DCS cure using pure02 or Nitrox mix

[DevonDiver]

You mean underwater, of course.

I'm not trying to pick nits here, I just want this to be totally clear, since it seems the OP hasn't been taught this. It is of course quite OK - and a good thing - to provide O2 on the boat/shore if one suspects a DCS hit, or if the diver owes deco on surfacing.

Yes, of course.

Unless you've thought of a way to exceed 1.0 ppO2 whilst sitting on a dive boat

 

[Storker]

Unless you've thought of a way to exceed 1.0 ppO2 whilst sitting on a dive boat

You mean like they could on board the Calypso?

 

[dreamdive]

7) If you want to go by the absolute Buhlmann maximum "ceiling", basically trading operational advantage for DCS risk (i.e. getting you out of the water as fast as possible), that would be a GF of 100/100, so you would be riding the "M value line" and staying just below the ceiling. A bad idea with a high likelihood of DCS, but I think that might be what the OP is asking. That profile would be 2 minutes at 30 feet, 4 minutes at 20 feet, and 35 minutes at 15 feet. About 200 CUF for that dive, doable with double 119s (leaving aside the increased SAC rate from this emergency).

Doctormike, I hate to break it to you, but before GF lots of deco divers were diving pure Buehlman without getting bend. Getting bend does not mean you will die but drowning most likely will lead to death. Another option is to ascend and get out BEFORE you run out of gas and breath 100% on the boat, observe for any signs and symptoms for DCS and take it from there.

Question for Sipadiver: What are you going to do with the information you 'gained' from here? I am worried that you will take away partially correct or apply partially applicable procedures to your dive operation. There is so much misinformation and myth out there already. I agree with doctormike that being curious is great but if you really want to get to the bottom of this and learn i.e. understand what is going on, you may want to start taking advanced courses in decompression and supplement with scientific literature.

 

[Searcaigh]

Out of curiosity I ran the scenario on Multideco just to see how much gas would be required

DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0m
Conservatism = GF 15/75


Dec to 40m (4) Air 10m/min descent.
Level 40m 36:00 (40) Air 1.04 ppO2, 40m ead
Asc to 24m (42) Air -6m/min ascent.
Stop at 24m 0:20 (43) Air 0.71 ppO2, 24m ead
Stop at 21m 2:00 (45) Air 0.65 ppO2, 21m ead
Stop at 18m 3:00 (48) Air 0.59 ppO2, 18m ead
Stop at 15m 6:00 (54) Air 0.52 ppO2, 15m ead
Stop at 12m 7:00 (61) Air 0.46 ppO2, 12m ead
Stop at 9m 13:00 (74) Air 0.40 ppO2, 9m ead
Stop at 6m 3:00 (77) Oxygen 1.60 ppO2, 0m ead
Stop at 5m 20:00 (97) Oxygen 1.50 ppO2, 0m ead
Surface (102) Oxygen -1m/min ascent.


OTU's this dive: 92
CNS Total: 39.4%


3549.6 ltr Air
401.6 ltr Oxygen
3951.2 ltr TOTAL

If using EAN30

DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0m
Conservatism = GF 15/75


Dec to 40m (4) Nitrox 30 10m/min descent.
Level 40m 36:00 (40) Nitrox 30 1.49 ppO2, 34m ead
Asc to 21m (43) Nitrox 30 -6m/min ascent.
Stop at 21m 0:50 (44) Nitrox 30 0.93 ppO2, 17m ead
Stop at 18m 1:00 (45) Nitrox 30 0.84 ppO2, 15m ead
Stop at 15m 2:00 (47) Nitrox 30 0.75 ppO2, 12m ead
Stop at 12m 4:00 (51) Nitrox 30 0.66 ppO2, 9m ead
Stop at 9m 6:00 (57) Nitrox 30 0.57 ppO2, 7m ead
Stop at 6m 2:00 (59) Oxygen 1.60 ppO2, 0m ead
Stop at 5m 15:00 (74) Oxygen 1.50 ppO2, 0m ead
Surface (79) Oxygen -1m/min ascent.


OTU's this dive: 114
CNS Total: 51.7%


3176.5 ltr Nitrox 30
310.8 ltr Oxygen
3487.4 ltr TOTAL

 

[DevonDiver]

Question for Sipadiver: What are you going to do with the information you 'gained' from here?

I suspect it's kind of the level of theoretical knowledge that a DM-in-training used to get.... before they hacked away the DM theory training to point of irrelevance

 

[jcaplins]

You may also want to consider in your scenario if your emergency O2 bottle is even equipped to use underwater. Medical and scuba cylinders have different valves and regulators.

 

[sipadiver]

?

