Why not treat DCS yourself?

[WetSEAL]

I appreciate the genuine replies, thank you.

Hmm...ok. But then you are effectively arguing for a LONG period of training that necessitates quite a few actual dives and experience building. That's why it's discussed as so far beyond OW.

If it's warranted, then sure. Suppose that evidence comes out showing, convincingly, that the majority of DCI cases which would otherwise require many hours in a chamber, if reacted to promptly, could instead be resolved by just 10-30 minutes of some IWR protocol, with effectively zero chance of oxygen toxicity, and no need for costly trip to the hospital. If such a finding became mainstream, I imagine that most regular recreational divers would gladly take a few extra classes to get that training and feel safer (I sure would), and that it would not take very long for the general thinking on this subject to change, and before long everyone in the diving community would be criticizing those that opt out of such training, regarding them as negligent and irresponsible "vacation divers" who put a burden on the health care system by opting for "chamber first treatment," due to their own negligence and lack of sufficient training, in the same way that we now think of divers that don't bother to follow basic safety precautions like carrying an octopus or a modern SPG.

Under the right circumstances. Yes, IWR can be an effective, and sometimes the only, treatment to DCS. BUT...doing it SAFELY is a "whole nuther ball of wax." There's a reasonable chance you'll DIE doing it if done improperly. That is why so much emphasis is given to training, experience, proficiency. No taksies backsies.

In Dr. Mitchell's paper, he said he still wasn't aware of a single incident of oxygen toxicity during IWR (surprising), and only a handful of cases where the patient got worse after starting IWR, and in every single case where the patient got worse during IWR they were attempting IWR on air not oxygen -- and these appeared to be people that did not have formal training on IWR either. That doesn't seem to support the notion that "there's a reasonable chance you'll DIE doing IWR," it makes it sound like fear mongering.

Also, in this thread I've specifically been asking about IWR done for shorter durations that don't exceed oxygen toxicity thresholds, so risk would be further reduced.

Because it seems like you're not listening. Your questions have been addressed repeatedly and thoroughly, and you ask more. Seems like trolling behavior.

They really haven't though. People have given a lot of reasons why IWR isn't always a good option, which seem valid, but none of those reasons seem to apply to the circumstances and use case of IWR I was talking about.

I'm talking about a diver with all requisite training (ie, advanced nitrox, rescue, oxygen therapy, etc), who experiences some mild symptoms of DCI immediately after surfacing. Diver still feels comfortable, feels capable of going back into the water, and no other adverse conditions. It's not clear whether or not a hyperbaric chamber is really needed, or would just be an excessive waste of time and money. Diver could just take O2 on the surface, and hope conditions resolve, but is considering doing a little light IWR as an added measure.

I'm not talking about full on emergency IWR done for hours, pushing way past oxygen toxicity thresholds, wearing full face masks and being monitored with a team of professionals. I'm talking about, say, 5-10 minutes done at 15-25 feet on say 80-100% O2, with a buddy, just to see if it helps to resolve symptoms. I don't think there's a significant risk of toxicity on such a dive, but there seems to be some evidence that short recompressions are enough to provide complete relief in some cases, and it might provide more relief of symptoms that just taking pure O2 on the surface...so why not try it?

To be clear: I'm not advocating for IWR in the above scenario. I'm just saying, I haven't heard a compelling reason given why the person shouldn't try it. It's not an established IWR protocol, it hasn't been studied, the potential benefits haven't been quantified...but it seems to avoid the known risks, and there is some anecdotal evidence to suggest there may be benefits. The primary danger of IWR, oxygen toxicity, doesn't seem relevant because it's so short. Inadequate exposure protection/adverse conditions is a special case scenario that doesn't effect the general case. DCI conditions worsening as a result of IWR doesn't seem to be justified by data.

Now [I]imagine[/I] doing the same again for one hour and imagine the pins-and-needles sensation after that hour. It'll hurt bad. You'll feel worse than while your arm was just numb. My personal experience was that it can take way longer than those 20 minutes mentioned in the statistics, while breathing 100% oxygen.

That's interesting to hear, thank you for sharing. Did you already detail your IWR experience? If so which post # was it? I'd be curious to read about it.

For example you brought up Type I DCI (as one of many topics in a prior post) and my first thought was that IWR was unnecessary. I could be wrong. I would find it useful to discuss this single isolated aspect.

