DCS cure using pure02 or Nitrox mix

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

I think the problem with this hypothetical discussion is that the diver who accidently outs themselves into deco is a poor candidate for emergency in-water decompression. They would have no idea how much a few minutes of going into deco would add to their stop and would be highly unlikely to have the air,much less nitrox or oxygen readily available, not to mention the skills to hold a long stop. Let's not even begin to discuss the fact that they will probably not have the presence of mind to do this.

Yeah, but I think that the OP was asking from the point of view of a DM in a remote location, what should HE do to help in this situation. And he did ask about bringing down extra gas to the shallow stop depth, which is not unreasonable, IMHO.

So I do think that in water decompression - even on the fly, with some sort of dive pro helping out - is a lot safer than skipped deco and surface O2. And even if it was just a question of spending extra time at this shallow depth without calculating a precise profile, ANY extra back gas deco is going to be less decompression stress than just surfacing. Remember, this doesn't have to be up to the standards of a technical course, the diver is just hanging onto a line at 15 feet, and he doesn't have to hold a stop in blue water precisely.
 
I don't know where talk of panicked divers entered the discussion.

Panic is the removal of conscious decision making. The question of best options becomes irrelevant if someone panics. If they head for the surface and blow deco, that's life.... the only issue then becomes treatment of DCS.

There's some situations where people are just sh$the out of luck. If you have deco obligation and insufficient gas, or let yourself panic... then you become a statistic...

As others have said... emergency deco is a 'do the best you can' last grasp at avoiding a hard consequence.

If in doubt... Hang.
If you have gas... Hang.
If you get more gas... Hang longer.
If that gas is nitrox... Use it.
If that gas is O2.... Use it SHALLOW, at your own risk.

Here's a thought for the OP... at what depth could you deco on O2? MOD is 6m. Standard emergency deco on tables is 5m. Computer will probably stop you at 3m (assuming such idiocy shouldn't exist to run past ndl to necessitate 6m or deeper stops...)
 
Question: Are you aware of any documented cases of a diver with DCS symptoms and undetectable bubbles using Doppler instruments? (Sincere question, not intended to be confrontational or snarky)

To reinforce your statement, there are also many identified and unidentified human variables. The only reliable and absolute DCS prevention is stay at sea level (people can also be bent in unpressurized aircraft).

Maybe some of this will help the OP and some other readers: It is difficult to believe that bubbles never play any role in DCS, at least in severe DCS cases. Doppler studies actually show blocked vessels and autopsies show dead tissue. Like everything in medicine though, I also don’t believe that the simple physics of bubble formation is the only bad actor. DCS may not always be the result of blocked blood flow due to bubbles, but it is caused by gas being released from tissues more rapidly than the body can accommodate. That in turn may cause physiological responses that produce symptoms long before compromised circulation has an impact.

Hello Akimbo,

Food for Thought: 21 years ago, in his master’s thesis, Sawatzky systematically analyzed maximum Doppler scores and DCS incidence in a total of 3,234 dives. He found only one incidence of DCS not accompanied by detectable bubbles, giving a negative predictive value of 0.99 and a sensitivity of detectable bubbles as a test for DCS of 0.99. However, Sawatzky also detected bubbles without any symptoms of DCS, which gave a PPV of only 0.04! This illustrates that having detectable bubbles yields only a 4% chance of developing DCS! Even when using high bubble grades as test criterion, the PPV is low. (PPV - positive predictive value).

Please let me reiterate that I NEVER stated nor do I believe that bubbles do not play a role! HOWEVER, given the above and other studies, it is hard to argue that bubbles ALONE cause DCS. Current scientific endeavor in DCS research focus on exactly on that - what is the or are the cofactor or cofactors.

So please don't restate or suggest that I said or intended to imply that bubbles never play a role - I don't. But it is also incorrect to state that bubbles will cause DCS! If that were the case, most of us would get bend.

In the past with the understanding at THAT time, the only means to reduce the risk of DCS (since we cannot prevent it or else you don't dive or go to space), was to follow tables, de-nitrogenate, attempt to compress micro-nuclei, etc. i.e. control the bubble.

As more data and studies became available, the focus to control the bubble has changed. Although still important, we now know that most of us bubble regardless of following decompression procedures and only very few get bend. So the new question is: Why do some bend and not others?

