In Water Recompression

[thin_air]

I would like to have more discussion on this apparent disagreement that has been unacknowledged so far:

My thoughts on the matter:
- There isn't much hard data that I can find on divers getting recompressed within ~5min of symptom onset (i hope DDM can confirm or deny this). Early recompression is within 90min in some studies.
- There seems to be anecdotal data of early recompression working (such as 100days-a-year's post).
- Current literature in other medical field puts a strong emphasis on earlier reperfusion improving outcomes (specifically in stroke and MI patients, where a symptom onset to treatment time of 60-90min is targeted)
- It will be difficult to power a study enough that one can find small changes in outcomes for the patient population we are looking out
- We know that Sur-D works, so recompression prior to symptom onset is very effective
- It would be quite strange if the function of (time to recompression from symptom onset) to (clinical outcome) was discontinuous, we know that when (TTR from symptom onset) is negative, the outcomes are good, and we know that when (TTR from symptom onset) goes towards infinity (no treatment), outcomes are worse

First citation
"Fifty-nine divers with DCS treated in less than 6 hours from onset of symptoms to hyperbaric recompression were included retrospectively."
"There was a relationship between a longer delay to treatment and incomplete recovery"

Second citation
"The medical histories of 28 divers treated at a hyperbaric facility in the Maldive Islands in the Indian Ocean were evaluated."
"Divers presenting later than 17 hours after surfacing (the median time to treatment after surfacing for the whole group) were likely to have more intense symptoms on VASS (median 100%) than those who presented earlier for treatment (median 30%, P = 0.02)."

I don't feel these quotes do justice to the data stated in the articles
- from the first article: "TTR did not appear to influence the final outcome when univariate analysis was applied with a cut-off of 90 min.... ... we noted a relationship between TTR and incomplete recovery (P = 0.03), but the increase risk appeared negligible with an adjusted OR of only 1.01..."
- for the second article, that statement speaks only to severity on presentation, not outcome from their outcome "Neither more HBOT nor a worse outcome of DCS could be related to delay to treatment longer than 17 hours."

Hi thin_air,

Our (DDM's) opinion on in-water recompression is that it may be a reasonable part of an emergency plan when it is administered by an appropriately trained, experienced, and equipped team. Certainly there are times when it's appropriate, as there are times when administering 100% O2 on the surface and observing is appropriate. It's up to that team to weigh the risks and the benefits of recompressing in the water on the spot vs transporting to a recompression facility, and at the risk of sounding elitist, not every dive team is qualified to do that. Sometimes they don't know what they don't know.

Part of what I'd consider the irony of in-water recompression is that the injured divers who could most benefit from recompression, i.e. those with the most severe symptoms and are most in need of immediate recompression, are also the ones who are most likely to be harmed by it. It's hard to establish solid go/no-go criteria since there is so much individual variability. It's worthwhile to look at established references like the US Navy Diving Manual: "In divers with severe Type II symptoms, or symptoms of arterial gas embolism (e.g., unconsciousness, paralysis, vertigo, respiratory distress (chokes), shock, etc.), the risk of increased harm to the diver from in-water recompression probably outweighs any anticipated benefit." (p 17-16)

Having a plan and a bunch of switched on dudes (and dudettes)to execute that plan is generally better than the alternatives. I think part of the disconnect in many of these conversations is the failure to differentiate patient populations, something like this:
- minor type 1/2 that resolves upon reaching depth
- minor type 1/2 that doesn't resolve upon reaching depth
- major type 1/2 that resolves upon reaching depth
- major type 1/2 that doesn't resolve upon reaching depth

For minor type 1 (and possibly 2) hits, we probably aren't having a huge effect on morbidity with IWR vs surface O2.
For major hits that resolve at depth, the risk to the patient is probably less then those that don't resolve, as they're "normal" at depth.
For the major hits that don't resolve upon reaching depth, the question (as i have it in my mind) becomes what is the risk of keeping them at depth longer with their symptoms and the associated risks vs how quickly can we surface them again and provide surface care to manage their symptoms (and reduce their in water time with severe symptoms that increase the risk of a poor outcome).