I mentioned type 1 DCI as it was defined in Dr. Mitchell's paper, but really this thread has always and only been about type 1 DCI -- I've been primarily interested in IWR as a potential treatment for minor symptoms of DCS, where some relief might be gained by a short and "light IWR" session, avoiding the risks of O2 toxicity.[/user]

 

[Miyaru]

@WetSEAL
Can you elaborate on a diver showing signs and experiencing symptoms of DCI, and still feeling comfortable?

I can think of one such case: diver does Open Water course dives 1 and 2, uneventful dives to max. 12 meters, each 45 minutes with a 60 minute surface interval. Roughly 4 hours after surfacing from dive 2, diver develops a skin rash and swelling in the neck/chest area. Diver felt sort of comfortable, but was worried at the same time. Recompression treatment in the chamber resolved the issue. A few weeks later, back home, this diver was diagnosed with a PFO.

In this case, a recompression chamber was available within 20 hours traveling time. Would you have considered a "light IWR" session, unaware of the PFO existence and unable & uncapable of correctly diagnosing the diver?

You keep skipping the first part I mentioned and only look at your own idea of "light IWR". It's totally unrealistic and many other people here have tried in several different ways to get that message across.

 

[KeithG]

I appreciate the genuine replies, thank you.



If it's warranted, then sure. Suppose that evidence comes out showing, convincingly, that the majority of DCI cases which would otherwise require many hours in a chamber, if reacted to promptly, could instead be resolved by just 10-30 minutes of some IWR protocol, with effectively zero chance of oxygen toxicity, and no need for costly trip to the hospital. If such a finding became mainstream, I imagine that most regular recreational divers would gladly take a few extra classes to get that training and feel safer (I sure would), and that it would not take very long for the general thinking on this subject to change, and before long everyone in the diving community would be criticizing those that opt out of such training, regarding them as negligent and irresponsible "vacation divers" who put a burden on the health care system by opting for "chamber first treatment," due to their own negligence and lack of sufficient training, in the same way that we now think of divers that don't bother to follow basic safety precautions like carrying an octopus or a modern SPG.



In Dr. Mitchell's paper, he said he still wasn't aware of a single incident of oxygen toxicity during IWR (surprising), and only a handful of cases where the patient got worse after starting IWR, and in every single case where the patient got worse during IWR they were attempting IWR on air not oxygen -- and these appeared to be people that did not have formal training on IWR either. That doesn't seem to support the notion that "there's a reasonable chance you'll DIE doing IWR," it makes it sound like fear mongering.

Also, in this thread I've specifically been asking about IWR done for shorter durations that don't exceed oxygen toxicity thresholds, so risk would be further reduced.



They really haven't though. People have given a lot of reasons why IWR isn't always a good option, which seem valid, but none of those reasons seem to apply to the circumstances and use case of IWR I was talking about.

I'm talking about a diver with all requisite training (ie, advanced nitrox, rescue, oxygen therapy, etc), who experiences some mild symptoms of DCI immediately after surfacing. Diver still feels comfortable, feels capable of going back into the water, and no other adverse conditions. It's not clear whether or not a hyperbaric chamber is really needed, or would just be an excessive waste of time and money. Diver could just take O2 on the surface, and hope conditions resolve, but is considering doing a little light IWR as an added measure.

I'm not talking about full on emergency IWR done for hours, pushing way past oxygen toxicity thresholds, wearing full face masks and being monitored with a team of professionals. I'm talking about, say, 5-10 minutes done at 15-25 feet on say 80-100% O2, with a buddy, just to see if it helps to resolve symptoms. I don't think there's a significant risk of toxicity on such a dive, but there seems to be some evidence that short recompressions are enough to provide complete relief in some cases, and it might provide more relief of symptoms that just taking pure O2 on the surface...so why not try it?

To be clear: I'm not advocating for IWR in the above scenario. I'm just saying, I haven't heard a compelling reason given why the person shouldn't try it. It's not an established IWR protocol, it hasn't been studied, the potential benefits haven't been quantified...but it seems to avoid the known risks, and there is some anecdotal evidence to suggest there may be benefits. The primary danger of IWR, oxygen toxicity, doesn't seem relevant because it's so short. Inadequate exposure protection/adverse conditions is a special case scenario that doesn't effect the general case. DCI conditions worsening as a result of IWR doesn't seem to be justified by data.



That's interesting to hear, thank you for sharing. Did you already detail your IWR experience? If so which post # was it? I'd be curious to read about it.



I mentioned type 1 DCI as it was defined in Dr. Mitchell's paper, but really this thread has always and only been about type 1 DCI -- I've been primarily interested in IWR as a potential treatment for minor symptoms of DCS, where some relief might be gained by a short and "light IWR" session, avoiding the risks of O2 toxicity.[/user]

You did again. Too many topics (for me) in 1 post.