The typical "undeserved hit' is an example of that question. Why did this person bend when he/she did everything right? And, that is precisely what some scientist currently focus on.

Articles on this and other topics are posted on the Add Helium website: Add Helium - The Rebreather Epicenter for divers to read themselves if curious.

Thank you for your question. It allowed me to clean up/clear up any misunderstandings.
 
... Please let me reiterate that I NEVER stated nor do I believe that bubbles do not play a role! HOWEVER, given the above and other studies, it is hard to argue that bubbles ALONE cause DCS....

I should have been more careful in selecting my words. My first drafts went-on and on about bubble size, density, and distribution but I erased it because I thought the overall point I was trying to make was getting lost. My apologies.

... Bubbles alone do NOT cause DCS and there are multiple scientific studies that indicate that...

That's consistent with my very limited understanding. I first learned that Doppler ultrasonic bubble detectors could find bubbles that were "too small to cause symptoms" in the early 1970s. Most of our dive team became Guinea pigs for EDU (US Navy Experimental Diving Unit) during a few sat dives. I was the only diver aboard trained in electronics so I got to interact quite a bit with the EDU docs. They were already looking into how the micro bubbles formed into larger ones and were questioning if the bubbles caused all the symptoms or if some physiological responses to micro bubbles were also triggers.

I am optimistic that one day there will be a decompression computer that will read bubbles or some "biomarker" to optimize the schedule for each of us on a particular day. All the indirect factors like cold, exertion, age, physical condition, or what we had for breakfast become superfluous when your body can "tell" you directly how close you are to getting bent. The down-side is it will really muck-up gas planning and sticking with a buddy during water stops.

Granted I will probably be long dead, but it gives me some small pleasure contemplating it.
 
Last edited:
Dreamdive, you are of course correct that bubbles alone probably don't cause DCS. But I think that it's important to acknowledge that just because the pathophysiology of DCS isn't as simple as bubbles=hit, it doesn't mean that physics aren't the main driver of this disease. Greater overpressure gradients drive more gas into a free state.

Yes, the CLINICAL scenario that we are interested in is affected by many other factors - body fat, ambient temperature, intrapulmonary and other shunts, workload, pulmonary alveolar function, etc... But most of that stuff is fixed for a given dive, and while this all means that you can't accurately predict the overpressure threshold that will cause DCS in any individual, you can say that greater decompression stress is associated with a greater overall incidence of injury, for a large population. Any dive computer or table or other algorithm is always going to be playing a game of population-based risk reduction.

Bubbles are just one aspect of decompression that we can easily visualize and actually measure to some degree. And as Akimbo said, it would be great if we could monitor our actual decompression stress in real time, with metrics that more accurately reflect our personal internal gas status. But we can't. What we can do is use a mathematical model to predict something about the physics of the situation, and then use the vast amount of accumulated empirical data (which was used to create tables and algorithms) to set arbitrary limits on overpressure which are acceptable in terms of balancing safety against decompression efficiency.
 
… it would be great if we could monitor our actual decompression stress in real time, with metrics that more accurately reflect our personal internal gas status. But we can't...

But we can't yet. Did I mention that I am an optimist? :wink:

---------- Post added November 15th, 2015 at 01:36 PM ----------

I think there is some evidence that divers with clotting disorders are more prone to DCS. I suspect that the nitrogen bubbles somehow cause an inflammatory response and clotting cascade activation. I know they are more prone to avascular necrosis of the bones. Of course we also know that PFO makes the diver higher risk...

I have been thinking about this and a similar if not related consideration is past injuries. I have known one military and several commercial divers who would take a joint hit at the site of an old injury every third or fourth decompression dive. All of them became dive supervisors and were older than most of the divers. Occasionally they would need to make a jump because the entire rotation was burned through for the day -- no repeds on Sur-D-O2 (Surface Decompression using Oxygen) dives. HeO2 or air didn't seem to make any difference, all surface supplied.

We finally started to just run a Table 5 or 6 treatment on them instead of the Sur-D table. They were always the last dive of the day anyway so there was no need to clear the chamber for the next guy.

