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DAN – Oxygen First Aid for Divers


Emergency oxygen is the first line of treatment for all cases of both decompression sickness (DCS) and arterial gas embolism (AGE) that do not require CPR. As divers we need to understand not only how to provide oxygen first aid, but when to use different methods of oxygen delivery, and why oxygen can help an injured diver. Like any first aid skill, oxygen administration requires proper training, specific equipment, and regular knowledge and skills updates. Prompt and effective delivery of oxygen first aid can alleviate or eliminate symptoms of DCS, improve patient outcomes, and save lives. Take a moment to refresh your knowledge of oxygen first aid and prepare yourself to respond to any diving emergency.


The most important aspect of responding to any emergency is providing for your own safety. Before approaching any injured diver, assess the scene and make sure that rendering aid will not put you at risk. Then, follow these steps:

  • Send for help
  • Verify that your oxygen cylinder is full, and get the injured divers consent to render aid. If a diver is unresponsive permission to help is assumed, but a conscious diver must consent to oxygen administration.
  • Begin to administer first aid. If a diver is not breathing on their own, they may require ventilation. This should not be attempted by an untrained rescuer, and you should begin CPR immediately.
  • Deliver oxygen in the greatest concentration possible. A demand valve can deliver a fraction of inhaled oxygen of up to 95%, but not all divers may be able to tolerate it. A constant flow system like a non-rebreather mask may be easier to tolerate but can only deliver a fraction of oxygen up to 80%. Remember that it is more beneficial to provide a diver a high inspired fraction of oxygen that depletes your supplies on the way to the hospital, than it is to breathe a lower inspired fraction of O2 the entire way to medical care, as long as that supply lasts 30 minutes or longer. 


Oxygen therapy poses no real risks to those not suffering from DCS, and prompt delivery of oxygen can immediately alleviate some symptoms and increase the likelihood of a positive outcome for the injured diver. Typical symptoms of DCS are joint pain, discoloration of the skin, numbness or paralysis, headache, nausea, weakness, vertigo, impaired mental status, and difficulty breathing. These symptoms do vary greatly and some cases of DCS can be difficult to recognize, so oxygen first aid should be provided if there are any suspicious symptoms.


Breathing high concentrations of oxygen at the surface may alleviate or entirely resolve some symptoms of DCS. The partial pressure gradient created by oxygen first aid effectively speeds the rate at which inert gas is passed into the lungs, and slows and reduces bubble formation. The benefits of oxygen for decompression, elimination of inert gases, and oxygenation of hypoxic tissues significantly outweigh the minute risk of oxygen toxicity out of the water. Oxygen is provided in the highest fraction available from the time of injury until the time that qualified medical care is reached to temporarily reduce the symptoms of DCS and improve the likelihood of a positive treatment outcome following hyperbaric oxygen therapy.

For more information on oxygen first aid, or where you can take emergency first aid courses, visit DAN.org.