Apnoeic diving safety - experimental approaches to oxygen augmentation.

Area of Science:

• Physiology
• Diving Medicine
• Respiratory Physiology

Background:

• Apnoeic black-out during ascent is a critical risk for divers.
• Current safety measures for apnoeic black-out are debated.
• Progressive tunnel vision precedes complete loss of consciousness in black-out.

Purpose of the Study:

• To investigate the efficacy of oxygen augmentation during ascent in apnoeic divers.
• To determine if oxygen injection can delay the onset of hypoxic black-out.
• To assess the impact of oxygen augmentation on oxygen availability to the diver.

Main Methods:

• Experiments conducted on 111 apnoeic divers.
• Oxygen (50-100 ml) injected into the trachea via a syringe at the onset of black-out symptoms during 10m dives.
• Simulated involuntary ventilatory activity used to mix gases.
• Lung-brain circulation time estimated at 5.2 seconds.

Main Results:

• Oxygen augmentation was shown to delay unconsciousness in distressed apnoeic divers.
• The gas injection method raised the amount of available oxygen to the diver by 25-50%.
• Increased intrathoracic pressure potentially aids oxygen delivery to capillaries.

Conclusions:

• Oxygen augmentation via tracheal injection is a viable method to delay hypoxic black-out.
• The technique is effective for 10m dives and increases diver safety.
• Further research may explore integration with other existing safety devices.