So let's talk Type I. Does anyone think IWR is appropriate? Not in my limited knowledge. O2 is recommended.

 

[Kevrumbo]

If the pain is so acute and intractable despite surface O2 and analgesics, a type I DCS patient is going to insist on Oxygen IWR given that the dive-op has the necessary equipment and gas supply. The practical reality is unless there is a physician available at this remote site who can provide an opiate pain-killer injection, you're not going to convince the patient to "take the pain" (while citing your equivocating reference studies on the delay of HBOT @Duke Dive Medicine and @Dr Simon Mitchell ) and waiting endless hours for evacuation & transport to a proper hyperbaric facility.

For more serious and acute type II, pulmonary DCS and near drowning AGE, all you can do is provide palliative treatment while awaiting transport to a "frontier" emergency Advanced Cardiac Life Support (ACLS) and hyperbaric medical clinic.

 

[KeithG]

If the pain is so acute and intractable despite surface O2 and analgesics, a type I DCS patient is going to insist on Oxygen IWR given that the dive-op has the necessary equipment and gas supply. The practical reality is unless there is a physician available at this remote site who can provide an opiate pain-killer injection, you're not going to convince the patient to "take the pain" (while citing your equivocating reference studies on the delay of HBOT @Duke Dive Medicine and @Dr Simon Mitchell ) and waiting endless hours for evacuation & transport to a proper hyperbaric facility.

For more serious and acute type II, pulmonary DCS and near drowning AGE, all you can do is provide palliative treatment while awaiting transport to a "frontier" emergency Advanced Cardiac Life Support (ACLS) and hyperbaric medical clinic.

How painful is type I? Both of the cases I know about required just an aspirin.

 

[PfcAJ]

How painful is type I? Both of the cases I know about required just an aspirin.

Depends.

“Annoying” to “worst pain ever” seems to be the range.

 

[John C. Ratliff]

There is one other missing medical problem associated with DCI which is a asymptomatic, and that is aseptic bone necrosis. If circulation is impaired within the bone, that section of bone may die without symptoms. The diver may feel fine, but months to years later fine (s)he had severe bone problems when a fracture occurs in the weakened bone, and it doesn't heal. I have a whole book about aseptic bone necrosis in my home library concerning divers, and I would be interested if any of our medically trained divers had thoughts on this. Relief of symptoms is one thing, but eliminating the effects of DCI may be another, requiring a longer, chamber protocol.

SeaRat

 

[Dr Simon Mitchell]

Hello WetSEAL,

I am going to address you long post over two of my own because of the character limit.

Thank you for your interest in our work. You will have gathered that David and I are generally positive about the concept of IWR for the right patient in the right place with the right support team. In that regard we are sometimes on the same page as you . However, some of the relevant issues are more nuanced than you have interpreted them to be. I will try to address these in relation to your specific questions below.

Others in this thread have also mentioned patient deterioration as a risk, which confused me because it is known that recompression would immediatley reduce the size of nitrogen bubbles and one would naturally expect this to provide immediate relief of symptoms (a point you noted in your paper as well).

Indeed, one might expect immediate relief based on an assumption that the presence of a bubble is the only important player in the pathophysiology. It is virtually certain that bubbles are the initial injurious agent in DCS, but bubbles incite various other processes (such as activation of inflammatory cascades) that may persist even if the bubble is removed. Part of the logic underpinning very early intervention in DCS is to remove the bubbles quickly enough to prevent these other processes from occurring, and it makes sense that the earlier the better. The success of early recompression reported in our paper almost certainly affirms this logic. However, these secondary processes may onset more quickly or more strongly in some patients, and even early reduction in bubbles may be less successful in treating symptoms in such divers. I have certainly seen cases (at the more serious end of the spectrum) who have continued to deteriorate despite early recompression in on-site chambers. If you focus on the fact that once bubbles form and cause some damage the bubbles themselves are no longer the only players in the pathophysiology, then it will be easier to understand why patients can deteriorate despite early recompression.

You also provide some concrete statistics related to this...In the various studies you've quoted, it seems that in most of them 95-98% of patients treated with O2 IWR have a complete relief of symptoms, and the only examples you mentioned of deteriorating symptoms during IWR were when air was used instead of O2. If there are no documented examples of patient deterioration during O2 IWR, then why is it still considered a serious risk factor?