I don't know who's doing what with respect to IWR in the tech-rec diving community. I'd love to find out. When I see posts like some of the previous ones here, though, I get concerned about it being misapplied, with possibly serious consequences. A good example is the post above about divers returning to diving hours after IWR for DCS involving paralysis. That's incredibly dangerous and the unfortunate consequence of getting away with it is that the behavior is reinforced and perpetuated. Again, classic normalization of deviance. Of course people are going to do what they will, and in the grand scheme of things I believe you're right about the pendulum swinging to and fro. All my colleagues and I can do is provide information based on what we know to be best practice at present.

I do appreciate the effort that you and your colleagues put forth in helping educate those who don't do hyperbarics on a daily basis, it certainly helps move the field along and helps us make better decisions.

As for what happens out in the real world, I suspect there is a non-trivial amount of divers who return for a reped (as Akimbo calls it) or IWR. For example, I do staged deco dives from shore, and have on multiple locations started walking out of the water (with doubles +/- 1 or 2 stage/deco bottles), gotten thigh deep in water and turned right back around because something doesn't feel "right", and did a short dive on O2 or 50% in the 3-6m range, then come back to exit in 20min and all is well.
Where does this fall on the spectrum, I don't know, but it's been working alright for me so far (although now i just pad my 6m stops significantly and use a more conservative GF). It would seem the spectrum goes something along the lines of padding stops, a reped (getting back in to do more deco with no symptoms), the grey area of getting back in with subclinical DCI symptoms, getting back in for IWR with minor symptoms and lastly trying to treat major symptoms with IWR.
This is gross oversimplification, but if it can help push people to the left of that spectrum (that is to say, towards padding stops) then a small victory can be achieved.

There will always be those who will use tools at their disposal inappropriately. If you don't understand what you are doing and why, this may very well be you. If the only exposure someone has to IWR and DCI treatment is this thread (or even all conversations on this forum) then they aren't in the strongest position to do IWR. I would hate for that to blunt the conversation.

 

[Duke Dive Medicine]

@ DDM I appreciate your well founded concern,I am just reporting events.To be honest,of the group I refer to,the one guy with permanent damage delayed treatment and was helo'd in.His injury kind of cemented their belief in immediate IWR.
Of course,if someone does have an issue other than a simple bubble and jumps back in it could have severe consequences.

It also seems to align with @ Akimbo's thoughts on preventing lasting injury immediately rather than treating damaged tissue later.

I'm happy not to have had to make a decision regarding that,I've jumped back in on 02 but never to treat a perceived DCS incident.I also try to emphasize when here on SB I am relating incidents and not advocating diving or recompression practices.

Apologies, maybe I should clarify. It wasn't so much the IWR for paralysis that was alarming; that's arguably appropriate under certain circumstances. It was the immediate resumption of diving afterward, which is not appropriate and potentially dangerous. And I agree, those are the conundrums involved in the decision-making... Is the diver deteriorating enough despite surface O2, and far enough away from help, that IWR is a reasonable choice? Is the team certain of the diagnosis? If not, what are the potential hazards of putting the diver under water for treatment? A simple case of limb pain, lymphatic DCS, type I skin rash, or isolated type II skin rash in a healthy diver who is otherwise fine carries a much lower risk of complications during IWR than does a paraplegic diver who's hypothermic, dehydrated and hemodynamically unstable.

Best regards,
DDM

 

[Duke Dive Medicine]

As for what happens out in the real world, I suspect there is a non-trivial amount of divers who return for a reped (as Akimbo calls it) or IWR. For example, I do staged deco dives from shore, and have on multiple locations started walking out of the water (with doubles +/- 1 or 2 stage/deco bottles), gotten thigh deep in water and turned right back around because something doesn't feel "right", and did a short dive on O2 or 50% in the 3-6m range, then come back to exit in 20min and all is well.
Where does this fall on the spectrum, I don't know, but it's been working alright for me so far (although now i just pad my 6m stops significantly and use a more conservative GF). It would seem the spectrum goes something along the lines of padding stops, a reped (getting back in to do more deco with no symptoms), the grey area of getting back in with subclinical DCI symptoms, getting back in for IWR with minor symptoms and lastly trying to treat major symptoms with IWR.
This is gross oversimplification, but if it can help push people to the left of that spectrum (that is to say, towards padding stops) then a small victory can be achieved.

