Probing the limits of human deep diving.

Area of Science:

• Hyperbaric physiology
• Diving medicine
• Gas toxicology

Background:

• Compressed air limits divers to 45m due to nitrogen narcosis and oxygen toxicity.
• Oxygen-helium (Heliox) allows greater depths but can cause high pressure nervous syndrome (h.p.n.s.) beyond 160m.
• h.p.n.s. symptoms include tremors, nausea, fatigue, and cognitive impairment.

Purpose of the Study:

• To investigate the efficacy of Trimix (Heliox with nitrogen) in ameliorating h.p.n.s. symptoms.
• To determine the effects of varying nitrogen percentages (5-10%) and compression rates on h.p.n.s. and nitrogen narcosis.
• To assess the safety and feasibility of deep dives using Trimix.

Main Methods:

• Simulated dives (ATLANTIS project) to depths exceeding 600m using Trimix.
• Varied compression rates (slow/rapid) and nitrogen concentrations (5-10% by volume).
• Comprehensive physiological and psychological monitoring, including performance tests, EEG, cardiovascular function, and blood analysis.

Main Results:

• Trimix with 5-10% nitrogen effectively reduced or eliminated h.p.n.s. symptoms at extreme depths.
• Slow, staged compressions over days were crucial for safe deep diving.
• Divers safely reached 686m, demonstrating the viability of the Trimix technique.

Conclusions:

• Trimix is a safe and effective breathing gas for deep diving, mitigating h.p.n.s.
• Slow exponential compression over extended periods is essential for deep dives.
• Careful diver selection and optimized gas mixtures are key to successful extreme depth exploration.