If the loss of oxygen supply is permanent, what should be done?

In the event of a permanent loss of oxygen supply during a dive, the most appropriate action is to complete decompression using a mixture of 50% nitrogen and 50% oxygen. This approach allows for maintaining a safe respiratory environment, reducing the risk of hypoxia while effectively facilitating decompression.

Using a nitrogen-oxygen mix provides a balance that helps to mitigate the potential dangers associated with breathing pure oxygen at depth, such as oxygen toxicity. It also allows for the safe removal of nitrogen from the body during the ascent, which is crucial to prevent decompression sickness. The carefully calibrated composition of 50% nitrogen and 50% oxygen can help ensure that a diver remains adequately supplied with oxygen while also allowing for effective management of nitrogen levels.

Returning to the surface without completing proper decompression may lead to serious health issues, including decompression sickness, due to the accumulation of nitrogen in the tissues under higher pressures. Completing decompression entirely on air or using surface air would not provide adequate oxygen levels to support physiological needs in the situation of permanent loss of oxygen supply, potentially resulting in dangerous consequences.