I am very interested in studying that. We really don't know how much IWR goes on, how it's applied, why, where, etc. A colleague and I are in the process of developing an online survey to try to gather some data. Of course surveys themselves are problematic in that there's response bias, but it would be more data than we have now. Another SB member and I have been having an offline conversation about how to study the effectiveness of padding tables; the gears are slowly turning on a study to model the probability of DCS with extended shallow stops on O2. We'll see what comes of that.

Best regards,
DDM

 

[Johnoly]

.... We really don't know how much IWR goes on, how it's applied, why, where, etc.

... A colleague and I are in the process of developing an online survey to try to gather some data.

If you want the most valuable info, you need meet and greets with those that practice IWR to gain their trust and get them to talk to you. They'll tell you what the times, depths, and mixes they used as well as the outcome.You need to do an onsite trip to the Saint Pete Open and also the Hell Diver's tournament. Then just walk the long weigh in line and talk to divers about IWR. Or if they can introduce you to others who have done IWR. These guys won't fill out a survey. They won't talk about an injury online. You need boots on the ground to go talk to them.

 

[Duke Dive Medicine]

Thank you for that!

 

[Kevrumbo]

A properly planned civilian liveaboard sport technical dive expedition should have an onboard Recompression Chamber in place -preferably 6ATA capable, auxiliary lock access with at least two person capacity (the patient and tender). A Physician with hyperbaric medicine experience should be part of the dive group charter as well. (See: Diving from the MV Windward - Indies Trader and Boat specification | MV EMPRESS - Dive Safari Komodo Ambon Alor Raja Ampat on the liveaboard EMPRESS )

@thin_air :
A better consult and source of comment on circumstances, and the efficacy of a patient electively choosing O2 IWR versus standard chamber HBO on these expeditions is @Dr Simon Mitchell (subject to Patient-Doctor confidentiality), and who is scheduled to attend this TekDiveUSA Conference.

 

[oldschoolto]

That's pie in the sky wishing... A chamber on every dive boat ? or even every live aboard ? It'll never happen, And then have a doctor to boot... We would be paying $1000 a dive...

Jim....

 

[Kevrumbo]

That's pie in the sky wishing... A chamber on every dive boat ? or even every live aboard ? It'll never happen, And then have a doctor to boot... We would be paying $1000 a dive...

Jim....

If you're diving 45m and deeper with mandatory decompression profiles over two weeks (eg Bikini Atoll), with the next nearest chamber a 30 hour return back to port, then it would be prudent to have an onboard 6ata Recompression Chamber rather than solely relying on O2 IWR. . .

 

[Cowfish Aesthetic]

Is there any meaningful difference in patients' reaction to IWR and HBOT if we take away the fact that one takes place in the water? If not, it seems to me that we could learn a lot about the potential risks of IWR from HBOT treatment. That is, what percentage of HBOT patients suffer side-effects that would be problematic underwater (loss of consciousness, convulsions, etc.). And what percentage of patients initially suspected of DCI are later determined to be suffering from something else?

 

[Akimbo]

A reasonably close estimate is a liveaboard would have to give up at least one and probably two paying passenger spots to fit a double-lock and support gear (space, power, and weight). That raises the cost enough to be non-competitive for most recreational divers, before amortizing the chamber and compressors. Few if any liveaboards are configured so all that gear can be lifted aboard when a charter calls for it. It would be different if a boat could survive on tech divers only. Someday perhaps.

The trouble with having a chamber onboard is divers would want to run Sur-D-O2, which would make dive computers apoplectic.