In Water Recompression

[100days-a-year]

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 love pubmed!
First citation doesn't seem altogether germane to the 12 to 24 delay before recompression premise being that all divers were recompressed within 6 hours of symptom onset.
Second citation seems to draw a conclusion contradictory to the facts they found.

 

[Akimbo]

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

Everything you quoted is true. Let's not lose sight of the fact that IWR is a dangerous crapshoot between symptom progression making IWR far too dangerous to consider and relieving those symptoms. Unfortunately, those symptoms can progress while you are in the water doing IWR. I have discussed the advantages of a chamber over IWR above.

See US Navy Diving Manual, 17-5.2 Guidance on Recompression Treatment Acrobat page 864:

17-5.2 Guidance on Recompression Treatment. Certain facets of recompression treatment have been mentioned previously, but are so important that they cannot be stressed too strongly:

• Treat promptly and adequately.
• The effectiveness of treatment decreases as the length of time between the onset of symptoms and the treatment increases.
• Do not ignore seemingly minor symptoms. They can quickly become major symptoms.

See Inert Gas Washout, Alert Diver, Q3 Summer 2017

"The vast majority of the inert gas is offgassed within a few hours, and almost all of it leaves recreational divers' bodies within about 24 hours."​

See: 17-5.4 Recompression Treatment When No Recompression Chamber is Available, Acrobat page 865-867. Of note:

17‑5.4.2.3 Symptoms After In-Water Recompression. The occurrence of Type II symptoms after in-water recompression is an ominous sign and could progress to severe, debilitating decompression sickness. It should be considered life-threatening. Operational considerations and remoteness of the dive site will dictate the speed with which the diver can be evacuated to a recompression facility.​

There's a big difference between outcomes at Duke versus the outcome from a chamber onboard the dive support boat. Getting a diver in a chamber within minutes of symptom onset prevents a lot of tissue damage. Getting a DCS patient hours after most of the dissolved diluent has left the body, but also left behind a lot of tissue damage, means that treatment is for the damaged tissue instead of eliminating the cause of damage. The difference is the diver may require months of treatment or may not fully recover -- but will be alive. A bad outcome from IWR has a much higher probability of requiring a body bag.

 

[Duke Dive Medicine]

I have never heard this version of zebras before, the only versions i've heard have been based on the one Kevrumbo stated below. We agree that there is a potential for misdiagnosis, but the problem of uncertainty is always present in anything involving biology, the variables are so great we can't possibly know with absolute certainty what's going on. Where do we draw the line, 99% or 90% or 50% chance of being correct with our Dx?





In treating undifferentiated patients, you have to start somewhere, especially in a resource limited environment. The unconscious diver on the surface who is significantly overweight, was smoking on the boat and got winded walking down the dock with no gear and only got 5ft down before LOC is probably having a medical event, the otherwise healthy mid 20s diver doing his third aggressive dive of the day is probably having something closer to what Kevrumbo stated.

While my initial response in either case will be similar, my provisional Dx is vastly different and will change my diagnostic priorities and treatment after initial the initial resuscitation.

I work in remote areas, providing medical care with limited resources and equipment. Within a minute of seeing a patient they all have a "probably" Dx, then the remainder of my history and exam tries to confirm or rebut that Dx.



If you have access to a chamber and related folks all this (IWR) is a pretty moot point.
Having a well trained team with all the IWR gear is a great idea, but isn't happening in the vast majority of remote dive sites.

Perhaps the discussion we should be having is when is IWR contraindicated?
If we are discussing who should be doing IWR and when:
My default answer to this is the same whether i'm training a rescue team, someone new to the remote medicine arena, or discussing medicine with my wife and her colleagues and residents (who work in an academic centre with all the bells and whistles).
When you get to a situation and go "WTH do i do now/WTH is going on/WTH is this going?" thats when you get help/use a lifeline/call DAN.

The threshold for IWR should be different for everyone/every team based on their skills, knowledge, experience and resources available.

Now going on a philosophical tangent: Will IWR be used inappropriately at some point, yes. No doubt about it. But if we try to establish a limit to IWR that will prevent all of these cases, it will be far too conservative and we will be missing out on timely treatment of a good many cases where IWR could provide a noticeable benefit to the patient.
As with most things in life, the pendulum will swing too far one way, and then too far the other (IWR used to be a taboo subject with no-one talking much about it, now it's becoming more accepted and agencies have courses on it, next people will overuse it and eventually the pendulum will settle somewhere close to the middle)

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)

Even that says "probably", so it implies that those performing IWR must exercise clinical judgement, as would also be required in the case examples you and others have offered. Even before one is 50% or 75% or 90% convinced that a diver has DCS, one has to know what the other percent could be, and as you noted, that depends on a variety of things. I'm personally not the be-all-end-all of differential DCS diagnosis (just lucky enough to work with some people who are) and if I was on a dive station getting ready to administer IWR I'd do exactly as you suggested and get on the phone with somebody back home to double-check myself unless I was very certain of my diagnosis.

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.

Best regards,
DDM

 

[boulderjohn]

Second citation seems to draw a conclusion contradictory to the facts they found.

It seemed that way to me, too.

 

[Duke Dive Medicine]

It depends a lot on how you define access. There's no debate that a chamber onboard makes IWR pointless. A chamber that is 4-12 hours away by the time you get ashore, sort through all the delays in transportation, diagnosis, clearance of insurance/payment, and get the chamber staff assembled can make IWR a very attractive -- depending on the support and symptoms.

