Does hyperbaric oxygen cause narcosis or hyperexcitability? A quantitative EEG analysis.

Area of Science:

• Hyperbaric physiology
• Neuroscience
• Diving medicine

Background:

• Divers experience higher oxygen partial pressures at depth.
• The narcotic effects of oxygen under hyperbaric conditions are debated.
• Hyperbaric oxygen may induce dose-dependent cerebral hyperexcitability.

Purpose of the Study:

• To determine if hyperbaric oxygen has narcotic effects similar to nitrogen.
• To investigate the hyperexcitability effects of hyperbaric oxygen.
• To assess the impact of hyperbaric oxygen on cognitive function and brain activity.

Main Methods:

• Twelve participants breathed normobaric air, normobaric 100% oxygen, and hyperbaric 100% oxygen at 142 and 284 kPa.
• Psychometric performance, electroencephalography (EEG), and task load perception were measured.
• EEG data were analyzed using functional connectivity (global efficiency) and temporal complexity (default-mode-network complexity) algorithms.

Main Results:

• Hyperbaric oxygen did not alter EEG global efficiency or psychometric performance.
• A significant reduction in default-mode-network complexity and task load perception was observed with hyperbaric oxygen.
• EEG global efficiency changes seen with hyperbaric air (suggesting nitrogen narcosis) were absent with hyperbaric oxygen.
• Hyperbaric oxygen disturbed EEG temporal patterns, indicating potential early cortical hyperexcitability.

Conclusions:

• Hyperbaric oxygen is unlikely to be narcotic in a manner comparable to nitrogen.
• Findings suggest hyperbaric oxygen may induce early cortical hyperexcitability.
• Results inform divers about suitable gas mixtures and potential physiological effects of oxygen at depth.