Come to think of it, I don't recall ever reading anything about injuries and DCS in the popular diving press. Another factor may be that they all "probably" had some diving-induced bone disease from daily deep dives using experimental and proprietary decompression tables.

Outside of the world's navies, deep bounce (meaning non-saturation) decompression tables were closely guarded secrets in the 1960s through the early 1990s. Dr. Workman actually worked for Taylor Diving and Salvage after retiring from the Navy and several other well-known hyperbaric researchers were under contract from different commercial oilfield diving contractors to develop proprietary tables. Information sharing improved a lot once deep bounce diving became displaced by saturation diving.
 
Last edited:
Yeah, but I think that the OP was asking from the point of view of a DM in a remote location, what should HE do to help in this situation. And he did ask about bringing down extra gas to the shallow stop depth, which is not unreasonable, IMHO.

So I do think that in water decompression - even on the fly, with some sort of dive pro helping out - is a lot safer than skipped deco and surface O2. And even if it was just a question of spending extra time at this shallow depth without calculating a precise profile, ANY extra back gas deco is going to be less decompression stress than just surfacing. Remember, this doesn't have to be up to the standards of a technical course, the diver is just hanging onto a line at 15 feet, and he doesn't have to hold a stop in blue water precisely.

Thanks. I thought I made myself clear that it wasn't a panic situation and that the diver in question had simply be trapped under water for 40 minutes at 40Meters.

And I also thought I did mention that it was at a remote location - remote as in - no recompression chambers are anywhere nearby and it would take a long time before you can even reach the nearest clinic.

We're divers - we do go out to remote destinations - in the unlikely event that some accident of this nature happens - I just want to know what sort of things we can do to lower the chance of DCS.

---------- Post added November 15th, 2015 at 08:47 PM ----------

AJ:
The real question to me is: how much good will a stop at 5m do versus the safety of the boat? In case of emergency I would opt getting the diver on the boat asap administering pure O2 in a steady enviroment, in stead of breathing pure O2 at 5m with a lot of stress and danger. A trained diver doing a controlled ascent with 100% O2 is very different from this case. And after all, it's just 0,5 bar difference. Even if he can hold that stop exactly, it's not much extra pressure difference.

That's a good question!

Would it be better for a diver to come to the surface to breathe o2 or would it be better for him to stay at 5m?

I always assumed that once he comes up to 5M - the nitrogen bubbles in his body would burst and start DCS - if he stayed below depth at 5 Meters he would be "safe" for a few hours... Am I wrong?

---------- Post added November 15th, 2015 at 08:59 PM ----------

AJ:
The real question to me is: how much good will a stop at 5m do versus the safety of the boat? In case of emergency I would opt getting the diver on the boat asap administering pure O2 in a steady enviroment, in stead of breathing pure O2 at 5m with a lot of stress and danger. A trained diver doing a controlled ascent with 100% O2 is very different from this case. And after all, it's just 0,5 bar difference. Even if he can hold that stop exactly, it's not much extra pressure difference.

That's a good question!

Would it be better for a diver to come to the surface to breathe o2 or would it be better for him to stay at 5m?

I always assumed that once he comes up to 5M - the nitrogen bubbles in his body would burst and start DCS - if he stayed below depth at 5 Meters he would be "safe" for a few hours provided he could breathe air tanks... Am I wrong?
 
Would it be better for a diver to come to the surface to breathe o2 or would it be better for him to stay at 5m?

I always assumed that once he comes up to 5M - the nitrogen bubbles in his body would burst and start DCS - if he stayed below depth at 5 Meters he would be "safe" for a few hours... Am I wrong?

Your description of the situation is an extreme oversimplification, an inaccurate description of DCS pathophysiology and relying on arbitrary depths, but since you aren't nitrox or deco trained, I can understand your phrasing, and I think that I know what you are asking.

Decompression is a continuum, it's not like there's some sort of bright line at 5 meters depth.

But as some in this thread (including me) have mentioned - inadvertent deco is a lot safer than skipped deco. If the diver has gas left, or if you can somehow get him more gas, he should absolutely try to pay off as much of that deco obligation as he can before surfacing.
 
Thanks. I thought I made myself clear that it wasn't a panic situation and that the diver in question had simply be trapped under water for 40 minutes at 40Meters.
Your - hopefully hypothetical - diver would be dead already, unless they carried more gas than most rec divers do.

