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CSM FAQ - CSM vs. other monitors

7.1 Q: What is the essential difference between CSM and the BIS monitor?
A: Aside from the differences in size, price and ease of use, the CSM and the BIS calculate their indexes using different processes.
The CSM uses four parameters from the EEG combined into a fuzzy logic classifier, while the BIS basically applies a double spectral analysis (hence the word bispectral) of the EEG activity.
By applying a fuzzy logic-based system, the CSM achieves a faster response; hence what is shown on the screen is closer to real time.

7.2 Q: Is the CSI scale comparable to the BIS scale?
A: Yes, the different ranges in CSI are the same as in the BIS. Meaning e.g. that 40 to 60 is an adequate level of normal anaesthesia in both monitors.

7.3 Q: What is the essential difference between CSM and the A-line monitor?
A: The CSM is a “passive” monitor, meaning that it does not stimulate the patient in any way in order to measure anaesthetic depth.
The A-line monitor (AEP Monitor – Alaris AEP Monitor – AEP Monitor/2) is said to be “active”, meaning that it analyses the response of the brain to a specific form of stimulation. The A-line monitor extracts a neurological signal called the Auditory Evoked Potential (AEP), which is the response of the brain to sound. These evoked potentials respond to changes in the patient’s anaesthetic depth by modifying its shape. These changes are then quantified by the monitor into a numerical index.

7.4 Q: Is the CSI scale comparable to the AAI scale?
A: The different ranges in CSI are not the same as in the AAI. Meaning e.g. that CSI 40 to 60 is an adequate level of normal anaesthesia while it for the AAI is 15 to 25.

7.5 Q: What is the difference between CSM MK I and CSM MK 2?
A: CSM MK 2 has the following extra features
  • Backlight
  • Date and Time info in the data
  • EEG waveform
  • Fixed connection to a CSM Link
  • Auto connection to a CSM Link
  • Possible to have pay per usage

7.6 Q: Does the CSI in MK I differ from the CSI in MK 2?
A: No, The CSI calculation is the same.

7.7 Q: Does the CSI in MK 2 perform better than the CSI in MK I?
A: The CSM MK I can be upgraded (with new firmware) to have the same performance on the CSI as the CSM MK 2.
Contact Danmeter A/S for further information about upgrading devices.

7.8 Q: Does concurrent measurement of Somatosensory Evoked potentials affect the CSI?
A: There have been no specific reports about CSI alterations due to the concurrent measurement of SSEP. Nevertheless, the amount of interference on the EEG produced by the evoked potentials themselves is very small (in technical terms, a signal to noise ratio of about 1/30, which is unlikely to cause major interferences in the EEG signal used for the CSI calculation).
The greatest source of potential problems may come from the impedance measurements made by the EP equipments in order to test their electrodes. The currents this equipments use may produce a number of interference peaks which can have an effect on the EEG measurement performed by the CSM, potentially influencing the CSI calculation.
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