Breathing O2 during surface interval

[jale]

I got a few "light hits" (joins) and I treated myself with 2 or 3hours breathing oxy with a mask on.
Used to breath also oxy before taking a plane when I didn't have at least 8h before flying.
There are even tables for breathing oxy during SI and I remember having to do some calculations to get a certif...
The take away, is that oxy is your friend but you need to know what you are doing and why.

 

[happy-diver]

Cleaned me out when I was a few times borderline nicotine overdosed

 

[Degenerate]

Very interesting. Your estimate on my dive profiles are close.
However didn’t experience DSI symptoms until after second day second dive
Dive 1: 105’ 30 minutes Air SI :56
Dive 2: 98’ 32 min Air (this is when DCI symptoms started.)

How were the dive profiles for those two dives?
If you were around 100' for most of the time then I'm not that surprised you got bent.

 

[uncfnp]

FWIW. Quite a few divers have surface O2 for emergency use. If you plan to continue to dive to the NDL limits and have the resources, it would be a good idea to have oxygen available. Use of surface O2, even at 100% is generally safe. Have you taken Emergency Oxygen course?

Now, using O2 as a deco gas is another matter. If you are serious about this, do it right, and that will entail some effort and money. Not sure one episode would be worth the time and expense.

Looks like your computer allows conservative settings. This would be a much simpler option.

 

[The Chairman]

Not sure one episode would be worth the time and expense.

I would argue that you don't need an episode to start using O2. I've been diving since 1969 and have never been bent. I've been in a chamber twice and I've had subclinical DCS (very, very tired), but I've never had a diagnosis of being bent. I use 5-minute safety stops and O2 often so I don't get bent.

 

[tarponchik]

Read it. This backs up @The Chairman's point. According to this, the tissues most susceptible to oxygen toxicity are the lungs. And "the earliest signs of pulmonary toxicity begin with evidence of tracheobronchitis, or inflammation of the upper airways, after an asymptomatic period between 4 and 22 hours at greater than 95% oxygen, with some studies suggesting symptoms usually begin after approximately 14 hours at this level of oxygen.

In other words, an hour or two of breathing O2 at 1atm isn't going to hurt you.

If you do this often and regularly, who knows. On molecular level, your organism has defense mechanisms against oxygen. There must be a reason for that, don't you think?

 

[lowwall]

If you do this often and regularly, who knows. On molecular level, your organism has defense mechanisms against oxygen. There must be a reason for that, don't you think?

I'm not advocating this. I was responding to an earlier snarky post that actually said the opposite of what the poster was implying.

Do pick up an antioxidant smoothie on your way home

Oxidative Stress: Harms and Benefits for Human Health

 

[mc42]

Very interesting. Your estimate on my dive profiles are close.

Here are actuals:
Dive 1: 111’ 33 minutes 32% SI 1:27
Dive 2: 108’ 34 minutes 32%

However didn’t experience DSI symptoms until after second day second dive
Dive 1: 105’ 30 minutes Air SI :56
Dive 2: 98’ 32 min Air (this is when DCI symptoms started.)

here are the probabilities based on your profiles (assumed square and 3 min SS)
1: 0.65%
2: 0.72% (calculator currently can’t take into account repetitive dives, so it’s likely higher)

Day 2
1: tops out at 25 minutes (0.9%; rough approximation of trend gives 1.8% for 30 mins)
2: ditto (plus no repetitive dive calculation), so much greater than 1.8%

So at least with this model, you exceeded its probabilistic calculations for day 2. Because the calculator can only do single dive calculations, I did a geometrical approximation which gave each additional minute 15% more risk based open the preceding trends. The second dive would be even riskier with the nitrogen loading from the first dive.

More importantly, you also exceeded the PADI RDP limits on both air dives which triggers a mandatory emergency deco stop for no less than 15 minutes, gas supply permitting, and halt to all diving for 24 hours if an NDL is exceeded by 5 minutes.

You may have avoided the hit by following the guidelines and avoiding that second dive.

 

[beldridg]

Very interesting. Your estimate on my dive profiles are close.

Here are actuals:
Dive 1: 111’ 33 minutes 32% SI 1:27
Dive 2: 108’ 34 minutes 32%

However didn’t experience DSI symptoms until after second day second dive
Dive 1: 105’ 30 minutes Air SI :56
Dive 2: 98’ 32 min Air (this is when DCI symptoms started.)

Thanks for posting the data.

Why did you switch from Nx32 to Air on the second day? That seems like it is "going in the wrong direction" in terms of multi-day repetitive diving safety. Also, I have to ask: are you sure you switched your computer from 32% to 21% before the dives on the second day?

Can you also clarify if the times you listed are bottom times or total dive run times?

If they are bottom times, I'm not surprised at all that you had symptoms. If they were bottom times, according to the NOAA tables, you were into deco obligations on the first dive and needed a longer surface interval to even get back in the water for the second dive.

- brett

 

[Hortondon]

How were the dive profiles for those two dives?
If you were around 100' for most of the time then I'm not that surprised you got bent.[/QUOTE

here are the probabilities based on your profiles (assumed square and 3 min SS)
1: 0.65%
2: 0.72% (calculator currently can’t take into account repetitive dives, so it’s likely higher)

Day 2
1: tops out at 25 minutes (0.9%; rough approximation of trend gives 1.8% for 30 mins)
2: ditto (plus no repetitive dive calculation), so much greater than 1.8%

So at least with this model, you exceeded its probabilistic calculations for day 2. Because the calculator can only do single dive calculations, I did a geometrical approximation which gave each additional minute 15% more risk based open the preceding trends. The second dive would be even riskier with the nitrogen loading from the first dive.

More importantly, you also exceeded the PADI RDP limits on both air dives which triggers a mandatory emergency deco stop for no less than 15 minutes, gas supply permitting, and halt to all diving for 24 hours if an NDL is exceeded by 5 minutes.

You may have avoided the hit by following the guidelines and avoiding that second dive.

interesting information. Computer never went into deco mode and no warnings for exceeded depth or deco. Just went back to log to verify this is accurate. Max depth on air at 1.4 bar is 196 feet.