Oxygen Toxicity and Scuba Diving
Oxygen toxicity is a condition which affects divers who expose themselves to high concentrations of oxygen by diving deep or using mixed gasses. Recreational divers who adhere to safety guidelines and follow the limits of recreational diving have little or no chance of experiencing this condition.
Oxygen is needed for life, but up to a certain point, it becomes toxic. The human body uses oxygen to perform essential cell functions. The metabolism of this oxygen and the collision of oxygen molecules creates free radicals which can cause significant damage to cells of the body. The cells of the human body usually inactivate these free radicals as soon as they are formed but when the rate in which there taken into the body exceeds the rate at which they are being eliminated, oxygen then becomes toxic.
Nitrox, also known as ‘Enriched Air’ is a blend of pure nitrogen and oxygen. Nitrox has an oxygen percentage between 22 and 40 % while the air we breathe is about 21% oxygen and 79% nitrogen. Scuba divers risk oxygen toxicity if they take in an excessively high partial pressure of oxygen or are exposed to elevated partial pressures of oxygen for extended periods. Divers risk oxygen toxicity when they dive beyond recreational depth limits on air diving, scuba diving on enriched air nitrox, or a mixture of another gas with a high oxygen percentage, and using enriched air or oxygen for decompression stops.
When training for deep, enriched air, divers must learn to monitor their exposure to elevated partial pressures of oxygen because the longer he stays exposed to elevated partial pressures of oxygen, the more likely he is to be exposed to oxygen toxicity. There is a point at which he must stop this exposure or run a risk of oxygen toxicity. Tracking oxygen toxicity can be done by either the use of oxygen toxicity units, oxygen clocks or a dive computer.
Recreational divers can reduce their chances of oxygen toxicity by adhering to the recreational depth limits of 130 feet. In general, divers should adhere to the safety rules below:
- Staying within depth limits of 130 feet as anything shallower will expose the diver to toxic oxygen. Therefore, divers should monitor their depths to ensure they stay within them and most training organisations recommend an optimum partial pressure of oxygen of 1.4 ata.
- Maintain buoyancy control and awareness always
- Take air breaks occasionally to reduce the risk of pulmonary oxygen toxicity
- Track your total oxygen exposure. If diving with mixed gasses or nitrox use an oxygen toxicity unit, a dive computer or an oxygen clock calculator to track your overall oxygen exposure.
- Keep your carbon dioxide levels low. Strenuous exercises and poor functioning regulators can elevate divers CO2 levels, causing them to retain oxygen and increase their predisposition to oxygen toxicity.
- Avoid oxygen exciters which can be found in decongestants containing Pseudoephedrine HCl as they accelerate the onset of oxygen toxicity.