Breathing O2 during surface interval

[Angelo Farina]

Even if the benefit is dubious is there any reason NOT to breath pure O2, aside from the trouble and expense? There’s no side effects from it at around one bar are there?

Oxygen is toxic. It also causes irritation of mucoses.
Over exposure to oxygen for long periods can cause problems to your lungs.
Breathing pure oxygen can be a very effective treatment of DCS, but I would not breath pure oxygen just for precaution.
You risk adverse effects without any proven benefit...

 

[The Chairman]

I suggest to all divers to do a full five-minute deco stop and not just three. The difference I feel since I started this is amazing. Also, limit activity. You don't need to help haul tanks if you don't have to.

 

[The Chairman]

I would not breath pure oxygen just for precaution.

I would. If you're feeling even just a tad bit fatigued, go on O2. Athletes do it all the time after they've exerted themselves. Other than fire, there is no contraindication for using O2 at atmospheric pressures.

 

[M-Cameron]

Im hardly an expert on this.....but couldnt you potential run into CNS oxygen exposure limit issues?

if you do a few substantial dives pushing 1.4...then hop back up to the surface where you sit at a 1.0..then hop back down pushing a 1.4 again?....thats a lot of time with a high PO2

 

[The Chairman]

Im hardly an expert on this.....but couldnt you potential run into CNS oxygen exposure issues?

On the surface? With no Oxygen during his deco stops? No. Even then, any minor irritation beats DCS any time.

As a caveat... if I feel a need to go on O2 (not just as a prophylactic), my diving is done for the day and possibly two days. There's no need to push yourself and get hit. There is no such thing as an underserved "hit". We might not understand it, but it's a sign that you need to adjust your diving to be a bit more cautious. There's a popular Captain in the Keys that uses oxygen during all of his safety stops won't go below 60fsw and even then, he won't do that more than twice a day. On the boat, he'll do a few five-minute stints on oxygen on the ride back in.

 

[MaxBottomtime]

I would. If you're feeling even just a tad bit fatigued, go on O2. Athletes do it all the time after they've exerted themselves. Other than fire, there is no contraindication for using O2 at atmospheric pressures.

Skeptical Scalpel: Why supplemental oxygen is not considered a performance-enhancing drug

 

[uncfnp]

@Hortondon I may have missed it but what was your “hit?” What dive computer do you use?

 

[The Chairman]

Skeptical Scalpel: Why supplemental oxygen is not considered a performance-enhancing drug

Yeah, they need to rid their bodies of CO2 more than they need O2. There's really not much benefit for them, except psychological. However, as divers, we need to get rid of N2, and breathing oxygen is quite effective since it increases the partial pressure tension of N2 considerably. My point was, that it doesn't hurt the athlete to breathe straight O2 after their 100-meter dash to get a touchdown.

 

[mc42]

Since you mentioned NDL dives, I ran a 100' dive with 32% through the SAUL probabilistic decompression algorithm and it came up with a 0.169% chance of DCS for a 30 minute dive; 0.047% for a 25 minute dive. So your risk is less than a third if you shorten your dive by 5 minutes. The algorithm does include a 3 minute safety stop. A 30 minute dive is the PADI RDP NDL, and those tables are aggressive compared to what a dive computer may come up with.

These numbers, with your undeserved DCS hit, seem to hint towards increasing the conservatism (shorter dive or longer safety stop, or both) during the dive to avoid the hit altogether, rather than trying to mend it out of water.

If I had the O2 available, it would probably have a bigger impact used underwater rather than at the surface (if feasible of course). You'd get the benefit of the higher ambient pressure keeping the bubble sizes under control, while simultaneously keeping the tissue gradient high (0% N2 in your breathing mix) to offgas quickly. Even just a few extra minutes on O2 or Nitrox underwater might have a bigger impact than at the surface for reducing your risk factors.

Another thing to think about is having to deal with the O2 logistics - if your surface O2 session is say 30 minutes (based upon the prior post) you would probably get 2 sessions out of an AL40 cylinder of O2 depending on fill and type of breathing apparatus.

In a pinch, I might just breathe down the remainder of whatever Nitrox I had left in my cylinder at the surface as that would be better than air.

 

[lowwall]

If I have nitrox, I keep breathing it from when I surface to when I'm on the boat or beach. I figure it can't hurt and it's already paid for, so why not?