---------- Post added November 13th, 2015 at 05:01 PM ----------

7) If you want to go by the absolute Buhlmann maximum "ceiling", basically trading operational advantage for DCS risk (i.e. getting you out of the water as fast as possible), that would be a GF of 100/100, so you would be riding the "M value line" and staying just below the ceiling. A bad idea with a high likelihood of DCS, but I think that might be what the OP is asking. That profile would be 2 minutes at 30 feet, 4 minutes at 20 feet, and 35 minutes at 15 feet. About 200 CUF for that dive, doable with double 119s (leaving aside the increased SAC rate from this emergency).

Doctormike, I hate to break it to you, but before GF lots of deco divers were diving pure Buehlman without getting bend. Getting bend does not mean you will die but drowning most likely will lead to death. Another option is to ascend and get out BEFORE you run out of gas and breath 100% on the boat, observe for any signs and symptoms for DCS and take it from there.

Question for Sipadiver: What are you going to do with the information you 'gained' from here? I am worried that you will take away partially correct or apply partially applicable procedures to your dive operation. There is so much misinformation and myth out there already. I agree with doctormike that being curious is great but if you really want to get to the bottom of this and learn i.e. understand what is going on, you may want to start taking advanced courses in decompression and supplement with scientific literature.

I'm just curious. That's why I ask.

I'm studying for my dive master course and I thought of a hypothetical situation where a diver had spent too long deep (breathing normal air) - 40m for 40minutes.

So he's slowly ascending and drop tanks have been given to help him decompress.

I asked whether (drop tanks) 02 and Nitro would help prevent DCS - in other words, tanks with pure 02 (or Nitrox) were lowered to the 5M level to help him breathe out the the nitrogen in his body.

I do a bit of live-on-board diving to remote areas and if a diver has indeed spent too long a time at depth inadvertently - rather than get him back to the surface onto the boat- would it help if drop tanks of o2 (or nitrox) be lowered down to 5M to help him degas?

---------- Post added November 13th, 2015 at 05:17 PM ----------

Much of what you are asking is the course material for the deco procedures course, and probably best learned in that context, rather than having you try to piece it together from a few internet forum posts... however, it's good that you are interested, and maybe I can explain things a bit so that you will have some useful insight into this topic. Sorry I don't speak metric that well..


1) I wouldn't use the term "safety stop". That implies some extra time for a diver with no deco obligation. What you are describing is "unplanned deco". "Omitted deco" would be what you would happen if you surfaced without doing the required decompression.


2) As far as maximum safe depth, this is something that would be covered in a nitrox class (you can do DM without nitrox? Didn't realize that). For deco gas, we generally use a ppO2 of 1.6 ATA, so for 100% O2 that's about 20 feet.


3) Yes, mixes with lower nitrogen content (enriched air nitrox, EAN) do result in faster decompression, for a given profile. But as mentioned elsewhere, an untrained diver breathing a high O2 mix now involves the risk of oxygen toxicity if he or she inadvertently goes below the maximum operating depth (ppO2 1.6) of the gas involved.


4) The question of whether you can safely complete the required deco obligation at at standard 15 foot "safety stop" would be determined by whether or not your ceiling (the shallowest depth that you can safely ascend to before stopping to decompress) is above 15 feet. The ceiling changes during the dive based on accumulated nitrogen.


5) I put the particular case that you described (40 minutes, 40 meters, breathing air) into multi deco, just to give you an idea of the deco obligation involved. Using some standard assumptions (GF 30/75), you would need to stop for 1 minute at 60 feet, 4 minutes at 50 feet, 6 minutes at 40 feet, 10 minutes at 30 feet, 7 minutes at 20 feet and SIXTY TWO minutes at your "safety stop" depth of 15 feet! A total of 92 minutes of deco. At my SAC rate, it would require 254 CUF of gas, more than I have in my double 119s.


6) If you had the ability to switch to 100% O2 at 20 feet, you would still have to make those deeper stops, but you would only need to spend 3 minutes at 20 feet and 17 minutes at 15 feet.


7) If you want to go by the absolute Buhlmann maximum "ceiling", basically trading operational advantage for DCS risk (i.e. getting you out of the water as fast as possible), that would be a GF of 100/100, so you would be riding the "M value line" and staying just below the ceiling. A bad idea with a high likelihood of DCS, but I think that might be what the OP is asking. That profile would be 2 minutes at 30 feet, 4 minutes at 20 feet, and 35 minutes at 15 feet. About 200 CUF for that dive, doable with double 119s (leaving aside the increased SAC rate from this emergency).


8) So what would probably be actually done in the OP's hypothetical situation would be for the diver to stay on the line at 15 feet, drain his back gas tank and maybe another air tank if it could be lowered to him, go on the 100% O2 once on the boat and head for a chamber.

Thank you. I was thinking more along the lines of emergency droptanks being lowered to the diver while he is still at depth. Sometimes a chamber isn't so readily accessible.

