Should You Breathe Oxygen Before a Dive?

Physically fit sport divers doing conservative profiles (e.g., slow ascents, deep stops and safety stops) have only a tiny risk of getting decompression sickness. Still, DCS incidents range from inconvenient to disabling. Any additional steps for protection are worthy of consideration - - some hyperbaric medical researchers from France think breathing oxygen before a dive may be a good one.

Focusing on a technique to reduce altitude decompression sickness risk in aviators and astronauts, the researchers recently published an interesting study on the effects of breathing oxygen (O2) prior to a dive, and what it did to subsequent bubble formation in the bloodstream. Divers performed two openwater dives to 98 feet for 30 minutes, with a six-minute safety stop at 10 feet and surface interval of 100 minutes. Beforehand, researchers broke the divers into four groups with these pre-dive conditions: (1) Air administered prior to both dives; (2) O2 administered prior to both dives; (3) O2 administered prior to the first dive and air prior to the second; and (4) air administered prior the first dive and O2 prior to the second.

Post-dive Doppler venous gas bubble scores were reduced in all pre-oxygenation dives. This effect was maintained after a second dive, without needing to pre-breathe additional oxygen. Not surprisingly, O2 pre-breathing for every dive produced the greatest reduction in bubbles. The authors concluded that O2 pre-breathing has a prolonged protective effect because it decreases venous gas emboli formation, and could therefore be beneficial for multi-day repetitive diving.

So are these results meaningful and practical to the recreational diver? Possibly, but not yet practically. The amount of O2 pre-breathed in the study - - 10.5 cubic feet per dive - - would be too much for most operators to supply, except if they charged hefty fees. If you brought your own oxygen bottles along, we can see other divers getting jealous and wanting a toke.

The protective effects of pre-breathing O2 against suffering actual DCS remain to be proven. So while you may feel it worthwhile to bring your own oxygen tank, we don’t see this catching on with dive boats unless future studies show blockbuster results or the amount of oxygen can be reduced.

- - Doc Vikingo

“Pre-dive normobaric oxygen reduces bubble formation in scuba divers,” by O. Castagna, E. Gempp and JE Blatteau, European Journal of Applied Physiology, February 14, 2009.