Heliox at 4 ATA Reduces Error Rates Compared to Trimix and Air, but It Does Not Affect Short-Term Memory in...

Area of Science:

• Hyperbaric physiology
• Neuroscience
• Diving medicine

Background:

• Hyperbaric conditions during diving can impair cognitive functions like accuracy and reaction time.
• Inert gas narcosis, oxygen toxicity, and CO2 retention are potential cognitive stressors.
• Heliox and trimix are proposed breathing gas mixtures to mitigate these effects, but evidence at recreational depths is limited.

Purpose of the Study:

• To investigate the short-term effects of hyperbaric exposure at 4 ATA (30 msw) on cognitive functioning.
• To compare the cognitive performance across different breathing gas mixtures: air, trimix, and heliox.
• To determine if heliox offers cognitive advantages over air and trimix at recreational diving depths.

Main Methods:

• A controlled study involving neuropsychological testing of participants at 1 ATA (pre-exposure), 4 ATA (during exposure), and 1 ATA (post-decompression).
• Participants were exposed to hyperbaric conditions while breathing air, trimix, or heliox.
• Cognitive performance was assessed using tasks measuring accuracy and reaction time, specifically the Simon task.

Main Results:

• Breathing heliox at 4 ATA resulted in a significantly lower error rate (1.12%) on the Simon task compared to baseline (1.89%).
• In contrast, participants breathing air showed a near doubling of their error rate at 4 ATA (4.38%) compared to baseline (2.3%).
• Heliox demonstrated an accuracy-preserving strategy, while air promoted speed at the expense of accuracy.

Conclusions:

• Breathing heliox minimizes cognitive errors under conditions of cognitive conflict during hyperbaric exposure.
• Heliox appears to be a preferable breathing gas mixture for diving, even at recreational depths, due to its ability to preserve accuracy.
• Prioritizing error prevention over speed is crucial for operational safety in diving, supporting the use of heliox.