IMO, the importance of time to treatment is vastly understated by the hyperbaric medical community worldwide because the whole system can't respond fast enough to make the difference. You aren't really bent after 12 hours since the great majority of dissolved diluent has already left your body. Your tissues are damaged from the bents at that point, not being damaged by diluent gas blocking blood flow. HBOT is a useful therapy but true DCS treatment is far too late.

I think that's a bit of an overgeneralization. True, we've evolved from a "air-evacuate-everything" mentality because we've found there's little difference in outcomes for Type I and milder neurological symptoms with some delay in treatment; outcome normally depends on the severity of initial symptom presentation. That's what the Mutzbauer paper was saying. Severe symptoms, e.g. unconsciousness, paralysis, and respiratory compromise certainly merit rapid evacuation and immediate recompression. The question of remoteness and the possibility of IWR are worth discussing though. If you're 12 hours by boat from the nearest airstrip, the local Coast Guard helicopter is broken, and you have a diver with profound pulmonary DCS who will almost certainly die without recompression, is IWR worth attempting? If the team has the right equipment and qualified medical personnel you could make an argument for it, but that's highly conditional and everyone has to be prepared for the likely outcome, including the diver involved.

Best regards,
DDM

 

[Akimbo]

I think that's a bit of an overgeneralization.

Like everything else, it depends on our life experiences and the scenarios we have in mind when we craft the statement. I hope that people are looking close enough to realize that we really aren't very far apart. The balance between IWR and evac is a very delicate one in most cases. One thing for sure, evac is the only option in all scenarios where the team is not well prepared.

17-5.2 Guidance on Recompression Treatment. Certain facets of recompression treatment have been mentioned previously, but are so important that they cannot be stressed too strongly:

• Treat promptly and adequately.
• The effectiveness of treatment decreases as the length of time between the onset of symptoms and the treatment increases.
• Do not ignore seemingly minor symptoms. They can quickly become major symptoms.

Aside from the very real problem of correct diagnosis, the practical reality is it is almost impossible for most recreational divers to get in a shore-based chamber fast enough for the above to apply. That's not necessarily the case with IWR. This section relates to compressing and eliminating the diluent gas, not treating damaged tissue. That timeframe is pretty small.

See Inert Gas Washout, Alert Diver, Q3 Summer 2017

"The vast majority of the inert gas is offgassed within a few hours, and almost all of it leaves recreational divers' bodies within about 24 hours."

Very prompt IWR has the potential to treat DCS in order to prevent increased tissue damage and escalation of symptoms. But it can also kill you if you are having another serious medical problem or DCS symptoms get worse.

17‑5.4.2.3 Symptoms After In-Water Recompression. The occurrence of Type II symptoms after in-water recompression is an ominous sign and could progress to severe, debilitating decompression sickness.

It is a conundrum.

Edit: For me, waiting more than an hour to start IWR will dramatically increase my inclination to evacuate to a chamber.

 

[Kevrumbo]

I think that's a bit of an overgeneralization. True, we've evolved from a "air-evacuate-everything" mentality because we've found there's little difference in outcomes for Type I and milder neurological symptoms with some delay in treatment; outcome normally depends on the severity of initial symptom presentation. That's what the Mutzbauer paper was saying. Severe symptoms, e.g. unconsciousness, paralysis, and respiratory compromise certainly merit rapid evacuation and immediate recompression. The question of remoteness and the possibility of IWR are worth discussing though. If you're 12 hours by boat from the nearest airstrip, the local Coast Guard helicopter is broken, and you have a diver with profound pulmonary DCS who will almost certainly die without recompression, is IWR worth attempting? If the team has the right equipment and qualified medical personnel you could make an argument for it, but that's highly conditional and everyone has to be prepared for the likely outcome, including the diver involved.

Best regards,
DDM

Like everything else, it depends on our life experiences and the scenarios we have in mind when we craft the statement. I hope that people are looking close enough to realize that we really aren't very far apart. The balance between IWR and evac is a very delicate one in most cases. One thing for sure, evac is the only option in all scenarios where the team is not well prepared.

Aside from the very real problem of correct diagnosis, the practical reality is it is almost impossible for most recreational divers to get in a shore-based chamber fast enough for the above to apply. That's not necessarily the case with IWR. This section relates to compressing and eliminating the diluent gas, not treating damaged tissue. That timeframe is pretty small.

Very prompt IWR has the potential to treat DCS in order to prevent increased tissue damage and escalation of symptoms. But it can also kill you if you are having another serious medical problem or DCS symptoms get worse.

It is a conundrum.

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

This is a fascinating subject and I'm very interested in the responses to John's post #67.

It's more a dilemma and at worst case, a draconian choice.

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 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.

 

[oldschoolto]

I think common sense comes in to play.. If you have to shorten your DECO because of gas management or needing to help another diver for some reason jumping back in is the fastest and best move IMHO... That is why I'm a big fan of hanging a DECO bottle on the down line... Better to have the gas and not need it than to need it and not have it.. AND, AND.. There is a big differences between a seasoned diver and a vacation diver doing it..

Jim...

 

[Akimbo]

I think common sense comes in to play.. If you have to shorten your DECO because of gas management or needing to help another diver for some reason jumping back in is the fastest and best move IMHO...

Jumping back in and hanging off at 20' on O2 without symptoms is a reped. Asking someone to keep an eye on you is getting closer to IWR, but is still a reped. I call it prophylactic decompression. I do it all the time without missing planned deco, but I leave my computer on deck.

 

[100days-a-year]

@ 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.