Nitrox for shallow water artifact diving??

[mc42]

Conshelf II supported 6 divers for 30 days at 10M in 1963. All the documents and films that I can remember indicate they all came straight to the surface with no DCS.

I was watching the documentary recently, and I remembered at the beginning Cousteau visits the crew in the main habitat, then has to return to the Calypso, but mentions in the narration that he will have to decompress for an hour at 10' under the hull of the ship.

I can't recall other mentions of having decompression obligations, but there seems to have been a distinction between those in the habitat and those servicing them - bringing food and mail down in pressure pots, the barber from the ship coming down to cut hair, etc. - that seems to suggest those in the habitat couldn't necessarily surface at will.

 

[Mr. Manfrenjensenden]

And I'm still trying to find a case of DCS using air diving above 33FSW. Can you help me with that?

Me, maybe... but I was on nitrox. Standard, non-sawtooth dive profiles of a 10am shore dive on 32% for ~45 mins to max of 35 feet followed by a 2pm shore dive on 32% for ~45 mins to max of 30 feet, and I spent little time at those depths so they overstate my nitrogen on-gassing. Ascents (such as they were) were slow and I did standard safety stops. This was the first day of a trip so I was completely off-gassed before these dives and the surface interval was more than three hours. I had a recurrence of previously-experienced bilateral nerve symptoms (finger tingling) that evening that my hyperbaric medicine specialist thinks probably was DCS, no matter that it doesn't make sense given the dives I did. Subsequently tested negative for a PFO, nerve conduction tests were normal, etc. This occurred in late 2019, so by the time he cleared me to go back to diving (shallow only, only on nitrox, one dive/day) the pandemic hit and I haven't had a chance to get in the water since to see what happens.

 

[Subcooled]

So what is it doing @ 25FSW on a 2hour dive? No much it would seem since I have never read of a case of DCS doing a 2hr @25FSW. Or any dive of any length of time at that depth. Have you?

any length of time at that depth: 8m/26ft for 3 days: Bubble formation and decompression sickness on direct ascent from shallow air saturation diving - PubMed
- I'm not a hyperbaric expert, just good at web search

This thread is not about saturation diving. Hence this info is not 100% relevant...

 

[Subcooled]

If staying at 25' it is ongassing until saturated. The expectation is that the human body can withstand saturation at that depth and a quick return to the surface. Human bodies may differ.

Apparently they do differ: 8m/26ft dives: "On the other hand, in the 8-m dive, four subjects suffered from DCS and required recompression treatment. The minimum depth for detectable bubble formation was assessed at around 6 m and the direct ascent from saturation at 8 m seems to have a high risk of DCS." [source]

 

[Subcooled]

I was talking to a buddy about being so tired after chasing artifacts in shallow water and burning down two 133 s which last forever in shallow water...My dives are forty feet or less and most of the time 20 ft or less. He told me nitrox diving would help with the next day tiredness...What do you guys think??

Short answer: use nitrox 32 and ascend slowly to 10ft, then stay there for a while (=relax), then ascend very very slowly to the surface, then rest. Stay well hydrated the whole week. Drink plenty of water each day and after the dive. Sleep well and eat healthy food. Wear good enough exposure protection as extended submersion makes you cold = tired. Efficient swimming (avoid unnecessary muscle tensions and lie flat) is also quite important!

Using nitrox 32 instead of nitrox 21 (=air) means that you cut down the amount of nitrogen from 78% (air) to 67% (ean32). One percentage for other gasses. There is 14% less nitrogen then (67 of 78 is 86%). 14% is not a huge amount but it helps a lot if you are pushing the limits that your body can tolerate. Rest, food, hydration, mental state, position in water, efficient use of muscles, staying warm all lessen your tiredness. If you use something like 60% or 80% oxygen (MOD 44ft or 25ft) then nitrogen loading is greatly reduced and replaced with another problem: the oxygen will burn your lungs. I know a diver who did just that. He doesn't dive anymore. And do not forget all the other factors that I named and that make you tired.

 

[AfterDark]

any length of time at that depth: 8m/26ft for 3 days: Bubble formation and decompression sickness on direct ascent from shallow air saturation diving - PubMed
- I'm not a hyperbaric expert, just good at web search

This thread is not about saturation diving. Hence this info is not 100% relevant...

Relevant enough, thank you 1st I've read of this. Unlikely the OP it going spend 3 days on one dive looking for artifacts. It does illustrate how extreme a "dive" at that depth would be to cause trouble.

 

[AfterDark]

Me, maybe... but I was on nitrox. Standard, non-sawtooth dive profiles of a 10am shore dive on 32% for ~45 mins to max of 35 feet followed by a 2pm shore dive on 32% for ~45 mins to max of 30 feet, and I spent little time at those depths so they overstate my nitrogen on-gassing. Ascents (such as they were) were slow and I did standard safety stops. This was the first day of a trip so I was completely off-gassed before these dives and the surface interval was more than three hours. I had a recurrence of previously-experienced bilateral nerve symptoms (finger tingling) that evening that my hyperbaric medicine specialist thinks probably was DCS, no matter that it doesn't make sense given the dives I did. Subsequently tested negative for a PFO, nerve conduction tests were normal, etc. This occurred in late 2019, so by the time he cleared me to go back to diving (shallow only, only on nitrox, one dive/day) the pandemic hit and I haven't had a chance to get in the water since to see what happens.

You don't qualify you went deeper than 33FSW. On nitrox you say? Hope your issue is resolved.
Those dives and SIs should have been fine. Did you play ball or exercise during the SI? Good luck

 

[Wibble]

Never had any instruction on tables? That's OK. Nobody uses them much anymore.

Oooh. I thought that too...

Now about my dive yesterday. On a boat in the English Channel diving on a small wreck (Frogner) with a mere 6 people on the boat (hich takes 12, so loads of space. Opposite me are a couple diving mixed systems (him a Kiss, her a twinset/doubles). Dangling in front of me was a roll of gaffa tape (duct tape?) where she'd written her dive plan with a reserve plan. She tore off the tape and stuck it to her drysuit. Without blinking she told me there was a backup on her wetnotes.

She likes to dive like that and that's so nice to see someone sticking to the tried and trusted method. Also she pointed out that the Suunto Gecko was in gauge mode and she didn't have an expensive dive computer. Great answer.

But like dragging rock over plastic to get music; was fine some time ago, but I'll stick with my 8-track iPhone. Much easier to look at the dive time and TTS and leave the computers to work out the deco plan.

 

[100days-a-year]

Which of the preceding best represent your view?

 

[Mr. Manfrenjensenden]

You don't qualify you went deeper than 33FSW. On nitrox you say? Hope your issue is resolved.
Those dives and SIs should have been fine. Did you play ball or exercise during the SI? Good luck

I doubt the 30 seconds I spent at that extra two feet of depth changed my situation, but if you've put a hard line at 33 feet, then ok.

No exercise during the surface interval.