Does the evoked response measure inert gas narcosis?

Area of Science:

• Neuroscience
• Physiology
• Marine Biology

Background:

• Inert gas narcosis is a physiological condition affecting divers and individuals exposed to high-pressure environments.
• Assessing the depth of narcosis is crucial for safety, but reliable non-behavioral measures are needed.
• Cortical evoked responses (CERs) have been proposed as a potential objective indicator of narcosis.

Purpose of the Study:

• To critically evaluate the scientific validity of using changes in cortical evoked responses as a measure of inert gas narcosis in humans.
• To establish criteria for accepting non-behavioral measures as indicators of narcosis.
• To review existing experimental data on CERs under hyperbaric conditions.

Main Methods:

• Defined three essential criteria for a non-behavioral measure to be considered a valid indicator of narcosis.
• Analyzed two classes of experiments using CERs in hyperbaric settings.
• Critically examined arguments supporting the validity of CERs as a narcosis measure.

Main Results:

• Experiments in the first class, assessing CERs against multiple validity criteria, consistently indicated that CERs are not a valid measure of narcosis.
• The second class of experiments assumed CER validity without appropriate design, rendering their results inconclusive.
• Previous arguments supporting CER validity were found to be unsound.

Conclusions:

• The cortical evoked response is not a valid or reliable measure for assessing inert gas narcosis in humans.
• Factors beyond the narcotic potency of breathing gas mixtures significantly influence CER amplitude.
• Further research is needed to identify reliable non-behavioral indicators of narcosis.