EEG functional connectivity is sensitive for nitrogen narcosis at 608 kPa
Xavier C E Vrijdag1, Hanna van Waart2, Rebecca M Pullon2,3
1Department of Anaesthesiology, School of Medicine, University of Auckland, Private bag 92019, Auckland, 1142, New Zealand. x.vrijdag@auckland.ac.nz.
Scientific Reports
|March 23, 2022
Summary
Divers breathing compressed air experience nitrogen narcosis, impairing cognition. This study found electroencephalogram (EEG) functional connectivity increases with nitrogen exposure, offering a potential metric for narcosis. Heliox breathing did not affect connectivity.
Area of Science:
- Neuroscience
- Diving Physiology
- Biomedical Engineering
Background:
- Nitrogen narcosis is a cognitive impairment divers experience under hyperbaric conditions.
- Helium is a non-narcotic gas used in diving to mitigate nitrogen's effects.
- Objective measurement of narcosis is crucial for diver safety.
Purpose of the Study:
- To explore electroencephalogram (EEG) functional connectivity as a metric for nitrogen narcosis.
- To quantify the relationship between hyperbaric nitrogen exposure and EEG functional connectivity.
- To differentiate the effects of air versus heliox breathing on brain activity.
Main Methods:
- Twelve participants underwent 32-channel EEG recordings while breathing air and heliox at hyperbaric pressures (284 and 608 kPa).
- Mutual information was used to estimate spatial functional connectivity, summarized by global efficiency.
- Psychometric tests were administered to assess cognitive function.
Main Results:
- Hyperbaric air breathing significantly increased global EEG functional connectivity by 35% at 608 kPa compared to surface conditions (p=0.001).
- A similar trend was observed at 284 kPa, indicating a dose-dependent effect.
- EEG functional connectivity showed a modest association with psychometric impairment (r²=0.60, p=0.02).
- Heliox breathing did not significantly alter functional connectivity.
Conclusions:
- Functional connectivity measured by EEG increases with hyperbaric nitrogen exposure, suggesting its potential as a specific indicator of nitrogen narcosis.
- This metric's sensitivity to nitrogen, but not helium, supports its targeted application in assessing narcosis.
- Findings contribute to developing objective measures for diver safety and performance monitoring.