An Al80 filled to nominal pressure holds some 2250 surface liters of air. A normal metric rec tank like a 15x200, 12x232 or 10x300 holds some 3000 surface liters of air. With a fairly decent surface RMV of 15 l/min (0.53 cuFt/min), a full Al80 would last for 30 minutes at 40 meters. A full 15x200 would last for 40 minutes. However since the diver used some gas to descend, their tank wouldn't be full at 40m, so they're SOL.

Even with a surface RMV as low as 12 l/min, an Al80 wouldn't last for 40 minutes at 40m.

And I also thought I did mention that it was at a remote location - remote as in - no recompression chambers are anywhere nearby and it would take a long time before you can even reach the nearest clinic.

We're divers - we do go out to remote destinations - in the unlikely event that some accident of this nature happens - I just want to know what sort of things we can do to lower the chance of DCS.

Dive proper profiles, i.e. the deeper part first, then shallower.
Dive conservatively and don't ride the NDLs.
Use nitrox if available, if suitable and if the diver has received the training.
Have oxygen available on the boat and be liberal about using it, e.g. for divers who have experienced fast ascents, particularly after a long dive, if someone has exceeded their NDL or if there is even a remote suspicion of DCS.

If SHTF and emergency deco is required, see DevonDiver's post #32.
 
Dreamdive, you are of course correct that bubbles alone probably don't cause DCS. But I think that it's important to acknowledge that just because the pathophysiology of DCS isn't as simple as bubbles=hit, it doesn't mean that physics aren't the main driver of this disease. Greater overpressure gradients drive more gas into a free state.

Yes, the CLINICAL scenario that we are interested in is affected by many other factors - body fat, ambient temperature, intrapulmonary and other shunts, workload, pulmonary alveolar function, etc... But most of that stuff is fixed for a given dive, and while this all means that you can't accurately predict the overpressure threshold that will cause DCS in any individual, you can say that greater decompression stress is associated with a greater overall incidence of injury, for a large population. Any dive computer or table or other algorithm is always going to be playing a game of population-based risk reduction.

Bubbles are just one aspect of decompression that we can easily visualize and actually measure to some degree. And as Akimbo said, it would be great if we could monitor our actual decompression stress in real time, with metrics that more accurately reflect our personal internal gas status. But we can't. What we can do is use a mathematical model to predict something about the physics of the situation, and then use the vast amount of accumulated empirical data (which was used to create tables and algorithms) to set arbitrary limits on overpressure which are acceptable in terms of balancing safety against decompression efficiency.

Mike, it has been suggested that there is a difference between "explosive decompression", which is driven by pressure gradients and other forms of DCS. BTW, I am not the one suggesting this but follow what others are saying in the literature. Honestly, I don't like discussions on DCS on forums because the topic is so difficult. As you might agree, even among 'experts' there is divergence of opinion. This is overall beneficial because the issue of DCS is unsolved. Just because one can measure something, does not mean that it is causal to the phenomena. (I believe it was either Mollerlokken or Bruback who stated this in regards to bubble studies). The best tool we currently have at our disposition is a dive computer who manages 'real time' tissue loading. Tables are out. A continued argument appears to be how that loading information is being managed by various algorithms. Some argue that shorter decompression times are better over longer ones. The idea being that by going shallower more quickly rather than doing 'deeper stops', you ongas less which you have to offgas later. The other side is WHERE we should do our decompression, ie deeper vs shallower.

What actually constitutes decompression stress? Bubble loads? Current research is looking into biomarkers as a way to qualify this. But, it looks like we don't have enough information, yet.

"while this all means that you can't accurately predict the overpressure threshold that will cause DCS", I stopped thinking of DCS as an overpressure threshold issue unless it is AGE or "explosive deco" because I have seen complete white out in the left side of the heart with NO symptoms whatsoever. We see divers with PFO's doing He dives for years before getting hit - that raises the question "Why Now??".

Tracy: One study including Plavix showed reduced mortality due to DCS in a rat study - FYI. (PM me if you want it. I am on the road right now.)
 
https://www.shearwater.com/products/perdix-ai/

Back
Top Bottom