I think you are over-interpreting the very limited data available and perhaps misinterpreting the pedigree of some of the data in the paper. One of the principle problems is that there are very few data providing reliable descriptions of outcomes after IWR and virtually none describing the pattern of response in detail. Thus, to argue that there are no documented examples of something where there is virtually no documentation at all would be somewhat disingenuous.

I think that when you say “In the various studies you've quoted, it seems that in most of them 95-98% of patients treated with O2 IWR have a complete relief of symptoms” you are misattributing the various source of US Navy data we have cited as pertaining to IWR. These datasets relate to early recompression in chambers, almost invariably to higher pressures than would be used in IWR. Thus they are not ideally suited to characterizing the likely incidence of deterioration despite recompression during IWR.

I should be clear that I am not fundamentally disagreeing with the notion that deterioration may be uncommon during early application of IWR, but to your specific point, we “still consider it a serious risk” because clinical experience tells us it can happen.

A related point is that the significance of a potential adverse event is evaluated not only in relation to its prevalence, but also its potential consequences if it occurs. You have to remember that IWR takes an injured diver back into a hostile non-respirable environment where the potential consequences of a deterioration are significant, and perhaps life threatening. Thus, even if deterioration is rare, it remains a relevant factor to consider in weighing the risks and benefits of IWR.

2) As for CNS-O2, you noted that "the inspired P02 threshold below which seizures never occur irrespective of duration has not been identified but is lower than exposures recommended for IWR." I am not quite sure what this means.

It means that I cannot tell you what inspired PO2 relevant to diving can be respired indefinitely with certainty that seizures will never occur (eg, is it 1.1, or 1.2 or something else?); but I can tell you that it is lower than any inspired PO2 that has been recommended for IWR (which is usually around 1.9). Put another way, if you perform IWR as recommended by just about anyone who has ventured an opinion on it, there is a risk of a seizure.

You said that you "are not aware of any reports of an oxygen toxicity event during IWR", and this presumably includes all of the data you have surveyed.

Yes, but it was simply an observation and not advanced as a strong argument that seizures won’t occur during IWR. Indeed, in the same sentence, we point out that seizures have occurred in technical diving oxygen exposures of the same magnitude. Clearly it can happen. Returning to the point I made earlier, we just don’t have enough prospectively gathered (or retrospectively gathered for that matter) data to make sense of the risk of cerebral oxygen toxicity in IWR. The Navy studies of early recompression in chambers are of no relevance at all because the risk of a seizure is markedly lower in a chamber.

In the data you have surveyed however, you have demonstrated statistically significant benefits of IWR -- for example, you demonstrated that patient outcome prognosis are significantly reduced when recompression is delayed more than 2 hours, and that the median time from surfacing to treatment at a civilian recompression facility was 2 days. The overall remission rates from chamber treatment you quoted were in the 63-83% range, whereas most of the IWR studies had complete remission closer to 95% of the time. In other words, if we look collectively at all the data you have summarized, it seems you have demonstrated that immediate IWR leads to statistically improving health outcomes as opposed to chamber treatment with the usual delays, and yet in this same data there are no documented examples of O2 IWR risks (eg, no documented reduced patient outcomes due to CNS-O2).

Once again, I think you are confusing the data David pulled from the US Navy sources with IWR data. These navy data all pertain to early compression in recompression chambers. The relevance we draw is the apparent efficacy of very early recompression, but you can’t confidently equate the outcomes directly with those of IWR.

Therefore, I'm having a hard time understanding why IWR is not recommended for say type 1 DCI symptoms based on this data. It seems like an unfair bias to use hypothetical cases of CNS-O2 that did not occur in the meta analysis and give those risks arbitrarily higher weight than the observed and measured risks associated with delayed treatment that were demonstrated in the study. Am I simply misinterpreting this data?

Can I be clear that we did not perform a meta-analysis, and I reiterate that we literally have no data on hard outcomes after IWR. Read the paper again. The only relevant data to actual outcomes of IWR appear on pages 85 and 86 under the heading “Reports of in water recompression”. It is not a lot and the vast majority of it is not validated by medical experts.

Can I also be clear that the overarching tone of our paper is positive about IWR – certainly in comparison to previous medical commentary on the matter. However, in evaluating its application we must always remain cognisant of benefit vs risk. Your question about Type 1 DCS is a perfect example. The reason we are reticent about endorsing IWR for mild symptoms is that the natural history of mild symptoms of DCS is for them to resolve no matter what you do. Indeed, as a result there is a consensus that it is reasonable not to recompress such patients at all if recompression is difficult to access. This issue is fully discussed in reference 45 (available on line) of the paper. Thus, one could ask why would we expose a diver to an intervention (IWR) with rare but life-threatening risks to treat a problem that is going to get better no matter what you do?

