Age and deco diving, pure oxygen

[lowviz]

As an older (~60) diver entering technical diving, I'm trying to determine an optimal (all things considered, not just N2) oxygen concentration for accelerated nitrogen washout. My concern revolves around a study (Conscious Volunteers Developed Hypoxemia and Pulmonary Colla... : Anesthesiology) that wouldn't be repeated today. Basically, older divers are more prone to absorption atelectasis, especially when using breathing patterns that conserve gas. Would 80% oxygen be a better choice than pure 02? Lots to read if you search on this, but I haven't found a definitive answer yet...

 

[TSandM]

I wouldn't say that's a breathing pattern that conserves gas. Nobody is going to spend several minutes at a time breathing at residual volume. It's very uncomfortable. If you are sitting on deco, it's highly likely you'll be cycling your lung volumes around normal end expiration, which shouldn't cause any airway obstruction and makes absorption atelectasis unlikely.

This was a very small study, and the atelectasis was demonstrated on a single subject. I would not base my deco decisions on it. There are plenty of divers in their 40s and 50s doing decompression on 100% O2 without incident.

 

[lowviz]

Thanks, Lynne.

It isn't a particularly big issue with me, just can't help wondering if 80% isn't better. Especially on rough seas where holding 15' is sometimes dicey. Wouldn't mind the extra hang time if I knew that the 20% nitrogen was preventing atelectasis in the far reaches of my lung tissue. Just thinking of my second dive and full lung capacity. Probably an insignificant effect, but every bit helps.

 

[TSandM]

The 80% versus 100% argument won't ever go away, but the people who trained me feel that, if you have buoyancy issues that put you at risk for using 100% at 20 feet, you probably shouldn't be doing staged decompression diving. That made some sense to me.

 

[battles2a5]

I agree with Lynn. Being able to hold a stop should not be a consideration for gas selection. You should be looking for the best gas for the job and in most cases, 100% is a more efficient decompression gas than 80%. I know plenty of guys your age and older that have been using 100% for ages w/o ill effect. When you start getting into the bigger dives you will have to deal w/ the same oxygen issues that the younger people do, but that's just part of the game.