 

[doctormike]

Doctormike, I hate to break it to you, but before GF lots of deco divers were diving pure Buehlman without getting bend.

Yeah, and lots of people drove in cars and survived before there were seat belts. Seriously, it you are advocating GF 100/100 in 2015 because people (young Navy divers) once did it and most of them didn't get bent, I'm going to have to strongly disagree with you. There is nothing magic about that M-value line, it's not like you are safe just as long as you don't cross it, and the line has no idea what your personal factors are.

Getting bend does not mean you will die but drowning most likely will lead to death.

I'm not sure what that means in this context. I wasn't suggesting drowning as an alternative to DCS, don't know how you drew that conclusion.

Another option is to ascend and get out BEFORE you run out of gas and breath 100% on the boat, observe for any signs and symptoms for DCS and take it from there.

Obviously no one is suggesting staying underwater water without breathing gas. But if you are implying that a diver who has access to gas should surface owing a deco obligation and just hope that surface O2 will fix it, I'm going to have to strongly disagree with you again. The OP was asking about extending the time underwater, possibly with extra tanks supplied from the surface. If that's an option, it is FAR better than surfacing owing deco. The only time you would do that would be if there was no other option (i.e. OOG). Even without extra tanks, you would certainly drain your back gas as low as possible to give yourself the best opportunity to offgas. Even if you can't clear your deco obligation, the more inert gas you offgas before surfacing, the lower your decompression stress.

What you are suggesting is different from the "bend and mend" approach that commercial and military divers have done in the past, where a recompression chamber was available on the deck of the support boat. Supplemental O2 is good first aid, but nowhere near as good as preventing bubbles from forming in the first place.




---------- Post added November 13th, 2015 at 05:53 PM ----------

Thank you. I was thinking more along the lines of emergency droptanks being lowered to the diver while he is still at depth.

Yes, and some boats will actually have a long hose with a regulator in the water at 15-20 feet attached to a large gas supply on the boat. This is good if you surface with more of a deco obligation than your back gas will allow you to pay. You can even hook that hose up to 100% O2, since there is no way that you can breathe it below the depth of the reg, but that's beyond the scope of this discussion.

However, if you are working in a remote area where this risk exists, and no nearby chamber, your captain might want to consider that option rather than dropping tanks overboard.

Sometimes a chamber isn't so readily accessible.

Well, I suppose the effort made to get to a chamber would be proportional to the actual DCS risk. If you blew off a few minutes of deco, went on O2 immediately, had no symptoms and were in Bikini Atol, you might not look for an airlift.

But if you do have symptoms, even if they go away on O2, DAN will recommend a chamber ride. Guess how I know that...?

 

[Akimbo]

... I know that breathing pure02 at 2 atmosphere is deadly...

Risky, not deadly (as-in an implied certainty). A PPO2 of 2.0 is considered high in the water by today's standards but is not unheard of. Perhaps this thread will be useful: Oxygen Toxicity Limits & Symptoms

---------- Post added November 13th, 2015 at 04:33 PM ----------

... But at 5m what would the effect be for 10minutes?...

5m/16.4' on 100% O2 has a 1.5 PPO2. I frequently decompress and recompress on pure O2 at 20', if conditions allow being relaxed/not physically stressed.

 

[dreamdive]

I asked whether (drop tanks) 02 and Nitro would help prevent DCS - in other words, tanks with pure 02 (or Nitrox) were lowered to the 5M level to help him breathe out the the nitrogen in his body.

First: DCS prevention is questionable either way but perhaps one should think of DCS risk reduction. Since we don't know what causes DCS definitively, we cannot talk about pure DCS prevention. Bubbles alone do NOT cause DCS and there are multiple scientific studies that indicate that.

If you have oxygen or Nitrox available to give to a diver who finds him/herself in deco is (under current scientific understanding) superior to breathing in water than out. I am just worried that some divers will be under the misconception that it's OK to go into deco as long as you lower them a tank of nitrox. Staying within NDL limits is your best course of "prevention".

DoctorMike, Yeah, and lots of people drove in cars and survived before there were seat belts. Seriously, it you are advocating GF 100/100 in 2015 because people (young Navy divers) once did it and most of them didn't get bent, I'm going to have to strongly disagree with you. There is nothing magic about that M-value line, it's not like you are safe just as long as you don't cross it, and the line has no idea what your personal factors are
n

I know many not so young or healthy divers who are diving 90/90's. I also know that staying way below the M-value is not safer, either. I know that crossing the M-value does not necessarily kill you. Show me the study that says that diving a 30/70's is any safer. If you believe bubble scores, then you also have to admit that most divers bubble but don't bent. This is a very sensitive topic and has been vehemently discussed on other forums. It is a complicated topic and as our understanding of DCS grows, it gets even more complicated. Being able to apply GF's intelligently is not something currently taught in most decompression classes of the various agencies. It's a problem.