The caveat to this, which we mention in the paper, is rapidly progressive symptoms which nevertheless fit the qualitative categorisation of mild (eg musculoskeletal pain), but which (based on their rapid progression) may be developing into something more serious. Under these circumstances we suggest it would certainly be reasonable for properly trained and equipped teams to start preparing.

Do you believe this recommendation is supported by the data directly, or do you just not feel comfortable making a recommendation that contradicts the status quo due to the controversy surrounding it without additional evidence?

We are not afraid to state what the data allow us to reasonably conclude. But at present the treatment of mild symptoms with IWR is probably not justified on risk vs benefit grounds. That is not to say you can’t do it. But in doing so you will be accepting some risk (that is probably small) for benefit that is dubious.

Simon M

 

[Dr Simon Mitchell]

Part 2....

2) Is it possible that the risk of CNS-O2 is actually reduced by the high concentration of nitrogen likely to be in a diver conducting IWR...? I personally do not understand the processes of oxygen toxicity enough to know if this makes sense, but I wonder...if a diver is experiencing symptoms of DCI, they must have a high level of nitrogen loading, and perhaps the presence of these nitrogen bubbles gives something for the O2 to bind to which significantly delays the risk of CNS-O2. Perhaps this might explain why your meta analysis data does not document any examples of CNS-O2, despite that conventional safety thresholds for O2 toxicity are grossly exceeded?

I believe you are over-thinking this. It is extremely difficult to be precise about the risk of oxygen toxicity or all of the things that affect it. And just to remind you that we hardly have any data on safety outcomes of IWR, so emphasising the fact that we don’t know about any seizures is inappropriate.

3) Another point, which was not discussed in your paper but which I am curious about, is the discussion of milder IWR treatment for milder DCI symptoms. In your paper you have recommended not using IWR to treat mild Type 1 DCI symptoms (presumably because of the risk of CNS-O2), but it seems that some of the IWR procedures with only minor tweaking could be put well under the conventional recreational diving PP02 safety thresholds, thereby eliminating all significant sources of CNS-O2 risk.

Yes, perhaps, but then you would run into questions of efficacy. If you reduce pressure and duration of oxygen, then at some point it will cease being beneficial.

For example, you described a "provisional" protocol during the development of USN TT5/6 that suggested terminating treatment early if a complete relief of symptoms is seen within 10 min at 33 fsw.

You have misinterpreted what is said in the paper. The protocol was not termination of treatment, but rather continuation (as described) at 33 fsw instead of progressing “deeper”. The continuation prescribed another hour of treatment.

But again, yes, in principle, you can cobble together approaches to IWR that are less risky. Whether you want to do so in order to treatment DCS manifestations that are going to get better anyway is another question entirely.

You noted that the Intl Assoc of Nitrox and Tech Divers recommended IWR at even shallower depth of 25 fsw. 10 minutes at 25 fsw is really not far outside of conventional safe exposure limits, and if one relaxes this just a little bit -- say one breathes 80% O2 at 25 fsw, then this is only about 1.4 PP0 which, according to NOAA Diving Manual, is safe for recreational diving for up to 140 minutes -- plenty of time to at least try out the first provisional test, and see if symptoms resolve after 10-30 minutes, with zero risk of CNS-O2.

It is not zero risk, and remember, the technical divers that we would consider capable / suitable of safely conducting IWR will likely have a significant oxygen exposure (often more than 100% of the NOAA limits) just prior to developing their symptoms. There will also begin to be questions about efficacy the more you dilute your IWR protocol.

I hope these comments clarify things for you.

Simon M

 

[PfcAJ]

There is one other missing medical problem associated with DCI which is a asymptomatic, and that is aseptic bone necrosis. If circulation is impaired within the bone, that section of bone may die without symptoms. The diver may feel fine, but months to years later fine (s)he had severe bone problems when a fracture occurs in the weakened bone, and it doesn't heal. I have a whole book about aseptic bone necrosis in my home library concerning divers, and I would be interested if any of our medically trained divers had thoughts on this. Relief of symptoms is one thing, but eliminating the effects of DCI may be another, requiring a longer, chamber protocol.

SeaRat

If you’re asymptomatic then there’s nothing to prompt treatment.

My hunch is that asymptomatic DON is more common in technical Divers than one would expect. I had a mid-shaft femoral DON leision myself. The ONLY reason I know about it is because I injured my knee and needed an MRI. No symptoms whatsoever associated with it.