine monitor system offers a cost-effective alternative to other monitors. The system is currently in use at some of the nation's leading healthcare institutions.

Masimo - PSi Algorithm Chart

Grounded in Sound Science

The algorithm relies upon stepwise comparisons against extensive EEG records developed by the Brain Research Laboratory at New York University School of Medicine. These records encompass five databases with patient data recorded under a variety of clinical and anaesthetic conditions.

Using EEG Data From Both Sides of the Brain

Multiple sub-algorithms enhance the sensitivity of PSi algorithm to changes in activity. The "arousal observer" sub-algorithm detects subtle early changes in EEG that signify decreasing sedation. This sub-algorithm also scrutinises changes in activity occurring between pairs of leads for evidence of patterns signaling waning sedation levels.

Read PSi 25-50 Range of Optimal Hypnotic State for General Anaesthesia to learn more about the studies supporting the development of the algorithm.

PSi Guidelines

PSi Guidelines


A Greater Volume of Data to Enhance Your Anaesthetic Control

Brain function monitoring with SedLine helps the anaesthesia provider deliver the desired level of targeted sedation throughout all phases of anaesthesia. SedLine uses a sophisticated algorithm based on extensive EEG records to process EEG data and determine the PSi value as a measure of anaesthetic depth. The PSi corresponds to a patient's current level of sedation/anaesthesia along a scale of 0 to 100, where 100 represents being fully awake2. Guidelines for interpreting the full range of values are presented below. Read PSi 25-50 Range of Optimal Hypnotic State for General Anaesthesia to learn more about the studies supporting the development of these guidelines.

The PSi values reflect loss of consciousness, arousals, emergence and response to noxious stimuli. For ease in use, the numeric PSi values are colour coded on the display to promote immediate assessment of patient status. 4-channel real-time EEG data is presented as waveforms and as a Density Spectral Array (DSA) to enable quick and easy confirmation of PSi values.

Masimo - PSi Guidelines


  1. 1.

    John ER, Prichep LS, Kox W, et al. Invariant Reversible QEEG Effects of Anesthetics. Conscious Cogn.0 2001;10:165-183.

  2. 2.

    Prichep LS, Gugino LD, John ER, et al. The Patient State Index as an indicator of the level of hypnosis under general anesthesia. Br J Anaesth. 2004,92:393-399. Available online at


Masimo - Thumbnail of SedLine Studies

Follow the link for available SedLine studies.

Masimo - Brochure, Next Generation SedLine


Masimo - Next Generation SedLine Paediatric Brochure


Masimo - Product Information, Root with SedLine Brain Function Monitoring

Product Information

Masimo - SedLine Sedation Monitor Paediatric, Product Information

Product Information

Masimo - Root Product Information

Product Information

Masimo - Quick Reference Guide SedLine

Quick Reference

Masimo - Brochure Perioperative Care Solutions
Masimo - Product Information RD SedLine Sensor

Product Information