Likelihood of getting oxygen toxicity at 1.4 PPO

[northernone]

Just hopping in with a little story.

I have little concern for a ppo2 of 1.4, but serious respect for the consequences of an oxtox event underwater. So I plan my margins accordingly.

I've gone down after a disoriented runaway buddy to mid 170s. I'm glad I was on air and not a gas with a MOD closer to our planned depth.

Nitrox 40 might have put me in an uncomfortable risk assessment situation (ppo2 of 2.5) for going down after him. Particularly if I was uncertain how deep I would catch him. I'd prefer 70m on air, narcosis I can manage. Hard to manage oxtox.

It's rare, and comes down to which risks are serious enough and likely enough to need planned around.

For myself I very rarely will dive without a hard bottom within reach. I like to be able to 'take my fins off and walk home' if needed.

We all have our personal 'nope' factors, logical or not.

Cameron

 

[BRT]

Obviously you misunderstand the technique.

Let go of rock then fly dsmb - as it would be foolish to let it go while you're hooked on. Ascend to SS level, carry out extended stop, slow ascent to surface. Maybe 10 mins can't tell you exactly I was busy

I'll try to get the originals of the video clips posted to a closed FB group.

If you you think I'm lying, I'm happy to host you and throw you in to our currents on a trip and see how you fair

Nope, I understand the technique. Go with the flow. That is a lot of flow.

 

[Shawn Sorah]

I do 3 hour dives using a CCR using 1.4 ppo2 and i have many dives at 4 hours at 1.3 ppo2, 6 hrs at 1.2 ppo2. And that's on a CCR.... so if you were on OC 1.4 ppo2 is nothing, but keep this in mind a CCR keeps your ppo2 the same throughout a dive, when using OC your ppo2 will change with depth....

 

[MrVegas]

I was the one that had posted about doing the Stuart Cove dives on Nitrox -- I'm just posting this to finish the story for anyone that may be interested. The dives were a lot of fun and structured basically as advertised. 1st dive was 39 minutes -- drop in about 35-40 feet, swim to the wall, down to about 75 feet (for me and my son) along the wall for a while, then up to about 40 feet and back to the boat. Most divers stayed 80 feet or above -- a couple of people went down to about 100-110. Surface interval was only about 25-30 minutes (move the boat and get back in the water). 2nd dive was 50 minutes around a small wreck and a reef at about 35-45 feet for the whole dive.

We used 32%. Nitrox was obviously not necessary for the dives, and I think there were only two others on the boat (out of maybe 16?) that used it. I'd probably do it again, though, just because of the short surface interval. With regard to MOD, I don't think there was much danger of disappearing into the depths on the wall dive in this case. (We obviously didn't push it and stayed shallower than the divemaster.)

 

[tursiops]

A 20 MPH current. That would be interesting.

And unlikely.

 

[BoatingDave]

I think the simple answer to the question is that there is insufficient data for science to have reached any sort of conclusion on "likelihood." There is just no way at present to give a numerical answer of the likelihood or odds at any given PPO2.

That is correct. I am a pulmonologist and I consider the risk on a continuum. For any given diver, the risk is not zero at 1.4, but has been shown to be generally safe over many years. However, there is likely more risk for that same diver at 1.6, though quantification of that risk increase is difficult.